diff --git a/.mailmap b/.mailmap
index 14797092475a2..e5aad52ef4b79 100644
--- a/.mailmap
+++ b/.mailmap
@@ -114,6 +114,7 @@ James Deng <cnjamesdeng@gmail.com> <cnJamesDeng@gmail.com>
 James Miller <bladeon@gmail.com> <james@aatch.net>
 James Perry <james.austin.perry@gmail.com>
 Jason Fager <jfager@gmail.com>
+Jason Liquorish <jason@liquori.sh> <Bassetts@users.noreply.github.com>
 Jason Orendorff <jorendorff@mozilla.com> <jason.orendorff@gmail.com>
 Jason Orendorff <jorendorff@mozilla.com> <jason@mozmac-2.local>
 Jason Toffaletti <toffaletti@gmail.com> Jason Toffaletti <jason@topsy.com>
diff --git a/Cargo.lock b/Cargo.lock
index f15f81e76e1cb..b8fbfbf8ad3f5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3552,6 +3552,7 @@ dependencies = [
  "log",
  "rustc",
  "rustc_ast_pretty",
+ "rustc_codegen_ssa",
  "rustc_codegen_utils",
  "rustc_data_structures",
  "rustc_error_codes",
@@ -3629,6 +3630,7 @@ version = "0.0.0"
 name = "rustc_hir"
 version = "0.0.0"
 dependencies = [
+ "lazy_static 1.4.0",
  "rustc_ast_pretty",
  "rustc_data_structures",
  "rustc_errors",
@@ -3748,7 +3750,6 @@ dependencies = [
 name = "rustc_macros"
 version = "0.1.0"
 dependencies = [
- "itertools 0.8.0",
  "proc-macro2 1.0.3",
  "quote 1.0.2",
  "syn 1.0.11",
@@ -3812,7 +3813,6 @@ name = "rustc_mir_build"
 version = "0.0.0"
 dependencies = [
  "arena",
- "itertools 0.8.0",
  "log",
  "rustc",
  "rustc_apfloat",
diff --git a/src/bootstrap/bootstrap.py b/src/bootstrap/bootstrap.py
index 1935759a5628e..50e1726240fff 100644
--- a/src/bootstrap/bootstrap.py
+++ b/src/bootstrap/bootstrap.py
@@ -80,7 +80,7 @@ def _download(path, url, probably_big, verbose, exception):
             option = "-s"
         run(["curl", option,
              "-y", "30", "-Y", "10",    # timeout if speed is < 10 bytes/sec for > 30 seconds
-             "--connect-timeout", "30", # timeout if cannot connect within 30 seconds
+             "--connect-timeout", "30",  # timeout if cannot connect within 30 seconds
              "--retry", "3", "-Sf", "-o", path, url],
             verbose=verbose,
             exception=exception)
@@ -332,7 +332,6 @@ def __init__(self):
         self.use_vendored_sources = ''
         self.verbose = False
 
-
     def download_stage0(self):
         """Fetch the build system for Rust, written in Rust
 
@@ -351,7 +350,7 @@ def support_xz():
             try:
                 with tempfile.NamedTemporaryFile(delete=False) as temp_file:
                     temp_path = temp_file.name
-                with tarfile.open(temp_path, "w:xz") as tar:
+                with tarfile.open(temp_path, "w:xz"):
                     pass
                 return True
             except tarfile.CompressionError:
@@ -825,7 +824,7 @@ def check_vendored_status(self):
                 if not os.path.exists(vendor_dir):
                     print('error: vendoring required, but vendor directory does not exist.')
                     print('       Run `cargo vendor` without sudo to initialize the '
-                        'vendor directory.')
+                          'vendor directory.')
                     raise Exception("{} not found".format(vendor_dir))
 
         if self.use_vendored_sources:
@@ -839,7 +838,7 @@ def check_vendored_status(self):
                     "\n"
                     "[source.vendored-sources]\n"
                     "directory = '{}/vendor'\n"
-                .format(self.rust_root))
+                    .format(self.rust_root))
         else:
             if os.path.exists('.cargo'):
                 shutil.rmtree('.cargo')
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index 1fdd5d13e7fe7..3d2eead6788bf 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -393,11 +393,12 @@ def set(key, value):
 
 
 def is_number(value):
-  try:
-    float(value)
-    return True
-  except ValueError:
-    return False
+    try:
+        float(value)
+        return True
+    except ValueError:
+        return False
+
 
 # Here we walk through the constructed configuration we have from the parsed
 # command line arguments. We then apply each piece of configuration by
diff --git a/src/ci/cpu-usage-over-time.py b/src/ci/cpu-usage-over-time.py
index daf21670b3339..78ac060368193 100644
--- a/src/ci/cpu-usage-over-time.py
+++ b/src/ci/cpu-usage-over-time.py
@@ -148,11 +148,11 @@ def idle_since(self, prev):
     print('unknown platform', sys.platform)
     sys.exit(1)
 
-cur_state = State();
+cur_state = State()
 print("Time,Idle")
 while True:
-    time.sleep(1);
-    next_state = State();
+    time.sleep(1)
+    next_state = State()
     now = datetime.datetime.utcnow().isoformat()
     idle = next_state.idle_since(cur_state)
     print("%s,%s" % (now, idle))
diff --git a/src/etc/debugger_pretty_printers_common.py b/src/etc/debugger_pretty_printers_common.py
index 385ce8efab87b..b3f8f50636bee 100644
--- a/src/etc/debugger_pretty_printers_common.py
+++ b/src/etc/debugger_pretty_printers_common.py
@@ -212,7 +212,6 @@ def __classify_struct(self):
         # REGULAR STRUCT
         return TYPE_KIND_REGULAR_STRUCT
 
-
     def __classify_union(self):
         assert self.get_dwarf_type_kind() == DWARF_TYPE_CODE_UNION
 
@@ -233,7 +232,6 @@ def __classify_union(self):
         else:
             return TYPE_KIND_REGULAR_UNION
 
-
     def __conforms_to_field_layout(self, expected_fields):
         actual_fields = self.get_fields()
         actual_field_count = len(actual_fields)
@@ -363,6 +361,7 @@ def extract_tail_head_ptr_and_cap_from_std_vecdeque(vec_val):
     assert data_ptr.type.get_dwarf_type_kind() == DWARF_TYPE_CODE_PTR
     return (tail, head, data_ptr, capacity)
 
+
 def extract_length_and_ptr_from_slice(slice_val):
     assert (slice_val.type.get_type_kind() == TYPE_KIND_SLICE or
             slice_val.type.get_type_kind() == TYPE_KIND_STR_SLICE)
@@ -376,8 +375,10 @@ def extract_length_and_ptr_from_slice(slice_val):
     assert data_ptr.type.get_dwarf_type_kind() == DWARF_TYPE_CODE_PTR
     return (length, data_ptr)
 
+
 UNQUALIFIED_TYPE_MARKERS = frozenset(["(", "[", "&", "*"])
 
+
 def extract_type_name(qualified_type_name):
     """Extracts the type name from a fully qualified path"""
     if qualified_type_name[0] in UNQUALIFIED_TYPE_MARKERS:
@@ -393,6 +394,7 @@ def extract_type_name(qualified_type_name):
     else:
         return qualified_type_name[index + 2:]
 
+
 try:
     compat_str = unicode  # Python 2
 except NameError:
diff --git a/src/etc/dec2flt_table.py b/src/etc/dec2flt_table.py
index 85395d2ecdfc7..4979882ffeaff 100755
--- a/src/etc/dec2flt_table.py
+++ b/src/etc/dec2flt_table.py
@@ -14,7 +14,6 @@
 even larger, and it's already uncomfortably large (6 KiB).
 """
 from __future__ import print_function
-import sys
 from math import ceil, log
 from fractions import Fraction
 from collections import namedtuple
@@ -82,6 +81,7 @@ def error(f, e, z):
     ulp_err = abs_err / Fraction(2) ** z.exp
     return float(ulp_err)
 
+
 HEADER = """
 //! Tables of approximations of powers of ten.
 //! DO NOT MODIFY: Generated by `src/etc/dec2flt_table.py`
diff --git a/src/etc/gdb_rust_pretty_printing.py b/src/etc/gdb_rust_pretty_printing.py
index 5da01b96fa5e3..0914c22eb13f0 100755
--- a/src/etc/gdb_rust_pretty_printing.py
+++ b/src/etc/gdb_rust_pretty_printing.py
@@ -9,7 +9,7 @@
 if sys.version_info[0] >= 3:
     xrange = range
 
-rust_enabled = 'set language rust' in gdb.execute('complete set language ru', to_string = True)
+rust_enabled = 'set language rust' in gdb.execute('complete set language ru', to_string=True)
 
 # The btree pretty-printers fail in a confusing way unless
 # https://sourceware.org/bugzilla/show_bug.cgi?id=21763 is fixed.
@@ -21,9 +21,10 @@
     if int(_match.group(1)) > 8 or (int(_match.group(1)) == 8 and int(_match.group(2)) >= 1):
         gdb_81 = True
 
-#===============================================================================
+# ===============================================================================
 # GDB Pretty Printing Module for Rust
-#===============================================================================
+# ===============================================================================
+
 
 class GdbType(rustpp.Type):
 
@@ -133,39 +134,39 @@ def rust_pretty_printer_lookup_function(gdb_val):
 
     if type_kind == rustpp.TYPE_KIND_REGULAR_STRUCT:
         return RustStructPrinter(val,
-                                 omit_first_field = False,
-                                 omit_type_name = False,
-                                 is_tuple_like = False)
+                                 omit_first_field=False,
+                                 omit_type_name=False,
+                                 is_tuple_like=False)
 
     if type_kind == rustpp.TYPE_KIND_STRUCT_VARIANT:
         return RustStructPrinter(val,
-                                 omit_first_field = True,
-                                 omit_type_name = False,
-                                 is_tuple_like = False)
+                                 omit_first_field=True,
+                                 omit_type_name=False,
+                                 is_tuple_like=False)
 
     if type_kind == rustpp.TYPE_KIND_STR_SLICE:
         return RustStringSlicePrinter(val)
 
     if type_kind == rustpp.TYPE_KIND_TUPLE:
         return RustStructPrinter(val,
-                                 omit_first_field = False,
-                                 omit_type_name = True,
-                                 is_tuple_like = True)
+                                 omit_first_field=False,
+                                 omit_type_name=True,
+                                 is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_TUPLE_STRUCT:
         return RustStructPrinter(val,
-                                 omit_first_field = False,
-                                 omit_type_name = False,
-                                 is_tuple_like = True)
+                                 omit_first_field=False,
+                                 omit_type_name=False,
+                                 is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_CSTYLE_VARIANT:
         return RustCStyleVariantPrinter(val.get_child_at_index(0))
 
     if type_kind == rustpp.TYPE_KIND_TUPLE_VARIANT:
         return RustStructPrinter(val,
-                                 omit_first_field = True,
-                                 omit_type_name = False,
-                                 is_tuple_like = True)
+                                 omit_first_field=True,
+                                 omit_type_name=False,
+                                 is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_SINGLETON_ENUM:
         variant = get_field_at_index(gdb_val, 0)
@@ -189,9 +190,9 @@ def rust_pretty_printer_lookup_function(gdb_val):
     return None
 
 
-#=------------------------------------------------------------------------------
+# =------------------------------------------------------------------------------
 # Pretty Printer Classes
-#=------------------------------------------------------------------------------
+# =------------------------------------------------------------------------------
 class RustEmptyPrinter(object):
     def __init__(self, val):
         self.__val = val
@@ -355,6 +356,7 @@ def children_of_node(boxed_node, height, want_values):
             else:
                 yield keys[i]['value']['value']
 
+
 class RustStdBTreeSetPrinter(object):
     def __init__(self, val):
         self.__val = val
@@ -429,6 +431,7 @@ def to_string(self):
     def display_hint(self):
         return "string"
 
+
 class RustCStyleVariantPrinter(object):
     def __init__(self, val):
         assert val.type.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_ENUM
diff --git a/src/etc/generate-deriving-span-tests.py b/src/etc/generate-deriving-span-tests.py
index afa6bbdae4e9e..c42f942c63cf5 100755
--- a/src/etc/generate-deriving-span-tests.py
+++ b/src/etc/generate-deriving-span-tests.py
@@ -8,7 +8,8 @@
 sample usage: src/etc/generate-deriving-span-tests.py
 """
 
-import os, stat
+import os
+import stat
 
 TEST_DIR = os.path.abspath(
     os.path.join(os.path.dirname(__file__), '../test/ui/derives/'))
@@ -56,6 +57,7 @@
 
 ENUM_TUPLE, ENUM_STRUCT, STRUCT_FIELDS, STRUCT_TUPLE = range(4)
 
+
 def create_test_case(type, trait, super_traits, error_count):
     string = [ENUM_STRING, ENUM_STRUCT_VARIANT_STRING, STRUCT_STRING, STRUCT_TUPLE_STRING][type]
     all_traits = ','.join([trait] + super_traits)
@@ -63,8 +65,9 @@ def create_test_case(type, trait, super_traits, error_count):
     error_deriving = '#[derive(%s)]' % super_traits if super_traits else ''
 
     errors = '\n'.join('//~%s ERROR' % ('^' * n) for n in range(error_count))
-    code = string.format(traits = all_traits, errors = errors)
-    return TEMPLATE.format(error_deriving=error_deriving, code = code)
+    code = string.format(traits=all_traits, errors=errors)
+    return TEMPLATE.format(error_deriving=error_deriving, code=code)
+
 
 def write_file(name, string):
     test_file = os.path.join(TEST_DIR, 'derives-span-%s.rs' % name)
@@ -86,10 +89,10 @@ def write_file(name, string):
 
 traits = {
     'Default': (STRUCT, [], 1),
-    'FromPrimitive': (0, [], 0), # only works for C-like enums
+    'FromPrimitive': (0, [], 0),  # only works for C-like enums
 
-    'Decodable': (0, [], 0), # FIXME: quoting gives horrible spans
-    'Encodable': (0, [], 0), # FIXME: quoting gives horrible spans
+    'Decodable': (0, [], 0),  # FIXME: quoting gives horrible spans
+    'Encodable': (0, [], 0),  # FIXME: quoting gives horrible spans
 }
 
 for (trait, supers, errs) in [('Clone', [], 1),
diff --git a/src/etc/generate-keyword-tests.py b/src/etc/generate-keyword-tests.py
index bc046a8f42d0b..77c3d2758c6dc 100755
--- a/src/etc/generate-keyword-tests.py
+++ b/src/etc/generate-keyword-tests.py
@@ -11,7 +11,6 @@
 
 import sys
 import os
-import datetime
 import stat
 
 
diff --git a/src/etc/htmldocck.py b/src/etc/htmldocck.py
index e8be2b9b53710..7789b24b62c83 100644
--- a/src/etc/htmldocck.py
+++ b/src/etc/htmldocck.py
@@ -131,6 +131,7 @@
 except NameError:
     unichr = chr
 
+
 class CustomHTMLParser(HTMLParser):
     """simplified HTML parser.
 
@@ -169,21 +170,25 @@ def close(self):
         HTMLParser.close(self)
         return self.__builder.close()
 
+
 Command = namedtuple('Command', 'negated cmd args lineno context')
 
+
 class FailedCheck(Exception):
     pass
 
+
 class InvalidCheck(Exception):
     pass
 
+
 def concat_multi_lines(f):
     """returns a generator out of the file object, which
     - removes `\\` then `\n` then a shared prefix with the previous line then
       optional whitespace;
     - keeps a line number (starting from 0) of the first line being
       concatenated."""
-    lastline = None # set to the last line when the last line has a backslash
+    lastline = None  # set to the last line when the last line has a backslash
     firstlineno = None
     catenated = ''
     for lineno, line in enumerate(f):
@@ -208,6 +213,7 @@ def concat_multi_lines(f):
     if lastline is not None:
         print_err(lineno, line, 'Trailing backslash at the end of the file')
 
+
 LINE_PATTERN = re.compile(r'''
     (?<=(?<!\S)@)(?P<negated>!?)
     (?P<cmd>[A-Za-z]+(?:-[A-Za-z]+)*)
@@ -252,7 +258,7 @@ def flatten(node):
 
 def normalize_xpath(path):
     if path.startswith('//'):
-        return '.' + path # avoid warnings
+        return '.' + path  # avoid warnings
     elif path.startswith('.//'):
         return path
     else:
@@ -316,7 +322,7 @@ def get_dir(self, path):
 
 def check_string(data, pat, regexp):
     if not pat:
-        return True # special case a presence testing
+        return True  # special case a presence testing
     elif regexp:
         return re.search(pat, data, flags=re.UNICODE) is not None
     else:
@@ -353,7 +359,7 @@ def check_tree_text(tree, path, pat, regexp):
                 ret = check_string(value, pat, regexp)
                 if ret:
                     break
-    except Exception as e:
+    except Exception:
         print('Failed to get path "{}"'.format(path))
         raise
     return ret
@@ -363,6 +369,7 @@ def get_tree_count(tree, path):
     path = normalize_xpath(path)
     return len(tree.findall(path))
 
+
 def stderr(*args):
     if sys.version_info.major < 3:
         file = codecs.getwriter('utf-8')(sys.stderr)
@@ -371,6 +378,7 @@ def stderr(*args):
 
     print(*args, file=file)
 
+
 def print_err(lineno, context, err, message=None):
     global ERR_COUNT
     ERR_COUNT += 1
@@ -381,31 +389,33 @@ def print_err(lineno, context, err, message=None):
     if context:
         stderr("\t{}".format(context))
 
+
 ERR_COUNT = 0
 
+
 def check_command(c, cache):
     try:
         cerr = ""
-        if c.cmd == 'has' or c.cmd == 'matches': # string test
+        if c.cmd == 'has' or c.cmd == 'matches':  # string test
             regexp = (c.cmd == 'matches')
-            if len(c.args) == 1 and not regexp: # @has <path> = file existence
+            if len(c.args) == 1 and not regexp:  # @has <path> = file existence
                 try:
                     cache.get_file(c.args[0])
                     ret = True
                 except FailedCheck as err:
                     cerr = str(err)
                     ret = False
-            elif len(c.args) == 2: # @has/matches <path> <pat> = string test
+            elif len(c.args) == 2:  # @has/matches <path> <pat> = string test
                 cerr = "`PATTERN` did not match"
                 ret = check_string(cache.get_file(c.args[0]), c.args[1], regexp)
-            elif len(c.args) == 3: # @has/matches <path> <pat> <match> = XML tree test
+            elif len(c.args) == 3:  # @has/matches <path> <pat> <match> = XML tree test
                 cerr = "`XPATH PATTERN` did not match"
                 tree = cache.get_tree(c.args[0])
                 pat, sep, attr = c.args[1].partition('/@')
-                if sep: # attribute
+                if sep:  # attribute
                     tree = cache.get_tree(c.args[0])
                     ret = check_tree_attr(tree, pat, attr, c.args[2], regexp)
-                else: # normalized text
+                else:  # normalized text
                     pat = c.args[1]
                     if pat.endswith('/text()'):
                         pat = pat[:-7]
@@ -413,16 +423,16 @@ def check_command(c, cache):
             else:
                 raise InvalidCheck('Invalid number of @{} arguments'.format(c.cmd))
 
