Backport only: avoid ICE on bad placeholder type

src/librustc_typeck/collect.rs

@@ -319,7 +319,7 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
     }
 
     fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
-        self.tcx().sess.delay_span_bug(span, "bad placeholder type");
+        placeholder_type_error(self.tcx(), span, &[], vec![span], false);
         self.tcx().types.err
     }
 

src/test/ui/did_you_mean/bad-assoc-ty.rs

@@ -17,6 +17,7 @@ type D = (u8, u8)::AssocTy;
 type E = _::AssocTy;
 //~^ ERROR missing angle brackets in associated item path
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 type F = &'static (u8)::AssocTy;
 //~^ ERROR missing angle brackets in associated item path

src/test/ui/did_you_mean/bad-assoc-ty.stderr

@@ -29,25 +29,25 @@ LL | type E = _::AssocTy;
    |          ^^^^^^^^^^ help: try: `<_>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:21:19
+  --> $DIR/bad-assoc-ty.rs:22:19
    |
 LL | type F = &'static (u8)::AssocTy;
    |                   ^^^^^^^^^^^^^ help: try: `<(u8)>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:27:10
+  --> $DIR/bad-assoc-ty.rs:28:10
    |
 LL | type G = dyn 'static + (Send)::AssocTy;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `<dyn 'static + (Send)>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:44:10
+  --> $DIR/bad-assoc-ty.rs:45:10
    |
 LL | type I = ty!()::AssocTy;
    |          ^^^^^^^^^^^^^^ help: try: `<ty!()>::AssocTy`
 
 error: missing angle brackets in associated item path
-  --> $DIR/bad-assoc-ty.rs:37:19
+  --> $DIR/bad-assoc-ty.rs:38:19
    |
 LL |     ($ty: ty) => ($ty::AssocTy);
    |                   ^^^^^^^^^^^^ help: try: `<$ty>::AssocTy`
@@ -87,26 +87,32 @@ error[E0121]: the type placeholder `_` is not allowed within types on item signa
 LL | type E = _::AssocTy;
    |          ^ not allowed in type signatures
 
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:17:10
+   |
+LL | type E = _::AssocTy;
+   |          ^ not allowed in type signatures
+
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:21:19
+  --> $DIR/bad-assoc-ty.rs:22:19
    |
 LL | type F = &'static (u8)::AssocTy;
    |                   ^^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:27:10
+  --> $DIR/bad-assoc-ty.rs:28:10
    |
 LL | type G = dyn 'static + (Send)::AssocTy;
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<(dyn std::marker::Send + 'static) as Trait>::AssocTy`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:33:10
+  --> $DIR/bad-assoc-ty.rs:34:10
    |
 LL | type H = Fn(u8) -> (u8)::Output;
    |          ^^^^^^^^^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<(dyn std::ops::Fn(u8) -> u8 + 'static) as Trait>::Output`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:37:19
+  --> $DIR/bad-assoc-ty.rs:38:19
    |
 LL |     ($ty: ty) => ($ty::AssocTy);
    |                   ^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
@@ -117,12 +123,12 @@ LL | type J = ty!(u8);
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0223]: ambiguous associated type
-  --> $DIR/bad-assoc-ty.rs:44:10
+  --> $DIR/bad-assoc-ty.rs:45:10
    |
 LL | type I = ty!()::AssocTy;
    |          ^^^^^^^^^^^^^^ help: use fully-qualified syntax: `<u8 as Trait>::AssocTy`
 
-error: aborting due to 19 previous errors
+error: aborting due to 20 previous errors
 
 Some errors have detailed explanations: E0121, E0223.
 For more information about an error, try `rustc --explain E0121`.

src/test/ui/self/self-infer.rs

@@ -2,7 +2,9 @@ struct S;
 
 impl S {
     fn f(self: _) {} //~ERROR the type placeholder `_` is not allowed within types on item sig
+    //~^ ERROR the type placeholder `_` is not allowed within types on item sig
     fn g(self: &_) {} //~ERROR the type placeholder `_` is not allowed within types on item sig
+    //~^ ERROR the type placeholder `_` is not allowed within types on item sig
 }
 
 fn main() {}

src/test/ui/self/self-infer.stderr

@@ -1,3 +1,9 @@
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/self-infer.rs:4:16
+   |
+LL |     fn f(self: _) {}
+   |                ^ not allowed in type signatures
+
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/self-infer.rs:4:16
    |
@@ -10,7 +16,13 @@ LL |     fn f<T>(self: T) {}
    |         ^^^       ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/self-infer.rs:5:17
+  --> $DIR/self-infer.rs:6:17
+   |
+LL |     fn g(self: &_) {}
+   |                 ^ not allowed in type signatures
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/self-infer.rs:6:17
    |
 LL |     fn g(self: &_) {}
    |                 ^ not allowed in type signatures
@@ -20,6 +32,6 @@ help: use type parameters instead
 LL |     fn g<T>(self: &T) {}
    |         ^^^        ^
 
-error: aborting due to 2 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0121`.

src/test/ui/typeck/typeck_type_placeholder_item.rs

@@ -19,19 +19,24 @@ static TEST5: (_, _) = (1, 2);
 
 fn test6(_: _) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test6_b<T>(_: _, _: T) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test6_c<T, K, L, A, B>(_: _, _: (T, K, L, A, B)) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test7(x: _) { let _x: usize = x; }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn test8(_f: fn() -> _) { }
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 struct Test9;
 
@@ -41,6 +46,7 @@ impl Test9 {
 
     fn test10(&self, _x : _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 fn test11(x: &usize) -> &_ {
@@ -59,12 +65,16 @@ impl Clone for Test9 {
 
     fn clone_from(&mut self, other: _) { *self = Test9; }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 struct Test10 {
     a: _,
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     b: (_, _),
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 pub fn main() {
@@ -92,13 +102,16 @@ pub fn main() {
 
     fn fn_test6(_: _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     fn fn_test7(x: _) { let _x: usize = x; }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     fn fn_test8(_f: fn() -> _) { }
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
     //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
     struct FnTest9;
 
@@ -108,6 +121,7 @@ pub fn main() {
 
         fn fn_test10(&self, _x : _) { }
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     impl Clone for FnTest9 {
@@ -116,12 +130,16 @@ pub fn main() {
 
         fn clone_from(&mut self, other: _) { *self = FnTest9; }
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     struct FnTest10 {
         a: _,
         //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
         b: (_, _),
+        //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+        //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     }
 
     fn fn_test11(_: _) -> (_, _) { panic!() }
@@ -138,28 +156,40 @@ pub fn main() {
 trait T {
     fn method_test1(&self, x: _);
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn method_test2(&self, x: _) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn method_test3(&self) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test1(x: _);
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test2(x: _) -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
     fn assoc_fn_test3() -> _;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    //~| ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
 struct BadStruct<_>(_);
 //~^ ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 trait BadTrait<_> {}
 //~^ ERROR expected identifier, found reserved identifier `_`
 impl BadTrait<_> for BadStruct<_> {}
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 fn impl_trait() -> impl BadTrait<_> {
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
     unimplemented!()
 }
 
@@ -168,18 +198,22 @@ struct BadStruct1<_, _>(_);
 //~| ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the name `_` is already used
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 struct BadStruct2<_, T>(_, T);
 //~^ ERROR expected identifier, found reserved identifier `_`
 //~| ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 type X = Box<_>;
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 
 struct Struct;
 trait Trait<T> {}
 impl Trait<usize> for Struct {}
 type Y = impl Trait<_>;
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR the type placeholder `_` is not allowed within types on item signatures
 fn foo() -> Y {
     Struct
 }