Auto merge of #108576 - megakorre:rustdock_additional_typecheck_before_clean, r=GuillaumeGomez

rustdoc: run more HIR validation to mirror rustc

# Explanation

While investigating these issues: https://github.com/rust-lang/rust/issues/107093, https://github.com/rust-lang/rust/issues/106079
I thought it maybe would be useful to test running `rustdoc` on all rust files under `tests/ui` grepping for files that causes any ICEs.
And these are the files I found would cause ICEs.
```
// These are handled by this fix.
tests/ui/late-bound-lifetimes/mismatched_arg_count.rs
tests/ui/associated-consts/issue-102335-const.rs
tests/ui/const-generics/generic_const_exprs/issue-102768.rs
tests/ui/const-generics/const-arg-type-arg-misordered.rs
tests/ui/generic-associated-types/parse/trait-path-type-error-once-implemented.rs
tests/ui/typeck/issue-88643.rs
tests/ui/typeck/issue-75889.rs
tests/ui/typeck/issue-83621-placeholder-static-in-extern.rs
// These are not they will still produce a ICE after this change
tests/ui/limits/issue-56762.rs
tests/ui/union/projection-as-union-type-error-2.rs
tests/ui/union/projection-as-union-type-error.rs
```

I reduces the issues handled by this PR down to the tests added in the PR. That includes the linked issues.
But the 3 files that are not handled I will leave for a future PR.

This PR adds the `type_collecting` step from `hir_analysis::check_crate` to the rustdoc typechecks.
It had the following comment on it.
```
// this ensures that later parts of type checking can assume that items
// have valid types and not error
```
Adding the check report the same errors as rustc does for these input.
And not ICE when the lint checker walks the HIR or when in the `rustdoc::clean` pass.

This PR updates the expected errors of some existing rustdoc-ui tests (some now report less errors).
These new reported errors does mirror the errors reported by rustc.

# Performance
It does more checking so it will probably regress. We should run ``@bors` try `@rust-timer` queue` and see.

# Discussion

Maybe instead of calling a subset of the checks in `hir_analysis::check_crate` and having comments that say they should be kept in sync. We could instead call `check_crate` directly and pass in some flag. Maybe `check_toplevel_signatures_only` or something like that. That flag would have to skip most of the checks in that function tough.

src/librustdoc/core.rs

@@ -303,6 +303,9 @@ pub(crate) fn run_global_ctxt(
 
     // HACK(jynelson) this calls an _extremely_ limited subset of `typeck`
     // and might break if queries change their assumptions in the future.
+    tcx.sess.time("type_collecting", || {
+        tcx.hir().for_each_module(|module| tcx.ensure().collect_mod_item_types(module))
+    });
 
     // NOTE: This is copy/pasted from typeck/lib.rs and should be kept in sync with those changes.
     tcx.sess.time("item_types_checking", || {

tests/rustdoc-ui/const_arg_in_type_position.rs

@@ -0,0 +1,6 @@
+type Array<T, const N: usize> = [T; N];
+
+fn foo<const N: usize>() -> Array<N, ()> {
+    //~^ ERROR constant provided when a type was expected
+    unimplemented!()
+}

tests/rustdoc-ui/const_arg_in_type_position.stderr

@@ -0,0 +1,9 @@
+error[E0747]: constant provided when a type was expected
+  --> $DIR/const_arg_in_type_position.rs:3:35
+   |
+LL | fn foo<const N: usize>() -> Array<N, ()> {
+   |                                   ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0747`.

tests/rustdoc-ui/invalid_associated_const.rs

@@ -0,0 +1,10 @@
+#![feature(associated_const_equality)]
+
+trait T {
+    type A: S<C<X = 0i32> = 34>;
+    //~^ ERROR associated type bindings are not allowed here
+}
+
+trait S {
+    const C: i32;
+}

tests/rustdoc-ui/invalid_associated_const.stderr

@@ -0,0 +1,9 @@
+error[E0229]: associated type bindings are not allowed here
+  --> $DIR/invalid_associated_const.rs:4:17
+   |
+LL |     type A: S<C<X = 0i32> = 34>;
+   |                 ^^^^^^^^ associated type not allowed here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0229`.