-        elif c.cmd == 'count': # count test
-            if len(c.args) == 3: # @count <path> <pat> <count> = count test
+        elif c.cmd == 'count':  # count test
+            if len(c.args) == 3:  # @count <path> <pat> <count> = count test
                 expected = int(c.args[2])
                 found = get_tree_count(cache.get_tree(c.args[0]), c.args[1])
                 cerr = "Expected {} occurrences but found {}".format(expected, found)
                 ret = expected == found
             else:
                 raise InvalidCheck('Invalid number of @{} arguments'.format(c.cmd))
-        elif c.cmd == 'has-dir': # has-dir test
-            if len(c.args) == 1: # @has-dir <path> = has-dir test
+        elif c.cmd == 'has-dir':  # has-dir test
+            if len(c.args) == 1:  # @has-dir <path> = has-dir test
                 try:
                     cache.get_dir(c.args[0])
                     ret = True
@@ -448,11 +458,13 @@ def check_command(c, cache):
     except InvalidCheck as err:
         print_err(c.lineno, c.context, str(err))
 
+
 def check(target, commands):
     cache = CachedFiles(target)
     for c in commands:
         check_command(c, cache)
 
+
 if __name__ == '__main__':
     if len(sys.argv) != 3:
         stderr('Usage: {} <doc dir> <template>'.format(sys.argv[0]))
diff --git a/src/etc/lldb_batchmode.py b/src/etc/lldb_batchmode.py
index 7c2e91474c1f1..d9c4bc5562f00 100644
--- a/src/etc/lldb_batchmode.py
+++ b/src/etc/lldb_batchmode.py
@@ -157,6 +157,7 @@ def watchdog():
 # ~main
 ####################################################################################################
 
+
 if len(sys.argv) != 3:
     print("usage: python lldb_batchmode.py target-path script-path")
     sys.exit(1)
diff --git a/src/etc/lldb_rust_formatters.py b/src/etc/lldb_rust_formatters.py
index fdc1c4fa0cc38..0c4021b36fb6f 100644
--- a/src/etc/lldb_rust_formatters.py
+++ b/src/etc/lldb_rust_formatters.py
@@ -1,10 +1,10 @@
 import lldb
-import re
 import debugger_pretty_printers_common as rustpp
 
-#===============================================================================
+# ===============================================================================
 # LLDB Pretty Printing Module for Rust
-#===============================================================================
+# ===============================================================================
+
 
 class LldbType(rustpp.Type):
 
@@ -84,16 +84,16 @@ def print_val(lldb_val, internal_dict):
         type_kind == rustpp.TYPE_KIND_EMPTY):
         return print_struct_val(val,
                                 internal_dict,
-                                omit_first_field = False,
-                                omit_type_name = False,
-                                is_tuple_like = False)
+                                omit_first_field=False,
+                                omit_type_name=False,
+                                is_tuple_like=False)
 
     if type_kind == rustpp.TYPE_KIND_STRUCT_VARIANT:
         return print_struct_val(val,
                                 internal_dict,
-                                omit_first_field = True,
-                                omit_type_name = False,
-                                is_tuple_like = False)
+                                omit_first_field=True,
+                                omit_type_name=False,
+                                is_tuple_like=False)
 
     if type_kind == rustpp.TYPE_KIND_SLICE:
         return print_vec_slice_val(val, internal_dict)
@@ -110,16 +110,16 @@ def print_val(lldb_val, internal_dict):
     if type_kind == rustpp.TYPE_KIND_TUPLE:
         return print_struct_val(val,
                                 internal_dict,
-                                omit_first_field = False,
-                                omit_type_name = True,
-                                is_tuple_like = True)
+                                omit_first_field=False,
+                                omit_type_name=True,
+                                is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_TUPLE_STRUCT:
         return print_struct_val(val,
                                 internal_dict,
-                                omit_first_field = False,
-                                omit_type_name = False,
-                                is_tuple_like = True)
+                                omit_first_field=False,
+                                omit_type_name=False,
+                                is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_CSTYLE_VARIANT:
         return val.type.get_unqualified_type_name()
@@ -127,9 +127,9 @@ def print_val(lldb_val, internal_dict):
     if type_kind == rustpp.TYPE_KIND_TUPLE_VARIANT:
         return print_struct_val(val,
                                 internal_dict,
-                                omit_first_field = True,
-                                omit_type_name = False,
-                                is_tuple_like = True)
+                                omit_first_field=True,
+                                omit_type_name=False,
+                                is_tuple_like=True)
 
     if type_kind == rustpp.TYPE_KIND_SINGLETON_ENUM:
         return print_val(lldb_val.GetChildAtIndex(0), internal_dict)
@@ -157,9 +157,9 @@ def print_val(lldb_val, internal_dict):
     return lldb_val.GetValue()
 
 
-#=--------------------------------------------------------------------------------------------------
+# =---------------------------------------------------------------------------------------
 # Type-Specialized Printing Functions
-#=--------------------------------------------------------------------------------------------------
+# =---------------------------------------------------------------------------------------
 
 def print_struct_val(val, internal_dict, omit_first_field, omit_type_name, is_tuple_like):
     """
@@ -212,6 +212,7 @@ def render_child(child_index):
     return template % {"type_name": type_name,
                        "body": body}
 
+
 def print_pointer_val(val, internal_dict):
     """Prints a pointer value with Rust syntax"""
     assert val.type.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_PTR
@@ -253,18 +254,21 @@ def print_std_vec_val(val, internal_dict):
                                               length,
                                               internal_dict)
 
+
 def print_str_slice_val(val, internal_dict):
     (length, data_ptr) = rustpp.extract_length_and_ptr_from_slice(val)
     return read_utf8_string(data_ptr, length)
 
+
 def print_std_string_val(val, internal_dict):
     vec = val.get_child_at_index(0)
     (length, data_ptr, cap) = rustpp.extract_length_ptr_and_cap_from_std_vec(vec)
     return read_utf8_string(data_ptr, length)
 
-#=--------------------------------------------------------------------------------------------------
+# =-----------------------------------------------------------------------
 # Helper Functions
-#=--------------------------------------------------------------------------------------------------
+# =-----------------------------------------------------------------------
+
 
 def print_array_of_values(array_name, data_ptr_val, length, internal_dict):
     """Prints a contiguous memory range, interpreting it as values of the
diff --git a/src/liballoc/alloc.rs b/src/liballoc/alloc.rs
index 9fb0de63e6fc5..f41404bf8cab9 100644
--- a/src/liballoc/alloc.rs
+++ b/src/liballoc/alloc.rs
@@ -200,21 +200,27 @@ unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
         align as *mut u8
     } else {
         let layout = Layout::from_size_align_unchecked(size, align);
-        let ptr = alloc(layout);
-        if !ptr.is_null() { ptr } else { handle_alloc_error(layout) }
+        match Global.alloc(layout) {
+            Ok(ptr) => ptr.as_ptr(),
+            Err(_) => handle_alloc_error(layout),
+        }
     }
 }
 
 #[cfg_attr(not(test), lang = "box_free")]
 #[inline]
+// This signature has to be the same as `Box`, otherwise an ICE will happen.
+// When an additional parameter to `Box` is added (like `A: AllocRef`), this has to be added here as
+// well.
+// For example if `Box` is changed to  `struct Box<T: ?Sized, A: AllocRef>(Unique<T>, A)`,
+// this function has to be changed to `fn box_free<T: ?Sized, A: AllocRef>(Unique<T>, A)` as well.
 pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
-    let ptr = ptr.as_ptr();
-    let size = size_of_val(&*ptr);
-    let align = min_align_of_val(&*ptr);
+    let size = size_of_val(ptr.as_ref());
+    let align = min_align_of_val(ptr.as_ref());
     // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
     if size != 0 {
         let layout = Layout::from_size_align_unchecked(size, align);
-        dealloc(ptr as *mut u8, layout);
+        Global.dealloc(ptr.cast().into(), layout);
     }
 }
 
diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index d65aee0923280..3ac4bd82a3a10 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -196,12 +196,14 @@ impl<T> Box<T> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit() -> Box<mem::MaybeUninit<T>> {
         let layout = alloc::Layout::new::<mem::MaybeUninit<T>>();
-        if layout.size() == 0 {
-            return Box(NonNull::dangling().into());
+        unsafe {
+            let ptr = if layout.size() == 0 {
+                NonNull::dangling()
+            } else {
+                Global.alloc(layout).unwrap_or_else(|_| alloc::handle_alloc_error(layout)).cast()
+            };
+            Box::from_raw(ptr.as_ptr())
         }
-        let ptr =
-            unsafe { Global.alloc(layout).unwrap_or_else(|_| alloc::handle_alloc_error(layout)) };
-        Box(ptr.cast().into())
     }
 
     /// Constructs a new `Box` with uninitialized contents, with the memory
@@ -264,15 +266,14 @@ impl<T> Box<[T]> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     pub fn new_uninit_slice(len: usize) -> Box<[mem::MaybeUninit<T>]> {
         let layout = alloc::Layout::array::<mem::MaybeUninit<T>>(len).unwrap();
-        let ptr = if layout.size() == 0 {
-            NonNull::dangling()
-        } else {
-            unsafe {
+        unsafe {
+            let ptr = if layout.size() == 0 {
+                NonNull::dangling()
+            } else {
                 Global.alloc(layout).unwrap_or_else(|_| alloc::handle_alloc_error(layout)).cast()
-            }
-        };
-        let slice = unsafe { slice::from_raw_parts_mut(ptr.as_ptr(), len) };
-        Box(Unique::from(slice))
+            };
+            Box::from_raw(slice::from_raw_parts_mut(ptr.as_ptr(), len))
+        }
     }
 }
 
@@ -308,7 +309,7 @@ impl<T> Box<mem::MaybeUninit<T>> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub unsafe fn assume_init(self) -> Box<T> {
-        Box(Box::into_unique(self).cast())
+        Box::from_raw(Box::into_raw(self) as *mut T)
     }
 }
 
@@ -346,7 +347,7 @@ impl<T> Box<[mem::MaybeUninit<T>]> {
     #[unstable(feature = "new_uninit", issue = "63291")]
     #[inline]
     pub unsafe fn assume_init(self) -> Box<[T]> {
-        Box(Unique::new_unchecked(Box::into_raw(self) as _))
+        Box::from_raw(Box::into_raw(self) as *mut [T])
     }
 }
 
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index e1b549bed18a6..144654946a2ac 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -280,7 +280,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
             // 0, getting to here necessarily means the `RawVec` is overfull.
             assert!(elem_size != 0, "capacity overflow");
 
-            let (new_cap, uniq) = match self.current_layout() {
+            let (new_cap, ptr) = match self.current_layout() {
                 Some(cur) => {
                     // Since we guarantee that we never allocate more than
                     // `isize::MAX` bytes, `elem_size * self.cap <= isize::MAX` as
@@ -297,7 +297,7 @@ impl<T, A: AllocRef> RawVec<T, A> {
                     alloc_guard(new_size).unwrap_or_else(|_| capacity_overflow());
                     let ptr_res = self.a.realloc(NonNull::from(self.ptr).cast(), cur, new_size);
                     match ptr_res {
-                        Ok(ptr) => (new_cap, ptr.cast().into()),
+                        Ok(ptr) => (new_cap, ptr),
                         Err(_) => handle_alloc_error(Layout::from_size_align_unchecked(
                             new_size,
                             cur.align(),
@@ -308,13 +308,14 @@ impl<T, A: AllocRef> RawVec<T, A> {
                     // Skip to 4 because tiny `Vec`'s are dumb; but not if that
                     // would cause overflow.
                     let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 };
-                    match self.a.alloc_array::<T>(new_cap) {
-                        Ok(ptr) => (new_cap, ptr.into()),
-                        Err(_) => handle_alloc_error(Layout::array::<T>(new_cap).unwrap()),
+                    let layout = Layout::array::<T>(new_cap).unwrap();
+                    match self.a.alloc(layout) {
+                        Ok(ptr) => (new_cap, ptr),
+                        Err(_) => handle_alloc_error(layout),
                     }
                 }
             };
-            self.ptr = uniq;
+            self.ptr = ptr.cast().into();
             self.cap = new_cap;
         }
     }
diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 38df843d258d3..71f7f971eabaf 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -593,9 +593,8 @@ pub unsafe trait GlobalAlloc {
 ///
 /// * the starting address for that memory block was previously
 ///   returned by a previous call to an allocation method (`alloc`,
-///   `alloc_zeroed`, `alloc_excess`, `alloc_one`, `alloc_array`) or
-///   reallocation method (`realloc`, `realloc_excess`, or
-///   `realloc_array`), and
+///   `alloc_zeroed`, `alloc_excess`) or reallocation method
+///   (`realloc`, `realloc_excess`), and
 ///
 /// * the memory block has not been subsequently deallocated, where
 ///   blocks are deallocated either by being passed to a deallocation
@@ -606,11 +605,6 @@ pub unsafe trait GlobalAlloc {
 /// methods in the `AllocRef` trait state that allocation requests
 /// must be non-zero size, or else undefined behavior can result.
 ///
-/// * However, some higher-level allocation methods (`alloc_one`,
-///   `alloc_array`) are well-defined on zero-sized types and can
-///   optionally support them: it is left up to the implementor
-///   whether to return `Err`, or to return `Ok` with some pointer.
-///
 /// * If an `AllocRef` implementation chooses to return `Ok` in this
 ///   case (i.e., the pointer denotes a zero-sized inaccessible block)
 ///   then that returned pointer must be considered "currently
@@ -853,6 +847,59 @@ pub unsafe trait AllocRef {
         result
     }
 
+    /// Behaves like `realloc`, but also ensures that the new contents
+    /// are set to zero before being returned.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe for the same reasons that `realloc` is.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err` only if the new layout
+    /// does not meet the allocator's size
+    /// and alignment constraints of the allocator, or if reallocation
+    /// otherwise fails.
+    ///
+    /// Implementations are encouraged to return `Err` on memory
+    /// exhaustion rather than panicking or aborting, but this is not
+    /// a strict requirement. (Specifically: it is *legal* to
+    /// implement this trait atop an underlying native allocation
+    /// library that aborts on memory exhaustion.)
+    ///
+    /// Clients wishing to abort computation in response to a
+    /// reallocation error are encouraged to call the [`handle_alloc_error`] function,
+    /// rather than directly invoking `panic!` or similar.
+    ///
+    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
+    unsafe fn realloc_zeroed(
+        &mut self,
+        ptr: NonNull<u8>,
+        layout: Layout,
+        new_size: usize,
+    ) -> Result<NonNull<u8>, AllocErr> {
+        let old_size = layout.size();
+
+        if new_size >= old_size {
+            if let Ok(()) = self.grow_in_place_zeroed(ptr, layout, new_size) {
+                return Ok(ptr);
+            }
+        } else if new_size < old_size {
+            if let Ok(()) = self.shrink_in_place(ptr, layout, new_size) {
+                return Ok(ptr);
+            }
+        }
+
+        // otherwise, fall back on alloc + copy + dealloc.
+        let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
+        let result = self.alloc_zeroed(new_layout);
+        if let Ok(new_ptr) = result {
+            ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), cmp::min(old_size, new_size));
+            self.dealloc(ptr, layout);
+        }
+        result
+    }
+
     /// Behaves like `alloc`, but also ensures that the contents
     /// are set to zero before being returned.
     ///
@@ -904,6 +951,31 @@ pub unsafe trait AllocRef {
         self.alloc(layout).map(|p| Excess(p, usable_size.1))
     }
 
+    /// Behaves like `alloc`, but also returns the whole size of
+    /// the returned block. For some `layout` inputs, like arrays, this
+    /// may include extra storage usable for additional data.
+    /// Also it ensures that the contents are set to zero before being returned.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe for the same reasons that `alloc` is.
+    ///
+    /// # Errors
+    ///
+    /// Returning `Err` indicates that either memory is exhausted or
+    /// `layout` does not meet allocator's size or alignment
+    /// constraints, just as in `alloc`.
+    ///
+    /// Clients wishing to abort computation in response to an
+    /// allocation error are encouraged to call the [`handle_alloc_error`] function,
+    /// rather than directly invoking `panic!` or similar.
+    ///
+    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
+    unsafe fn alloc_excess_zeroed(&mut self, layout: Layout) -> Result<Excess, AllocErr> {
+        let usable_size = self.usable_size(&layout);
+        self.alloc_zeroed(layout).map(|p| Excess(p, usable_size.1))
+    }
+
     /// Behaves like `realloc`, but also returns the whole size of
     /// the returned block. For some `layout` inputs, like arrays, this
     /// may include extra storage usable for additional data.
@@ -934,6 +1006,37 @@ pub unsafe trait AllocRef {
         self.realloc(ptr, layout, new_size).map(|p| Excess(p, usable_size.1))
     }
 
+    /// Behaves like `realloc`, but also returns the whole size of
+    /// the returned block. For some `layout` inputs, like arrays, this
+    /// may include extra storage usable for additional data.
+    /// Also it ensures that the contents are set to zero before being returned.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe for the same reasons that `realloc` is.
+    ///
+    /// # Errors
+    ///
+    /// Returning `Err` indicates that either memory is exhausted or
+    /// `layout` does not meet allocator's size or alignment
+    /// constraints, just as in `realloc`.
+    ///
+    /// Clients wishing to abort computation in response to a
+    /// reallocation error are encouraged to call the [`handle_alloc_error`] function,
+    /// rather than directly invoking `panic!` or similar.
+    ///
+    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
+    unsafe fn realloc_excess_zeroed(
+        &mut self,
+        ptr: NonNull<u8>,
+        layout: Layout,
+        new_size: usize,
+    ) -> Result<Excess, AllocErr> {
+        let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
+        let usable_size = self.usable_size(&new_layout);
+        self.realloc_zeroed(ptr, layout, new_size).map(|p| Excess(p, usable_size.1))
+    }
+
     /// Attempts to extend the allocation referenced by `ptr` to fit `new_size`.
     ///
     /// If this returns `Ok`, then the allocator has asserted that the
@@ -983,6 +1086,34 @@ pub unsafe trait AllocRef {
         if new_size <= u { Ok(()) } else { Err(CannotReallocInPlace) }
     }
 
