Auto merge of #104334 - compiler-errors:ufcs-sugg-wrong-def-id, r=estebank

Use impl's def id when calculating type to specify in UFCS

Fixes #104327
Fixes #104328

Also addresses #102670 (comment)

Author: bors

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2312,18 +2312,19 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         let trait_impls = self.tcx.trait_impls_of(data.trait_ref.def_id);
 
                         if trait_impls.blanket_impls().is_empty()
-                            && let Some((impl_ty, _)) = trait_impls.non_blanket_impls().iter().next()
-                            && let Some(impl_def_id) = impl_ty.def() {
-                            let message = if trait_impls.non_blanket_impls().len() == 1 {
+                            && let Some(impl_def_id) = trait_impls.non_blanket_impls().values().flatten().next()
+                        {
+                            let non_blanket_impl_count = trait_impls.non_blanket_impls().values().flatten().count();
+                            let message = if non_blanket_impl_count == 1 {
                                 "use the fully-qualified path to the only available implementation".to_string()
                             } else {
                                 format!(
                                     "use a fully-qualified path to a specific available implementation ({} found)",
-                                    trait_impls.non_blanket_impls().len()
+                                    non_blanket_impl_count
                                 )
                             };
                             let mut suggestions = vec![(
-                                trait_path_segment.ident.span.shrink_to_lo(),
+                                path.span.shrink_to_lo(),
                                 format!("<{} as ", self.tcx.type_of(impl_def_id))
                             )];
                             if let Some(generic_arg) = trait_path_segment.args {

src/test/ui/associated-types/associated-types-unconstrained.stderr

@@ -6,6 +6,11 @@ LL |     fn bar() -> isize;
 ...
 LL |     let x: isize = Foo::bar();
    |                    ^^^^^^^^ cannot call associated function of trait
+   |
+help: use the fully-qualified path to the only available implementation
+   |
+LL |     let x: isize = <isize as Foo>::bar();
+   |                    +++++++++    +
 
 error: aborting due to previous error
 

src/test/ui/error-codes/E0790.stderr

@@ -37,8 +37,8 @@ LL |     inner::MyTrait::my_fn();
    |
 help: use the fully-qualified path to the only available implementation
    |
-LL |     inner::<MyStruct as MyTrait>::my_fn();
-   |            ++++++++++++        +
+LL |     <MyStruct as inner::MyTrait>::my_fn();
+   |     ++++++++++++               +
 
 error[E0790]: cannot refer to the associated constant on trait without specifying the corresponding `impl` type
   --> $DIR/E0790.rs:30:13
@@ -51,8 +51,8 @@ LL |     let _ = inner::MyTrait::MY_ASSOC_CONST;
    |
 help: use the fully-qualified path to the only available implementation
    |
-LL |     let _ = inner::<MyStruct as MyTrait>::MY_ASSOC_CONST;
-   |                    ++++++++++++        +
+LL |     let _ = <MyStruct as inner::MyTrait>::MY_ASSOC_CONST;
+   |             ++++++++++++               +
 
 error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
   --> $DIR/E0790.rs:50:5

src/test/ui/suggestions/issue-104327.rs

@@ -0,0 +1,12 @@
+trait Bar {}
+
+trait Foo {
+    fn f() {}
+}
+
+impl Foo for dyn Bar {}
+
+fn main() {
+    Foo::f();
+    //~^ ERROR cannot call associated function on trait without specifying the corresponding `impl` type
+}

src/test/ui/suggestions/issue-104327.stderr

@@ -0,0 +1,17 @@
+error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
+  --> $DIR/issue-104327.rs:10:5
+   |
+LL |     fn f() {}
+   |     --------- `Foo::f` defined here
+...
+LL |     Foo::f();
+   |     ^^^^^^ cannot call associated function of trait
+   |
+help: use the fully-qualified path to the only available implementation
+   |
+LL |     <(dyn Bar + 'static) as Foo>::f();
+   |     +++++++++++++++++++++++    +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0790`.

src/test/ui/suggestions/issue-104328.rs

@@ -0,0 +1,12 @@
+#![feature(object_safe_for_dispatch)]
+
+trait Foo {
+    fn f() {}
+}
+
+impl Foo for dyn Sized {}
+
+fn main() {
+    Foo::f();
+    //~^ ERROR cannot call associated function on trait without specifying the corresponding `impl` type
+}

src/test/ui/suggestions/issue-104328.stderr

@@ -0,0 +1,17 @@
+error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
+  --> $DIR/issue-104328.rs:10:5
+   |
+LL |     fn f() {}
+   |     --------- `Foo::f` defined here
+...
+LL |     Foo::f();
+   |     ^^^^^^ cannot call associated function of trait
+   |
+help: use the fully-qualified path to the only available implementation
+   |
+LL |     <(dyn Sized + 'static) as Foo>::f();
+   |     +++++++++++++++++++++++++    +
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0790`.

src/test/ui/traits/static-method-generic-inference.stderr

@@ -9,8 +9,8 @@ LL |     let _f: base::Foo = base::HasNew::new();
    |
 help: use the fully-qualified path to the only available implementation
    |
-LL |     let _f: base::Foo = base::<Foo as HasNew>::new();
-   |                               +++++++       +
+LL |     let _f: base::Foo = <Foo as base::HasNew>::new();
+   |                         +++++++             +
 
 error: aborting due to previous error