tests/rustdoc-ui/invalid_const_in_lifetime_position.rs

@@ -0,0 +1,6 @@
+trait X {
+    type Y<'a>;
+}
+fn f<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
+//~^ ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+//~| ERROR associated type takes 0 generic arguments but 1 generic argument

tests/rustdoc-ui/invalid_const_in_lifetime_position.stderr

@@ -0,0 +1,33 @@
+error[E0107]: associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
+  --> $DIR/invalid_const_in_lifetime_position.rs:4:26
+   |
+LL | fn f<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
+   |                          ^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/invalid_const_in_lifetime_position.rs:2:10
+   |
+LL |     type Y<'a>;
+   |          ^ --
+help: add missing lifetime argument
+   |
+LL | fn f<'a>(arg : Box<dyn X<Y<'_, 1> = &'a ()>>) {}
+   |                            +++
+
+error[E0107]: associated type takes 0 generic arguments but 1 generic argument was supplied
+  --> $DIR/invalid_const_in_lifetime_position.rs:4:26
+   |
+LL | fn f<'a>(arg : Box<dyn X<Y<1> = &'a ()>>) {}
+   |                          ^--- help: remove these generics
+   |                          |
+   |                          expected 0 generic arguments
+   |
+note: associated type defined here, with 0 generic parameters
+  --> $DIR/invalid_const_in_lifetime_position.rs:2:10
+   |
+LL |     type Y<'a>;
+   |          ^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0107`.

tests/rustdoc-ui/invalid_infered_static_and_const.rs

@@ -0,0 +1,2 @@
+const FOO: dyn Fn() -> _ = ""; //~ ERROR E0121
+static BOO: dyn Fn() -> _ = ""; //~ ERROR E0121

tests/rustdoc-ui/invalid_infered_static_and_const.stderr

@@ -0,0 +1,15 @@
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for constant items
+  --> $DIR/invalid_infered_static_and_const.rs:1:24
+   |
+LL | const FOO: dyn Fn() -> _ = "";
+   |                        ^ not allowed in type signatures
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for static items
+  --> $DIR/invalid_infered_static_and_const.rs:2:25
+   |
+LL | static BOO: dyn Fn() -> _ = "";
+   |                         ^ not allowed in type signatures
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0121`.

tests/rustdoc-ui/issue-105742.rs

@@ -1,19 +1,50 @@
 // compile-flags: -Znormalize-docs
-
 use std::ops::Index;
 
 pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
+    //~^ expected 1 lifetime argument
+    //~| expected 1 generic argument
+    //~| the trait `SVec` cannot be made into an object
+    //~| `SVec` cannot be made into an object
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
     let _ = s;
 }
 
 pub trait SVec: Index<
     <Self as SVec>::Item,
+    //~^ expected 1 lifetime argument
+    //~| expected 1 generic argument
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
     Output = <Index<<Self as SVec>::Item,
+    //~^ expected 1 lifetime argument
+    //~| expected 1 generic argument
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
     Output = <Self as SVec>::Item> as SVec>::Item,
+    //~^ expected 1 lifetime argument
+    //~| expected 1 generic argument
+    //~| expected 1 lifetime argument
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| expected 1 generic argument
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
+    //~| missing generics for associated type `SVec::Item`
 > {
     type Item<'a, T>;
 
     fn len(&self) -> <Self as SVec>::Item;
-    //~^ ERROR
-    //~^^ ERROR
+    //~^ expected 1 lifetime argument
+    //~| missing generics for associated type `SVec::Item`
+    //~| expected 1 generic argument
+    //~| missing generics for associated type `SVec::Item`
 }

