Handle diagnostics customization on the fluent side (for one specific diagnostic)

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -368,18 +368,6 @@ fn check_opaque_type_parameter_valid(
     for (i, arg) in opaque_type_key.substs.iter().enumerate() {
         let arg_is_param = match arg.unpack() {
             GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
-            GenericArgKind::Lifetime(lt) if lt.is_static() => {
-                tcx.sess
-                    .struct_span_err(span, "non-defining opaque type use in defining scope")
-                    .span_label(
-                        tcx.def_span(opaque_generics.param_at(i, tcx).def_id),
-                        "cannot use static lifetime; use a bound lifetime \
-                                    instead or remove the lifetime parameter from the \
-                                    opaque type",
-                    )
-                    .emit();
-                return false;
-            }
             GenericArgKind::Lifetime(lt) => {
                 matches!(*lt, ty::ReEarlyBound(_) | ty::ReFree(_))
             }

compiler/rustc_error_messages/locales/en-US/borrowck.ftl

@@ -123,4 +123,7 @@ borrowck_cannot_move_when_borrowed =
 
 borrowck_opaque_type_non_generic_param =
     expected generic {$kind} parameter, found `{$ty}`
-    .label = this generic parameter must be used with a generic {$kind} parameter
+    .label = {STREQ($ty, "'static") ->
+        [true] cannot use static lifetime; use a bound lifetime instead or remove the lifetime parameter from the opaque type
+        *[other] this generic parameter must be used with a generic {$kind} parameter
+    }

compiler/rustc_error_messages/locales/en-US/infer.ftl

@@ -147,8 +147,6 @@ infer_region_explanation = {$pref_kind ->
 }{$desc_kind ->
     *[should_not_happen] [{$desc_kind}]
     [restatic] the static lifetime
-    [reempty] the empty lifetime
-    [reemptyuni] the empty lifetime in universe {$desc_arg}
     [revar] lifetime {$desc_arg}
 
     [as_defined] the lifetime `{$desc_arg}` as defined here

compiler/rustc_error_messages/src/lib.rs

@@ -182,6 +182,9 @@ pub fn fluent_bundle(
     trace!(?locale);
     let mut bundle = new_bundle(vec![locale]);
 
+    // Add convenience functions available to ftl authors.
+    register_functions(&mut bundle);
+
     // Fluent diagnostics can insert directionality isolation markers around interpolated variables
     // indicating that there may be a shift from right-to-left to left-to-right text (or
     // vice-versa). These are disabled because they are sometimes visible in the error output, but
@@ -244,6 +247,15 @@ pub fn fluent_bundle(
     Ok(Some(bundle))
 }
 
+fn register_functions(bundle: &mut FluentBundle) {
+    bundle
+        .add_function("STREQ", |positional, _named| match positional {
+            [FluentValue::String(a), FluentValue::String(b)] => format!("{}", (a == b)).into(),
+            _ => FluentValue::Error,
+        })
+        .expect("Failed to add a function to the bundle.");
+}
+
 /// Type alias for the result of `fallback_fluent_bundle` - a reference-counted pointer to a lazily
 /// evaluated fluent bundle.
 pub type LazyFallbackBundle = Lrc<Lazy<FluentBundle, impl FnOnce() -> FluentBundle>>;
@@ -256,6 +268,9 @@ pub fn fallback_fluent_bundle(
 ) -> LazyFallbackBundle {
     Lrc::new(Lazy::new(move || {
         let mut fallback_bundle = new_bundle(vec![langid!("en-US")]);
+
+        register_functions(&mut fallback_bundle);
+
         // See comment in `fluent_bundle`.
         fallback_bundle.set_use_isolating(with_directionality_markers);
 

tests/ui/type-alias-impl-trait/bounds-are-checked.rs

@@ -8,7 +8,7 @@ type X<'a> = impl Into<&'static str> + From<&'a str>;
 fn f<'a: 'static>(t: &'a str) -> X<'a> {
     //~^ WARNING unnecessary lifetime parameter
     t
-    //~^ ERROR non-defining opaque type use
+    //~^ ERROR expected generic lifetime parameter, found `'static`
 }
 
 fn extend_lt<'a>(o: &'a str) -> &'static str {

tests/ui/type-alias-impl-trait/bounds-are-checked.stderr

@@ -6,7 +6,7 @@ LL | fn f<'a: 'static>(t: &'a str) -> X<'a> {
    |
    = help: you can use the `'static` lifetime directly, in place of `'a`
 
-error: non-defining opaque type use in defining scope
+error[E0792]: expected generic lifetime parameter, found `'static`
   --> $DIR/bounds-are-checked.rs:10:5
    |
 LL | type X<'a> = impl Into<&'static str> + From<&'a str>;
@@ -17,3 +17,4 @@ LL |     t
 
 error: aborting due to previous error; 1 warning emitted
 
+For more information about this error, try `rustc --explain E0792`.

tests/ui/type-alias-impl-trait/generic_nondefining_use.rs

@@ -19,7 +19,7 @@ fn concrete_ty() -> OneTy<u32> {
 
 fn concrete_lifetime() -> OneLifetime<'static> {
     6u32
-    //~^ ERROR non-defining opaque type use in defining scope
+    //~^ ERROR expected generic lifetime parameter, found `'static`
 }
 
 fn concrete_const() -> OneConst<{ 123 }> {

tests/ui/type-alias-impl-trait/generic_nondefining_use.stderr

@@ -7,7 +7,7 @@ LL | type OneTy<T> = impl Debug;
 LL |     5u32
    |     ^^^^
 
-error: non-defining opaque type use in defining scope
+error[E0792]: expected generic lifetime parameter, found `'static`
   --> $DIR/generic_nondefining_use.rs:21:5
    |
 LL | type OneLifetime<'a> = impl Debug;