Auto merge of #40651 - frewsxcv:rollup, r=frewsxcv

Rollup of 13 pull requests

- Successful merges: #40441, #40445, #40562, #40564, #40583, #40588, #40589, #40590, #40603, #40611, #40621, #40646, #40648
- Failed merges:

Author: bors

src/bootstrap/clean.rs

@@ -22,9 +22,9 @@ use std::path::Path;
 use Build;
 
 pub fn clean(build: &Build) {
-    rm_rf(build, "tmp".as_ref());
-    rm_rf(build, &build.out.join("tmp"));
-    rm_rf(build, &build.out.join("dist"));
+    rm_rf("tmp".as_ref());
+    rm_rf(&build.out.join("tmp"));
+    rm_rf(&build.out.join("dist"));
 
     for host in build.config.host.iter() {
         let entries = match build.out.join(host).read_dir() {
@@ -38,12 +38,12 @@ pub fn clean(build: &Build) {
                 continue
             }
             let path = t!(entry.path().canonicalize());
-            rm_rf(build, &path);
+            rm_rf(&path);
         }
     }
 }
 
-fn rm_rf(build: &Build, path: &Path) {
+fn rm_rf(path: &Path) {
     if !path.exists() {
         return
     }
@@ -55,7 +55,7 @@ fn rm_rf(build: &Build, path: &Path) {
         let file = t!(file).path();
 
         if file.is_dir() {
-            rm_rf(build, &file);
+            rm_rf(&file);
         } else {
             // On windows we can't remove a readonly file, and git will
             // often clone files as readonly. As a result, we have some

src/doc/unstable-book/src/SUMMARY.md

@@ -71,6 +71,7 @@
 - [repr_simd](repr-simd.md)
 - [rustc_attrs](rustc-attrs.md)
 - [rustc_diagnostic_macros](rustc-diagnostic-macros.md)
+- [rvalue_static_promotion](rvalue-static-promotion.md)
 - [sanitizer_runtime](sanitizer-runtime.md)
 - [simd](simd.md)
 - [simd_ffi](simd-ffi.md)

src/doc/unstable-book/src/rvalue-static-promotion.md

@@ -0,0 +1,23 @@
+# `rvalue_static_promotion`
+
+The tracking issue for this feature is: [#38865]
+
+[#38865]: https://github.com/rust-lang/rust/issues/38865
+
+------------------------
+
+The `rvalue_static_promotion` feature allows directly creating `'static` references to
+constant `rvalue`s, which in particular allowing for more concise code in the common case
+in which a `'static` reference is all that's needed.
+
+
+## Examples
+
+```rust
+#![feature(rvalue_static_promotion)]
+
+fn main() {
+    let DEFAULT_VALUE: &'static u32 = &42;
+    assert_eq!(*DEFAULT_VALUE, 42);
+}
+```

src/libcollections/slice.rs

@@ -230,7 +230,7 @@ impl<T> [T] {
         core_slice::SliceExt::first_mut(self)
     }
 
-    /// Returns the first and all the rest of the elements of a slice.
+    /// Returns the first and all the rest of the elements of a slice, or `None` if it is empty.
     ///
     /// # Examples
     ///
@@ -248,7 +248,7 @@ impl<T> [T] {
         core_slice::SliceExt::split_first(self)
     }
 
-    /// Returns the first and all the rest of the elements of a slice.
+    /// Returns the first and all the rest of the elements of a slice, or `None` if it is empty.
     ///
     /// # Examples
     ///
@@ -268,7 +268,7 @@ impl<T> [T] {
         core_slice::SliceExt::split_first_mut(self)
     }
 
-    /// Returns the last and all the rest of the elements of a slice.
+    /// Returns the last and all the rest of the elements of a slice, or `None` if it is empty.
     ///
     /// # Examples
     ///
@@ -287,7 +287,7 @@ impl<T> [T] {
 
     }
 
-    /// Returns the last and all the rest of the elements of a slice.
+    /// Returns the last and all the rest of the elements of a slice, or `None` if it is empty.
     ///
     /// # Examples
     ///
@@ -437,8 +437,8 @@ impl<T> [T] {
     /// The caller must ensure that the slice outlives the pointer this
     /// function returns, or else it will end up pointing to garbage.
     ///
-    /// Modifying the slice may cause its buffer to be reallocated, which
-    /// would also make any pointers to it invalid.
+    /// Modifying the container referenced by this slice may cause its buffer
+    /// to be reallocated, which would also make any pointers to it invalid.
     ///
     /// # Examples
     ///
@@ -463,8 +463,8 @@ impl<T> [T] {
     /// The caller must ensure that the slice outlives the pointer this
     /// function returns, or else it will end up pointing to garbage.
     ///
-    /// Modifying the slice may cause its buffer to be reallocated, which
-    /// would also make any pointers to it invalid.
+    /// Modifying the container referenced by this slice may cause its buffer
+    /// to be reallocated, which would also make any pointers to it invalid.
     ///
     /// # Examples
     ///

src/librustc/middle/mem_categorization.rs

@@ -195,6 +195,21 @@ pub struct cmt_<'tcx> {
 pub type cmt<'tcx> = Rc<cmt_<'tcx>>;
 
 impl<'tcx> cmt_<'tcx> {
+    pub fn get_def(&self) -> Option<ast::NodeId> {
+        match self.cat {
+            Categorization::Deref(ref cmt, ..) |
+            Categorization::Interior(ref cmt, _) |
+            Categorization::Downcast(ref cmt, _) => {
+                if let Categorization::Local(nid) = cmt.cat {
+                    Some(nid)
+                } else {
+                    None
+                }
+            }
+            _ => None
+        }
+    }
+
     pub fn get_field(&self, name: ast::Name) -> Option<DefId> {
         match self.cat {
             Categorization::Deref(ref cmt, ..) |
@@ -843,11 +858,10 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
         let promotable = self.tcx().rvalue_promotable_to_static.borrow().get(&id).cloned()
                                    .unwrap_or(false);
 
