Detect when a lifetime is being reused in suggestion

Author: estebank

compiler/rustc_infer/messages.ftl

@@ -164,7 +164,10 @@ infer_label_bad = {$bad_kind ->
 infer_lf_bound_not_satisfied = lifetime bound not satisfied
 infer_lifetime_mismatch = lifetime mismatch
 
-infer_lifetime_param_suggestion = consider introducing a named lifetime parameter{$is_impl ->
+infer_lifetime_param_suggestion = consider {$is_reuse ->
+    [true] reusing
+    *[false] introducing
+} a named lifetime parameter{$is_impl ->
     [true] {" "}and update trait if needed
     *[false] {""}
 }

compiler/rustc_infer/src/errors/mod.rs

@@ -517,6 +517,7 @@ impl Subdiagnostic for AddLifetimeParamsSuggestion<'_> {
                 Applicability::MaybeIncorrect,
             );
             diag.arg("is_impl", is_impl);
+            diag.arg("is_reuse", !introduce_new);
 
             true
         };

tests/ui/lifetimes/issue-90170-elision-mismatch.stderr

@@ -35,7 +35,7 @@ LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&u8>, y: &u8) { x.push(y); }
    |                                               |        let's call the lifetime of this reference `'1`
    |                                               let's call the lifetime of this reference `'2`
    |
-help: consider introducing a named lifetime parameter
+help: consider reusing a named lifetime parameter
    |
 LL | pub fn foo3<'a>(_other: &'a [u8], x: &mut Vec<&'a u8>, y: &'a u8) { x.push(y); }
    |                                                ++          ++

tests/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-if-else-using-impl.stderr

@@ -9,7 +9,7 @@ LL |
 LL |         if x > y { x } else { y }
    |                    ^ associated function was supposed to return data with lifetime `'a` but it is returning data with lifetime `'1`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn foo<'a>(x: &'a i32, y: &'a i32) -> &'a i32 {
    |                    ++

tests/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-return-type-is-anon.stderr

@@ -8,7 +8,7 @@ LL |     fn foo<'a>(&self, x: &'a i32) -> &i32 {
 LL |         x
    |         ^ method was supposed to return data with lifetime `'1` but it is returning data with lifetime `'a`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn foo<'a>(&self, x: &'a i32) -> &'a i32 {
    |                                       ++

tests/ui/lifetimes/lifetime-errors/ex1-return-one-existing-name-self-is-anon.stderr

@@ -9,7 +9,7 @@ LL |
 LL |         if true { x } else { self }
    |                              ^^^^ method was supposed to return data with lifetime `'a` but it is returning data with lifetime `'1`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn foo<'a>(&'a self, x: &'a Foo) -> &'a Foo {
    |                 ++

tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-return-type-is-anon.stderr

@@ -8,7 +8,7 @@ LL |     fn foo<'a>(&self, x: &i32) -> &i32 {
 LL |         x
    |         ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn foo<'a>(&self, x: &'a i32) -> &'a i32 {
    |                           ++          ++

tests/ui/lifetimes/lifetime-errors/ex3-both-anon-regions-self-is-anon.stderr

@@ -8,7 +8,7 @@ LL |     fn foo<'a>(&self, x: &Foo) -> &Foo {
 LL |         if true { x } else { self }
    |                   ^ method was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn foo<'a>(&self, x: &'a Foo) -> &'a Foo {
    |                           ++          ++

tests/ui/self/arbitrary_self_types_pin_lifetime_mismatch-async.stderr

@@ -35,7 +35,7 @@ LL |     async fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() { arg }
    |                  |               let's call the lifetime of this reference `'1`
    |                  lifetime `'a` defined here
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     async fn bar<'a>(self: Alias<&'a Self>, arg: &'a ()) -> &() { arg }
    |                                   ++

tests/ui/self/arbitrary_self_types_pin_lifetime_mismatch.stderr

@@ -38,7 +38,7 @@ LL |     fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &() {
 LL |         arg
    |         ^^^ method was supposed to return data with lifetime `'1` but it is returning data with lifetime `'a`
    |
-help: consider introducing a named lifetime parameter and update trait if needed
+help: consider reusing a named lifetime parameter and update trait if needed
    |
 LL |     fn bar<'a>(self: Alias<&Self>, arg: &'a ()) -> &'a () {
    |                                                     ++