+    /// Behaves like `grow_in_place`, but also ensures that the new
+    /// contents are set to zero before being returned.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe for the same reasons that `grow_in_place` is.
+    ///
+    /// # Errors
+    ///
+    /// Returns `Err(CannotReallocInPlace)` when the allocator is
+    /// unable to assert that the memory block referenced by `ptr`
+    /// could fit `layout`.
+    ///
+    /// Note that one cannot pass `CannotReallocInPlace` to the `handle_alloc_error`
+    /// function; clients are expected either to be able to recover from
+    /// `grow_in_place` failures without aborting, or to fall back on
+    /// another reallocation method before resorting to an abort.
+    unsafe fn grow_in_place_zeroed(
+        &mut self,
+        ptr: NonNull<u8>,
+        layout: Layout,
+        new_size: usize,
+    ) -> Result<(), CannotReallocInPlace> {
+        self.grow_in_place(ptr, layout, new_size)?;
+        ptr.as_ptr().add(layout.size()).write_bytes(0, new_size - layout.size());
+        Ok(())
+    }
+
     /// Attempts to shrink the allocation referenced by `ptr` to fit `new_size`.
     ///
     /// If this returns `Ok`, then the allocator has asserted that the
@@ -1035,195 +1166,4 @@ pub unsafe trait AllocRef {
         // new_layout.size() <= layout.size()        [required by this method]
         if l <= new_size { Ok(()) } else { Err(CannotReallocInPlace) }
     }
-
-    // == COMMON USAGE PATTERNS ==
-    // alloc_one, dealloc_one, alloc_array, realloc_array. dealloc_array
-
-    /// Allocates a block suitable for holding an instance of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `realloc`/`dealloc` methods of this allocator.
-    ///
-    /// Note to implementors: If this returns `Ok(ptr)`, then `ptr`
-    /// must be considered "currently allocated" and must be
-    /// acceptable input to methods such as `realloc` or `dealloc`,
-    /// *even if* `T` is a zero-sized type. In other words, if your
-    /// `AllocRef` implementation overrides this method in a manner
-    /// that can return a zero-sized `ptr`, then all reallocation and
-    /// deallocation methods need to be similarly overridden to accept
-    /// such values as input.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `T` does not meet allocator's size or alignment constraints.
-    ///
-    /// For zero-sized `T`, may return either of `Ok` or `Err`, but
-    /// will *not* yield undefined behavior.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the [`handle_alloc_error`] function,
-    /// rather than directly invoking `panic!` or similar.
-    ///
-    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
-    fn alloc_one<T>(&mut self) -> Result<NonNull<T>, AllocErr>
-    where
-        Self: Sized,
-    {
-        let k = Layout::new::<T>();
-        if k.size() > 0 { unsafe { self.alloc(k).map(|p| p.cast()) } } else { Err(AllocErr) }
-    }
-
-    /// Deallocates a block suitable for holding an instance of `T`.
-    ///
-    /// The given block must have been produced by this allocator,
-    /// and must be suitable for storing a `T` (in terms of alignment
-    /// as well as minimum and maximum size); otherwise yields
-    /// undefined behavior.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure both:
-    ///
-    /// * `ptr` must denote a block of memory currently allocated via this allocator
-    ///
-    /// * the layout of `T` must *fit* that block of memory.
-    unsafe fn dealloc_one<T>(&mut self, ptr: NonNull<T>)
-    where
-        Self: Sized,
-    {
-        let k = Layout::new::<T>();
-        if k.size() > 0 {
-            self.dealloc(ptr.cast(), k);
-        }
-    }
-
-    /// Allocates a block suitable for holding `n` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `realloc`/`dealloc` methods of this allocator.
-    ///
-    /// Note to implementors: If this returns `Ok(ptr)`, then `ptr`
-    /// must be considered "currently allocated" and must be
-    /// acceptable input to methods such as `realloc` or `dealloc`,
-    /// *even if* `T` is a zero-sized type. In other words, if your
-    /// `AllocRef` implementation overrides this method in a manner
-    /// that can return a zero-sized `ptr`, then all reallocation and
-    /// deallocation methods need to be similarly overridden to accept
-    /// such values as input.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `[T; n]` does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// For zero-sized `T` or `n == 0`, may return either of `Ok` or
-    /// `Err`, but will *not* yield undefined behavior.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the [`handle_alloc_error`] function,
-    /// rather than directly invoking `panic!` or similar.
-    ///
-    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
-    fn alloc_array<T>(&mut self, n: usize) -> Result<NonNull<T>, AllocErr>
-    where
-        Self: Sized,
-    {
-        match Layout::array::<T>(n) {
-            Ok(layout) if layout.size() > 0 => unsafe { self.alloc(layout).map(|p| p.cast()) },
-            _ => Err(AllocErr),
-        }
-    }
-
-    /// Reallocates a block previously suitable for holding `n_old`
-    /// instances of `T`, returning a block suitable for holding
-    /// `n_new` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `realloc`/`dealloc` methods of this allocator.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must be currently allocated via this allocator,
-    ///
-    /// * the layout of `[T; n_old]` must *fit* that block of memory.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `[T; n_new]` does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// For zero-sized `T` or `n_new == 0`, may return either of `Ok` or
-    /// `Err`, but will *not* yield undefined behavior.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    ///
-    /// Clients wishing to abort computation in response to a
-    /// reallocation error are encouraged to call the [`handle_alloc_error`] function,
-    /// rather than directly invoking `panic!` or similar.
-    ///
-    /// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
-    unsafe fn realloc_array<T>(
-        &mut self,
-        ptr: NonNull<T>,
-        n_old: usize,
-        n_new: usize,
-    ) -> Result<NonNull<T>, AllocErr>
-    where
-        Self: Sized,
-    {
-        match (Layout::array::<T>(n_old), Layout::array::<T>(n_new)) {
-            (Ok(k_old), Ok(k_new)) if k_old.size() > 0 && k_new.size() > 0 => {
-                debug_assert!(k_old.align() == k_new.align());
-                self.realloc(ptr.cast(), k_old, k_new.size()).map(NonNull::cast)
-            }
-            _ => Err(AllocErr),
-        }
-    }
-
-    /// Deallocates a block suitable for holding `n` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure both:
-    ///
-    /// * `ptr` must denote a block of memory currently allocated via this allocator
-    ///
-    /// * the layout of `[T; n]` must *fit* that block of memory.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either `[T; n]` or the given
-    /// memory block does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    unsafe fn dealloc_array<T>(&mut self, ptr: NonNull<T>, n: usize) -> Result<(), AllocErr>
-    where
-        Self: Sized,
-    {
-        match Layout::array::<T>(n) {
-            Ok(k) if k.size() > 0 => Ok(self.dealloc(ptr.cast(), k)),
-            _ => Err(AllocErr),
-        }
-    }
 }
diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index 2e7e8fdd72491..7d48280661a64 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -2,7 +2,6 @@
 //!
 //! [rustc guide]: https://rust-lang.github.io/rustc-guide/hir.html
 
-pub mod check_attr;
 pub mod exports;
 pub mod map;
 
diff --git a/src/librustc/ich/impls_hir.rs b/src/librustc/ich/impls_hir.rs
index 625d8a4670f22..1a763e43d557d 100644
--- a/src/librustc/ich/impls_hir.rs
+++ b/src/librustc/ich/impls_hir.rs
@@ -251,12 +251,6 @@ impl<'a> ToStableHashKey<StableHashingContext<'a>> for hir::def_id::DefIndex {
     }
 }
 
-impl<'a> HashStable<StableHashingContext<'a>> for crate::middle::lang_items::LangItem {
-    fn hash_stable(&self, _: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        ::std::hash::Hash::hash(self, hasher);
-    }
-}
-
 impl<'a> HashStable<StableHashingContext<'a>> for hir::TraitCandidate {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
diff --git a/src/librustc/macros.rs b/src/librustc/macros.rs
index 2bda0c0bef02d..88ddd96eec8f5 100644
--- a/src/librustc/macros.rs
+++ b/src/librustc/macros.rs
@@ -1,40 +1,3 @@
-macro_rules! enum_from_u32 {
-    ($(#[$attr:meta])* pub enum $name:ident {
-        $($variant:ident = $e:expr,)*
-    }) => {
-        $(#[$attr])*
-        pub enum $name {
-            $($variant = $e),*
-        }
-
-        impl $name {
-            pub fn from_u32(u: u32) -> Option<$name> {
-                $(if u == $name::$variant as u32 {
-                    return Some($name::$variant)
-                })*
-                None
-            }
-        }
-    };
-    ($(#[$attr:meta])* pub enum $name:ident {
-        $($variant:ident,)*
-    }) => {
-        $(#[$attr])*
-        pub enum $name {
-            $($variant,)*
-        }
-
-        impl $name {
-            pub fn from_u32(u: u32) -> Option<$name> {
-                $(if u == $name::$variant as u32 {
-                    return Some($name::$variant)
-                })*
-                None
-            }
-        }
-    }
-}
-
 #[macro_export]
 macro_rules! bug {
     () => ( bug!("impossible case reached") );
diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs
index 9e33ee8da2152..c8e284be6fc09 100644
--- a/src/librustc/middle/lang_items.rs
+++ b/src/librustc/middle/lang_items.rs
@@ -9,401 +9,14 @@
 
 pub use self::LangItem::*;
 
-use crate::hir::check_attr::Target;
-use crate::middle::cstore::ExternCrate;
-use crate::middle::weak_lang_items;
 use crate::ty::{self, TyCtxt};
 
-use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::struct_span_err;
-use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_hir::itemlikevisit::ItemLikeVisitor;
-use rustc_macros::HashStable;
-use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
-use syntax::ast;
+use rustc_target::spec::PanicStrategy;
 
