Auto merge of #25688 - nham:E0055_E0192, r=alexcrichton

 - Adds explanations for E0055, E0089, E0192, E0261-E0263, E0318
 - Improves explanations for E0250, E0368, E0372.
 - Converts 15 diagnostics to have error codes (E0380-E0394). Adds an explanation for E0380.
 - The E0087-E0090 messages currently look like "expected {} parameter(s) found {} parameter(s)". This changes them to either use "parameter" or "parameters", based on the number.

This is, in part, more progress towards #24407

Author: bors

src/librustc/diagnostics.rs

@@ -396,6 +396,54 @@ enum Method { GET, POST }
 ```
 "##,
 
+E0261: r##"
+When using a lifetime like `'a` in a type, it must be declared before being
+used.
+
+These two examples illustrate the problem:
+
+```
+// error, use of undeclared lifetime name `'a`
+fn foo(x: &'a str) { }
+
+struct Foo {
+    // error, use of undeclared lifetime name `'a`
+    x: &'a str,
+}
+```
+
+These can be fixed by declaring lifetime parameters:
+
+```
+fn foo<'a>(x: &'a str) { }
+
+struct Foo<'a> {
+    x: &'a str,
+}
+```
+"##,
+
+E0262: r##"
+Declaring certain lifetime names in parameters is disallowed. For example,
+because the `'static` lifetime is a special built-in lifetime name denoting
+the lifetime of the entire program, this is an error:
+
+```
+// error, illegal lifetime parameter name `'static`
+fn foo<'static>(x: &'static str) { }
+```
+"##,
+
+E0263: r##"
+A lifetime name cannot be declared more than once in the same scope. For
+example:
+
+```
+// error, lifetime name `'a` declared twice in the same scope
+fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str) { }
+```
+"##,
+
 E0265: r##"
 This error indicates that a static or constant references itself.
 All statics and constants need to resolve to a value in an acyclic manner.
@@ -814,9 +862,6 @@ register_diagnostics! {
     E0136,
     E0138,
     E0139,
-    E0261, // use of undeclared lifetime name
-    E0262, // illegal lifetime parameter name
-    E0263, // lifetime name declared twice in same scope
     E0264, // unknown external lang item
     E0266, // expected item
     E0269, // not all control paths return a value
@@ -846,5 +891,7 @@ register_diagnostics! {
     E0315, // cannot invoke closure outside of its lifetime
     E0316, // nested quantification of lifetimes
     E0370, // discriminant overflow
-    E0378  // method calls limited to constant inherent methods
+    E0378, // method calls limited to constant inherent methods
+    E0394  // cannot refer to other statics by value, use the address-of
+           // operator or a constant instead
 }

src/librustc/middle/check_const.rs

@@ -762,9 +762,9 @@ impl<'a, 'tcx> euv::Delegate<'tcx> for CheckCrateVisitor<'a, 'tcx> {
                         // statics cannot be consumed by value at any time, that would imply
                         // that they're an initializer (what a const is for) or kept in sync
                         // over time (not feasible), so deny it outright.
-                        self.tcx.sess.span_err(consume_span,
-                            "cannot refer to other statics by value, use the \
-                             address-of operator or a constant instead");
+                        span_err!(self.tcx.sess, consume_span, E0394,
+                                  "cannot refer to other statics by value, use the \
+                                   address-of operator or a constant instead");
                     }
                     break;
                 }

src/librustc_borrowck/borrowck/mod.rs

@@ -603,11 +603,12 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
         let (ol, moved_lp_msg) = match the_move.kind {
             move_data::Declared => {
-                self.tcx.sess.span_err(
-                    use_span,
-                    &format!("{} of possibly uninitialized variable: `{}`",
-                            verb,
-                            self.loan_path_to_string(lp)));
+                span_err!(
+                    self.tcx.sess, use_span, E0381,
+                    "{} of possibly uninitialized variable: `{}`",
+                    verb,
+                    self.loan_path_to_string(lp));
+
                 (self.loan_path_to_string(moved_lp),
                  String::new())
             }
@@ -644,12 +645,10 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                 let msg = if !has_fork && partial { "partially " }
                           else if has_fork && !has_common { "collaterally "}
                           else { "" };
-                self.tcx.sess.span_err(
-                    use_span,
-                    &format!("{} of {}moved value: `{}`",
-                            verb,
-                            msg,
-                            nl));
+                span_err!(
+                    self.tcx.sess, use_span, E0382,
+                    "{} of {}moved value: `{}`",
+                    verb, msg, nl);
                 (ol, moved_lp_msg)
             }
         };
@@ -762,23 +761,21 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
             &self,
             span: Span,
             lp: &LoanPath<'tcx>) {
-        self.tcx
-            .sess
-            .span_err(span,
-                      &format!("partial reinitialization of uninitialized \
-                               structure `{}`",
-                               self.loan_path_to_string(lp)));
+        span_err!(
+            self.tcx.sess, span, E0383,
+            "partial reinitialization of uninitialized structure `{}`",
+            self.loan_path_to_string(lp));
