Skip suggestion with equal spans attribute affected in suggest_trait_and_bounds

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

Author: xizheyin

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -885,10 +885,10 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 // `end_span` is the end of the poly trait ref (Foo + 'baz + Bar><)
                 let end_span = last_bound.span();
                 // `last_bound_span` is the last bound of the poly trait ref (Foo + >'baz< + Bar)
-                let last_bound_span = spans.last().cloned().unwrap();
+                let last_bound_span = spans.last().cloned();
                 let mut multi_span: MultiSpan = spans.clone().into();
                 for sp in spans {
-                    let msg = if sp == last_bound_span {
+                    let msg = if Some(sp) == last_bound_span {
                         format!(
                             "...because of {these} bound{s}",
                             these = pluralize!("this", bounds.len() - 1),
@@ -917,11 +917,13 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                         sugg.push((base_error.span.shrink_to_hi().to(end_span), String::new()));
                     }
 
-                    err.multipart_suggestion(
-                        "if you meant to use a type and not a trait here, remove the bounds",
-                        sugg,
-                        Applicability::MaybeIncorrect,
-                    );
+                    if !sugg.is_empty() {
+                        err.multipart_suggestion(
+                            "if you meant to use a type and not a trait here, remove the bounds",
+                            sugg,
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
                 }
             }
         }

tests/ui/trait-bounds/attribute-affected-trait-bound-issue-137129.rs

@@ -0,0 +1,11 @@
+#![core::contracts::ensures]
+//~^ ERROR use of unstable library feature `contracts` [E0658]
+//~| ERROR inner macro attributes are unstable [E0658]
+//~| ERROR expected trait, found struct `A` [E0404]
+//~| ERROR `#[prelude_import]` is for use by rustc only [E0658]
+struct A {
+    b: dyn A + 'static,
+}
+fn c() {}
+
+fn main(){}

tests/ui/trait-bounds/attribute-affected-trait-bound-issue-137129.stderr

@@ -0,0 +1,45 @@
+error[E0658]: use of unstable library feature `contracts`
+  --> $DIR/attribute-affected-trait-bound-issue-137129.rs:1:4
+   |
+LL | #![core::contracts::ensures]
+   |    ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #128044 <https://github.com/rust-lang/rust/issues/128044> for more information
+   = help: add `#![feature(contracts)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0658]: inner macro attributes are unstable
+  --> $DIR/attribute-affected-trait-bound-issue-137129.rs:1:4
+   |
+LL | #![core::contracts::ensures]
+   |    ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #54726 <https://github.com/rust-lang/rust/issues/54726> for more information
+   = help: add `#![feature(custom_inner_attributes)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0404]: expected trait, found struct `A`
+  --> $DIR/attribute-affected-trait-bound-issue-137129.rs:1:1
+   |
+LL | / #![core::contracts::ensures]
+...  |
+LL | | fn main(){}
+   | |___________^ not a trait
+   |
+help: `+` is used to constrain a "trait object" type with lifetimes or auto-traits; structs and enums can't be bound in that way
+
+error[E0658]: `#[prelude_import]` is for use by rustc only
+  --> $DIR/attribute-affected-trait-bound-issue-137129.rs:1:1
+   |
+LL | / #![core::contracts::ensures]
+...  |
+LL | | fn main(){}
+   | |___________^
+   |
+   = help: add `#![feature(prelude_import)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0404, E0658.
+For more information about an error, try `rustc --explain E0404`.