Provide more context on resolve error caused from incorrect RTN

When encountering a resolve E0575 error for an associated method (when a type was expected), see if it could have been an intended return type notation bound.

```
error[E0575]: expected associated type, found associated function `Trait::method`
  --> $DIR/bad-inputs-and-output.rs:31:36
   |
LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
   |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
   |
help: you might have meant to use the return type notation syntax
   |
LL - fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
LL + fn foo_qualified<T: Trait>() where T::method(..): Send {}
   |
```

3 files changed, 70 insertions, 11 deletions

diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed
new file mode 100644
index 00000000000..7af986267aa
--- /dev/null
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.fixed
@@ -0,0 +1,40 @@
+//@ edition: 2021
+//@ run-rustfix
+#![feature(return_type_notation)]
+#![allow(dead_code)]
+
+trait Trait {
+    async fn method() {}
+}
+
+fn foo<T: Trait<method(..): Send>>() {}
+//~^ ERROR argument types not allowed with return type notation
+
+fn bar<T: Trait<method(..): Send>>() {}
+//~^ ERROR return type not allowed with return type notation
+
+fn baz<T: Trait<method(..): Send>>() {}
+//~^ ERROR return type notation arguments must be elided with `..`
+
+fn foo_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR argument types not allowed with return type notation
+
+fn bar_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type not allowed with return type notation
+
+fn bay_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type not allowed with return type notation
+
+fn baz_path<T: Trait>() where T::method(..): Send {}
+//~^ ERROR return type notation arguments must be elided with `..`
+
+fn foo_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn bar_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn baz_qualified<T: Trait>() where T::method(..): Send {}
+//~^ ERROR expected associated type
+
+fn main() {}
diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
index 90fd2c2b4f3..983836e6433 100644
--- a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.rs
@@ -1,6 +1,7 @@
 //@ edition: 2021
-
+//@ run-rustfix
 #![feature(return_type_notation)]
+#![allow(dead_code)]
 
 trait Trait {
     async fn method() {}
diff --git a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
index bd02b7d6534..e1245a04c7f 100644
--- a/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
+++ b/tests/ui/associated-type-bounds/return-type-notation/bad-inputs-and-output.stderr
@@ -1,5 +1,5 @@
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:24:45
+  --> $DIR/bad-inputs-and-output.rs:25:45
    |
 LL | fn bay_path<T: Trait>() where T::method(..) -> (): Send {}
    |                                             ^^^^^
@@ -11,25 +11,43 @@ LL + fn bay_path<T: Trait>() where T::method(..): Send {}
    |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:30:36
+  --> $DIR/bad-inputs-and-output.rs:31:36
    |
 LL | fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn foo_qualified<T: Trait>() where <T as Trait>::method(i32): Send {}
+LL + fn foo_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:33:36
+  --> $DIR/bad-inputs-and-output.rs:34:36
    |
 LL | fn bar_qualified<T: Trait>() where <T as Trait>::method() -> (): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn bar_qualified<T: Trait>() where <T as Trait>::method() -> (): Send {}
+LL + fn bar_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error[E0575]: expected associated type, found associated function `Trait::method`
-  --> $DIR/bad-inputs-and-output.rs:36:36
+  --> $DIR/bad-inputs-and-output.rs:37:36
    |
 LL | fn baz_qualified<T: Trait>() where <T as Trait>::method(): Send {}
    |                                    ^^^^^^^^^^^^^^^^^^^^^^ not a associated type
+   |
+help: you might have meant to use the return type notation syntax
+   |
+LL - fn baz_qualified<T: Trait>() where <T as Trait>::method(): Send {}
+LL + fn baz_qualified<T: Trait>() where T::method(..): Send {}
+   |
 
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:9:23
+  --> $DIR/bad-inputs-and-output.rs:10:23
    |
 LL | fn foo<T: Trait<method(i32): Send>>() {}
    |                       ^^^^^
@@ -41,7 +59,7 @@ LL + fn foo<T: Trait<method(..): Send>>() {}
    |
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:12:25
+  --> $DIR/bad-inputs-and-output.rs:13:25
    |
 LL | fn bar<T: Trait<method() -> (): Send>>() {}
    |                         ^^^^^^
@@ -53,7 +71,7 @@ LL + fn bar<T: Trait<method(..): Send>>() {}
    |
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:15:23
+  --> $DIR/bad-inputs-and-output.rs:16:23
    |
 LL | fn baz<T: Trait<method(): Send>>() {}
    |                       ^^
@@ -64,7 +82,7 @@ LL | fn baz<T: Trait<method(..): Send>>() {}
    |                        ++
 
 error: argument types not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:18:40
+  --> $DIR/bad-inputs-and-output.rs:19:40
    |
 LL | fn foo_path<T: Trait>() where T::method(i32): Send {}
    |                                        ^^^^^
@@ -76,7 +94,7 @@ LL + fn foo_path<T: Trait>() where T::method(..): Send {}
    |
 
 error: return type not allowed with return type notation
-  --> $DIR/bad-inputs-and-output.rs:21:42
+  --> $DIR/bad-inputs-and-output.rs:22:42
    |
 LL | fn bar_path<T: Trait>() where T::method() -> (): Send {}
    |                                          ^^^^^^
@@ -88,7 +106,7 @@ LL + fn bar_path<T: Trait>() where T::method(..): Send {}
    |
 
 error: return type notation arguments must be elided with `..`
-  --> $DIR/bad-inputs-and-output.rs:27:40
+  --> $DIR/bad-inputs-and-output.rs:28:40
    |
 LL | fn baz_path<T: Trait>() where T::method(): Send {}
    |                                        ^^