-// The actual lang items defined come at the end of this file in one handy table.
-// So you probably just want to nip down to the end.
-macro_rules! language_item_table {
-    (
-        $( $variant:ident, $name:expr, $method:ident, $target:path; )*
-    ) => {
-
-enum_from_u32! {
-    /// A representation of all the valid language items in Rust.
-    #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
-    pub enum LangItem {
-        $($variant,)*
-    }
-}
-
-impl LangItem {
-    /// Returns the `name` in `#[lang = "$name"]`.
-    /// For example, `LangItem::EqTraitLangItem`,
-    /// that is `#[lang = "eq"]` would result in `"eq"`.
-    fn name(self) -> &'static str {
-        match self {
-            $( $variant => $name, )*
-        }
-    }
-}
-
-#[derive(HashStable)]
-pub struct LanguageItems {
-    /// Mappings from lang items to their possibly found `DefId`s.
-    /// The index corresponds to the order in `LangItem`.
-    pub items: Vec<Option<DefId>>,
-    /// Lang items that were not found during collection.
-    pub missing: Vec<LangItem>,
-}
-
-impl LanguageItems {
-    /// Construct an empty collection of lang items and no missing ones.
-    pub fn new() -> Self {
-        fn init_none(_: LangItem) -> Option<DefId> { None }
-
-        Self {
-            items: vec![$(init_none($variant)),*],
-            missing: Vec::new(),
-        }
-    }
-
-    /// Returns the mappings to the possibly found `DefId`s for each lang item.
-    pub fn items(&self) -> &[Option<DefId>] {
-        &*self.items
-    }
-
-    /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
-    /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
-    /// returns an error message as a string.
-    pub fn require(&self, it: LangItem) -> Result<DefId, String> {
-        self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
-    }
-
-    /// Returns the kind of closure that `id`, which is one of the `Fn*` traits, corresponds to.
-    /// If `id` is not one of the `Fn*` traits, `None` is returned.
-    pub fn fn_trait_kind(&self, id: DefId) -> Option<ty::ClosureKind> {
-        match Some(id) {
-            x if x == self.fn_trait() => Some(ty::ClosureKind::Fn),
-            x if x == self.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
-            x if x == self.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
-            _ => None
-        }
-    }
-
-    $(
-        /// Returns the corresponding `DefId` for the lang item
-        #[doc = $name]
-        /// if it exists.
-        #[allow(dead_code)]
-        pub fn $method(&self) -> Option<DefId> {
-            self.items[$variant as usize]
-        }
-    )*
-}
-
-struct LanguageItemCollector<'tcx> {
-    items: LanguageItems,
-    tcx: TyCtxt<'tcx>,
-    /// A mapping from the name of the lang item to its order and the form it must be of.
-    item_refs: FxHashMap<&'static str, (usize, Target)>,
-}
-
-impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> {
-    fn visit_item(&mut self, item: &hir::Item<'_>) {
-        if let Some((value, span)) = extract(&item.attrs) {
-            let actual_target = Target::from_item(item);
-            match self.item_refs.get(&*value.as_str()).cloned() {
-                // Known lang item with attribute on correct target.
-                Some((item_index, expected_target)) if actual_target == expected_target => {
-                    let def_id = self.tcx.hir().local_def_id(item.hir_id);
-                    self.collect_item(item_index, def_id);
-                },
-                // Known lang item with attribute on incorrect target.
-                Some((_, expected_target)) => {
-                    struct_span_err!(
-                        self.tcx.sess, span, E0718,
-                        "`{}` language item must be applied to a {}",
-                        value, expected_target,
-                    ).span_label(
-                        span,
-                        format!(
-                            "attribute should be applied to a {}, not a {}",
-                            expected_target, actual_target,
-                        ),
-                    ).emit();
-                },
-                // Unknown lang item.
-                _ => {
-                    struct_span_err!(
-                        self.tcx.sess, span, E0522,
-                        "definition of an unknown language item: `{}`",
-                        value
-                    ).span_label(
-                        span,
-                        format!("definition of unknown language item `{}`", value)
-                    ).emit();
-                },
-            }
-        }
-    }
-
-    fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {
-        // At present, lang items are always items, not trait items.
-    }
-
-    fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {
-        // At present, lang items are always items, not impl items.
-    }
-}
-
-impl LanguageItemCollector<'tcx> {
-    fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
-        let mut item_refs = FxHashMap::default();
-
-        $( item_refs.insert($name, ($variant as usize, $target)); )*
-
-        LanguageItemCollector {
-            tcx,
-            items: LanguageItems::new(),
-            item_refs,
-        }
-    }
-
-    fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
-        // Check for duplicates.
-        if let Some(original_def_id) = self.items.items[item_index] {
-            if original_def_id != item_def_id {
-                let name = LangItem::from_u32(item_index as u32).unwrap().name();
-                let mut err = match self.tcx.hir().span_if_local(item_def_id) {
-                    Some(span) => struct_span_err!(
-                        self.tcx.sess,
-                        span,
-                        E0152,
-                        "found duplicate lang item `{}`",
-                        name
-                    ),
-                    None => {
-                        match self.tcx.extern_crate(item_def_id) {
-                            Some(ExternCrate {dependency_of, ..}) => {
-                                self.tcx.sess.struct_err(&format!(
-                                "duplicate lang item in crate `{}` (which `{}` depends on): `{}`.",
-                                self.tcx.crate_name(item_def_id.krate),
-                                self.tcx.crate_name(*dependency_of),
-                                name))
-                            },
-                            _ => {
-                                self.tcx.sess.struct_err(&format!(
-                                "duplicate lang item in crate `{}`: `{}`.",
-                                self.tcx.crate_name(item_def_id.krate),
-                                name))
-                            }
-                        }
-                    },
-                };
-                if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
-                    err.span_note(span, "the lang item is first defined here");
-                } else {
-                    match self.tcx.extern_crate(original_def_id) {
-                        Some(ExternCrate {dependency_of, ..}) => {
-                            err.note(&format!(
-                            "the lang item is first defined in crate `{}` (which `{}` depends on)",
-                                      self.tcx.crate_name(original_def_id.krate),
-                                      self.tcx.crate_name(*dependency_of)));
-                        },
-                        _ => {
-                            err.note(&format!("the lang item is first defined in crate `{}`.",
-                                      self.tcx.crate_name(original_def_id.krate)));
-                        }
-                    }
-                }
-                err.emit();
-            }
-        }
-
-        // Matched.
-        self.items.items[item_index] = Some(item_def_id);
-    }
-}
-
-/// Extracts the first `lang = "$name"` out of a list of attributes.
-/// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
-/// are also extracted out when found.
-pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
-    attrs.iter().find_map(|attr| Some(match attr {
-        _ if attr.check_name(sym::lang) => (attr.value_str()?, attr.span),
-        _ if attr.check_name(sym::panic_handler) => (sym::panic_impl, attr.span),
-        _ if attr.check_name(sym::alloc_error_handler) => (sym::oom, attr.span),
-        _ => return None,
-    }))
-}
-
-/// Traverses and collects all the lang items in all crates.
-pub fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems {
-    // Initialize the collector.
-    let mut collector = LanguageItemCollector::new(tcx);
-
-    // Collect lang items in other crates.
-    for &cnum in tcx.crates().iter() {
-        for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
-            collector.collect_item(item_index, def_id);
-        }
-    }
-
-    // Collect lang items in this crate.
-    tcx.hir().krate().visit_all_item_likes(&mut collector);
-
-    // Extract out the found lang items.
-    let LanguageItemCollector { mut items, .. } = collector;
-
-    // Find all required but not-yet-defined lang items.
-    weak_lang_items::check_crate(tcx, &mut items);
-
-    items
-}
-
-// End of the macro
-    }
-}
-
-language_item_table! {
-//  Variant name,                Name,                 Method name,             Target;
-    BoolImplItem,                "bool",               bool_impl,               Target::Impl;
-    CharImplItem,                "char",               char_impl,               Target::Impl;
-    StrImplItem,                 "str",                str_impl,                Target::Impl;
-    SliceImplItem,               "slice",              slice_impl,              Target::Impl;
-    SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;
-    StrAllocImplItem,            "str_alloc",          str_alloc_impl,          Target::Impl;
-    SliceAllocImplItem,          "slice_alloc",        slice_alloc_impl,        Target::Impl;
-    SliceU8AllocImplItem,        "slice_u8_alloc",     slice_u8_alloc_impl,     Target::Impl;
-    ConstPtrImplItem,            "const_ptr",          const_ptr_impl,          Target::Impl;
-    MutPtrImplItem,              "mut_ptr",            mut_ptr_impl,            Target::Impl;
-    I8ImplItem,                  "i8",                 i8_impl,                 Target::Impl;
-    I16ImplItem,                 "i16",                i16_impl,                Target::Impl;
-    I32ImplItem,                 "i32",                i32_impl,                Target::Impl;
-    I64ImplItem,                 "i64",                i64_impl,                Target::Impl;
-    I128ImplItem,                "i128",               i128_impl,               Target::Impl;
-    IsizeImplItem,               "isize",              isize_impl,              Target::Impl;
-    U8ImplItem,                  "u8",                 u8_impl,                 Target::Impl;
-    U16ImplItem,                 "u16",                u16_impl,                Target::Impl;
-    U32ImplItem,                 "u32",                u32_impl,                Target::Impl;
-    U64ImplItem,                 "u64",                u64_impl,                Target::Impl;
-    U128ImplItem,                "u128",               u128_impl,               Target::Impl;
-    UsizeImplItem,               "usize",              usize_impl,              Target::Impl;
-    F32ImplItem,                 "f32",                f32_impl,                Target::Impl;
-    F64ImplItem,                 "f64",                f64_impl,                Target::Impl;
-    F32RuntimeImplItem,          "f32_runtime",        f32_runtime_impl,        Target::Impl;
-    F64RuntimeImplItem,          "f64_runtime",        f64_runtime_impl,        Target::Impl;
-
-    SizedTraitLangItem,          "sized",              sized_trait,             Target::Trait;
-    UnsizeTraitLangItem,         "unsize",             unsize_trait,            Target::Trait;
-    // trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
-    StructuralPeqTraitLangItem,  "structural_peq",     structural_peq_trait,    Target::Trait;
-    // trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
-    StructuralTeqTraitLangItem,  "structural_teq",     structural_teq_trait,    Target::Trait;
-    CopyTraitLangItem,           "copy",               copy_trait,              Target::Trait;
-    CloneTraitLangItem,          "clone",              clone_trait,             Target::Trait;
-    SyncTraitLangItem,           "sync",               sync_trait,              Target::Trait;
-    FreezeTraitLangItem,         "freeze",             freeze_trait,            Target::Trait;
-
-    DropTraitLangItem,           "drop",               drop_trait,              Target::Trait;
-
-    CoerceUnsizedTraitLangItem,  "coerce_unsized",     coerce_unsized_trait,    Target::Trait;
-    DispatchFromDynTraitLangItem,"dispatch_from_dyn",  dispatch_from_dyn_trait, Target::Trait;
-
-    AddTraitLangItem,            "add",                add_trait,               Target::Trait;
-    SubTraitLangItem,            "sub",                sub_trait,               Target::Trait;
-    MulTraitLangItem,            "mul",                mul_trait,               Target::Trait;
-    DivTraitLangItem,            "div",                div_trait,               Target::Trait;
-    RemTraitLangItem,            "rem",                rem_trait,               Target::Trait;
-    NegTraitLangItem,            "neg",                neg_trait,               Target::Trait;
-    NotTraitLangItem,            "not",                not_trait,               Target::Trait;
-    BitXorTraitLangItem,         "bitxor",             bitxor_trait,            Target::Trait;
-    BitAndTraitLangItem,         "bitand",             bitand_trait,            Target::Trait;
-    BitOrTraitLangItem,          "bitor",              bitor_trait,             Target::Trait;
-    ShlTraitLangItem,            "shl",                shl_trait,               Target::Trait;
-    ShrTraitLangItem,            "shr",                shr_trait,               Target::Trait;
-    AddAssignTraitLangItem,      "add_assign",         add_assign_trait,        Target::Trait;
-    SubAssignTraitLangItem,      "sub_assign",         sub_assign_trait,        Target::Trait;
-    MulAssignTraitLangItem,      "mul_assign",         mul_assign_trait,        Target::Trait;
-    DivAssignTraitLangItem,      "div_assign",         div_assign_trait,        Target::Trait;
-    RemAssignTraitLangItem,      "rem_assign",         rem_assign_trait,        Target::Trait;
-    BitXorAssignTraitLangItem,   "bitxor_assign",      bitxor_assign_trait,     Target::Trait;
-    BitAndAssignTraitLangItem,   "bitand_assign",      bitand_assign_trait,     Target::Trait;
-    BitOrAssignTraitLangItem,    "bitor_assign",       bitor_assign_trait,      Target::Trait;
-    ShlAssignTraitLangItem,      "shl_assign",         shl_assign_trait,        Target::Trait;
-    ShrAssignTraitLangItem,      "shr_assign",         shr_assign_trait,        Target::Trait;
-    IndexTraitLangItem,          "index",              index_trait,             Target::Trait;
-    IndexMutTraitLangItem,       "index_mut",          index_mut_trait,         Target::Trait;
-
-    UnsafeCellTypeLangItem,      "unsafe_cell",        unsafe_cell_type,        Target::Struct;
-    VaListTypeLangItem,          "va_list",            va_list,                 Target::Struct;
-
-    DerefTraitLangItem,          "deref",              deref_trait,             Target::Trait;
-    DerefMutTraitLangItem,       "deref_mut",          deref_mut_trait,         Target::Trait;
-    ReceiverTraitLangItem,       "receiver",           receiver_trait,          Target::Trait;
-
-    FnTraitLangItem,             "fn",                 fn_trait,                Target::Trait;
-    FnMutTraitLangItem,          "fn_mut",             fn_mut_trait,            Target::Trait;
-    FnOnceTraitLangItem,         "fn_once",            fn_once_trait,           Target::Trait;
-
-    FutureTraitLangItem,         "future_trait",       future_trait,            Target::Trait;
-    GeneratorStateLangItem,      "generator_state",    gen_state,               Target::Enum;
-    GeneratorTraitLangItem,      "generator",          gen_trait,               Target::Trait;
-    UnpinTraitLangItem,          "unpin",              unpin_trait,             Target::Trait;
-    PinTypeLangItem,             "pin",                pin_type,                Target::Struct;
-
-    // Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`.
-    EqTraitLangItem,             "eq",                 eq_trait,                Target::Trait;
-    PartialOrdTraitLangItem,     "partial_ord",        partial_ord_trait,       Target::Trait;
-
-    // A number of panic-related lang items. The `panic` item corresponds to
-    // divide-by-zero and various panic cases with `match`. The
-    // `panic_bounds_check` item is for indexing arrays.
-    //
-    // The `begin_unwind` lang item has a predefined symbol name and is sort of
-    // a "weak lang item" in the sense that a crate is not required to have it
-    // defined to use it, but a final product is required to define it
-    // somewhere. Additionally, there are restrictions on crates that use a weak
-    // lang item, but do not have it defined.
-    PanicFnLangItem,             "panic",              panic_fn,                Target::Fn;
-    PanicBoundsCheckFnLangItem,  "panic_bounds_check", panic_bounds_check_fn,   Target::Fn;
-    PanicInfoLangItem,           "panic_info",         panic_info,              Target::Struct;
-    PanicLocationLangItem,       "panic_location",     panic_location,          Target::Struct;
-    PanicImplLangItem,           "panic_impl",         panic_impl,              Target::Fn;
-    // Libstd panic entry point. Necessary for const eval to be able to catch it
-    BeginPanicFnLangItem,        "begin_panic",        begin_panic_fn,          Target::Fn;
-
-    ExchangeMallocFnLangItem,    "exchange_malloc",    exchange_malloc_fn,      Target::Fn;
-    BoxFreeFnLangItem,           "box_free",           box_free_fn,             Target::Fn;
-    DropInPlaceFnLangItem,       "drop_in_place",      drop_in_place_fn,        Target::Fn;
-    OomLangItem,                 "oom",                oom,                     Target::Fn;
-    AllocLayoutLangItem,         "alloc_layout",       alloc_layout,            Target::Struct;
-
-    StartFnLangItem,             "start",              start_fn,                Target::Fn;
-
-    EhPersonalityLangItem,       "eh_personality",     eh_personality,          Target::Fn;
-    EhUnwindResumeLangItem,      "eh_unwind_resume",   eh_unwind_resume,        Target::Fn;
-    EhCatchTypeinfoLangItem,     "eh_catch_typeinfo",  eh_catch_typeinfo,       Target::Static;
-
-    OwnedBoxLangItem,            "owned_box",          owned_box,               Target::Struct;
-
-    PhantomDataItem,             "phantom_data",       phantom_data,            Target::Struct;
-
-    ManuallyDropItem,            "manually_drop",      manually_drop,           Target::Struct;
-
-    MaybeUninitLangItem,         "maybe_uninit",       maybe_uninit,            Target::Union;
-
-    // Align offset for stride != 1; must not panic.
-    AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
-
-    TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
-
-    Arc,                         "arc",                arc,                     Target::Struct;
-    Rc,                          "rc",                 rc,                      Target::Struct;
-}
+pub use rustc_hir::weak_lang_items::link_name;
+pub use rustc_hir::{LangItem, LanguageItems};
 
 impl<'tcx> TyCtxt<'tcx> {
     /// Returns the `DefId` for a given `LangItem`.
@@ -417,4 +30,36 @@ impl<'tcx> TyCtxt<'tcx> {
             }
         })
     }
+
+    pub fn fn_trait_kind_from_lang_item(&self, id: DefId) -> Option<ty::ClosureKind> {
+        let items = self.lang_items();
+        match Some(id) {
+            x if x == items.fn_trait() => Some(ty::ClosureKind::Fn),
+            x if x == items.fn_mut_trait() => Some(ty::ClosureKind::FnMut),
+            x if x == items.fn_once_trait() => Some(ty::ClosureKind::FnOnce),
+            _ => None,
+        }
+    }
+
+    pub fn is_weak_lang_item(&self, item_def_id: DefId) -> bool {
+        self.lang_items().is_weak_lang_item(item_def_id)
+    }
+}
+
+/// Returns `true` if the specified `lang_item` doesn't actually need to be
+/// present for this compilation.
+///
+/// Not all lang items are always required for each compilation, particularly in
+/// the case of panic=abort. In these situations some lang items are injected by
+/// crates and don't actually need to be defined in libstd.
+pub fn whitelisted(tcx: TyCtxt<'_>, lang_item: LangItem) -> bool {
+    // If we're not compiling with unwinding, we won't actually need these
+    // symbols. Other panic runtimes ensure that the relevant symbols are
+    // available to link things together, but they're never exercised.
+    if tcx.sess.panic_strategy() != PanicStrategy::Unwind {
+        return lang_item == LangItem::EhPersonalityLangItem
+            || lang_item == LangItem::EhUnwindResumeLangItem;
+    }
+
+    false
 }
diff --git a/src/librustc/middle/mod.rs b/src/librustc/middle/mod.rs
index c2959766c570a..b20f2cf3a85c1 100644
--- a/src/librustc/middle/mod.rs
+++ b/src/librustc/middle/mod.rs
@@ -33,4 +33,3 @@ pub mod recursion_limit;
 pub mod region;
 pub mod resolve_lifetime;
 pub mod stability;
-pub mod weak_lang_items;
diff --git a/src/librustc/middle/weak_lang_items.rs b/src/librustc/middle/weak_lang_items.rs
deleted file mode 100644
index 5571f8f2313d5..0000000000000
--- a/src/librustc/middle/weak_lang_items.rs
+++ /dev/null
@@ -1,167 +0,0 @@
-//! Validity checking for weak lang items
-
-use crate::middle::lang_items;
-use crate::session::config;
-
-use crate::hir::map::Map;
-use crate::ty::TyCtxt;
-use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::struct_span_err;
-use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
-use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
-use rustc_span::symbol::{sym, Symbol};
-use rustc_span::Span;
-use rustc_target::spec::PanicStrategy;
-use syntax::ast;
-
-macro_rules! weak_lang_items {
-    ($($name:ident, $item:ident, $sym:ident;)*) => (
-
-struct Context<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    items: &'a mut lang_items::LanguageItems,
-}
-
-/// Checks the crate for usage of weak lang items, returning a vector of all the
-/// language items required by this crate, but not defined yet.
-pub fn check_crate<'tcx>(tcx: TyCtxt<'tcx>,
-                             items: &mut lang_items::LanguageItems) {
-    // These are never called by user code, they're generated by the compiler.
-    // They will never implicitly be added to the `missing` array unless we do
-    // so here.
-    if items.eh_personality().is_none() {
-        items.missing.push(lang_items::EhPersonalityLangItem);
-    }
-    if tcx.sess.target.target.options.custom_unwind_resume &
-       items.eh_unwind_resume().is_none() {
-        items.missing.push(lang_items::EhUnwindResumeLangItem);
-    }
-
-    {
-        let mut cx = Context { tcx, items };
-        tcx.hir().krate().visit_all_item_likes(&mut cx.as_deep_visitor());
-    }
-    verify(tcx, items);
-}
-
-pub fn link_name(attrs: &[ast::Attribute]) -> Option<Symbol> {
-    lang_items::extract(attrs).and_then(|(name, _)| {
-        $(if name == sym::$name {
-            Some(sym::$sym)
-        } else)* {
-            None
-        }
-    })
-}
-
-/// Returns `true` if the specified `lang_item` doesn't actually need to be
-/// present for this compilation.
-///
-/// Not all lang items are always required for each compilation, particularly in
-/// the case of panic=abort. In these situations some lang items are injected by
-/// crates and don't actually need to be defined in libstd.
-pub fn whitelisted(tcx: TyCtxt<'_>, lang_item: lang_items::LangItem) -> bool {
-    // If we're not compiling with unwinding, we won't actually need these
-    // symbols. Other panic runtimes ensure that the relevant symbols are
-    // available to link things together, but they're never exercised.
-    if tcx.sess.panic_strategy() != PanicStrategy::Unwind {
-        return lang_item == lang_items::EhPersonalityLangItem ||
-            lang_item == lang_items::EhUnwindResumeLangItem
-    }
-
-    false
-}
-
-fn verify<'tcx>(tcx: TyCtxt<'tcx>,
-                    items: &lang_items::LanguageItems) {
-    // We only need to check for the presence of weak lang items if we're
-    // emitting something that's not an rlib.
-    let needs_check = tcx.sess.crate_types.borrow().iter().any(|kind| {
-        match *kind {
-            config::CrateType::Dylib |
-            config::CrateType::ProcMacro |
-            config::CrateType::Cdylib |
-            config::CrateType::Executable |
-            config::CrateType::Staticlib => true,
-            config::CrateType::Rlib => false,
-        }
-    });
-    if !needs_check {
-        return
-    }
-
-    let mut missing = FxHashSet::default();
-    for &cnum in tcx.crates().iter() {
-        for &item in tcx.missing_lang_items(cnum).iter() {
-            missing.insert(item);
-        }
-    }
-
-    $(
-        if missing.contains(&lang_items::$item) &&
-           !whitelisted(tcx, lang_items::$item) &&
-           items.$name().is_none() {
-            if lang_items::$item == lang_items::PanicImplLangItem {
-                tcx.sess.err(&format!("`#[panic_handler]` function required, \
-                                       but not found"));
-            } else if lang_items::$item == lang_items::OomLangItem {
-                tcx.sess.err(&format!("`#[alloc_error_handler]` function required, \
-                                       but not found"));
-            } else {
-                tcx.sess.err(&format!("language item required, but not found: `{}`",
-                                      stringify!($name)));
-            }
-        }
-    )*
-}
-
-impl<'a, 'tcx> Context<'a, 'tcx> {
-    fn register(&mut self, name: Symbol, span: Span) {
-        $(if name == sym::$name {
-            if self.items.$name().is_none() {
-                self.items.missing.push(lang_items::$item);
-            }
-        } else)* {
-            struct_span_err!(
-                self.tcx.sess, span, E0264,
-                "unknown external lang item: `{}`",
-                name
-            )
-            .emit();
-        }
-    }
-}
-
-impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
-    type Map = Map<'v>;
-
-    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Map<'v>> {
-        NestedVisitorMap::None
-    }
-
-    fn visit_foreign_item(&mut self, i: &hir::ForeignItem<'_>) {
-        if let Some((lang_item, _)) = lang_items::extract(&i.attrs) {
-            self.register(lang_item, i.span);
-        }
-        intravisit::walk_foreign_item(self, i)
-    }
-}
-
-impl<'tcx> TyCtxt<'tcx> {
-    pub fn is_weak_lang_item(&self, item_def_id: DefId) -> bool {
-        let lang_items = self.lang_items();
-        let did = Some(item_def_id);
-
-        $(lang_items.$name() == did)||*
-    }
-}
-
-) }
-
-weak_lang_items! {
-    panic_impl,         PanicImplLangItem,          rust_begin_unwind;
-    eh_personality,     EhPersonalityLangItem,      rust_eh_personality;
-    eh_unwind_resume,   EhUnwindResumeLangItem,     rust_eh_unwind_resume;
-    oom,                OomLangItem,                rust_oom;
-}
diff --git a/src/librustc/mir/interpret/error.rs b/src/librustc/mir/interpret/error.rs
index df3971a5ac3f1..86e7bb28e0069 100644
--- a/src/librustc/mir/interpret/error.rs
+++ b/src/librustc/mir/interpret/error.rs
@@ -128,10 +128,9 @@ impl<'tcx> ConstEvalErr<'tcx> {
         }
     }
 
-    /// Sets the message passed in via `message`, then adds the span labels for you, before applying
-    /// further modifications in `emit`. It's up to you to call emit(), stash(..), etc. within the
-    /// `emit` method. If you don't need to do any additional processing, just use
-    /// struct_generic.
+    /// Sets the message passed in via `message` and adds span labels before handing control back
+    /// to `emit` to do any final processing. It's the caller's responsibility to call emit(),
+    /// stash(), etc. within the `emit` function to dispose of the diagnostic properly.
     fn struct_generic(
         &self,
         tcx: TyCtxtAt<'tcx>,
diff --git a/src/librustc/traits/select.rs b/src/librustc/traits/select.rs
index 17337ff0c92a6..bf82d743c2b04 100644
--- a/src/librustc/traits/select.rs
+++ b/src/librustc/traits/select.rs
@@ -1634,7 +1634,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         obligation: &TraitObligation<'tcx>,
         candidates: &mut SelectionCandidateSet<'tcx>,
     ) -> Result<(), SelectionError<'tcx>> {
-        let kind = match self.tcx().lang_items().fn_trait_kind(obligation.predicate.def_id()) {
+        let kind = match self.tcx().fn_trait_kind_from_lang_item(obligation.predicate.def_id()) {
             Some(k) => k,
             None => {
                 return Ok(());
@@ -1677,7 +1677,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         candidates: &mut SelectionCandidateSet<'tcx>,
     ) -> Result<(), SelectionError<'tcx>> {
         // We provide impl of all fn traits for fn pointers.
-        if self.tcx().lang_items().fn_trait_kind(obligation.predicate.def_id()).is_none() {
+        if self.tcx().fn_trait_kind_from_lang_item(obligation.predicate.def_id()).is_none() {
             return Ok(());
         }
 
