Account for bad placeholder types in where clauses

4 files changed, 158 insertions, 55 deletions

diff --git a/src/test/ui/did_you_mean/bad-assoc-ty.rs b/src/test/ui/did_you_mean/bad-assoc-ty.rs
index 00845a17b11..e66b432ede2 100644
--- a/src/test/ui/did_you_mean/bad-assoc-ty.rs
+++ b/src/test/ui/did_you_mean/bad-assoc-ty.rs
@@ -49,4 +49,36 @@ trait K<A, B> {}
 fn foo<X: K<_, _>>(x: X) {}
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 
+fn bar<F>(_: F) where F: Fn() -> _ {}
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+
+fn baz<F: Fn() -> _>(_: F) {}
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+
+struct L<F>(F) where F: Fn() -> _;
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+struct M<F> where F: Fn() -> _ {
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    a: F,
+}
+enum N<F> where F: Fn() -> _ {
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+    Foo(F),
+}
+
+union O<F> where F: Fn() -> _ {
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+//~| ERROR unions with non-`Copy` fields are unstable
+    foo: F,
+}
+
+trait P<F> where F: Fn() -> _ {
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+}
+
+trait Q {
+    fn foo<F>(_: F) where F: Fn() -> _ {}
+    //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+}
+
 fn main() {}
diff --git a/src/test/ui/did_you_mean/bad-assoc-ty.stderr b/src/test/ui/did_you_mean/bad-assoc-ty.stderr
index 6d5f3d9f143..875c02bae4a 100644
--- a/src/test/ui/did_you_mean/bad-assoc-ty.stderr
+++ b/src/test/ui/did_you_mean/bad-assoc-ty.stderr
@@ -57,6 +57,19 @@ LL | type J = ty!(u8);
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
+error[E0658]: unions with non-`Copy` fields are unstable
+  --> $DIR/bad-assoc-ty.rs:69:1
+   |
+LL | / union O<F> where F: Fn() -> _ {
+LL | |
+LL | |
+LL | |     foo: F,
+LL | | }
+   | |_^
+   |
+   = note: see issue #55149 <https://github.com/rust-lang/rust/issues/55149> for more information
+   = help: add `#![feature(untagged_unions)]` to the crate attributes to enable
+
 error[E0223]: ambiguous associated type
   --> $DIR/bad-assoc-ty.rs:1:10
    |
@@ -129,8 +142,101 @@ LL | fn foo<X: K<_, _>>(x: X) {}
    |             ^  ^ not allowed in type signatures
    |             |
    |             not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | fn foo<X, T: K<T, T>>(x: X) {}
+   |         ^^^    ^  ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:52:34
+   |
+LL | fn bar<F>(_: F) where F: Fn() -> _ {}
+   |                                  ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | fn bar<F, T>(_: F) where F: Fn() -> T {}
+   |         ^^^                         ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:55:19
+   |
+LL | fn baz<F: Fn() -> _>(_: F) {}
+   |                   ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | fn baz<F, T: Fn() -> T>(_: F) {}
+   |         ^^^          ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:58:33
+   |
+LL | struct L<F>(F) where F: Fn() -> _;
+   |                                 ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | struct L<F, T>(F) where F: Fn() -> T;
+   |           ^^^                      ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:60:30
+   |
+LL | struct M<F> where F: Fn() -> _ {
+   |                              ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | struct M<F, T> where F: Fn() -> T {
+   |           ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:64:28
+   |
+LL | enum N<F> where F: Fn() -> _ {
+   |                            ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | enum N<F, T> where F: Fn() -> T {
+   |         ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:69:29
+   |
+LL | union O<F> where F: Fn() -> _ {
+   |                             ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | union O<F, T> where F: Fn() -> T {
+   |          ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:75:29
+   |
+LL | trait P<F> where F: Fn() -> _ {
+   |                             ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL | trait P<F, T> where F: Fn() -> T {
+   |          ^^^                   ^
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/bad-assoc-ty.rs:80:38
+   |
+LL |     fn foo<F>(_: F) where F: Fn() -> _ {}
+   |                                      ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |     fn foo<F, T>(_: F) where F: Fn() -> T {}
+   |             ^^^                         ^
 
-error: aborting due to 20 previous errors
+error: aborting due to 29 previous errors
 
-Some errors have detailed explanations: E0121, E0223.
+Some errors have detailed explanations: E0121, E0223, E0658.
 For more information about an error, try `rustc --explain E0121`.
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.rs b/src/test/ui/typeck/typeck_type_placeholder_item.rs
index 6cd2b8c75b6..5444fc62d82 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item.rs
+++ b/src/test/ui/typeck/typeck_type_placeholder_item.rs
@@ -158,12 +158,9 @@ 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!()
 }
 
@@ -178,14 +175,12 @@ struct BadStruct2<_, T>(_, T);
 
