Reduce verbosity when suggesting restricting type params

Author: estebank

src/librustc_typeck/check/method/suggest.rs

@@ -535,6 +535,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     report_candidates(span, &mut err, static_sources, sugg_span);
                 }
 
+                let mut restrict_type_params = false;
                 if !unsatisfied_predicates.is_empty() {
                     let def_span =
                         |def_id| self.tcx.sess.source_map().def_span(self.tcx.def_span(def_id));
@@ -647,6 +648,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .enumerate()
                         .collect::<Vec<(usize, String)>>();
                     for ((span, empty_where), obligations) in type_params.into_iter() {
+                        restrict_type_params = true;
                         err.span_suggestion_verbose(
                             span,
                             &format!(
@@ -685,7 +687,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }
 
-                if actual.is_numeric() && actual.is_fresh() {
+                if actual.is_numeric() && actual.is_fresh() || restrict_type_params {
                 } else {
                     self.suggest_traits_to_import(
                         &mut err,

src/test/ui/suggestions/missing-trait-bounds-for-method-call.stderr

@@ -12,12 +12,6 @@ LL |         self.foo();
            which is required by `Foo<T>: Bar`
            `T: std::default::Default`
            which is required by `Foo<T>: Bar`
-   = help: items from traits can only be used if the trait is implemented and in scope
-note: `Bar` defines an item `foo`, perhaps you need to implement it
-  --> $DIR/missing-trait-bounds-for-method-call.rs:6:1
-   |
-LL | trait Bar {
-   | ^^^^^^^^^
 help: consider restricting the type parameters to satisfy the obligations
    |
 LL | struct Foo<T> where T: Bar, T: std::default::Default {
@@ -35,12 +29,6 @@ LL |         self.foo();
    = note: the method `foo` exists but the following trait bounds were not satisfied:
            `T: std::default::Default`
            which is required by `Fin<T>: Bar`
-   = help: items from traits can only be used if the trait is implemented and in scope
-note: `Bar` defines an item `foo`, perhaps you need to implement it
-  --> $DIR/missing-trait-bounds-for-method-call.rs:6:1
-   |
-LL | trait Bar {
-   | ^^^^^^^^^
 help: consider restricting the type parameter to satisfy the obligation
    |
 LL | struct Fin<T> where T: Bar, T: std::default::Default {