@@ -2889,8 +2889,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         let kind = self
             .tcx()
-            .lang_items()
-            .fn_trait_kind(obligation.predicate.def_id())
+            .fn_trait_kind_from_lang_item(obligation.predicate.def_id())
             .unwrap_or_else(|| bug!("closure candidate for non-fn trait {:?}", obligation));
 
         // Okay to skip binder because the substs on closure types never
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index f2ad01b3d5961..2adf708641798 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -2716,10 +2716,6 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
         assert_eq!(id, LOCAL_CRATE);
         tcx.crate_name
     };
-    providers.get_lang_items = |tcx, id| {
-        assert_eq!(id, LOCAL_CRATE);
-        tcx.arena.alloc(middle::lang_items::collect(tcx))
-    };
     providers.maybe_unused_trait_import = |tcx, id| tcx.maybe_unused_trait_imports.contains(&id);
     providers.maybe_unused_extern_crates = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);
diff --git a/src/librustc/ty/instance.rs b/src/librustc/ty/instance.rs
index c7f19513f666e..b5e17661c5de1 100644
--- a/src/librustc/ty/instance.rs
+++ b/src/librustc/ty/instance.rs
@@ -450,7 +450,7 @@ fn resolve_associated_item<'tcx>(
             substs: generator_data.substs,
         }),
         traits::VtableClosure(closure_data) => {
-            let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
+            let trait_closure_kind = tcx.fn_trait_kind_from_lang_item(trait_id).unwrap();
             Some(Instance::resolve_closure(
                 tcx,
                 closure_data.closure_def_id,
diff --git a/src/librustc/ty/print/pretty.rs b/src/librustc/ty/print/pretty.rs
index 0da680d1f915e..274482cba64cc 100644
--- a/src/librustc/ty/print/pretty.rs
+++ b/src/librustc/ty/print/pretty.rs
@@ -724,7 +724,7 @@ pub trait PrettyPrinter<'tcx>:
             let mut resugared = false;
 
             // Special-case `Fn(...) -> ...` and resugar it.
-            let fn_trait_kind = self.tcx().lang_items().fn_trait_kind(principal.def_id);
+            let fn_trait_kind = self.tcx().fn_trait_kind_from_lang_item(principal.def_id);
             if !self.tcx().sess.verbose() && fn_trait_kind.is_some() {
                 if let ty::Tuple(ref args) = principal.substs.type_at(0).kind {
                     let mut projections = predicates.projection_bounds();
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 98a3e695fa079..7aaa70d6ec4d3 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -32,7 +32,7 @@ use syntax::expand::allocator::AllocatorKind;
 
 use rustc::dep_graph::DepGraph;
 use rustc::middle::cstore::{EncodedMetadata, MetadataLoaderDyn};
-use rustc::session::config::{OptLevel, OutputFilenames, PrintRequest};
+use rustc::session::config::{self, OptLevel, OutputFilenames, PrintRequest};
 use rustc::session::Session;
 use rustc::ty::{self, TyCtxt};
 use rustc::util::common::ErrorReported;
@@ -301,7 +301,7 @@ impl CodegenBackend for LlvmCodegenBackend {
             let rlink_data = json::encode(&codegen_results).map_err(|err| {
                 sess.fatal(&format!("failed to encode rlink: {}", err));
             })?;
-            let rlink_file = outputs.with_extension("rlink");
+            let rlink_file = outputs.with_extension(config::RLINK_EXT);
             fs::write(&rlink_file, rlink_data).map_err(|err| {
                 sess.fatal(&format!("failed to write file {}: {}", rlink_file.display(), err));
             })?;
diff --git a/src/librustc_codegen_ssa/base.rs b/src/librustc_codegen_ssa/base.rs
index 900150913842c..e9431d94863ef 100644
--- a/src/librustc_codegen_ssa/base.rs
+++ b/src/librustc_codegen_ssa/base.rs
@@ -28,8 +28,8 @@ use crate::{CachedModuleCodegen, CrateInfo, MemFlags, ModuleCodegen, ModuleKind}
 use rustc::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc::middle::cstore::EncodedMetadata;
 use rustc::middle::cstore::{self, LinkagePreference};
+use rustc::middle::lang_items;
 use rustc::middle::lang_items::StartFnLangItem;
-use rustc::middle::weak_lang_items;
 use rustc::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
 use rustc::session::config::{self, EntryFnType, Lto};
 use rustc::session::Session;
@@ -847,11 +847,8 @@ impl CrateInfo {
 
             // No need to look for lang items that are whitelisted and don't
             // actually need to exist.
-            let missing = missing
-                .iter()
-                .cloned()
-                .filter(|&l| !weak_lang_items::whitelisted(tcx, l))
-                .collect();
+            let missing =
+                missing.iter().cloned().filter(|&l| !lang_items::whitelisted(tcx, l)).collect();
             info.missing_lang_items.insert(cnum, missing);
         }
 
diff --git a/src/librustc_data_structures/macros.rs b/src/librustc_data_structures/macros.rs
index 83e6dbedee226..67fbe3058cdb9 100644
--- a/src/librustc_data_structures/macros.rs
+++ b/src/librustc_data_structures/macros.rs
@@ -17,3 +17,41 @@ macro_rules! static_assert_size {
         const _: [(); $size] = [(); ::std::mem::size_of::<$ty>()];
     };
 }
+
+#[macro_export]
+macro_rules! enum_from_u32 {
+    ($(#[$attr:meta])* pub enum $name:ident {
+        $($variant:ident = $e:expr,)*
+    }) => {
+        $(#[$attr])*
+        pub enum $name {
+            $($variant = $e),*
+        }
+
+        impl $name {
+            pub fn from_u32(u: u32) -> Option<$name> {
+                $(if u == $name::$variant as u32 {
+                    return Some($name::$variant)
+                })*
+                None
+            }
+        }
+    };
+    ($(#[$attr:meta])* pub enum $name:ident {
+        $($variant:ident,)*
+    }) => {
+        $(#[$attr])*
+        pub enum $name {
+            $($variant,)*
+        }
+
+        impl $name {
+            pub fn from_u32(u: u32) -> Option<$name> {
+                $(if u == $name::$variant as u32 {
+                    return Some($name::$variant)
+                })*
+                None
+            }
+        }
+    }
+}
diff --git a/src/librustc_driver/Cargo.toml b/src/librustc_driver/Cargo.toml
index 7a5966269b301..5b185f9a8b6b9 100644
--- a/src/librustc_driver/Cargo.toml
+++ b/src/librustc_driver/Cargo.toml
@@ -26,6 +26,7 @@ rustc_mir = { path = "../librustc_mir" }
 rustc_parse = { path = "../librustc_parse" }
 rustc_plugin_impl = { path = "../librustc_plugin_impl" }
 rustc_save_analysis = { path = "../librustc_save_analysis" }
+rustc_codegen_ssa = { path = "../librustc_codegen_ssa" }
 rustc_codegen_utils = { path = "../librustc_codegen_utils" }
 rustc_error_codes = { path = "../librustc_error_codes" }
 rustc_interface = { path = "../librustc_interface" }
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 52c6399498534..2e6dde6459a40 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -26,25 +26,27 @@ use rustc::session::{config, DiagnosticOutput, Session};
 use rustc::session::{early_error, early_warn};
 use rustc::ty::TyCtxt;
 use rustc::util::common::ErrorReported;
+use rustc_codegen_ssa::CodegenResults;
 use rustc_codegen_utils::codegen_backend::CodegenBackend;
 use rustc_data_structures::profiling::print_time_passes_entry;
 use rustc_data_structures::sync::SeqCst;
 use rustc_errors::{registry::Registry, PResult};
 use rustc_feature::{find_gated_cfg, UnstableFeatures};
 use rustc_hir::def_id::LOCAL_CRATE;
-use rustc_interface::util::get_builtin_codegen_backend;
+use rustc_interface::util::{collect_crate_types, get_builtin_codegen_backend};
 use rustc_interface::{interface, Queries};
 use rustc_lint::LintStore;
 use rustc_metadata::locator;
 use rustc_save_analysis as save;
 use rustc_save_analysis::DumpHandler;
-use rustc_serialize::json::ToJson;
+use rustc_serialize::json::{self, ToJson};
 
 use std::borrow::Cow;
 use std::cmp::max;
 use std::default::Default;
 use std::env;
 use std::ffi::OsString;
+use std::fs;
 use std::io::{self, Read, Write};
 use std::mem;
 use std::panic::{self, catch_unwind};
@@ -281,7 +283,8 @@ pub fn run_compiler(
                 &matches,
                 compiler.input(),
             )
-        });
+        })
+        .and_then(|| RustcDefaultCalls::try_process_rlink(sess, compiler));
 
         if should_stop == Compilation::Stop {
             return sess.compile_status();
@@ -588,6 +591,34 @@ fn show_content_with_pager(content: &String) {
 }
 
 impl RustcDefaultCalls {
+    fn process_rlink(sess: &Session, compiler: &interface::Compiler) -> Result<(), ErrorReported> {
+        if let Input::File(file) = compiler.input() {
+            // FIXME: #![crate_type] and #![crate_name] support not implemented yet
+            let attrs = vec![];
+            sess.crate_types.set(collect_crate_types(sess, &attrs));
+            let outputs = compiler.build_output_filenames(&sess, &attrs);
+            let rlink_data = fs::read_to_string(file).unwrap_or_else(|err| {
+                sess.fatal(&format!("failed to read rlink file: {}", err));
+            });
+            let codegen_results: CodegenResults = json::decode(&rlink_data).unwrap_or_else(|err| {
+                sess.fatal(&format!("failed to decode rlink: {}", err));
+            });
+            compiler.codegen_backend().link(&sess, Box::new(codegen_results), &outputs)
+        } else {
+            sess.fatal(&format!("rlink must be a file"))
+        }
+    }
+
+    pub fn try_process_rlink(sess: &Session, compiler: &interface::Compiler) -> Compilation {
+        if sess.opts.debugging_opts.link_only {
+            let result = RustcDefaultCalls::process_rlink(sess, compiler);
+            abort_on_err(result, sess);
+            Compilation::Stop
+        } else {
+            Compilation::Continue
+        }
+    }
+
     pub fn list_metadata(
         sess: &Session,
         metadata_loader: &dyn MetadataLoader,
@@ -663,7 +694,7 @@ impl RustcDefaultCalls {
                         println!("{}", id);
                         continue;
                     }
-                    let crate_types = rustc_interface::util::collect_crate_types(sess, attrs);
+                    let crate_types = collect_crate_types(sess, attrs);
                     for &style in &crate_types {
                         let fname = rustc_codegen_utils::link::filename_for_input(
                             sess, style, &id, &t_outputs,
diff --git a/src/librustc_hir/Cargo.toml b/src/librustc_hir/Cargo.toml
index 3ae943a4ce08b..cff6413253202 100644
--- a/src/librustc_hir/Cargo.toml
+++ b/src/librustc_hir/Cargo.toml
@@ -19,4 +19,5 @@ rustc_span = { path = "../librustc_span" }
 rustc_errors = { path = "../librustc_errors" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
+lazy_static = "1"
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
diff --git a/src/librustc_hir/lang_items.rs b/src/librustc_hir/lang_items.rs
new file mode 100644
index 0000000000000..cb5ebba463394
--- /dev/null
+++ b/src/librustc_hir/lang_items.rs
@@ -0,0 +1,261 @@
+//! Defines language items.
+//!
+//! Language items are items that represent concepts intrinsic to the language
+//! itself. Examples are:
+//!
+//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
+//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
+//! * Functions called by the compiler itself.
+
+pub use self::LangItem::*;
+
+use crate::def_id::DefId;
+use crate::Target;
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_macros::HashStable_Generic;
+use rustc_span::symbol::{sym, Symbol};
+use rustc_span::Span;
+use syntax::ast;
+
+use lazy_static::lazy_static;
+
+// The actual lang items defined come at the end of this file in one handy table.
+// So you probably just want to nip down to the end.
+macro_rules! language_item_table {
+    (
+        $( $variant:ident, $name:expr, $method:ident, $target:path; )*
+    ) => {
+
+        enum_from_u32! {
+            /// A representation of all the valid language items in Rust.
+            #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+            pub enum LangItem {
+                $($variant,)*
+            }
+        }
+
+        impl LangItem {
+            /// Returns the `name` in `#[lang = "$name"]`.
+            /// For example, `LangItem::EqTraitLangItem`,
+            /// that is `#[lang = "eq"]` would result in `"eq"`.
+            pub fn name(self) -> &'static str {
+                match self {
+                    $( $variant => $name, )*
+                }
+            }
+        }
+
+        #[derive(HashStable_Generic)]
+        pub struct LanguageItems {
+            /// Mappings from lang items to their possibly found `DefId`s.
+            /// The index corresponds to the order in `LangItem`.
+            pub items: Vec<Option<DefId>>,
+            /// Lang items that were not found during collection.
+            pub missing: Vec<LangItem>,
+        }
+
+        impl LanguageItems {
+            /// Construct an empty collection of lang items and no missing ones.
+            pub fn new() -> Self {
+                fn init_none(_: LangItem) -> Option<DefId> { None }
+
+                Self {
+                    items: vec![$(init_none($variant)),*],
+                    missing: Vec::new(),
+                }
+            }
+
+            /// Returns the mappings to the possibly found `DefId`s for each lang item.
+            pub fn items(&self) -> &[Option<DefId>] {
+                &*self.items
+            }
+
+            /// Requires that a given `LangItem` was bound and returns the corresponding `DefId`.
+            /// If it wasn't bound, e.g. due to a missing `#[lang = "<it.name()>"]`,
+            /// returns an error message as a string.
+            pub fn require(&self, it: LangItem) -> Result<DefId, String> {
+                self.items[it as usize].ok_or_else(|| format!("requires `{}` lang_item", it.name()))
+            }
+
+            $(
+                /// Returns the corresponding `DefId` for the lang item
+                #[doc = $name]
+                /// if it exists.
+                #[allow(dead_code)]
+                pub fn $method(&self) -> Option<DefId> {
+                    self.items[$variant as usize]
+                }
+            )*
+        }
+
+        lazy_static! {
+            /// A mapping from the name of the lang item to its order and the form it must be of.
+            pub static ref ITEM_REFS: FxHashMap<&'static str, (usize, Target)> = {
+                let mut item_refs = FxHashMap::default();
+                $( item_refs.insert($name, ($variant as usize, $target)); )*
+                item_refs
+            };
+        }
+
+// End of the macro
+    }
+}
+
+impl<CTX> HashStable<CTX> for LangItem {
+    fn hash_stable(&self, _: &mut CTX, hasher: &mut StableHasher) {
+        ::std::hash::Hash::hash(self, hasher);
+    }
+}
+
+/// Extracts the first `lang = "$name"` out of a list of attributes.
+/// The attributes `#[panic_handler]` and `#[alloc_error_handler]`
+/// are also extracted out when found.
+pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
+    attrs.iter().find_map(|attr| {
+        Some(match attr {
+            _ if attr.check_name(sym::lang) => (attr.value_str()?, attr.span),
+            _ if attr.check_name(sym::panic_handler) => (sym::panic_impl, attr.span),
+            _ if attr.check_name(sym::alloc_error_handler) => (sym::oom, attr.span),
+            _ => return None,
+        })
+    })
+}
+
+language_item_table! {
+//  Variant name,                Name,                 Method name,             Target;
+    BoolImplItem,                "bool",               bool_impl,               Target::Impl;
+    CharImplItem,                "char",               char_impl,               Target::Impl;
+    StrImplItem,                 "str",                str_impl,                Target::Impl;
+    SliceImplItem,               "slice",              slice_impl,              Target::Impl;
+    SliceU8ImplItem,             "slice_u8",           slice_u8_impl,           Target::Impl;
+    StrAllocImplItem,            "str_alloc",          str_alloc_impl,          Target::Impl;
+    SliceAllocImplItem,          "slice_alloc",        slice_alloc_impl,        Target::Impl;
+    SliceU8AllocImplItem,        "slice_u8_alloc",     slice_u8_alloc_impl,     Target::Impl;
+    ConstPtrImplItem,            "const_ptr",          const_ptr_impl,          Target::Impl;
+    MutPtrImplItem,              "mut_ptr",            mut_ptr_impl,            Target::Impl;
+    I8ImplItem,                  "i8",                 i8_impl,                 Target::Impl;
+    I16ImplItem,                 "i16",                i16_impl,                Target::Impl;
+    I32ImplItem,                 "i32",                i32_impl,                Target::Impl;
+    I64ImplItem,                 "i64",                i64_impl,                Target::Impl;
+    I128ImplItem,                "i128",               i128_impl,               Target::Impl;
+    IsizeImplItem,               "isize",              isize_impl,              Target::Impl;
+    U8ImplItem,                  "u8",                 u8_impl,                 Target::Impl;
+    U16ImplItem,                 "u16",                u16_impl,                Target::Impl;
+    U32ImplItem,                 "u32",                u32_impl,                Target::Impl;
+    U64ImplItem,                 "u64",                u64_impl,                Target::Impl;
+    U128ImplItem,                "u128",               u128_impl,               Target::Impl;
+    UsizeImplItem,               "usize",              usize_impl,              Target::Impl;
+    F32ImplItem,                 "f32",                f32_impl,                Target::Impl;
+    F64ImplItem,                 "f64",                f64_impl,                Target::Impl;
+    F32RuntimeImplItem,          "f32_runtime",        f32_runtime_impl,        Target::Impl;
+    F64RuntimeImplItem,          "f64_runtime",        f64_runtime_impl,        Target::Impl;
+
+    SizedTraitLangItem,          "sized",              sized_trait,             Target::Trait;
+    UnsizeTraitLangItem,         "unsize",             unsize_trait,            Target::Trait;
+    // trait injected by #[derive(PartialEq)], (i.e. "Partial EQ").
+    StructuralPeqTraitLangItem,  "structural_peq",     structural_peq_trait,    Target::Trait;
+    // trait injected by #[derive(Eq)], (i.e. "Total EQ"; no, I will not apologize).
+    StructuralTeqTraitLangItem,  "structural_teq",     structural_teq_trait,    Target::Trait;
+    CopyTraitLangItem,           "copy",               copy_trait,              Target::Trait;
+    CloneTraitLangItem,          "clone",              clone_trait,             Target::Trait;
+    SyncTraitLangItem,           "sync",               sync_trait,              Target::Trait;
+    FreezeTraitLangItem,         "freeze",             freeze_trait,            Target::Trait;
+
+    DropTraitLangItem,           "drop",               drop_trait,              Target::Trait;
+
+    CoerceUnsizedTraitLangItem,  "coerce_unsized",     coerce_unsized_trait,    Target::Trait;
+    DispatchFromDynTraitLangItem,"dispatch_from_dyn",  dispatch_from_dyn_trait, Target::Trait;
+
+    AddTraitLangItem,            "add",                add_trait,               Target::Trait;
+    SubTraitLangItem,            "sub",                sub_trait,               Target::Trait;
+    MulTraitLangItem,            "mul",                mul_trait,               Target::Trait;
+    DivTraitLangItem,            "div",                div_trait,               Target::Trait;
+    RemTraitLangItem,            "rem",                rem_trait,               Target::Trait;
+    NegTraitLangItem,            "neg",                neg_trait,               Target::Trait;
+    NotTraitLangItem,            "not",                not_trait,               Target::Trait;
+    BitXorTraitLangItem,         "bitxor",             bitxor_trait,            Target::Trait;
+    BitAndTraitLangItem,         "bitand",             bitand_trait,            Target::Trait;
+    BitOrTraitLangItem,          "bitor",              bitor_trait,             Target::Trait;
+    ShlTraitLangItem,            "shl",                shl_trait,               Target::Trait;
+    ShrTraitLangItem,            "shr",                shr_trait,               Target::Trait;
+    AddAssignTraitLangItem,      "add_assign",         add_assign_trait,        Target::Trait;
+    SubAssignTraitLangItem,      "sub_assign",         sub_assign_trait,        Target::Trait;
+    MulAssignTraitLangItem,      "mul_assign",         mul_assign_trait,        Target::Trait;
+    DivAssignTraitLangItem,      "div_assign",         div_assign_trait,        Target::Trait;
+    RemAssignTraitLangItem,      "rem_assign",         rem_assign_trait,        Target::Trait;
+    BitXorAssignTraitLangItem,   "bitxor_assign",      bitxor_assign_trait,     Target::Trait;
+    BitAndAssignTraitLangItem,   "bitand_assign",      bitand_assign_trait,     Target::Trait;
+    BitOrAssignTraitLangItem,    "bitor_assign",       bitor_assign_trait,      Target::Trait;
+    ShlAssignTraitLangItem,      "shl_assign",         shl_assign_trait,        Target::Trait;
+    ShrAssignTraitLangItem,      "shr_assign",         shr_assign_trait,        Target::Trait;
+    IndexTraitLangItem,          "index",              index_trait,             Target::Trait;
+    IndexMutTraitLangItem,       "index_mut",          index_mut_trait,         Target::Trait;
+
+    UnsafeCellTypeLangItem,      "unsafe_cell",        unsafe_cell_type,        Target::Struct;
+    VaListTypeLangItem,          "va_list",            va_list,                 Target::Struct;
+
+    DerefTraitLangItem,          "deref",              deref_trait,             Target::Trait;
+    DerefMutTraitLangItem,       "deref_mut",          deref_mut_trait,         Target::Trait;
+    ReceiverTraitLangItem,       "receiver",           receiver_trait,          Target::Trait;
+
+    FnTraitLangItem,             "fn",                 fn_trait,                Target::Trait;
+    FnMutTraitLangItem,          "fn_mut",             fn_mut_trait,            Target::Trait;
+    FnOnceTraitLangItem,         "fn_once",            fn_once_trait,           Target::Trait;
+
+    FutureTraitLangItem,         "future_trait",       future_trait,            Target::Trait;
+    GeneratorStateLangItem,      "generator_state",    gen_state,               Target::Enum;
+    GeneratorTraitLangItem,      "generator",          gen_trait,               Target::Trait;
+    UnpinTraitLangItem,          "unpin",              unpin_trait,             Target::Trait;
+    PinTypeLangItem,             "pin",                pin_type,                Target::Struct;
+
+    // Don't be fooled by the naming here: this lang item denotes `PartialEq`, not `Eq`.
+    EqTraitLangItem,             "eq",                 eq_trait,                Target::Trait;
+    PartialOrdTraitLangItem,     "partial_ord",        partial_ord_trait,       Target::Trait;
+
+    // A number of panic-related lang items. The `panic` item corresponds to
+    // divide-by-zero and various panic cases with `match`. The
+    // `panic_bounds_check` item is for indexing arrays.
+    //
+    // The `begin_unwind` lang item has a predefined symbol name and is sort of
+    // a "weak lang item" in the sense that a crate is not required to have it
+    // defined to use it, but a final product is required to define it
+    // somewhere. Additionally, there are restrictions on crates that use a weak
+    // lang item, but do not have it defined.
+    PanicFnLangItem,             "panic",              panic_fn,                Target::Fn;
+    PanicBoundsCheckFnLangItem,  "panic_bounds_check", panic_bounds_check_fn,   Target::Fn;
+    PanicInfoLangItem,           "panic_info",         panic_info,              Target::Struct;
+    PanicLocationLangItem,       "panic_location",     panic_location,          Target::Struct;
+    PanicImplLangItem,           "panic_impl",         panic_impl,              Target::Fn;
+    // Libstd panic entry point. Necessary for const eval to be able to catch it
+    BeginPanicFnLangItem,        "begin_panic",        begin_panic_fn,          Target::Fn;
+
+    ExchangeMallocFnLangItem,    "exchange_malloc",    exchange_malloc_fn,      Target::Fn;
+    BoxFreeFnLangItem,           "box_free",           box_free_fn,             Target::Fn;
+    DropInPlaceFnLangItem,       "drop_in_place",      drop_in_place_fn,        Target::Fn;
+    OomLangItem,                 "oom",                oom,                     Target::Fn;
+    AllocLayoutLangItem,         "alloc_layout",       alloc_layout,            Target::Struct;
+
+    StartFnLangItem,             "start",              start_fn,                Target::Fn;
+
+    EhPersonalityLangItem,       "eh_personality",     eh_personality,          Target::Fn;
+    EhUnwindResumeLangItem,      "eh_unwind_resume",   eh_unwind_resume,        Target::Fn;
+    EhCatchTypeinfoLangItem,     "eh_catch_typeinfo",  eh_catch_typeinfo,       Target::Static;
+
+    OwnedBoxLangItem,            "owned_box",          owned_box,               Target::Struct;
+
+    PhantomDataItem,             "phantom_data",       phantom_data,            Target::Struct;
+
+    ManuallyDropItem,            "manually_drop",      manually_drop,           Target::Struct;
+
+    MaybeUninitLangItem,         "maybe_uninit",       maybe_uninit,            Target::Union;
+
+    // Align offset for stride != 1; must not panic.
+    AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
+
+    TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
+
+    Arc,                         "arc",                arc,                     Target::Struct;
+    Rc,                          "rc",                 rc,                      Target::Struct;
+}
diff --git a/src/librustc_hir/lib.rs b/src/librustc_hir/lib.rs
index e4edd34bd6e23..d958dfc681b00 100644
--- a/src/librustc_hir/lib.rs
+++ b/src/librustc_hir/lib.rs
@@ -17,9 +17,15 @@ mod hir;
 pub mod hir_id;
 pub mod intravisit;
 pub mod itemlikevisit;
+pub mod lang_items;
 pub mod pat_util;
 pub mod print;
 mod stable_hash_impls;
+mod target;
+pub mod weak_lang_items;
+
 pub use hir::*;
 pub use hir_id::*;
+pub use lang_items::{LangItem, LanguageItems};
 pub use stable_hash_impls::HashStableContext;
+pub use target::{MethodKind, Target};
diff --git a/src/librustc/hir/check_attr.rs b/src/librustc_hir/target.rs
similarity index 98%
rename from src/librustc/hir/check_attr.rs
rename to src/librustc_hir/target.rs
index db5e31981c08f..501976fc3cb39 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc_hir/target.rs
@@ -4,8 +4,8 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-use rustc_hir as hir;
-use rustc_hir::{Item, ItemKind, TraitItem, TraitItemKind};
+use crate::hir;
+use crate::{Item, ItemKind, TraitItem, TraitItemKind};
 