 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
 }
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item.stderr b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
index dc86ab30dfe..955765e1175 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item.stderr
+++ b/src/test/ui/typeck/typeck_type_placeholder_item.stderr
@@ -11,25 +11,25 @@ LL | trait BadTrait<_> {}
    |                ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:170:19
+  --> $DIR/typeck_type_placeholder_item.rs:167:19
    |
 LL | struct BadStruct1<_, _>(_);
    |                   ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:170:22
+  --> $DIR/typeck_type_placeholder_item.rs:167:22
    |
 LL | struct BadStruct1<_, _>(_);
    |                      ^ expected identifier, found reserved identifier
 
 error: expected identifier, found reserved identifier `_`
-  --> $DIR/typeck_type_placeholder_item.rs:175:19
+  --> $DIR/typeck_type_placeholder_item.rs:172:19
    |
 LL | struct BadStruct2<_, T>(_, T);
    |                   ^ expected identifier, found reserved identifier
 
 error: associated constant in `impl` without body
-  --> $DIR/typeck_type_placeholder_item.rs:208:5
+  --> $DIR/typeck_type_placeholder_item.rs:203:5
    |
 LL |     const C: _;
    |     ^^^^^^^^^^-
@@ -37,7 +37,7 @@ LL |     const C: _;
    |               help: provide a definition for the constant: `= <expr>;`
 
 error[E0403]: the name `_` is already used for a generic parameter in this item's generic parameters
-  --> $DIR/typeck_type_placeholder_item.rs:170:22
+  --> $DIR/typeck_type_placeholder_item.rs:167:22
    |
 LL | struct BadStruct1<_, _>(_);
    |                   -  ^ already used
@@ -352,18 +352,6 @@ LL | struct BadStruct<T>(T);
    |                  ^  ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:159:32
-   |
-LL | impl BadTrait<_> for BadStruct<_> {}
-   |                                ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:159:15
-   |
-LL | impl BadTrait<_> for BadStruct<_> {}
-   |               ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
   --> $DIR/typeck_type_placeholder_item.rs:159:15
    |
 LL | impl BadTrait<_> for BadStruct<_> {}
@@ -377,13 +365,13 @@ LL | impl<T> BadTrait<T> for BadStruct<T> {}
    |     ^^^          ^                ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:164:34
+  --> $DIR/typeck_type_placeholder_item.rs:162:34
    |
 LL | fn impl_trait() -> impl BadTrait<_> {
    |                                  ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:170:25
+  --> $DIR/typeck_type_placeholder_item.rs:167:25
    |
 LL | struct BadStruct1<_, _>(_);
    |                         ^ not allowed in type signatures
@@ -394,7 +382,7 @@ LL | struct BadStruct1<T, _>(T);
    |                   ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:175:25
+  --> $DIR/typeck_type_placeholder_item.rs:172:25
    |
 LL | struct BadStruct2<_, T>(_, T);
    |                         ^ not allowed in type signatures
@@ -405,13 +393,7 @@ LL | struct BadStruct2<K, T>(K, T);
    |                   ^     ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:179:14
-   |
-LL | type X = Box<_>;
-   |              ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:179:14
+  --> $DIR/typeck_type_placeholder_item.rs:176:14
    |
 LL | type X = Box<_>;
    |              ^ not allowed in type signatures
@@ -531,37 +513,25 @@ LL |         fn clone_from<T>(&mut self, other: T) { *self = FnTest9; }
    |                      ^^^                   ^
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:164:34
-   |
-LL | fn impl_trait() -> impl BadTrait<_> {
-   |                                  ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:186:21
-   |
-LL | type Y = impl Trait<_>;
-   |                     ^ not allowed in type signatures
-
-error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:186:21
+  --> $DIR/typeck_type_placeholder_item.rs:182:21
    |
 LL | type Y = impl Trait<_>;
    |                     ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:195:14
+  --> $DIR/typeck_type_placeholder_item.rs:190:14
    |
 LL |     type B = _;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:197:14
+  --> $DIR/typeck_type_placeholder_item.rs:192:14
    |
 LL |     const C: _;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:199:14
+  --> $DIR/typeck_type_placeholder_item.rs:194:14
    |
 LL |     const D: _ = 42;
    |              ^
@@ -606,25 +576,25 @@ LL |         fn clone(&self) -> _ { FnTest9 }
    |                            help: replace with the correct return type: `main::FnTest9`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:204:14
+  --> $DIR/typeck_type_placeholder_item.rs:199:14
    |
 LL |     type A = _;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:206:14
+  --> $DIR/typeck_type_placeholder_item.rs:201:14
    |
 LL |     type B = _;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:208:14
+  --> $DIR/typeck_type_placeholder_item.rs:203:14
    |
 LL |     const C: _;
    |              ^ not allowed in type signatures
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item.rs:211:14
+  --> $DIR/typeck_type_placeholder_item.rs:206:14
    |
 LL |     const D: _ = 42;
    |              ^
@@ -632,7 +602,7 @@ LL |     const D: _ = 42;
    |              not allowed in type signatures
    |              help: replace `_` with the correct type: `i32`
 
-error: aborting due to 71 previous errors
+error: aborting due to 66 previous errors
 
 Some errors have detailed explanations: E0121, E0282, E0403.
 For more information about an error, try `rustc --explain E0121`.