add suggestion

compiler/rustc_lint/messages.ftl

@@ -412,7 +412,7 @@ lint_non_upper_case_global = {$sort} `{$name}` should have an upper case name
     .label = should have an UPPER_CASE name
 
 lint_noop_method_call = call to `.{$method}()` on a reference in this situation does nothing
-    .label = unnecessary method call
+    .suggestion = remove this redundant call
     .note = the type `{$orig_ty}` does not implement `{$trait_}`, so calling `{$method}` on `&{$orig_ty}` copies the reference, which does not do anything and can be removed
 
 lint_only_cast_u8_to_char = only `u8` can be cast into `char`

compiler/rustc_lint/src/lints.rs

@@ -1233,7 +1233,7 @@ pub struct NoopMethodCallDiag<'a> {
     pub method: Symbol,
     pub orig_ty: Ty<'a>,
     pub trait_: Symbol,
-    #[label]
+    #[suggestion(code = "", applicability = "machine-applicable")]
     pub label: Span,
 }