Suggest use another lifetime specifier instead of underscore lifetime

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

Author: xizheyin

compiler/rustc_resolve/src/late.rs

@@ -1929,7 +1929,9 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                             });
                         }
                     } else {
-                        self.r.dcx().emit_err(errors::UnderscoreLifetimeIsReserved { span: lifetime.ident.span });
+                        self.r.dcx().emit_err(errors::UnderscoreLifetimeIsReserved {
+                            span: lifetime.ident.span,
+                        });
                     };
                     self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
                     return;
@@ -2901,9 +2903,11 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 }
 
                 if param.ident.name == kw::UnderscoreLifetime {
-                    self.r
-                        .dcx()
-                        .emit_err(errors::UnderscoreLifetimeIsReserved { span: param.ident.span }); 
+                    let mut err = self.r.dcx().create_err(errors::UnderscoreLifetimeIsReserved {
+                        span: param.ident.span,
+                    });
+                    err.note("use another lifetime specifier");
+                    err.emit();
                     // Record lifetime res, so lowering knows there is something fishy.
                     self.record_lifetime_param(param.id, LifetimeRes::Error);
                     continue;

tests/ui/error-codes/E0637.stderr

@@ -3,6 +3,8 @@ error[E0637]: `'_` cannot be used here
    |
 LL | fn underscore_lifetime<'_>(str1: &'_ str, str2: &'_ str) -> &'_ str {
    |                        ^^ `'_` is a reserved lifetime name
+   |
+   = help: use another lifetime specifier
 
 error[E0106]: missing lifetime specifier
   --> $DIR/E0637.rs:1:62

tests/ui/lifetimes/lifetime-errors/raw-annomy-lifetime-issue-143152.rs

@@ -4,4 +4,4 @@ fn f<'r#_>(){}
 //~^ ERROR `_` cannot be a raw lifetime
 //~| ERROR `'_` cannot be used here [E0637]
 
-fn main() {}
+fn main() {}

tests/ui/lifetimes/lifetime-errors/raw-annomy-lifetime-issue-143152.stderr

@@ -9,6 +9,8 @@ error[E0637]: `'_` cannot be used here
    |
 LL | fn f<'r#_>(){}
    |      ^^^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error: aborting due to 2 previous errors
 

tests/ui/underscore-lifetime/in-binder.stderr

@@ -3,36 +3,48 @@ error[E0637]: `'_` cannot be used here
    |
 LL | impl<'_> IceCube<'_> {}
    |      ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/in-binder.rs:12:15
    |
 LL | struct Struct<'_> {
    |               ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/in-binder.rs:17:11
    |
 LL | enum Enum<'_> {
    |           ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/in-binder.rs:22:13
    |
 LL | union Union<'_> {
    |             ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/in-binder.rs:27:13
    |
 LL | trait Trait<'_> {
    |             ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/in-binder.rs:31:8
    |
 LL | fn foo<'_>() {
    |        ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error: aborting due to 6 previous errors
 

tests/ui/underscore-lifetime/underscore-lifetime-binders.stderr

@@ -15,12 +15,16 @@ error[E0637]: `'_` cannot be used here
    |
 LL | fn foo<'_>
    |        ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0637]: `'_` cannot be used here
   --> $DIR/underscore-lifetime-binders.rs:10:25
    |
 LL | fn meh() -> Box<dyn for<'_> Meh<'_>>
    |                         ^^ `'_` is a reserved lifetime name
+   |
+   = note: use another lifetime specifier
 
 error[E0106]: missing lifetime specifier
   --> $DIR/underscore-lifetime-binders.rs:10:33