 use std::fmt::{self, Display};
 
diff --git a/src/librustc_hir/weak_lang_items.rs b/src/librustc_hir/weak_lang_items.rs
new file mode 100644
index 0000000000000..79182caae8c80
--- /dev/null
+++ b/src/librustc_hir/weak_lang_items.rs
@@ -0,0 +1,48 @@
+//! Validity checking for weak lang items
+
+use crate::def_id::DefId;
+use crate::{lang_items, LangItem, LanguageItems};
+
+use rustc_data_structures::fx::FxHashMap;
+use rustc_span::symbol::{sym, Symbol};
+use syntax::ast;
+
+use lazy_static::lazy_static;
+
+macro_rules! weak_lang_items {
+    ($($name:ident, $item:ident, $sym:ident;)*) => (
+
+lazy_static! {
+    pub static ref WEAK_ITEMS_REFS: FxHashMap<Symbol, LangItem> = {
+        let mut map = FxHashMap::default();
+        $(map.insert(sym::$name, lang_items::$item);)*
+        map
+    };
+}
+
+pub fn link_name(attrs: &[ast::Attribute]) -> Option<Symbol> {
+    lang_items::extract(attrs).and_then(|(name, _)| {
+        $(if name == sym::$name {
+            Some(sym::$sym)
+        } else)* {
+            None
+        }
+    })
+}
+
+impl LanguageItems {
+    pub fn is_weak_lang_item(&self, item_def_id: DefId) -> bool {
+        let did = Some(item_def_id);
+
+        $(self.$name() == did)||*
+    }
+}
+
+) }
+
+weak_lang_items! {
+    panic_impl,         PanicImplLangItem,          rust_begin_unwind;
+    eh_personality,     EhPersonalityLangItem,      rust_eh_personality;
+    eh_unwind_resume,   EhUnwindResumeLangItem,     rust_eh_unwind_resume;
+    oom,                OomLangItem,                rust_oom;
+}
diff --git a/src/librustc_interface/interface.rs b/src/librustc_interface/interface.rs
index 2a667541ad3e7..e213a4d33a6fb 100644
--- a/src/librustc_interface/interface.rs
+++ b/src/librustc_interface/interface.rs
@@ -2,7 +2,7 @@ pub use crate::passes::BoxedResolver;
 use crate::util;
 
 use rustc::lint;
-use rustc::session::config::{self, ErrorOutputType, Input};
+use rustc::session::config::{self, ErrorOutputType, Input, OutputFilenames};
 use rustc::session::early_error;
 use rustc::session::{DiagnosticOutput, Session};
 use rustc::ty;
@@ -20,7 +20,7 @@ use rustc_span::source_map::{FileLoader, FileName, SourceMap};
 use std::path::PathBuf;
 use std::result;
 use std::sync::{Arc, Mutex};
-use syntax::ast::MetaItemKind;
+use syntax::ast::{self, MetaItemKind};
 use syntax::token;
 
 pub type Result<T> = result::Result<T, ErrorReported>;
@@ -61,6 +61,19 @@ impl Compiler {
     pub fn output_file(&self) -> &Option<PathBuf> {
         &self.output_file
     }
+    pub fn build_output_filenames(
+        &self,
+        sess: &Session,
+        attrs: &[ast::Attribute],
+    ) -> OutputFilenames {
+        util::build_output_filenames(
+            &self.input,
+            &self.output_dir,
+            &self.output_file,
+            &attrs,
+            &sess,
+        )
+    }
 }
 
 /// Converts strings provided as `--cfg [cfgspec]` into a `crate_cfg`.
diff --git a/src/librustc_macros/Cargo.toml b/src/librustc_macros/Cargo.toml
index c28fcb1a395ff..73eb0dd56d772 100644
--- a/src/librustc_macros/Cargo.toml
+++ b/src/librustc_macros/Cargo.toml
@@ -12,4 +12,3 @@ synstructure = "0.12.1"
 syn = { version = "1", features = ["full"] }
 proc-macro2 = "1"
 quote = "1"
-itertools = "0.8"
diff --git a/src/librustc_macros/src/query.rs b/src/librustc_macros/src/query.rs
index 6dc4f7f251595..294cdb7643fc9 100644
--- a/src/librustc_macros/src/query.rs
+++ b/src/librustc_macros/src/query.rs
@@ -1,4 +1,3 @@
-use itertools::Itertools;
 use proc_macro::TokenStream;
 use proc_macro2::{Delimiter, TokenTree};
 use quote::quote;
@@ -469,10 +468,7 @@ pub fn rustc_queries(input: TokenStream) -> TokenStream {
                 attributes.push(quote! { eval_always });
             };
 
-            let mut attribute_stream = quote! {};
-            for e in attributes.into_iter().intersperse(quote! {,}) {
-                attribute_stream.extend(e);
-            }
+            let attribute_stream = quote! {#(#attributes),*};
 
             // Add the query to the group
             group_stream.extend(quote! {
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index a8c66be359c4a..bfd30ff5da553 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -40,7 +40,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> &'tcx
         ),
         ty::InstanceDef::FnPtrShim(def_id, ty) => {
             let trait_ = tcx.trait_of_item(def_id).unwrap();
-            let adjustment = match tcx.lang_items().fn_trait_kind(trait_) {
+            let adjustment = match tcx.fn_trait_kind_from_lang_item(trait_) {
                 Some(ty::ClosureKind::FnOnce) => Adjustment::Identity,
                 Some(ty::ClosureKind::FnMut) | Some(ty::ClosureKind::Fn) => Adjustment::Deref,
                 None => bug!("fn pointer {:?} is not an fn", ty),
diff --git a/src/librustc_mir_build/Cargo.toml b/src/librustc_mir_build/Cargo.toml
index 9ff3ed1a93588..c109e9c618e73 100644
--- a/src/librustc_mir_build/Cargo.toml
+++ b/src/librustc_mir_build/Cargo.toml
@@ -11,7 +11,6 @@ doctest = false
 
 [dependencies]
 arena = { path = "../libarena" }
-itertools = "0.8"
 log = "0.4"
 rustc = { path = "../librustc" }
 rustc_apfloat = { path = "../librustc_apfloat" }
diff --git a/src/librustc_passes/check_attr.rs b/src/librustc_passes/check_attr.rs
index 855970d934264..5cabf3c0262a1 100644
--- a/src/librustc_passes/check_attr.rs
+++ b/src/librustc_passes/check_attr.rs
@@ -4,7 +4,6 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-use rustc::hir::check_attr::{MethodKind, Target};
 use rustc::hir::map::Map;
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
@@ -15,6 +14,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_hir::DUMMY_HIR_ID;
 use rustc_hir::{self, HirId, Item, ItemKind, TraitItem};
+use rustc_hir::{MethodKind, Target};
 use rustc_session::lint::builtin::{CONFLICTING_REPR_HINTS, UNUSED_ATTRIBUTES};
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::sym;
diff --git a/src/librustc_passes/lang_items.rs b/src/librustc_passes/lang_items.rs
new file mode 100644
index 0000000000000..5f5acc7fdf815
--- /dev/null
+++ b/src/librustc_passes/lang_items.rs
@@ -0,0 +1,174 @@
+//! Detecting language items.
+//!
+//! Language items are items that represent concepts intrinsic to the language
+//! itself. Examples are:
+//!
+//! * Traits that specify "kinds"; e.g., `Sync`, `Send`.
+//! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`.
+//! * Functions called by the compiler itself.
+
+use crate::weak_lang_items;
+
+use rustc::middle::cstore::ExternCrate;
+use rustc::ty::TyCtxt;
+
+use rustc_errors::struct_span_err;
+use rustc_hir as hir;
+use rustc_hir::def_id::{DefId, LOCAL_CRATE};
+use rustc_hir::itemlikevisit::ItemLikeVisitor;
+use rustc_hir::lang_items::{extract, ITEM_REFS};
+use rustc_hir::{LangItem, LanguageItems, Target};
+
+use rustc::ty::query::Providers;
+
+struct LanguageItemCollector<'tcx> {
+    items: LanguageItems,
+    tcx: TyCtxt<'tcx>,
+}
+
+impl ItemLikeVisitor<'v> for LanguageItemCollector<'tcx> {
+    fn visit_item(&mut self, item: &hir::Item<'_>) {
+        if let Some((value, span)) = extract(&item.attrs) {
+            let actual_target = Target::from_item(item);
+            match ITEM_REFS.get(&*value.as_str()).cloned() {
+                // Known lang item with attribute on correct target.
+                Some((item_index, expected_target)) if actual_target == expected_target => {
+                    let def_id = self.tcx.hir().local_def_id(item.hir_id);
+                    self.collect_item(item_index, def_id);
+                }
+                // Known lang item with attribute on incorrect target.
+                Some((_, expected_target)) => {
+                    struct_span_err!(
+                        self.tcx.sess,
+                        span,
+                        E0718,
+                        "`{}` language item must be applied to a {}",
+                        value,
+                        expected_target,
+                    )
+                    .span_label(
+                        span,
+                        format!(
+                            "attribute should be applied to a {}, not a {}",
+                            expected_target, actual_target,
+                        ),
+                    )
+                    .emit();
+                }
+                // Unknown lang item.
+                _ => {
+                    struct_span_err!(
+                        self.tcx.sess,
+                        span,
+                        E0522,
+                        "definition of an unknown language item: `{}`",
+                        value
+                    )
+                    .span_label(span, format!("definition of unknown language item `{}`", value))
+                    .emit();
+                }
+            }
+        }
+    }
+
+    fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {
+        // At present, lang items are always items, not trait items.
+    }
+
+    fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {
+        // At present, lang items are always items, not impl items.
+    }
+}
+
+impl LanguageItemCollector<'tcx> {
+    fn new(tcx: TyCtxt<'tcx>) -> LanguageItemCollector<'tcx> {
+        LanguageItemCollector { tcx, items: LanguageItems::new() }
+    }
+
+    fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
+        // Check for duplicates.
+        if let Some(original_def_id) = self.items.items[item_index] {
+            if original_def_id != item_def_id {
+                let name = LangItem::from_u32(item_index as u32).unwrap().name();
+                let mut err = match self.tcx.hir().span_if_local(item_def_id) {
+                    Some(span) => struct_span_err!(
+                        self.tcx.sess,
+                        span,
+                        E0152,
+                        "found duplicate lang item `{}`",
+                        name
+                    ),
+                    None => match self.tcx.extern_crate(item_def_id) {
+                        Some(ExternCrate { dependency_of, .. }) => {
+                            self.tcx.sess.struct_err(&format!(
+                                "duplicate lang item in crate `{}` (which `{}` depends on): `{}`.",
+                                self.tcx.crate_name(item_def_id.krate),
+                                self.tcx.crate_name(*dependency_of),
+                                name
+                            ))
+                        }
+                        _ => self.tcx.sess.struct_err(&format!(
+                            "duplicate lang item in crate `{}`: `{}`.",
+                            self.tcx.crate_name(item_def_id.krate),
+                            name
+                        )),
+                    },
+                };
+                if let Some(span) = self.tcx.hir().span_if_local(original_def_id) {
+                    err.span_note(span, "the lang item is first defined here");
+                } else {
+                    match self.tcx.extern_crate(original_def_id) {
+                        Some(ExternCrate { dependency_of, .. }) => {
+                            err.note(&format!(
+                                "the lang item is first defined in crate `{}` (which `{}` depends on)",
+                                self.tcx.crate_name(original_def_id.krate),
+                                self.tcx.crate_name(*dependency_of)
+                            ));
+                        }
+                        _ => {
+                            err.note(&format!(
+                                "the lang item is first defined in crate `{}`.",
+                                self.tcx.crate_name(original_def_id.krate)
+                            ));
+                        }
+                    }
+                }
+                err.emit();
+            }
+        }
+
+        // Matched.
+        self.items.items[item_index] = Some(item_def_id);
+    }
+}
+
+/// Traverses and collects all the lang items in all crates.
+fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> LanguageItems {
+    // Initialize the collector.
+    let mut collector = LanguageItemCollector::new(tcx);
+
+    // Collect lang items in other crates.
+    for &cnum in tcx.crates().iter() {
+        for &(def_id, item_index) in tcx.defined_lang_items(cnum).iter() {
+            collector.collect_item(item_index, def_id);
+        }
+    }
+
+    // Collect lang items in this crate.
+    tcx.hir().krate().visit_all_item_likes(&mut collector);
+
+    // Extract out the found lang items.
+    let LanguageItemCollector { mut items, .. } = collector;
+
+    // Find all required but not-yet-defined lang items.
+    weak_lang_items::check_crate(tcx, &mut items);
+
+    items
+}
+
+pub fn provide(providers: &mut Providers<'_>) {
+    providers.get_lang_items = |tcx, id| {
+        assert_eq!(id, LOCAL_CRATE);
+        tcx.arena.alloc(collect(tcx))
+    };
+}
diff --git a/src/librustc_passes/lib.rs b/src/librustc_passes/lib.rs
index c5e5bc969158f..afafbacb8fa88 100644
--- a/src/librustc_passes/lib.rs
+++ b/src/librustc_passes/lib.rs
@@ -23,6 +23,7 @@ mod diagnostic_items;
 pub mod entry;
 pub mod hir_stats;
 mod intrinsicck;
+mod lang_items;
 pub mod layout_test;
 mod lib_features;
 mod liveness;
@@ -31,12 +32,14 @@ mod reachable;
 mod region;
 pub mod stability;
 mod upvars;
+mod weak_lang_items;
 