     }
 
     pub fn report_reassigned_immutable_variable(&self,
                                                 span: Span,
                                                 lp: &LoanPath<'tcx>,
                                                 assign:
                                                 &move_data::Assignment) {
-        self.tcx.sess.span_err(
-            span,
-            &format!("re-assignment of immutable variable `{}`",
-                    self.loan_path_to_string(lp)));
+        span_err!(
+            self.tcx.sess, span, E0384,
+            "re-assignment of immutable variable `{}`",
+            self.loan_path_to_string(lp));
         self.tcx.sess.span_note(assign.span, "prior assignment occurs here");
     }
 
@@ -896,21 +893,19 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
 
         match cause {
             mc::AliasableOther => {
-                self.tcx.sess.span_err(
-                    span,
-                    &format!("{} in an aliasable location",
-                             prefix));
+                span_err!(
+                    self.tcx.sess, span, E0385,
+                    "{} in an aliasable location", prefix);
             }
             mc::AliasableReason::UnaliasableImmutable => {
-                self.tcx.sess.span_err(
-                    span,
-                    &format!("{} in an immutable container",
-                             prefix));
+                span_err!(
+                    self.tcx.sess, span, E0386,
+                    "{} in an immutable container", prefix);
             }
             mc::AliasableClosure(id) => {
-                self.tcx.sess.span_err(span,
-                                       &format!("{} in a captured outer \
-                                                variable in an `Fn` closure", prefix));
+                span_err!(
+                    self.tcx.sess, span, E0387,
+                    "{} in a captured outer variable in an `Fn` closure", prefix);
                 if let BorrowViolation(euv::ClosureCapture(_)) = kind {
                     // The aliasability violation with closure captures can
                     // happen for nested closures, so we know the enclosing
@@ -925,14 +920,14 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
             }
             mc::AliasableStatic(..) |
             mc::AliasableStaticMut(..) => {
-                self.tcx.sess.span_err(
-                    span,
-                    &format!("{} in a static location", prefix));
+                span_err!(
+                    self.tcx.sess, span, E0388,
+                    "{} in a static location", prefix);
             }
             mc::AliasableBorrowed => {
-                self.tcx.sess.span_err(
-                    span,
-                    &format!("{} in a `&` reference", prefix));
+                span_err!(
+                    self.tcx.sess, span, E0389,
+                    "{} in a `&` reference", prefix);
             }
         }
 

src/librustc_borrowck/diagnostics.rs

@@ -10,6 +10,31 @@
 
 #![allow(non_snake_case)]
 
+register_long_diagnostics! {
+
+E0381: r##"
+It is not allowed to use or capture an uninitialized variable. For example:
+
+```
+fn main() {
+    let x: i32;
+    let y = x; // error, use of possibly uninitialized variable
+```
+
+To fix this, ensure that any declared variables are initialized before being
+used.
+"##
+
+}
+
 register_diagnostics! {
-    E0373 // closure may outlive current fn, but it borrows {}, which is owned by current fn
+    E0373, // closure may outlive current fn, but it borrows {}, which is owned by current fn
+    E0382, // use of partially/collaterally moved value
+    E0383, // partial reinitialization of uninitialized structure
+    E0384, // reassignment of immutable variable
+    E0385, // {} in an aliasable location
+    E0386, // {} in an immutable container
+    E0387, // {} in a captured outer variable in an `Fn` closure
+    E0388, // {} in a static location
+    E0389  // {} in a `&` reference
 }

src/librustc_typeck/astconv.rs

@@ -437,13 +437,12 @@ fn create_substs_for_ast_path<'tcx>(
             // defaults. This will lead to an ICE if we are not
             // careful!
             if self_ty.is_none() && ty::type_has_self(default) {
-                tcx.sess.span_err(
-                    span,
-                    &format!("the type parameter `{}` must be explicitly specified \
-                              in an object type because its default value `{}` references \
-                              the type `Self`",
-                             param.name.user_string(tcx),
-                             default.user_string(tcx)));
+                span_err!(tcx.sess, span, E0393,
+                          "the type parameter `{}` must be explicitly specified \
+                           in an object type because its default value `{}` references \
+                           the type `Self`",
+                          param.name.user_string(tcx),
+                          default.user_string(tcx));
                 substs.types.push(TypeSpace, tcx.types.err);
             } else {
                 // This is a default type parameter.

src/librustc_typeck/check/mod.rs

@@ -4688,9 +4688,12 @@ pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
                 } else if i == type_count {
                     span_err!(fcx.tcx().sess, typ.span, E0087,
                         "too many type parameters provided: \
-                         expected at most {} parameter(s), \
