Migrate trait_fn_async

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -287,16 +287,7 @@ impl<'a> AstValidator<'a> {
 
     fn check_trait_fn_not_async(&self, fn_span: Span, asyncness: Async) {
         if let Async::Yes { span, .. } = asyncness {
-            struct_span_err!(
+            self.session.emit_err(TraitFnAsync { fn_span, span });
-                self.session,
-                fn_span,
-                E0706,
-                "functions in traits cannot be declared `async`"
-            )
-            .span_label(span, "`async` because of this")
-            .note("`async` trait functions are not currently supported")
-            .note("consider using the `async-trait` crate: https://crates.io/crates/async-trait")
-            .emit();
         }
     }
 

compiler/rustc_ast_passes/src/errors.rs

@@ -71,3 +71,14 @@ pub enum InvalidVisibilityNote {
     #[note(ast_passes::individual_foreign_items)]
     IndividualForeignItems,
 }
+
+#[derive(SessionDiagnostic)]
+#[error(ast_passes::trait_fn_async, code = "E0706")]
+#[note]
+#[note(ast_passes::note2)]
+pub struct TraitFnAsync {
+    #[primary_span]
+    pub fn_span: Span,
+    #[label]
+    pub span: Span,
+}

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

@@ -21,3 +21,9 @@ ast_passes_invalid_visibility =
     .implied = `pub` not permitted here because it's implied
     .individual_impl_items = place qualifiers on individual impl items instead
     .individual_foreign_items = place qualifiers on individual foreign items instead
+
+ast_passes_trait_fn_async =
+    functions in traits cannot be declared `async`
+    .label = `async` because of this
+    .note = `async` trait functions are not currently supported
+    .note2 = consider using the `async-trait` crate: https://crates.io/crates/async-trait