Add test for "const stability on macro"

compiler/rustc_expand/src/base.rs

@@ -774,8 +774,11 @@ impl SyntaxExtension {
             sess.parse_sess
                 .span_diagnostic
                 .struct_span_err(sp, "macros cannot have const stability attributes")
-                .span_label(sp, "invalid stability attribute")
-                .span_label(span, "in this macro")
+                .span_label(sp, "invalid const stability attribute")
+                .span_label(
+                    sess.source_map().guess_head_span(span),
+                    "const stability attribute affects this macro",
+                )
                 .emit();
         }
 

src/test/ui/attributes/const-stability-on-macro.rs

@@ -0,0 +1,13 @@
+#[rustc_const_stable(feature = "foo", since = "0")]
+//~^ ERROR macros cannot have const stability attributes
+macro_rules! foo {
+    () => {};
+}
+
+#[rustc_const_unstable(feature = "bar", issue="none")]
+//~^ ERROR macros cannot have const stability attributes
+macro_rules! bar {
+    () => {};
+}
+
+fn main() {}

src/test/ui/attributes/const-stability-on-macro.stderr

@@ -0,0 +1,20 @@
+error: macros cannot have const stability attributes
+  --> $DIR/const-stability-on-macro.rs:1:1
+   |
+LL | #[rustc_const_stable(feature = "foo", since = "0")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid const stability attribute
+LL |
+LL | macro_rules! foo {
+   | ---------------- const stability attribute affects this macro
+
+error: macros cannot have const stability attributes
+  --> $DIR/const-stability-on-macro.rs:7:1
+   |
+LL | #[rustc_const_unstable(feature = "bar", issue="none")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ invalid const stability attribute
+LL |
+LL | macro_rules! bar {
+   | ---------------- const stability attribute affects this macro
+
+error: aborting due to 2 previous errors
+