Check & before suggest remove deref when trait_selection

Signed-off-by: xizheyin <[email protected]>

Author: xizheyin

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

@@ -1525,7 +1525,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
                 expr = borrowed;
 
-                if maybe_suggest(suggested_ty, count, suggestions.clone()) {
+                if self.tcx.sess.source_map().span_to_snippet(span).unwrap().starts_with("&")
+                    && maybe_suggest(suggested_ty, count, suggestions.clone())
+                {
                     return true;
                 }
             }

tests/ui/traits/suggest-remove-deref-issue-140166.stderr

@@ -6,6 +6,7 @@ LL |     format_args!("{:?}", FlatMap(&Chars));
    |                   |
    |                   required by a bound introduced by this call
    |
+   = help: the trait `Trait` is implemented for `Chars`
 note: required for `FlatMap<&Chars>` to implement `Debug`
   --> $DIR/suggest-remove-deref-issue-140166.rs:7:16
    |
@@ -15,11 +16,6 @@ LL | impl<T: Trait> std::fmt::Debug for FlatMap<T> {
    |         unsatisfied trait bound introduced here
 note: required by a bound in `core::fmt::rt::Argument::<'_>::new_debug`
   --> $SRC_DIR/core/src/fmt/rt.rs:LL:COL
-help: consider removing the leading `&`-reference
-   |
-LL -     format_args!("{:?}", FlatMap(&Chars));
-LL +     format_args!("{:?}", latMap(&Chars));
-   |
 
 error: aborting due to 1 previous error