review comments + more tests

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1340,7 +1340,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             err,
                             path,
                             ty,
-                            impl_ty,
+                            Some(impl_ty),
                             item.kind,
                             self.tcx.def_kind_descr(item.kind.as_def_kind(), item.def_id),
                             sugg_span,
@@ -1377,7 +1377,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             err,
                             path,
                             rcvr_ty,
-                            rcvr_ty,
+                            None,
                             item.kind,
                             self.tcx.def_kind_descr(item.kind.as_def_kind(), item.def_id),
                             sugg_span,
@@ -3148,7 +3148,7 @@ fn print_disambiguation_help<'tcx>(
     err: &mut Diagnostic,
     trait_name: String,
     rcvr_ty: Ty<'_>,
-    self_ty: Ty<'_>,
+    impl_self_ty: Option<Ty<'_>>,
     kind: ty::AssocKind,
     def_kind_descr: &'static str,
     span: Span,
@@ -3174,20 +3174,21 @@ fn print_disambiguation_help<'tcx>(
                 .collect::<Vec<_>>()
                 .join(", "),
         );
-        let trait_name = if !fn_has_self_parameter {
-            format!("<{self_ty} as {trait_name}>")
+        let trait_name = if !fn_has_self_parameter && let Some(impl_self_ty) = impl_self_ty {
+            format!("<{impl_self_ty} as {trait_name}>")
         } else {
             trait_name
         };
         (span, format!("{trait_name}::{item_name}{args}"))
+    } else if let Some(impl_self_ty) = impl_self_ty {
+        (span.with_hi(item_name.span.lo()), format!("<{impl_self_ty} as {trait_name}>::"))
     } else {
-        (span.with_hi(item_name.span.lo()), format!("<{self_ty} as {trait_name}>::"))
+        (span.with_hi(item_name.span.lo()), format!("{trait_name}::"))
     };
     err.span_suggestion_verbose(
         span,
         format!(
-            "disambiguate the {} for {}",
-            def_kind_descr,
+            "disambiguate the {def_kind_descr} for {}",
             if let Some(candidate) = candidate {
                 format!("candidate #{candidate}")
             } else {

tests/ui/methods/disambiguate-multiple-blanket-impl.rs

@@ -1,19 +1,27 @@
 trait A {
+    type Type;
+    const CONST: usize;
     fn foo(&self);
 }
 
 trait B {
+    type Type;
+    const CONST: usize;
     fn foo(&self);
 }
 
 #[derive(Debug)]
 struct S;
 
 impl<T: std::fmt::Debug> A for T {
+    type Type = ();
+    const CONST: usize = 1; //~ NOTE candidate #1
     fn foo(&self) {} //~ NOTE candidate #1
 }
 
 impl<T: std::fmt::Debug> B for T {
+    type Type = ();
+    const CONST: usize = 2; //~ NOTE candidate #2
     fn foo(&self) {} //~ NOTE candidate #2
 }
 
@@ -23,5 +31,10 @@ fn main() {
     //~^ NOTE multiple `foo` found
     //~| HELP disambiguate
     //~| HELP disambiguate
+    S::CONST; //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `CONST` found
+    //~| HELP disambiguate
+    //~| HELP disambiguate
+    let _: S::Type; //~ ERROR ambiguous associated type
+    //~^ HELP use the fully-qualified path
 }
-

