Rollup merge of rust-lang#136497 - Jarcho:fn_ctxt, r=compiler-errors

Report generic mismatches when calling bodyless trait functions

Don't know if there's an open issue for this. Just happened to notice this when working in that area.

The awkward extra spans added to the diagnostics of some tests (e.g. `trait-with-missing-associated-type-restriction`) is consistent with what happens for normal functions. Should probably be removed since that span doesn't seem to note anything useful.

First and third commit are both cleanups removing some unnecessary work. Second commit has the actual fix.

fixes rust-lang#135124

Author: matthiaskrgr

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -0,0 +1,20 @@
+// Used to ICE due to a size mismatch between the actual fake signature of `fold` and the
+// generated signature used reporting the parameter mismatch at the call site.
+// See issue #135124
+
+trait A  {
+    fn y(&self)
+    {
+        fn call() -> impl Sized {}
+        self.fold(call(), call());
+    }
+    fn fold<T>(&self, _: T, &self._) {}
+    //~^ ERROR unexpected `self` parameter in function
+    //~| ERROR expected one of `)` or `,`, found `.`
+    //~| ERROR identifier `self` is bound more than once in this parameter list
+    //~| WARNING anonymous parameters are deprecated
+    //~| WARNING this is accepted in the current edition
+    //~| ERROR the placeholder `_` is not allowed within types
+}
+
+fn main() {}

tests/crashes/135124.rs

@@ -0,0 +1,46 @@
+error: unexpected `self` parameter in function
+  --> $DIR/error-recovery-mismatch.rs:11:29
+   |
+LL |     fn fold<T>(&self, _: T, &self._) {}
+   |                             ^^^^^ must be the first parameter of an associated function
+
+error: expected one of `)` or `,`, found `.`
+  --> $DIR/error-recovery-mismatch.rs:11:34
+   |
+LL |     fn fold<T>(&self, _: T, &self._) {}
+   |                                  ^
+   |                                  |
+   |                                  expected one of `)` or `,`
+   |                                  help: missing `,`
+
+error[E0415]: identifier `self` is bound more than once in this parameter list
+  --> $DIR/error-recovery-mismatch.rs:11:30
+   |
+LL |     fn fold<T>(&self, _: T, &self._) {}
+   |                              ^^^^ used as parameter more than once
+
+warning: anonymous parameters are deprecated and will be removed in the next edition
+  --> $DIR/error-recovery-mismatch.rs:11:35
+   |
+LL |     fn fold<T>(&self, _: T, &self._) {}
+   |                                   ^ help: try naming the parameter or explicitly ignoring it: `_: _`
+   |
+   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018!
+   = note: for more information, see issue #41686 <https://github.com/rust-lang/rust/issues/41686>
+   = note: `#[warn(anonymous_parameters)]` on by default
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for functions
+  --> $DIR/error-recovery-mismatch.rs:11:35
+   |
+LL |     fn fold<T>(&self, _: T, &self._) {}
+   |                                   ^ not allowed in type signatures
+   |
+help: use type parameters instead
+   |
+LL |     fn fold<T, U>(&self, _: T, &self.U) {}
+   |              +++                     ~
+
+error: aborting due to 4 previous errors; 1 warning emitted
+
+Some errors have detailed explanations: E0121, E0415.
+For more information about an error, try `rustc --explain E0121`.

tests/ui/fn/error-recovery-mismatch.rs

@@ -0,0 +1,10 @@
+trait Foo {
+    fn same_type<T>(_: T, _: T);
+}
+
+fn f<T: Foo, X, Y>(x: X, y: Y) {
+    T::same_type([x], Some(y));
+    //~^ ERROR mismatched types
+}
+
+fn main() {}

tests/ui/fn/error-recovery-mismatch.stderr

@@ -0,0 +1,23 @@
+error[E0308]: mismatched types
+  --> $DIR/param-mismatch-trait-fn.rs:6:23
+   |
+LL |     T::same_type([x], Some(y));
+   |     ------------ ---  ^^^^^^^ expected `[X; 1]`, found `Option<Y>`
+   |     |            |
+   |     |            expected all arguments to be this `[X; 1]` type because they need to match the type of this parameter
+   |     arguments to this function are incorrect
+   |
+   = note: expected array `[X; 1]`
+               found enum `Option<Y>`
+note: associated function defined here
+  --> $DIR/param-mismatch-trait-fn.rs:2:8
+   |
+LL |     fn same_type<T>(_: T, _: T);
+   |        ^^^^^^^^^ -  -     - this parameter needs to match the `[X; 1]` type of parameter #1
+   |                  |  |
+   |                  |  parameter #2 needs to match the `[X; 1]` type of this parameter
+   |                  parameter #1 and parameter #2 both reference this parameter `T`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/fn/param-mismatch-trait-fn.rs

@@ -32,7 +32,7 @@ note: method defined here
   --> $DIR/issue-61525.rs:2:8
    |
 LL |     fn query<Q>(self, q: Q);
-   |        ^^^^^
+   |        ^^^^^          -
 
 error: aborting due to 2 previous errors
 

tests/ui/fn/param-mismatch-trait-fn.stderr

@@ -94,7 +94,7 @@ note: method defined here
   --> $DIR/trait-with-missing-associated-type-restriction.rs:9:8
    |
 LL |     fn funk(&self, _: Self::A);
-   |        ^^^^
+   |        ^^^^        -
 help: consider constraining the associated type `<T as Trait<i32>>::A` to `{integer}`
    |
 LL | fn bar2<T: Trait<i32, A = {integer}>>(x: T) {

tests/ui/methods/issues/issue-61525.stderr

@@ -22,7 +22,7 @@ note: method defined here
   --> $DIR/issue-52893.rs:11:8
    |
 LL |     fn push(self, other: T) -> Self::PushRes;
-   |        ^^^^
+   |        ^^^^       -----
 
 error: aborting due to 1 previous error