Fix duplicated type annotation suggestion

Before, there was more or less duplicated suggestions to add type hints.
Fix by clearing more generic suggestions when a more specific suggestion
is possible.

This fixes rust-lang#93506 .

Author: danobi

compiler/rustc_errors/src/diagnostic.rs

@@ -614,6 +614,14 @@ impl Diagnostic {
         self
     }
 
+    /// Clear any existing suggestions.
+    pub fn clear_suggestions(&mut self) -> &mut Self {
+        if let Ok(suggestions) = &mut self.suggestions {
+            suggestions.clear();
+        }
+        self
+    }
+
     /// Helper for pushing to `self.suggestions`, if available (not disable).
     fn push_suggestion(&mut self, suggestion: CodeSuggestion) {
         if let Ok(suggestions) = &mut self.suggestions {

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -461,6 +461,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     forward!(pub fn set_is_lint(&mut self,) -> &mut Self);
 
     forward!(pub fn disable_suggestions(&mut self,) -> &mut Self);
+    forward!(pub fn clear_suggestions(&mut self,) -> &mut Self);
 
     forward!(pub fn multipart_suggestion(
         &mut self,

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

@@ -2074,6 +2074,9 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                         //    |
                         //    = note: cannot satisfy `_: Tt`
 
+                        // Clear any more general suggestions in favor of our specific one
+                        err.clear_suggestions();
+
                         err.span_suggestion_verbose(
                             span.shrink_to_hi(),
                             &format!(

src/test/ui/inference/erase-type-params-in-label.stderr

@@ -10,10 +10,6 @@ note: required by a bound in `foo`
    |
 LL | fn foo<T, K, W: Default, Z: Default>(t: T, k: K) -> Foo<T, K, W, Z> {
    |                 ^^^^^^^ required by this bound in `foo`
-help: consider giving `foo` an explicit type, where the type for type parameter `W` is specified
-   |
-LL |     let foo: Foo<i32, &str, W, Z> = foo(1, "");
-   |            ++++++++++++++++++++++
 help: consider specifying the type arguments in the function call
    |
 LL |     let foo = foo::<T, K, W, Z>(1, "");
@@ -31,10 +27,6 @@ note: required by a bound in `bar`
    |
 LL | fn bar<T, K, Z: Default>(t: T, k: K) -> Bar<T, K, Z> {
    |                 ^^^^^^^ required by this bound in `bar`
-help: consider giving `bar` an explicit type, where the type for type parameter `Z` is specified
-   |
-LL |     let bar: Bar<i32, &str, Z> = bar(1, "");
-   |            +++++++++++++++++++
 help: consider specifying the type arguments in the function call
    |
 LL |     let bar = bar::<T, K, Z>(1, "");

src/test/ui/inference/issue-71732.stderr

@@ -13,10 +13,6 @@ note: required by a bound in `HashMap::<K, V, S>::get`
    |
 LL |         K: Borrow<Q>,
    |            ^^^^^^^^^ required by this bound in `HashMap::<K, V, S>::get`
-help: consider specifying the generic argument
-   |
-LL |         .get::<Q>(&"key".into())
-   |             +++++
 help: consider specifying the type argument in the function call
    |
 LL |         .get::<Q>(&"key".into())

src/test/ui/traits/issue-77982.stderr

@@ -13,10 +13,6 @@ note: required by a bound in `HashMap::<K, V, S>::get`
    |
 LL |         K: Borrow<Q>,
    |            ^^^^^^^^^ required by this bound in `HashMap::<K, V, S>::get`
-help: consider specifying the generic argument
-   |
-LL |     opts.get::<Q>(opt.as_ref());
-   |             +++++
 help: consider specifying the type argument in the function call
    |
 LL |     opts.get::<Q>(opt.as_ref());

src/test/ui/traits/multidispatch-convert-ambig-dest.stderr

@@ -30,10 +30,6 @@ LL | fn test<T,U>(_: T, _: U)
    |    ---- required by a bound in this
 LL | where T : Convert<U>
    |           ^^^^^^^^^^ required by this bound in `test`
-help: consider specifying the generic arguments
-   |
-LL |     test::<i32, U>(22, std::default::Default::default());
-   |         ++++++++++
 help: consider specifying the type arguments in the function call
    |
 LL |     test::<T, U>(22, std::default::Default::default());

src/test/ui/type/type-annotation-needed.stderr

@@ -10,10 +10,6 @@ note: required by a bound in `foo`
    |
 LL | fn foo<T: Into<String>>(x: i32) {}
    |           ^^^^^^^^^^^^ required by this bound in `foo`
-help: consider specifying the generic argument
-   |
-LL |     foo::<T>(42);
-   |        +++++
 help: consider specifying the type argument in the function call
    |
 LL |     foo::<T>(42);