tests/rustdoc-ui/issue-105742.stderr

@@ -1,11 +1,329 @@
 error[E0107]: missing generics for associated type `SVec::Item`
-  --> $DIR/issue-105742.rs:16:38
+  --> $DIR/issue-105742.rs:15:21
+   |
+LL |     <Self as SVec>::Item,
+   |                     ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     <Self as SVec>::Item<'a>,
+   |                         ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:15:21
+   |
+LL |     <Self as SVec>::Item,
+   |                     ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     <Self as SVec>::Item<T>,
+   |                         +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:22:37
+   |
+LL |     Output = <Index<<Self as SVec>::Item,
+   |                                     ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Index<<Self as SVec>::Item<'a>,
+   |                                         ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:22:37
+   |
+LL |     Output = <Index<<Self as SVec>::Item,
+   |                                     ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Index<<Self as SVec>::Item<T>,
+   |                                         +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:30
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                              ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Self as SVec>::Item<'a>> as SVec>::Item,
+   |                                  ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:30
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                              ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Self as SVec>::Item<T>> as SVec>::Item,
+   |                                  +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:46
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                                              ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item<'a>,
+   |                                                  ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:46
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                                              ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item<T>,
+   |                                                  +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:4:40
+   |
+LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
+   |                                        ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item<'_> = T, Output = T>) {
+   |                                            ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:4:40
+   |
+LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
+   |                                        ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item<T> = T, Output = T>) {
+   |                                            +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:15:21
+   |
+LL |     <Self as SVec>::Item,
+   |                     ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     <Self as SVec>::Item<'a>,
+   |                         ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:15:21
+   |
+LL |     <Self as SVec>::Item,
+   |                     ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     <Self as SVec>::Item<T>,
+   |                         +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:22:37
+   |
+LL |     Output = <Index<<Self as SVec>::Item,
+   |                                     ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Index<<Self as SVec>::Item<'a>,
+   |                                         ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:22:37
+   |
+LL |     Output = <Index<<Self as SVec>::Item,
+   |                                     ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Index<<Self as SVec>::Item<T>,
+   |                                         +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:30
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                              ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Self as SVec>::Item<'a>> as SVec>::Item,
+   |                                  ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:30
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                              ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Self as SVec>::Item<T>> as SVec>::Item,
+   |                                  +++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:46
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                                              ^^^^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^ --
+help: add missing lifetime argument
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item<'a>,
+   |                                                  ++++
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:29:46
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item,
+   |                                              ^^^^ expected 1 generic argument
+   |
+note: associated type defined here, with 1 generic parameter: `T`
+  --> $DIR/issue-105742.rs:43:10
+   |
+LL |     type Item<'a, T>;
+   |          ^^^^     -
+help: add missing generic argument
+   |
+LL |     Output = <Self as SVec>::Item> as SVec>::Item<T>,
+   |                                                  +++
+
+error[E0038]: the trait `SVec` cannot be made into an object
+  --> $DIR/issue-105742.rs:4:31
+   |
+LL | pub fn next<'a, T>(s: &'a mut dyn SVec<Item = T, Output = T>) {
+   |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `SVec` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/issue-105742.rs:14:17
+   |
+LL |    pub trait SVec: Index<
+   |  ____________----__^
+   | |            |
+   | |            this trait cannot be made into an object...
+LL | |      <Self as SVec>::Item,
+LL | |
+LL | |
+...  |
+LL | |/     Output = <Index<<Self as SVec>::Item,
+LL | ||
+LL | ||
+LL | ||
+...  ||
+LL | ||
+LL | ||     Output = <Self as SVec>::Item> as SVec>::Item,
+   | ||_________________________________________________^ ...because it uses `Self` as a type parameter
+...  |
+LL | |
+LL | |  > {
+   | |__^ ...because it uses `Self` as a type parameter
+
+error[E0107]: missing generics for associated type `SVec::Item`
+  --> $DIR/issue-105742.rs:45:38
    |
 LL |     fn len(&self) -> <Self as SVec>::Item;
    |                                      ^^^^ expected 1 lifetime argument
    |
 note: associated type defined here, with 1 lifetime parameter: `'a`
-  --> $DIR/issue-105742.rs:14:10
+  --> $DIR/issue-105742.rs:43:10
    |
 LL |     type Item<'a, T>;
    |          ^^^^ --
@@ -15,13 +333,13 @@ LL |     fn len(&self) -> <Self as SVec>::Item<'_>;
    |                                          ++++
 