-                         found {} parameter(s)",
-                         type_count, data.types.len());
+                         expected at most {} parameter{}, \
+                         found {} parameter{}",
+                         type_count,
+                         if type_count == 1 {""} else {"s"},
+                         data.types.len(),
+                         if data.types.len() == 1 {""} else {"s"});
                     substs.types.truncate(space, 0);
                     break;
                 }
@@ -4713,9 +4716,11 @@ pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
                 } else if i == region_count {
                     span_err!(fcx.tcx().sess, lifetime.span, E0088,
                         "too many lifetime parameters provided: \
-                         expected {} parameter(s), found {} parameter(s)",
+                         expected {} parameter{}, found {} parameter{}",
                         region_count,
-                        data.lifetimes.len());
+                        if region_count == 1 {""} else {"s"},
+                        data.lifetimes.len(),
+                        if data.lifetimes.len() == 1 {""} else {"s"});
                     substs.mut_regions().truncate(space, 0);
                     break;
                 }
@@ -4805,9 +4810,12 @@ pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
             let qualifier =
                 if desired.len() != required_len { "at least " } else { "" };
             span_err!(fcx.tcx().sess, span, E0089,
-                "too few type parameters provided: expected {}{} parameter(s) \
-                , found {} parameter(s)",
-                qualifier, required_len, provided_len);
+                "too few type parameters provided: expected {}{} parameter{}, \
+                 found {} parameter{}",
+                qualifier, required_len,
+                if required_len == 1 {""} else {"s"},
+                provided_len,
+                if provided_len == 1 {""} else {"s"});
             substs.types.replace(space, repeat(fcx.tcx().types.err).take(desired.len()).collect());
             return;
         }
@@ -4858,9 +4866,12 @@ pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
         // Otherwise, too few were provided. Report an error and then
         // use inference variables.
         span_err!(fcx.tcx().sess, span, E0090,
-            "too few lifetime parameters provided: expected {} parameter(s), \
-             found {} parameter(s)",
-            desired.len(), provided_len);
+            "too few lifetime parameters provided: expected {} parameter{}, \
+             found {} parameter{}",
+            desired.len(),
+            if desired.len() == 1 {""} else {"s"},
+            provided_len,
+            if provided_len == 1 {""} else {"s"});
 
         substs.mut_regions().replace(
             space,

src/librustc_typeck/check/wf.rs

@@ -124,10 +124,9 @@ impl<'ccx, 'tcx> CheckTypeWellFormedVisitor<'ccx, 'tcx> {
                 reject_non_type_param_bounds(ccx.tcx, item.span, &trait_predicates);
                 if ty::trait_has_default_impl(ccx.tcx, local_def(item.id)) {
                     if !items.is_empty() {
-                        ccx.tcx.sess.span_err(
-                            item.span,
-                            "traits with default impls (`e.g. unsafe impl Trait for ..`) must \
-                            have no methods or associated items")
+                        span_err!(ccx.tcx.sess, item.span, E0380,
+                                  "traits with default impls (`e.g. unsafe impl \
+                                  Trait for ..`) must have no methods or associated items")
                     }
                 }
             }
@@ -353,10 +352,8 @@ impl<'ccx, 'tcx> CheckTypeWellFormedVisitor<'ccx, 'tcx> {
                          span: Span,
                          param_name: ast::Name)
     {
-        self.tcx().sess.span_err(
-            span,
-            &format!("parameter `{}` is never used",
-                     param_name.user_string(self.tcx())));
+        span_err!(self.tcx().sess, span, E0392,
+            "parameter `{}` is never used", param_name.user_string(self.tcx()));
 
         let suggested_marker_id = self.tcx().lang_items.phantom_data();
         match suggested_marker_id {

src/librustc_typeck/coherence/orphan.rs

@@ -48,10 +48,9 @@ impl<'cx, 'tcx> OrphanChecker<'cx, 'tcx> {
         match lang_def_id {
             Some(lang_def_id) if lang_def_id == impl_def_id => { /* OK */ },
             _ => {
-                self.tcx.sess.span_err(
-                    span,
-                    &format!("only a single inherent implementation marked with `#[lang = \"{}\"]` \
-                              is allowed for the `{}` primitive", lang, ty));
+                span_err!(self.tcx.sess, span, E0390,
+                          "only a single inherent implementation marked with `#[lang = \"{}\"]` \
+                           is allowed for the `{}` primitive", lang, ty);
             }
         }
     }

src/librustc_typeck/collect.rs

@@ -236,9 +236,8 @@ impl<'a,'tcx> CrateCtxt<'a,'tcx> {
         assert!(!cycle.is_empty());
         let tcx = self.tcx;
 
-        tcx.sess.span_err(
-            span,
-            &format!("unsupported cyclic reference between types/traits detected"));
+        span_err!(tcx.sess, span, E0391,
+            "unsupported cyclic reference between types/traits detected");
 
         match cycle[0] {
             AstConvRequest::GetItemTypeScheme(def_id) |