-        // Only promote `[T; 0]` before an RFC for rvalue promotions
-        // is accepted.
+        // When the corresponding feature isn't toggled, only promote `[T; 0]`.
         let promotable = match expr_ty.sty {
             ty::TyArray(_, 0) => true,
-            _ => promotable & false
+            _ => promotable && self.tcx().sess.features.borrow().rvalue_static_promotion,
         };
 
         // Compute maximum lifetime of this rvalue. This is 'static if

src/librustc_borrowck/borrowck/mod.rs

@@ -662,6 +662,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
     pub fn bckerr_to_diag(&self, err: &BckError<'tcx>) -> DiagnosticBuilder<'a> {
         let span = err.span.clone();
         let mut immutable_field = None;
+        let mut local_def = None;
 
         let msg = &match err.code {
             err_mutbl => {
@@ -711,6 +712,14 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                 }
                                 None
                             });
+                        local_def = err.cmt.get_def()
+                            .and_then(|nid| {
+                                if !self.tcx.hir.is_argument(nid) {
+                                    Some(self.tcx.hir.span(nid))
+                                } else {
+                                    None
+                                }
+                            });
 
                         format!("cannot borrow {} as mutable", descr)
                     }
@@ -741,6 +750,11 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
         if let Some((span, msg)) = immutable_field {
             db.span_label(span, &msg);
         }
+        if let Some(let_span) = local_def {
+            if let Ok(snippet) = self.tcx.sess.codemap().span_to_snippet(let_span) {
+                db.span_label(let_span, &format!("consider changing this to `mut {}`", snippet));
+            }
+        }
         db
     }
 
@@ -1109,6 +1123,11 @@ before rustc 1.16, this temporary lived longer - see issue #39283 \
                     } else {
                         db.span_label(*error_span, &format!("cannot borrow mutably"));
                     }
+                } else if let Categorization::Interior(ref cmt, _) = err.cmt.cat {
+                    if let mc::MutabilityCategory::McImmutable = cmt.mutbl {
+                        db.span_label(*error_span,
+                                      &"cannot mutably borrow immutable field");
+                    }
                 }
             }
         }

src/librustc_resolve/build_reduced_graph.rs

@@ -23,7 +23,7 @@ use {resolve_error, resolve_struct_error, ResolutionError};
 
 use rustc::middle::cstore::LoadedMacro;
 use rustc::hir::def::*;
-use rustc::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId};
+use rustc::hir::def_id::{CrateNum, BUILTIN_MACROS_CRATE, CRATE_DEF_INDEX, DefId};
 use rustc::ty;
 
 use std::cell::Cell;
@@ -496,6 +496,9 @@ impl<'a> Resolver<'a> {
         let def_id = self.macro_defs[&expansion];
         if let Some(id) = self.definitions.as_local_node_id(def_id) {
             self.local_macro_def_scopes[&id]
+        } else if def_id.krate == BUILTIN_MACROS_CRATE {
+            // FIXME(jseyfried): This happens when `include!()`ing a `$crate::` path, c.f, #40469.
+            self.graph_root
         } else {
             let module_def_id = ty::DefIdTree::parent(&*self, def_id).unwrap();
             self.get_extern_crate_root(module_def_id.krate)

src/librustdoc/clean/mod.rs

@@ -1387,7 +1387,7 @@ impl<'tcx> Clean<Item> for ty::AssociatedItem {
                         decl: decl,
                         abi: sig.abi(),
 
-                        // trait methods canot (currently, at least) be const
+                        // trait methods cannot (currently, at least) be const
                         constness: hir::Constness::NotConst,
                     })
                 } else {

src/librustdoc/html/render.rs

@@ -60,6 +60,7 @@ use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability;
 use rustc::hir;
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
+use rustc::session::config::nightly_options::is_nightly_build;
 use rustc_data_structures::flock;
 
 use clean::{self, AttributesExt, GetDefId, SelfTy, Mutability};
@@ -2316,9 +2317,10 @@ fn render_assoc_item(w: &mut fmt::Formatter,
             }
         };
         // FIXME(#24111): remove when `const_fn` is stabilized
-        let vis_constness = match UnstableFeatures::from_environment() {
-            UnstableFeatures::Allow => constness,
-            _ => hir::Constness::NotConst
+        let vis_constness = if is_nightly_build() {
+            constness
+        } else {
+            hir::Constness::NotConst
         };
         let prefix = format!("{}{}{:#}fn {}{:#}",
                              ConstnessSpace(vis_constness),

src/libstd/collections/hash/map.rs

@@ -222,8 +222,8 @@ const DISPLACEMENT_THRESHOLD: usize = 128;
 /// resistance against HashDoS attacks. The algorithm is randomly seeded, and a
 /// reasonable best-effort is made to generate this seed from a high quality,
 /// secure source of randomness provided by the host without blocking the
-/// program. Because of this, the randomness of the seed is dependant on the
-/// quality of the system's random number generator at the time it is created.
+/// program. Because of this, the randomness of the seed depends on the output
+/// quality of the system's random number generator when the seed is created.
 /// In particular, seeds generated when the system's entropy pool is abnormally
 /// low such as during system boot may be of a lower quality.
 ///