tests/ui/methods/disambiguate-multiple-blanket-impl.stderr

@@ -1,16 +1,29 @@
+error[E0223]: ambiguous associated type
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:38:12
+   |
+LL |     let _: S::Type;
+   |            ^^^^^^^
+   |
+help: use the fully-qualified path
+   |
+LL |     let _: <S as A>::Type;
+   |            ~~~~~~~~~~~~~~
+LL |     let _: <S as B>::Type;
+   |            ~~~~~~~~~~~~~~
+
 error[E0034]: multiple applicable items in scope
-  --> $DIR/disambiguate-multiple-blanket-impl.rs:22:8
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:30:8
    |
 LL |     S::foo(&s);
    |        ^^^ multiple `foo` found
    |
 note: candidate #1 is defined in an impl of the trait `A` for the type `T`
-  --> $DIR/disambiguate-multiple-blanket-impl.rs:13:5
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:19:5
    |
 LL |     fn foo(&self) {}
    |     ^^^^^^^^^^^^^
 note: candidate #2 is defined in an impl of the trait `B` for the type `T`
-  --> $DIR/disambiguate-multiple-blanket-impl.rs:17:5
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:25:5
    |
 LL |     fn foo(&self) {}
    |     ^^^^^^^^^^^^^
@@ -23,6 +36,32 @@ help: disambiguate the method for candidate #2
 LL |     <T as B>::foo(&s);
    |     ~~~~~~~~~~
 
-error: aborting due to previous error
+error[E0034]: multiple applicable items in scope
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:34:8
+   |
+LL |     S::CONST;
+   |        ^^^^^ multiple `CONST` found
+   |
+note: candidate #1 is defined in an impl of the trait `A` for the type `T`
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:18:5
+   |
+LL |     const CONST: usize = 1;
+   |     ^^^^^^^^^^^^^^^^^^
+note: candidate #2 is defined in an impl of the trait `B` for the type `T`
+  --> $DIR/disambiguate-multiple-blanket-impl.rs:24:5
+   |
+LL |     const CONST: usize = 2;
+   |     ^^^^^^^^^^^^^^^^^^
+help: disambiguate the associated constant for candidate #1
+   |
+LL |     <T as A>::CONST;
+   |     ~~~~~~~~~~
+help: disambiguate the associated constant for candidate #2
+   |
+LL |     <T as B>::CONST;
+   |     ~~~~~~~~~~
+
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0034`.
+Some errors have detailed explanations: E0034, E0223.
+For more information about an error, try `rustc --explain E0034`.

tests/ui/methods/disambiguate-multiple-impl.rs

@@ -1,18 +1,26 @@
 trait A {
+    type Type;
+    const CONST: usize;
     fn foo(&self);
 }
 
 trait B {
+    type Type;
+    const CONST: usize;
     fn foo(&self);
 }
 
 struct S;
 
 impl A for S {
+    type Type = ();
+    const CONST: usize = 1; //~ NOTE candidate #1
     fn foo(&self) {} //~ NOTE candidate #1
 }
 
 impl B for S {
+    type Type = ();
+    const CONST: usize = 2; //~ NOTE candidate #2
     fn foo(&self) {} //~ NOTE candidate #2
 }
 
@@ -22,5 +30,10 @@ fn main() {
     //~^ NOTE multiple `foo` found
     //~| HELP disambiguate
     //~| HELP disambiguate
+    let _: S::Type = (); //~ ERROR ambiguous associated type
+    //~| HELP use the fully-qualified path
+    let _ = S::CONST; //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `CONST` found
+    //~| HELP disambiguate
+    //~| HELP disambiguate
 }
-

tests/ui/methods/disambiguate-multiple-impl.stderr

@@ -1,16 +1,29 @@
+error[E0223]: ambiguous associated type
+  --> $DIR/disambiguate-multiple-impl.rs:33:12
+   |
+LL |     let _: S::Type = ();
+   |            ^^^^^^^
+   |
+help: use the fully-qualified path
+   |
+LL |     let _: <S as A>::Type = ();
+   |            ~~~~~~~~~~~~~~
+LL |     let _: <S as B>::Type = ();
+   |            ~~~~~~~~~~~~~~
+
 error[E0034]: multiple applicable items in scope
-  --> $DIR/disambiguate-multiple-impl.rs:21:8
+  --> $DIR/disambiguate-multiple-impl.rs:29:8
    |
 LL |     S::foo(&s);
    |        ^^^ multiple `foo` found
    |
 note: candidate #1 is defined in an impl of the trait `A` for the type `S`
-  --> $DIR/disambiguate-multiple-impl.rs:12:5
+  --> $DIR/disambiguate-multiple-impl.rs:18:5
    |
 LL |     fn foo(&self) {}
    |     ^^^^^^^^^^^^^
 note: candidate #2 is defined in an impl of the trait `B` for the type `S`
-  --> $DIR/disambiguate-multiple-impl.rs:16:5
+  --> $DIR/disambiguate-multiple-impl.rs:24:5
    |
 LL |     fn foo(&self) {}
    |     ^^^^^^^^^^^^^
@@ -23,6 +36,32 @@ help: disambiguate the method for candidate #2
 LL |     <S as B>::foo(&s);
    |     ~~~~~~~~~~
 
