Rollup merge of #128337 - bvanjoi:issue-121613, r=compiler-errors

skip assoc type during infer source visitor

Fixes #121613

Due to the generic arguments being lost during normalization, the associated type cannot retrieve the correct generics information, so this PR follows this [comment](https://github.com/rust-lang/rust/blob/master/compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs#L937-L942) and skips `DefKind::AssocTy`

r? `@lcnr`

compiler/rustc_trait_selection/src/error_reporting/infer/need_type_info.rs

@@ -934,13 +934,13 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
             // which makes this somewhat difficult and prevents us from just
             // using `self.path_inferred_arg_iter` here.
             hir::ExprKind::Struct(&hir::QPath::Resolved(_self_ty, path), _, _)
-            // FIXME(TaKO8Ki): Ideally we should support this. For that
-            // we have to map back from the self type to the
-            // type alias though. That's difficult.
+            // FIXME(TaKO8Ki): Ideally we should support other kinds,
+            // such as `TyAlias` or `AssocTy`. For that we have to map
+            // back from the self type to the type alias though. That's difficult.
             //
             // See the `need_type_info/issue-103053.rs` test for
             // a example.
-            if !matches!(path.res, Res::Def(DefKind::TyAlias, _)) => {
+            if matches!(path.res, Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Union, _)) => {
                 if let Some(ty) = self.opt_node_type(expr.hir_id)
                     && let ty::Adt(_, args) = ty.kind()
                 {

tests/ui/inference/need_type_info/incompat-call-after-qualified-path-0.rs

@@ -0,0 +1,24 @@
+// issue#121613
+
+#![feature(more_qualified_paths)]
+
+struct S {}
+
+struct Foo;
+
+trait A {
+    type Assoc;
+}
+
+impl A for Foo {
+    type Assoc = S;
+}
+
+fn f() {}
+
+fn main() {
+  <Foo as A>::Assoc {};
+  f(|a, b| a.cmp(b));
+  //~^ ERROR: type annotations needed
+  //~| ERROR: this function takes 0 arguments but 1 argument was supplied
+}

tests/ui/inference/need_type_info/incompat-call-after-qualified-path-0.stderr

@@ -0,0 +1,32 @@
+error[E0282]: type annotations needed
+  --> $DIR/incompat-call-after-qualified-path-0.rs:21:6
+   |
+LL |   f(|a, b| a.cmp(b));
+   |      ^     - type must be known at this point
+   |
+help: consider giving this closure parameter an explicit type
+   |
+LL |   f(|a: /* Type */, b| a.cmp(b));
+   |       ++++++++++++
+
+error[E0061]: this function takes 0 arguments but 1 argument was supplied
+  --> $DIR/incompat-call-after-qualified-path-0.rs:21:3
+   |
+LL |   f(|a, b| a.cmp(b));
+   |   ^ --------------- unexpected argument
+   |
+note: function defined here
+  --> $DIR/incompat-call-after-qualified-path-0.rs:17:4
+   |
+LL | fn f() {}
+   |    ^
+help: remove the extra argument
+   |
+LL -   f(|a, b| a.cmp(b));
+LL +   f();
+   |
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0061, E0282.
+For more information about an error, try `rustc --explain E0061`.

tests/ui/inference/need_type_info/incompat-call-after-qualified-path-1.rs

@@ -0,0 +1,28 @@
+// issue#121613
+
+#![feature(more_qualified_paths)]
+
+struct S<T> {
+    a: T
+}
+
+struct Foo;
+
+trait A {
+    type Assoc<T>;
+}
+
+impl A for Foo {
+    type Assoc<T> = S<T>;
+}
+
+fn f() {}
+
+fn main() {
+  <Foo as A>::Assoc::<i32> {
+    a: 1
+  };
+  f(|a, b| a.cmp(b));
+  //~^ ERROR: type annotations needed
+  //~| ERROR: this function takes 0 arguments but 1 argument was supplied
+}

tests/ui/inference/need_type_info/incompat-call-after-qualified-path-1.stderr

@@ -0,0 +1,32 @@
+error[E0282]: type annotations needed
+  --> $DIR/incompat-call-after-qualified-path-1.rs:25:6
+   |
+LL |   f(|a, b| a.cmp(b));
+   |      ^     - type must be known at this point
+   |
+help: consider giving this closure parameter an explicit type
+   |
+LL |   f(|a: /* Type */, b| a.cmp(b));
+   |       ++++++++++++
+
+error[E0061]: this function takes 0 arguments but 1 argument was supplied
+  --> $DIR/incompat-call-after-qualified-path-1.rs:25:3
+   |
+LL |   f(|a, b| a.cmp(b));
+   |   ^ --------------- unexpected argument
+   |
+note: function defined here
+  --> $DIR/incompat-call-after-qualified-path-1.rs:19:4
+   |
+LL | fn f() {}
+   |    ^
+help: remove the extra argument
+   |
+LL -   f(|a, b| a.cmp(b));
+LL +   f();
+   |
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0061, E0282.
+For more information about an error, try `rustc --explain E0061`.