Rollup merge of #89221 - aDotInTheVoid:macro-error-1, r=estebank

Give better error for `macro_rules! name!`

r? ``@estebank``

``@rustbot`` modify labels: +A-diagnostics +A-parser

compiler/rustc_parse/src/parser/item.rs

@@ -1547,6 +1547,20 @@ impl<'a> Parser<'a> {
         self.expect(&token::Not)?; // `!`
 
         let ident = self.parse_ident()?;
+
+        if self.eat(&token::Not) {
+            // Handle macro_rules! foo!
+            let span = self.prev_token.span;
+            self.struct_span_err(span, "macro names aren't followed by a `!`")
+                .span_suggestion(
+                    span,
+                    "remove the `!`",
+                    "".to_owned(),
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+
         let body = self.parse_mac_args()?;
         self.eat_semi_for_macro_if_needed(&body);
         self.complain_if_pub_macro(vis, true);