 error[E0107]: missing generics for associated type `SVec::Item`
-  --> $DIR/issue-105742.rs:16:38
+  --> $DIR/issue-105742.rs:45:38
    |
 LL |     fn len(&self) -> <Self as SVec>::Item;
    |                                      ^^^^ expected 1 generic argument
    |
 note: associated type defined here, with 1 generic parameter: `T`
-  --> $DIR/issue-105742.rs:14:10
+  --> $DIR/issue-105742.rs:43:10
    |
 LL |     type Item<'a, T>;
    |          ^^^^     -
@@ -30,6 +348,7 @@ help: add missing generic argument
 LL |     fn len(&self) -> <Self as SVec>::Item<T>;
    |                                          +++
 
-error: aborting due to 2 previous errors
+error: aborting due to 21 previous errors
 
-For more information about this error, try `rustc --explain E0107`.
+Some errors have detailed explanations: E0038, E0107.
+For more information about an error, try `rustc --explain E0038`.

tests/rustdoc-ui/issue-106226.stderr

@@ -1,9 +1,9 @@
-error[E0308]: mismatched types
-  --> $DIR/issue-106226.rs:2:14
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
+  --> $DIR/issue-106226.rs:2:11
    |
 LL | type F = [_; ()];
-   |              ^^ expected `usize`, found `()`
+   |           ^ not allowed in type signatures
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0121`.

tests/rustdoc-ui/issue-79465.rs

@@ -1,3 +1,2 @@
 pub fn f1<T>(x: T::A) {}
 //~^ ERROR
-//~^^ ERROR

tests/rustdoc-ui/issue-79465.stderr

@@ -4,12 +4,6 @@ error[E0220]: associated type `A` not found for `T`
 LL | pub fn f1<T>(x: T::A) {}
    |                    ^ associated type `A` not found
 
-error[E0220]: associated type `A` not found for `T`
-  --> $DIR/issue-79465.rs:1:20
-   |
-LL | pub fn f1<T>(x: T::A) {}
-   |                    ^ associated type `A` not found
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0220`.

tests/rustdoc-ui/issue-96287.rs

@@ -6,7 +6,6 @@ pub trait TraitWithAssoc {
 
 pub type Foo<V> = impl Trait<V::Assoc>;
 //~^ ERROR
-//~^^ ERROR
 
 pub trait Trait<U> {}
 

tests/rustdoc-ui/issue-96287.stderr

@@ -4,12 +4,6 @@ error[E0220]: associated type `Assoc` not found for `V`
 LL | pub type Foo<V> = impl Trait<V::Assoc>;
    |                                 ^^^^^ there is a similarly named associated type `Assoc` in the trait `TraitWithAssoc`
 
-error[E0220]: associated type `Assoc` not found for `V`
-  --> $DIR/issue-96287.rs:7:33
-   |
-LL | pub type Foo<V> = impl Trait<V::Assoc>;
-   |                                 ^^^^^ there is a similarly named associated type `Assoc` in the trait `TraitWithAssoc`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0220`.

tests/rustdoc-ui/mismatched_arg_count.rs

@@ -0,0 +1,8 @@
+trait Trait<'a> {
+    type Assoc;
+}
+
+type Alias<'a, T> = <T as Trait<'a>>::Assoc;
+
+fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
+//~^ error: type alias takes 1 lifetime argument but 2 lifetime arguments were supplied

tests/rustdoc-ui/mismatched_arg_count.stderr

@@ -0,0 +1,17 @@
+error[E0107]: type alias takes 1 lifetime argument but 2 lifetime arguments were supplied
+  --> $DIR/mismatched_arg_count.rs:7:29
+   |
+LL | fn bar<'a, T: Trait<'a>>(_: Alias<'a, 'a, T>) {}
+   |                             ^^^^^     -- help: remove this lifetime argument
+   |                             |
+   |                             expected 1 lifetime argument
+   |
+note: type alias defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/mismatched_arg_count.rs:5:6
+   |
+LL | type Alias<'a, T> = <T as Trait<'a>>::Assoc;
+   |      ^^^^^ --
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0107`.