 pub fn provide(providers: &mut Providers<'_>) {
     check_attr::provide(providers);
     check_const::provide(providers);
     diagnostic_items::provide(providers);
     entry::provide(providers);
+    lang_items::provide(providers);
     lib_features::provide(providers);
     loops::provide(providers);
     liveness::provide(providers);
diff --git a/src/librustc_passes/weak_lang_items.rs b/src/librustc_passes/weak_lang_items.rs
new file mode 100644
index 0000000000000..010712c28ba75
--- /dev/null
+++ b/src/librustc_passes/weak_lang_items.rs
@@ -0,0 +1,103 @@
+//! Validity checking for weak lang items
+
+use rustc::middle::lang_items;
+use rustc::middle::lang_items::whitelisted;
+use rustc::session::config;
+
+use rustc::hir::map::Map;
+use rustc::ty::TyCtxt;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::struct_span_err;
+use rustc_hir as hir;
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_hir::weak_lang_items::WEAK_ITEMS_REFS;
+use rustc_span::symbol::Symbol;
+use rustc_span::Span;
+
+struct Context<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    items: &'a mut lang_items::LanguageItems,
+}
+
+/// Checks the crate for usage of weak lang items, returning a vector of all the
+/// language items required by this crate, but not defined yet.
+pub fn check_crate<'tcx>(tcx: TyCtxt<'tcx>, items: &mut lang_items::LanguageItems) {
+    // These are never called by user code, they're generated by the compiler.
+    // They will never implicitly be added to the `missing` array unless we do
+    // so here.
+    if items.eh_personality().is_none() {
+        items.missing.push(lang_items::EhPersonalityLangItem);
+    }
+    if tcx.sess.target.target.options.custom_unwind_resume & items.eh_unwind_resume().is_none() {
+        items.missing.push(lang_items::EhUnwindResumeLangItem);
+    }
+
+    {
+        let mut cx = Context { tcx, items };
+        tcx.hir().krate().visit_all_item_likes(&mut cx.as_deep_visitor());
+    }
+    verify(tcx, items);
+}
+
+fn verify<'tcx>(tcx: TyCtxt<'tcx>, items: &lang_items::LanguageItems) {
+    // We only need to check for the presence of weak lang items if we're
+    // emitting something that's not an rlib.
+    let needs_check = tcx.sess.crate_types.borrow().iter().any(|kind| match *kind {
+        config::CrateType::Dylib
+        | config::CrateType::ProcMacro
+        | config::CrateType::Cdylib
+        | config::CrateType::Executable
+        | config::CrateType::Staticlib => true,
+        config::CrateType::Rlib => false,
+    });
+    if !needs_check {
+        return;
+    }
+
+    let mut missing = FxHashSet::default();
+    for &cnum in tcx.crates().iter() {
+        for &item in tcx.missing_lang_items(cnum).iter() {
+            missing.insert(item);
+        }
+    }
+
+    for (name, &item) in WEAK_ITEMS_REFS.iter() {
+        if missing.contains(&item) && !whitelisted(tcx, item) && items.require(item).is_err() {
+            if item == lang_items::PanicImplLangItem {
+                tcx.sess.err(&format!("`#[panic_handler]` function required, but not found"));
+            } else if item == lang_items::OomLangItem {
+                tcx.sess.err(&format!("`#[alloc_error_handler]` function required, but not found"));
+            } else {
+                tcx.sess.err(&format!("language item required, but not found: `{}`", name));
+            }
+        }
+    }
+}
+
+impl<'a, 'tcx> Context<'a, 'tcx> {
+    fn register(&mut self, name: Symbol, span: Span) {
+        if let Some(&item) = WEAK_ITEMS_REFS.get(&name) {
+            if self.items.require(item).is_err() {
+                self.items.missing.push(item);
+            }
+        } else {
+            struct_span_err!(self.tcx.sess, span, E0264, "unknown external lang item: `{}`", name)
+                .emit();
+        }
+    }
+}
+
+impl<'a, 'tcx, 'v> Visitor<'v> for Context<'a, 'tcx> {
+    type Map = Map<'v>;
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, Map<'v>> {
+        NestedVisitorMap::None
+    }
+
+    fn visit_foreign_item(&mut self, i: &hir::ForeignItem<'_>) {
+        if let Some((lang_item, _)) = hir::lang_items::extract(&i.attrs) {
+            self.register(lang_item, i.span);
+        }
+        intravisit::walk_foreign_item(self, i)
+    }
+}
diff --git a/src/librustc_session/config.rs b/src/librustc_session/config.rs
index 75b5e37b2df69..aeb7e891cec02 100644
--- a/src/librustc_session/config.rs
+++ b/src/librustc_session/config.rs
@@ -465,6 +465,7 @@ pub struct OutputFilenames {
 
 impl_stable_hash_via_hash!(OutputFilenames);
 
+pub const RLINK_EXT: &str = "rlink";
 pub const RUST_CGU_EXT: &str = "rcgu";
 
 impl OutputFilenames {
diff --git a/src/librustc_session/options.rs b/src/librustc_session/options.rs
index 0250c40bcdcf1..4b3645cce723a 100644
--- a/src/librustc_session/options.rs
+++ b/src/librustc_session/options.rs
@@ -966,4 +966,6 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "use Windows Control Flow Guard (`disabled`, `nochecks` or `checks`)"),
     no_link: bool = (false, parse_bool, [TRACKED],
         "compile without linking"),
+    link_only: bool = (false, parse_bool, [TRACKED],
+        "link the `.rlink` file generated by `-Z no-link`"),
 }
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index 707125b3fd522..396534b3caeb7 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -176,7 +176,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .next();
                 let kind = object_type
                     .principal_def_id()
-                    .and_then(|did| self.tcx.lang_items().fn_trait_kind(did));
+                    .and_then(|did| self.tcx.fn_trait_kind_from_lang_item(did));
                 (sig, kind)
             }
             ty::Infer(ty::TyVar(vid)) => self.deduce_expectations_from_obligations(vid),
@@ -214,7 +214,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // many viable options, so pick the most restrictive.
         let expected_kind = self
             .obligations_for_self_ty(expected_vid)
-            .filter_map(|(tr, _)| self.tcx.lang_items().fn_trait_kind(tr.def_id()))
+            .filter_map(|(tr, _)| self.tcx.fn_trait_kind_from_lang_item(tr.def_id()))
             .fold(None, |best, cur| Some(best.map_or(cur, |best| cmp::min(best, cur))));
 
         (expected_sig, expected_kind)
@@ -237,7 +237,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let trait_ref = projection.to_poly_trait_ref(tcx);
 
-        let is_fn = tcx.lang_items().fn_trait_kind(trait_ref.def_id()).is_some();
+        let is_fn = tcx.fn_trait_kind_from_lang_item(trait_ref.def_id()).is_some();
         let gen_trait = tcx.require_lang_item(lang_items::GeneratorTraitLangItem, cause_span);
         let is_gen = gen_trait == trait_ref.def_id();
         if !is_fn && !is_gen {
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index b661006d1ddd0..ea0e4719a24fd 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -20,8 +20,8 @@ use crate::astconv::{AstConv, Bounds, SizedByDefault};
 use crate::check::intrinsic::intrinsic_operation_unsafety;
 use crate::constrained_generic_params as cgp;
 use crate::lint;
+use crate::middle::lang_items;
 use crate::middle::resolve_lifetime as rl;
-use crate::middle::weak_lang_items;
 use rustc::hir::map::blocks::FnLikeNode;
 use rustc::hir::map::Map;
 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
@@ -2977,7 +2977,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
     if tcx.is_weak_lang_item(id) {
         codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
     }
-    if let Some(name) = weak_lang_items::link_name(&attrs) {
+    if let Some(name) = lang_items::link_name(&attrs) {
         codegen_fn_attrs.export_name = Some(name);
         codegen_fn_attrs.link_name = Some(name);
     }
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 356660763a755..ef35705650452 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -138,7 +138,7 @@ pub fn external_generic_args(
 
     match trait_did {
         // Attempt to sugar an external path like Fn<(A, B,), C> to Fn(A, B) -> C
-        Some(did) if cx.tcx.lang_items().fn_trait_kind(did).is_some() => {
+        Some(did) if cx.tcx.fn_trait_kind_from_lang_item(did).is_some() => {
             assert!(ty_kind.is_some());
             let inputs = match ty_kind {
                 Some(ty::Tuple(ref tys)) => tys.iter().map(|t| t.expect_ty().clean(cx)).collect(),
diff --git a/src/libstd/keyword_docs.rs b/src/libstd/keyword_docs.rs
index 5c7ee9bded9dc..58f4e76cd30b3 100644
--- a/src/libstd/keyword_docs.rs
+++ b/src/libstd/keyword_docs.rs
@@ -1100,10 +1100,28 @@ mod trait_keyword {}
 //
 /// A value of type [`bool`] representing logical **true**.
 ///
-/// The documentation for this keyword is [not yet complete]. Pull requests welcome!
+/// Logically `true` is not equal to [`false`].
+///
+/// ## Control structures that check for **true**
+///
+/// Several of Rust's control structures will check for a `bool` condition evaluating to **true**.
+///
+///   * The condition in an [`if`] expression must be of type `bool`.
+///     Whenever that condition evaluates to **true**, the `if` expression takes
+///     on the value of the first block. If however, the condition evaluates
+///     to `false`, the expression takes on value of the `else` block if there is one.
 ///
+///   * [`while`] is another control flow construct expecting a `bool`-typed condition.
+///     As long as the condition evaluates to **true**, the `while` loop will continually
+///     evaluate its associated block.
+///
+///   * [`match`] arms can have guard clauses on them.
+///
+/// [`if`]: keyword.if.html
+/// [`while`]: keyword.while.html
+/// [`match`]: ../reference/expressions/match-expr.html#match-guards
+/// [`false`]: keyword.false.html
 /// [`bool`]: primitive.bool.html
-/// [not yet complete]: https://github.com/rust-lang/rust/issues/34601
 mod true_keyword {}
 
 #[doc(keyword = "type")]
@@ -1186,12 +1204,33 @@ mod await_keyword {}
 
 #[doc(keyword = "dyn")]
 //
-/// Name the type of a [trait object].
+/// `dyn` is a prefix of a [trait object]'s type.
 ///
-/// The documentation for this keyword is [not yet complete]. Pull requests welcome!
+/// The `dyn` keyword is used to highlight that calls to methods on the associated `Trait`
+/// are dynamically dispatched. To use the trait this way, it must be 'object safe'.
+///
+/// Unlike generic parameters or `impl Trait`, the compiler does not know the concrete type that
+/// is being passed. That is, the type has been [erased].
+/// As such, a `dyn Trait` reference contains _two_ pointers.
+/// One pointer goes to the data (e.g., an instance of a struct).
+/// Another pointer goes to a map of method call names to function pointers
+/// (known as a virtual method table or vtable).
+///
+/// At run-time, when a method needs to be called on the `dyn Trait`, the vtable is consulted to get
+/// the function pointer and then that function pointer is called.
+///
+/// ## Trade-offs
+///
+/// The above indirection is the additional runtime cost of calling a function on a `dyn Trait`.
+/// Methods called by dynamic dispatch generally cannot be inlined by the compiler.
+///
+/// However, `dyn Trait` is likely to produce smaller code than `impl Trait` / generic parameters as
+/// the method won't be duplicated for each concrete type.
+///
+/// Read more about `object safety` and [trait object]s.
 ///
 /// [trait object]: ../book/ch17-02-trait-objects.html
-/// [not yet complete]: https://github.com/rust-lang/rust/issues/34601
+/// [erased]: https://en.wikipedia.org/wiki/Type_erasure
 mod dyn_keyword {}
 
 #[doc(keyword = "union")]
diff --git a/src/test/ui/allocator-alloc-one.rs b/src/test/ui/allocator-alloc-one.rs
deleted file mode 100644
index b821a2c593962..0000000000000
--- a/src/test/ui/allocator-alloc-one.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-// run-pass
-
-#![allow(stable_features)]
-
-#![feature(allocator_api, nonnull)]
-
-use std::alloc::{AllocRef, Global, Layout, handle_alloc_error};
-
-fn main() {
-    unsafe {
-        let ptr = Global.alloc_one::<i32>().unwrap_or_else(|_| {
-            handle_alloc_error(Layout::new::<i32>())
-        });
-        *ptr.as_ptr() = 4;
-        assert_eq!(*ptr.as_ptr(), 4);
-        Global.dealloc_one(ptr);
-    }
-}
diff --git a/src/test/ui/consts/const-int-unchecked.rs b/src/test/ui/consts/const-int-unchecked.rs
index 8ee029b6cc390..fb09f62854d61 100644
--- a/src/test/ui/consts/const-int-unchecked.rs
+++ b/src/test/ui/consts/const-int-unchecked.rs
@@ -1,4 +1,5 @@
 #![feature(core_intrinsics)]
+#![feature(const_int_unchecked_arith)]
 
 use std::intrinsics;
 
@@ -117,4 +118,25 @@ const SHR_I64_NEG_RANDOM: i64 = unsafe { intrinsics::unchecked_shr(5_i64, -30) }
 const SHR_I128_NEG_RANDOM: i128 = unsafe { intrinsics::unchecked_shr(5_i128, -93) };
 //~^ ERROR any use of this value will cause an error
 
