skip assoc type during infer source visitor

Author: bvanjoi

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

@@ -940,7 +940,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
             //
             // 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::TyAlias | DefKind::AssocTy, _)) => {
                 if let Some(ty) = self.opt_node_type(expr.hir_id)
                     && let ty::Adt(_, args) = ty.kind()
                 {

tests/crashes/121613-2.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/crashes/121613.rs

@@ -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-0.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-0.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`.