Migrate ast_lowering::path to SessionDiagnostic

compiler/rustc_ast_lowering/src/errors.rs

@@ -0,0 +1,29 @@
+use rustc_errors::{fluent, AddSubdiagnostic, Applicability, Diagnostic};
+use rustc_macros::SessionDiagnostic;
+use rustc_span::Span;
+
+#[derive(SessionDiagnostic, Clone, Copy)]
+#[error(ast_lowering::generic_type_with_parentheses, code = "E0214")]
+pub struct GenericTypeWithParentheses {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sub: Option<UseAngleBrackets>,
+}
+
+#[derive(Clone, Copy)]
+pub struct UseAngleBrackets {
+    pub open_param: Span,
+    pub close_param: Span,
+}
+
+impl AddSubdiagnostic for UseAngleBrackets {
+    fn add_to_diagnostic(self, diag: &mut Diagnostic) {
+        diag.multipart_suggestion(
+            fluent::ast_lowering::use_angle_brackets,
+            vec![(self.open_param, String::from("<")), (self.close_param, String::from(">"))],
+            Applicability::MaybeIncorrect,
+        );
+    }
+}