+// Other arithmetic functions:
+
+const _: u16 = unsafe { std::intrinsics::unchecked_add(40000u16, 30000) };
+//~^ ERROR any use of this value will cause an error
+
+const _: u32 = unsafe { std::intrinsics::unchecked_sub(14u32, 22) };
+//~^ ERROR any use of this value will cause an error
+
+const _: u16 = unsafe { std::intrinsics::unchecked_mul(300u16, 250u16) };
+//~^ ERROR any use of this value will cause an error
+
+const _: i32 = unsafe { std::intrinsics::unchecked_div(1, 0) };
+//~^ ERROR any use of this value will cause an error
+const _: i32 = unsafe { std::intrinsics::unchecked_div(i32::min_value(), -1) };
+//~^ ERROR any use of this value will cause an error
+
+const _: i32 = unsafe { std::intrinsics::unchecked_rem(1, 0) };
+//~^ ERROR any use of this value will cause an error
+const _: i32 = unsafe { std::intrinsics::unchecked_rem(i32::min_value(), -1) };
+//~^ ERROR any use of this value will cause an error
+
 fn main() {}
diff --git a/src/test/ui/consts/const-int-unchecked.stderr b/src/test/ui/consts/const-int-unchecked.stderr
index d569c6a201b2b..bf31e0b0732d8 100644
--- a/src/test/ui/consts/const-int-unchecked.stderr
+++ b/src/test/ui/consts/const-int-unchecked.stderr
@@ -1,5 +1,5 @@
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:14:29
+  --> $DIR/const-int-unchecked.rs:15:29
    |
 LL | const SHL_U8: u8 = unsafe { intrinsics::unchecked_shl(5_u8, 8) };
    | ----------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -9,7 +9,7 @@ LL | const SHL_U8: u8 = unsafe { intrinsics::unchecked_shl(5_u8, 8) };
    = note: `#[deny(const_err)]` on by default
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:16:31
+  --> $DIR/const-int-unchecked.rs:17:31
    |
 LL | const SHL_U16: u16 = unsafe { intrinsics::unchecked_shl(5_u16, 16) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -17,7 +17,7 @@ LL | const SHL_U16: u16 = unsafe { intrinsics::unchecked_shl(5_u16, 16) };
    |                               Overflowing shift by 16 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:18:31
+  --> $DIR/const-int-unchecked.rs:19:31
    |
 LL | const SHL_U32: u32 = unsafe { intrinsics::unchecked_shl(5_u32, 32) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -25,7 +25,7 @@ LL | const SHL_U32: u32 = unsafe { intrinsics::unchecked_shl(5_u32, 32) };
    |                               Overflowing shift by 32 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:20:31
+  --> $DIR/const-int-unchecked.rs:21:31
    |
 LL | const SHL_U64: u64 = unsafe { intrinsics::unchecked_shl(5_u64, 64) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -33,7 +33,7 @@ LL | const SHL_U64: u64 = unsafe { intrinsics::unchecked_shl(5_u64, 64) };
    |                               Overflowing shift by 64 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:22:33
+  --> $DIR/const-int-unchecked.rs:23:33
    |
 LL | const SHL_U128: u128 = unsafe { intrinsics::unchecked_shl(5_u128, 128) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -41,7 +41,7 @@ LL | const SHL_U128: u128 = unsafe { intrinsics::unchecked_shl(5_u128, 128) };
    |                                 Overflowing shift by 128 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:27:29
+  --> $DIR/const-int-unchecked.rs:28:29
    |
 LL | const SHL_I8: i8 = unsafe { intrinsics::unchecked_shl(5_i8, 8) };
    | ----------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -49,7 +49,7 @@ LL | const SHL_I8: i8 = unsafe { intrinsics::unchecked_shl(5_i8, 8) };
    |                             Overflowing shift by 8 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:29:31
+  --> $DIR/const-int-unchecked.rs:30:31
    |
 LL | const SHL_I16: i16 = unsafe { intrinsics::unchecked_shl(5_16, 16) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -57,7 +57,7 @@ LL | const SHL_I16: i16 = unsafe { intrinsics::unchecked_shl(5_16, 16) };
    |                               Overflowing shift by 16 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:31:31
+  --> $DIR/const-int-unchecked.rs:32:31
    |
 LL | const SHL_I32: i32 = unsafe { intrinsics::unchecked_shl(5_i32, 32) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -65,7 +65,7 @@ LL | const SHL_I32: i32 = unsafe { intrinsics::unchecked_shl(5_i32, 32) };
    |                               Overflowing shift by 32 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:33:31
+  --> $DIR/const-int-unchecked.rs:34:31
    |
 LL | const SHL_I64: i64 = unsafe { intrinsics::unchecked_shl(5_i64, 64) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -73,7 +73,7 @@ LL | const SHL_I64: i64 = unsafe { intrinsics::unchecked_shl(5_i64, 64) };
    |                               Overflowing shift by 64 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:35:33
+  --> $DIR/const-int-unchecked.rs:36:33
    |
 LL | const SHL_I128: i128 = unsafe { intrinsics::unchecked_shl(5_i128, 128) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -81,7 +81,7 @@ LL | const SHL_I128: i128 = unsafe { intrinsics::unchecked_shl(5_i128, 128) };
    |                                 Overflowing shift by 128 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:40:33
+  --> $DIR/const-int-unchecked.rs:41:33
    |
 LL | const SHL_I8_NEG: i8 = unsafe { intrinsics::unchecked_shl(5_i8, -1) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -89,7 +89,7 @@ LL | const SHL_I8_NEG: i8 = unsafe { intrinsics::unchecked_shl(5_i8, -1) };
    |                                 Overflowing shift by 255 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:42:35
+  --> $DIR/const-int-unchecked.rs:43:35
    |
 LL | const SHL_I16_NEG: i16 = unsafe { intrinsics::unchecked_shl(5_16, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -97,7 +97,7 @@ LL | const SHL_I16_NEG: i16 = unsafe { intrinsics::unchecked_shl(5_16, -1) };
    |                                   Overflowing shift by 65535 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:44:35
+  --> $DIR/const-int-unchecked.rs:45:35
    |
 LL | const SHL_I32_NEG: i32 = unsafe { intrinsics::unchecked_shl(5_i32, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -105,7 +105,7 @@ LL | const SHL_I32_NEG: i32 = unsafe { intrinsics::unchecked_shl(5_i32, -1) };
    |                                   Overflowing shift by 4294967295 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:46:35
+  --> $DIR/const-int-unchecked.rs:47:35
    |
 LL | const SHL_I64_NEG: i64 = unsafe { intrinsics::unchecked_shl(5_i64, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -113,7 +113,7 @@ LL | const SHL_I64_NEG: i64 = unsafe { intrinsics::unchecked_shl(5_i64, -1) };
    |                                   Overflowing shift by 18446744073709551615 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:48:37
+  --> $DIR/const-int-unchecked.rs:49:37
    |
 LL | const SHL_I128_NEG: i128 = unsafe { intrinsics::unchecked_shl(5_i128, -1) };
    | ------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -121,7 +121,7 @@ LL | const SHL_I128_NEG: i128 = unsafe { intrinsics::unchecked_shl(5_i128, -1) }
    |                                     Overflowing shift by 340282366920938463463374607431768211455 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:54:40
+  --> $DIR/const-int-unchecked.rs:55:40
    |
 LL | const SHL_I8_NEG_RANDOM: i8 = unsafe { intrinsics::unchecked_shl(5_i8, -6) };
    | ---------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -129,7 +129,7 @@ LL | const SHL_I8_NEG_RANDOM: i8 = unsafe { intrinsics::unchecked_shl(5_i8, -6)
    |                                        Overflowing shift by 250 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:56:42
+  --> $DIR/const-int-unchecked.rs:57:42
    |
 LL | const SHL_I16_NEG_RANDOM: i16 = unsafe { intrinsics::unchecked_shl(5_16, -13) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -137,7 +137,7 @@ LL | const SHL_I16_NEG_RANDOM: i16 = unsafe { intrinsics::unchecked_shl(5_16, -1
    |                                          Overflowing shift by 65523 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:58:42
+  --> $DIR/const-int-unchecked.rs:59:42
    |
 LL | const SHL_I32_NEG_RANDOM: i32 = unsafe { intrinsics::unchecked_shl(5_i32, -25) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -145,7 +145,7 @@ LL | const SHL_I32_NEG_RANDOM: i32 = unsafe { intrinsics::unchecked_shl(5_i32, -
    |                                          Overflowing shift by 4294967271 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:60:42
+  --> $DIR/const-int-unchecked.rs:61:42
    |
 LL | const SHL_I64_NEG_RANDOM: i64 = unsafe { intrinsics::unchecked_shl(5_i64, -30) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -153,7 +153,7 @@ LL | const SHL_I64_NEG_RANDOM: i64 = unsafe { intrinsics::unchecked_shl(5_i64, -
    |                                          Overflowing shift by 18446744073709551586 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:62:44
+  --> $DIR/const-int-unchecked.rs:63:44
    |
 LL | const SHL_I128_NEG_RANDOM: i128 = unsafe { intrinsics::unchecked_shl(5_i128, -93) };
    | -------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -161,7 +161,7 @@ LL | const SHL_I128_NEG_RANDOM: i128 = unsafe { intrinsics::unchecked_shl(5_i128
    |                                            Overflowing shift by 340282366920938463463374607431768211363 in `unchecked_shl`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:69:29
+  --> $DIR/const-int-unchecked.rs:70:29
    |
 LL | const SHR_U8: u8 = unsafe { intrinsics::unchecked_shr(5_u8, 8) };
    | ----------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -169,7 +169,7 @@ LL | const SHR_U8: u8 = unsafe { intrinsics::unchecked_shr(5_u8, 8) };
    |                             Overflowing shift by 8 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:71:31
+  --> $DIR/const-int-unchecked.rs:72:31
    |
 LL | const SHR_U16: u16 = unsafe { intrinsics::unchecked_shr(5_u16, 16) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -177,7 +177,7 @@ LL | const SHR_U16: u16 = unsafe { intrinsics::unchecked_shr(5_u16, 16) };
    |                               Overflowing shift by 16 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:73:31
+  --> $DIR/const-int-unchecked.rs:74:31
    |
 LL | const SHR_U32: u32 = unsafe { intrinsics::unchecked_shr(5_u32, 32) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -185,7 +185,7 @@ LL | const SHR_U32: u32 = unsafe { intrinsics::unchecked_shr(5_u32, 32) };
    |                               Overflowing shift by 32 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:75:31
+  --> $DIR/const-int-unchecked.rs:76:31
    |
 LL | const SHR_U64: u64 = unsafe { intrinsics::unchecked_shr(5_u64, 64) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -193,7 +193,7 @@ LL | const SHR_U64: u64 = unsafe { intrinsics::unchecked_shr(5_u64, 64) };
    |                               Overflowing shift by 64 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:77:33
+  --> $DIR/const-int-unchecked.rs:78:33
    |
 LL | const SHR_U128: u128 = unsafe { intrinsics::unchecked_shr(5_u128, 128) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -201,7 +201,7 @@ LL | const SHR_U128: u128 = unsafe { intrinsics::unchecked_shr(5_u128, 128) };
    |                                 Overflowing shift by 128 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:82:29
+  --> $DIR/const-int-unchecked.rs:83:29
    |
 LL | const SHR_I8: i8 = unsafe { intrinsics::unchecked_shr(5_i8, 8) };
    | ----------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -209,7 +209,7 @@ LL | const SHR_I8: i8 = unsafe { intrinsics::unchecked_shr(5_i8, 8) };
    |                             Overflowing shift by 8 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:84:31
+  --> $DIR/const-int-unchecked.rs:85:31
    |
 LL | const SHR_I16: i16 = unsafe { intrinsics::unchecked_shr(5_16, 16) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -217,7 +217,7 @@ LL | const SHR_I16: i16 = unsafe { intrinsics::unchecked_shr(5_16, 16) };
    |                               Overflowing shift by 16 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:86:31
+  --> $DIR/const-int-unchecked.rs:87:31
    |
 LL | const SHR_I32: i32 = unsafe { intrinsics::unchecked_shr(5_i32, 32) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -225,7 +225,7 @@ LL | const SHR_I32: i32 = unsafe { intrinsics::unchecked_shr(5_i32, 32) };
    |                               Overflowing shift by 32 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:88:31
+  --> $DIR/const-int-unchecked.rs:89:31
    |
 LL | const SHR_I64: i64 = unsafe { intrinsics::unchecked_shr(5_i64, 64) };
    | ------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -233,7 +233,7 @@ LL | const SHR_I64: i64 = unsafe { intrinsics::unchecked_shr(5_i64, 64) };
    |                               Overflowing shift by 64 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:90:33
+  --> $DIR/const-int-unchecked.rs:91:33
    |
 LL | const SHR_I128: i128 = unsafe { intrinsics::unchecked_shr(5_i128, 128) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -241,7 +241,7 @@ LL | const SHR_I128: i128 = unsafe { intrinsics::unchecked_shr(5_i128, 128) };
    |                                 Overflowing shift by 128 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:95:33
+  --> $DIR/const-int-unchecked.rs:96:33
    |
 LL | const SHR_I8_NEG: i8 = unsafe { intrinsics::unchecked_shr(5_i8, -1) };
    | --------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -249,7 +249,7 @@ LL | const SHR_I8_NEG: i8 = unsafe { intrinsics::unchecked_shr(5_i8, -1) };
    |                                 Overflowing shift by 255 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:97:35
+  --> $DIR/const-int-unchecked.rs:98:35
    |
 LL | const SHR_I16_NEG: i16 = unsafe { intrinsics::unchecked_shr(5_16, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -257,7 +257,7 @@ LL | const SHR_I16_NEG: i16 = unsafe { intrinsics::unchecked_shr(5_16, -1) };
    |                                   Overflowing shift by 65535 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:99:35
+  --> $DIR/const-int-unchecked.rs:100:35
    |
 LL | const SHR_I32_NEG: i32 = unsafe { intrinsics::unchecked_shr(5_i32, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -265,7 +265,7 @@ LL | const SHR_I32_NEG: i32 = unsafe { intrinsics::unchecked_shr(5_i32, -1) };
    |                                   Overflowing shift by 4294967295 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:101:35
+  --> $DIR/const-int-unchecked.rs:102:35
    |
 LL | const SHR_I64_NEG: i64 = unsafe { intrinsics::unchecked_shr(5_i64, -1) };
    | ----------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -273,7 +273,7 @@ LL | const SHR_I64_NEG: i64 = unsafe { intrinsics::unchecked_shr(5_i64, -1) };
    |                                   Overflowing shift by 18446744073709551615 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:103:37
+  --> $DIR/const-int-unchecked.rs:104:37
    |
 LL | const SHR_I128_NEG: i128 = unsafe { intrinsics::unchecked_shr(5_i128, -1) };
    | ------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -281,7 +281,7 @@ LL | const SHR_I128_NEG: i128 = unsafe { intrinsics::unchecked_shr(5_i128, -1) }
    |                                     Overflowing shift by 340282366920938463463374607431768211455 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:109:40
+  --> $DIR/const-int-unchecked.rs:110:40
    |
 LL | const SHR_I8_NEG_RANDOM: i8 = unsafe { intrinsics::unchecked_shr(5_i8, -6) };
    | ---------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -289,7 +289,7 @@ LL | const SHR_I8_NEG_RANDOM: i8 = unsafe { intrinsics::unchecked_shr(5_i8, -6)
    |                                        Overflowing shift by 250 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:111:42
+  --> $DIR/const-int-unchecked.rs:112:42
    |
 LL | const SHR_I16_NEG_RANDOM: i16 = unsafe { intrinsics::unchecked_shr(5_16, -13) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -297,7 +297,7 @@ LL | const SHR_I16_NEG_RANDOM: i16 = unsafe { intrinsics::unchecked_shr(5_16, -1
    |                                          Overflowing shift by 65523 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:113:42
+  --> $DIR/const-int-unchecked.rs:114:42
    |
 LL | const SHR_I32_NEG_RANDOM: i32 = unsafe { intrinsics::unchecked_shr(5_i32, -25) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -305,7 +305,7 @@ LL | const SHR_I32_NEG_RANDOM: i32 = unsafe { intrinsics::unchecked_shr(5_i32, -
    |                                          Overflowing shift by 4294967271 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:115:42
+  --> $DIR/const-int-unchecked.rs:116:42
    |
 LL | const SHR_I64_NEG_RANDOM: i64 = unsafe { intrinsics::unchecked_shr(5_i64, -30) };
    | -----------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
@@ -313,12 +313,68 @@ LL | const SHR_I64_NEG_RANDOM: i64 = unsafe { intrinsics::unchecked_shr(5_i64, -
    |                                          Overflowing shift by 18446744073709551586 in `unchecked_shr`
 
 error: any use of this value will cause an error
-  --> $DIR/const-int-unchecked.rs:117:44
+  --> $DIR/const-int-unchecked.rs:118:44
    |
 LL | const SHR_I128_NEG_RANDOM: i128 = unsafe { intrinsics::unchecked_shr(5_i128, -93) };
    | -------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
    |                                            |
    |                                            Overflowing shift by 340282366920938463463374607431768211363 in `unchecked_shr`
 
-error: aborting due to 40 previous errors
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:123:25
+   |
+LL | const _: u16 = unsafe { std::intrinsics::unchecked_add(40000u16, 30000) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         Overflow executing `unchecked_add`
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:126:25
+   |
+LL | const _: u32 = unsafe { std::intrinsics::unchecked_sub(14u32, 22) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         Overflow executing `unchecked_sub`
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:129:25
+   |
+LL | const _: u16 = unsafe { std::intrinsics::unchecked_mul(300u16, 250u16) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         Overflow executing `unchecked_mul`
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:132:25
+   |
+LL | const _: i32 = unsafe { std::intrinsics::unchecked_div(1, 0) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         dividing by zero
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:134:25
+   |
+LL | const _: i32 = unsafe { std::intrinsics::unchecked_div(i32::min_value(), -1) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         Overflow executing `unchecked_div`
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:137:25
+   |
+LL | const _: i32 = unsafe { std::intrinsics::unchecked_rem(1, 0) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         calculating the remainder with a divisor of zero
+
+error: any use of this value will cause an error
+  --> $DIR/const-int-unchecked.rs:139:25
+   |
+LL | const _: i32 = unsafe { std::intrinsics::unchecked_rem(i32::min_value(), -1) };
+   | ------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---
+   |                         |
+   |                         Overflow executing `unchecked_rem`
+
+error: aborting due to 47 previous errors
 
diff --git a/src/tools/publish_toolstate.py b/src/tools/publish_toolstate.py
index 61762ae1d9b04..967333c1ace4f 100755
--- a/src/tools/publish_toolstate.py
+++ b/src/tools/publish_toolstate.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-## This script publishes the new "current" toolstate in the toolstate repo (not to be
-## confused with publishing the test results, which happens in
-## `src/ci/docker/x86_64-gnu-tools/checktools.sh`).
-## It is set as callback for `src/ci/docker/x86_64-gnu-tools/repo.sh` by the CI scripts
-## when a new commit lands on `master` (i.e., after it passed all checks on `auto`).
+# This script publishes the new "current" toolstate in the toolstate repo (not to be
+# confused with publishing the test results, which happens in
+# `src/ci/docker/x86_64-gnu-tools/checktools.sh`).
+# It is set as callback for `src/ci/docker/x86_64-gnu-tools/repo.sh` by the CI scripts
+# when a new commit lands on `master` (i.e., after it passed all checks on `auto`).
 
 from __future__ import print_function
 
@@ -103,6 +103,7 @@ def validate_maintainers(repo, github_token):
         print("The build will fail due to this.")
         exit(1)
 
+
 def read_current_status(current_commit, path):
     '''Reads build status of `current_commit` from content of `history/*.tsv`
     '''
@@ -113,14 +114,17 @@ def read_current_status(current_commit, path):
                 return json.loads(status)
     return {}
 
+
 def gh_url():
     return os.environ['TOOLSTATE_ISSUES_API_URL']
 
+
 def maybe_delink(message):
     if os.environ.get('TOOLSTATE_SKIP_MENTIONS') is not None:
         return message.replace("@", "")
     return message
 
+
 def issue(
     tool,
     status,
@@ -164,6 +168,7 @@ def issue(
     ))
     response.read()
 
+
 def update_latest(
     current_commit,
     relevant_pr_number,
@@ -194,7 +199,7 @@ def update_latest(
         for status in latest:
             tool = status['tool']
             changed = False
-            create_issue_for_status = None # set to the status that caused the issue
+            create_issue_for_status = None  # set to the status that caused the issue
 
             for os, s in current_status.items():
                 old = status[os]