Use more targetted suggestion span for fully qualified path

Author: estebank

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -734,19 +734,22 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 if !impl_candidates.is_empty() && e.span.contains(span)
                     && let Some(expr) = exprs.first()
                     && let ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind
-                    && let [path_segment] = path.segments
+                    && let [_] = path.segments
                 {
                     let mut eraser = TypeParamEraser(self.tcx);
                     let candidate_len = impl_candidates.len();
                     let suggestions = impl_candidates.iter().map(|candidate| {
                         let candidate = candidate.super_fold_with(&mut eraser);
-                        format!(
-                            "{}::{}({})",
-                            candidate, segment.ident, path_segment.ident
-                        )
+                        vec![
+                            (expr.span.shrink_to_lo(), format!("{}::{}(", candidate, segment.ident)),
+                            if exprs.len() == 1 {
+                                (expr.span.shrink_to_hi().with_hi(e.span.hi()), ")".to_string())
+                            } else {
+                                (expr.span.shrink_to_hi().with_hi(exprs[1].span.lo()), ", ".to_string())
+                            },
+                        ]
                     });
-                    err.span_suggestions(
-                        e.span,
+                    err.multipart_suggestions(
                         &format!(
                             "use the fully qualified path for the potential candidate{}",
                             pluralize!(candidate_len),

src/test/ui/error-codes/E0283.stderr

@@ -14,7 +14,6 @@ LL |     let bar = foo_impl.into() * 1u32;
    |               |        |
    |               |        cannot infer type for type parameter `T` declared on the trait `Into`
    |               this method call resolves to `T`
-   |               help: use the fully qualified path for the potential candidate: `<Impl as Into<u32>>::into(foo_impl)`
    |
 note: multiple `impl`s satisfying `Impl: Into<_>` found
   --> $DIR/E0283.rs:17:1
@@ -24,6 +23,10 @@ LL | impl Into<u32> for Impl {
    = note: and another `impl` found in the `core` crate:
            - impl<T, U> Into<U> for T
              where U: From<T>;
+help: use the fully qualified path for the potential candidate
+   |
+LL |     let bar = <Impl as Into<u32>>::into(foo_impl) * 1u32;
+   |               ++++++++++++++++++++++++++        ~
 
 error: aborting due to 2 previous errors
 

src/test/ui/traits/do-not-mention-type-params-by-name-in-suggestion-issue-96292.rs

@@ -1,20 +1,20 @@
 struct Thing<X>(X);
 
 trait Method<T> {
-    fn method(self) -> T;
+    fn method(self, _: i32) -> T;
 }
 
 impl<X> Method<i32> for Thing<X> {
-    fn method(self) -> i32 { 0 }
+    fn method(self, _: i32) -> i32 { 0 }
 }
 
 impl<X> Method<u32> for Thing<X> {
-    fn method(self) -> u32 { 0 }
+    fn method(self, _: i32) -> u32 { 0 }
 }
 
 fn main() {
     let thing = Thing(true);
-    thing.method();
+    thing.method(42);
     //~^ ERROR type annotations needed
     //~| ERROR type annotations needed
 }

src/test/ui/traits/do-not-mention-type-params-by-name-in-suggestion-issue-96292.stderr

@@ -1,17 +1,17 @@
 error[E0282]: type annotations needed
   --> $DIR/do-not-mention-type-params-by-name-in-suggestion-issue-96292.rs:17:11
    |
-LL |     thing.method();
-   |     ------^^^^^^--
+LL |     thing.method(42);
+   |     ------^^^^^^----
    |     |     |
    |     |     cannot infer type for type parameter `T` declared on the trait `Method`
    |     this method call resolves to `T`
 
 error[E0283]: type annotations needed
   --> $DIR/do-not-mention-type-params-by-name-in-suggestion-issue-96292.rs:17:11
    |
-LL |     thing.method();
-   |     ------^^^^^^--
+LL |     thing.method(42);
+   |     ------^^^^^^----
    |     |     |
    |     |     cannot infer type for type parameter `T` declared on the trait `Method`
    |     this method call resolves to `T`
@@ -26,10 +26,10 @@ LL | impl<X> Method<u32> for Thing<X> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: use the fully qualified path for the potential candidates
    |
-LL |     <Thing<_> as Method<i32>>::method(thing);
-   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     <Thing<_> as Method<u32>>::method(thing);
-   |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     <Thing<_> as Method<i32>>::method(thing, 42);
+   |     ++++++++++++++++++++++++++++++++++     ~
+LL |     <Thing<_> as Method<u32>>::method(thing, 42);
+   |     ++++++++++++++++++++++++++++++++++     ~
 
 error: aborting due to 2 previous errors
 

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

@@ -36,14 +36,14 @@ LL |     opts.get(opt.as_ref());
            - impl AsRef<str> for String;
 help: use the fully qualified path for the potential candidates
    |
-LL |     opts.get(<String as AsRef<OsStr>>::as_ref(opt));
-   |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     opts.get(<String as AsRef<Path>>::as_ref(opt));
-   |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     opts.get(<String as AsRef<[u8]>>::as_ref(opt));
-   |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-LL |     opts.get(<String as AsRef<str>>::as_ref(opt));
-   |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     opts.get(<str as AsRef<Path>>::as_ref(opt));
+   |              +++++++++++++++++++++++++++++   ~
+LL |     opts.get(<str as AsRef<OsStr>>::as_ref(opt));
+   |              ++++++++++++++++++++++++++++++   ~
+LL |     opts.get(<str as AsRef<str>>::as_ref(opt));
+   |              ++++++++++++++++++++++++++++   ~
+LL |     opts.get(<str as AsRef<[u8]>>::as_ref(opt));
+   |              +++++++++++++++++++++++++++++   ~
      and 4 other candidates
 
 error[E0283]: type annotations needed