Better suggestion span for missing type parameter

Author: estebank

compiler/rustc_hir_analysis/src/errors.rs

@@ -454,11 +454,10 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for MissingTypeParams {
                 // The user wrote `Iterator`, so we don't have a type we can suggest, but at
                 // least we can clue them to the correct syntax `Iterator<Type>`.
                 err.span_suggestion(
-                    self.span,
+                    self.span.shrink_to_hi(),
                     fluent::hir_analysis_suggestion,
                     format!(
-                        "{}<{}>",
-                        snippet,
+                        "<{}>",
                         self.missing_type_params
                             .iter()
                             .map(|n| n.to_string())

tests/ui/associated-types/issue-22560.stderr

@@ -41,7 +41,7 @@ LL | type Test = dyn Add + Sub;
 help: set the type parameter to the desired type
    |
 LL | type Test = dyn Add<Rhs> + Sub;
-   |                 ~~~~~~~~
+   |                    +++++
 
 error[E0393]: the type parameter `Rhs` must be explicitly specified
   --> $DIR/issue-22560.rs:9:23
@@ -56,7 +56,7 @@ LL | type Test = dyn Add + Sub;
 help: set the type parameter to the desired type
    |
 LL | type Test = dyn Add + Sub<Rhs>;
-   |                       ~~~~~~~~
+   |                          +++++
 
 error: aborting due to 4 previous errors
 

tests/ui/const-generics/generic_const_exprs/expected-type-of-closure-body-to-be-a-closure-or-coroutine-ice-113776.stderr

@@ -29,7 +29,7 @@ LL | ) -> impl Iterator<Item = SubAssign> {
 help: set the type parameter to the desired type
    |
 LL | ) -> impl Iterator<Item = SubAssign<Rhs>> {
-   |                           ~~~~~~~~~~~~~~
+   |                                    +++++
 
 error[E0393]: the type parameter `Rhs` must be explicitly specified
   --> $DIR/expected-type-of-closure-body-to-be-a-closure-or-coroutine-ice-113776.rs:16:27
@@ -45,7 +45,7 @@ LL | ) -> impl Iterator<Item = SubAssign> {
 help: set the type parameter to the desired type
    |
 LL | ) -> impl Iterator<Item = SubAssign<Rhs>> {
-   |                           ~~~~~~~~~~~~~~
+   |                                    +++++
 
 error[E0277]: `()` is not an iterator
   --> $DIR/expected-type-of-closure-body-to-be-a-closure-or-coroutine-ice-113776.rs:16:6

tests/ui/error-codes/E0393.stderr

@@ -11,7 +11,7 @@ LL | fn together_we_will_rule_the_galaxy(son: &dyn A) {}
 help: set the type parameter to the desired type
    |
 LL | fn together_we_will_rule_the_galaxy(son: &dyn A<T>) {}
-   |                                               ~~~~
+   |                                                +++
 
 error: aborting due to 1 previous error
 

tests/ui/issues/issue-21950.stderr

@@ -20,7 +20,7 @@ LL |     let x = &10 as &dyn Add;
 help: set the type parameter to the desired type
    |
 LL |     let x = &10 as &dyn Add<Rhs>;
-   |                         ~~~~~~~~
+   |                            +++++
 
 error: aborting due to 2 previous errors
 

tests/ui/issues/issue-22370.stderr

@@ -11,7 +11,7 @@ LL | fn f(a: &dyn A) {}
 help: set the type parameter to the desired type
    |
 LL | fn f(a: &dyn A<T>) {}
-   |              ~~~~
+   |               +++
 
 error: aborting due to 1 previous error
 

tests/ui/type/type-parameter-defaults-referencing-Self.stderr

@@ -11,7 +11,7 @@ LL | fn foo(x: &dyn Foo) { }
 help: set the type parameter to the desired type
    |
 LL | fn foo(x: &dyn Foo<T>) { }
-   |                ~~~~~~
+   |                   +++
 
 error: aborting due to 1 previous error