-error: aborting due to previous error
+error[E0034]: multiple applicable items in scope
+  --> $DIR/disambiguate-multiple-impl.rs:35:16
+   |
+LL |     let _ = S::CONST;
+   |                ^^^^^ multiple `CONST` found
+   |
+note: candidate #1 is defined in an impl of the trait `A` for the type `S`
+  --> $DIR/disambiguate-multiple-impl.rs:17:5
+   |
+LL |     const CONST: usize = 1;
+   |     ^^^^^^^^^^^^^^^^^^
+note: candidate #2 is defined in an impl of the trait `B` for the type `S`
+  --> $DIR/disambiguate-multiple-impl.rs:23:5
+   |
+LL |     const CONST: usize = 2;
+   |     ^^^^^^^^^^^^^^^^^^
+help: disambiguate the associated constant for candidate #1
+   |
+LL |     let _ = <S as A>::CONST;
+   |             ~~~~~~~~~~
+help: disambiguate the associated constant for candidate #2
+   |
+LL |     let _ = <S as B>::CONST;
+   |             ~~~~~~~~~~
+
+error: aborting due to 3 previous errors
 
-For more information about this error, try `rustc --explain E0034`.
+Some errors have detailed explanations: E0034, E0223.
+For more information about an error, try `rustc --explain E0034`.

tests/ui/methods/disambiguate-multiple-trait-2.rs

@@ -0,0 +1,57 @@
+trait A {
+    type Type; //~ NOTE ambiguous `Type` from `A`
+    const CONST: usize = 1; //~ NOTE candidate #1
+    fn foo(&self); //~ NOTE candidate #1
+}
+
+trait B {
+    type Type; //~ NOTE ambiguous `Type` from `B`
+    const CONST: usize; //~ NOTE candidate #2
+    fn foo(&self); //~ NOTE candidate #2
+}
+
+trait C: A + B {}
+
+fn a<T: C>(t: T) {
+    t.foo(); //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `foo` found
+    //~| HELP disambiguate the method
+    //~| HELP disambiguate the method
+    let _ = T::CONST; //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `CONST` found
+    //~| HELP disambiguate
+    //~| HELP disambiguate
+    let _: T::Type; //~ ERROR ambiguous associated type
+    //~^ NOTE ambiguous associated type `Type`
+    //~| HELP use fully qualified syntax
+    //~| HELP use fully qualified syntax
+}
+
+#[derive(Debug)]
+struct S;
+
+impl<T: std::fmt::Debug> A for T {
+    type Type = ();
+    const CONST: usize = 1; //~ NOTE candidate #1
+    fn foo(&self) {} //~ NOTE candidate #1
+}
+
+impl<T: std::fmt::Debug> B for T {
+    type Type = ();
+    const CONST: usize = 1; //~ NOTE candidate #2
+    fn foo(&self) {} //~ NOTE candidate #2
+}
+
+fn main() {
+    let s = S;
+    S::foo(&s); //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `foo` found
+    //~| HELP disambiguate
+    //~| HELP disambiguate
+    let _ = S::CONST; //~ ERROR multiple applicable items in scope
+    //~^ NOTE multiple `CONST` found
+    //~| HELP disambiguate
+    //~| HELP disambiguate
+    let _: S::Type; //~ ERROR ambiguous associated type
+    //~^ HELP use the fully-qualified path
+}