Rollup merge of #106971 - oli-obk:tait_error, r=davidtwco

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

r? ```@davidtwco```

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);