use ! in macro disambiguation suggestion

Author: euclio

src/librustdoc/passes/collect_intra_doc_links.rs

@@ -528,6 +528,9 @@ fn ambiguity_error(
                     Def::Method(..) | Def::Fn(..) => {
                         ("add parentheses", format!("{}()", path_str))
                     }
+                    Def::Macro(..) => {
+                        ("add an exclamation mark", format!("{}!", path_str))
+                    }
                     _ => {
                         let type_ = match (def, ns) {
                             (Def::Const(..), _) => "const",

src/test/rustdoc-ui/intra-links-ambiguity.stderr

@@ -45,10 +45,10 @@ help: to link to the function, add parentheses
    |
 LL | /// [`multi_conflict()`] is a three-way conflict.
    |      ^^^^^^^^^^^^^^^^^^
-help: to link to the macro, prefix with the item type
+help: to link to the macro, add an exclamation mark
    |
-LL | /// [`macro@multi_conflict`] is a three-way conflict.
-   |      ^^^^^^^^^^^^^^^^^^^^^^
+LL | /// [`multi_conflict!`] is a three-way conflict.
+   |      ^^^^^^^^^^^^^^^^^
 
 error: `type_and_value` is both a module and a constant
   --> $DIR/intra-links-ambiguity.rs:33:16