add test to guard against inaccurate diagnostic

Also replaces an incomplete test

tests/ui/macros/invalid-fragment-specifier.rs

@@ -0,0 +1,10 @@
+macro_rules! test {
+    ($wrong:id) => {};
+} //~^ ERROR: invalid fragment specifier `id`
+
+// guard against breaking raw identifier diagnostic
+macro_rules! test_raw_identifer {
+    ($wrong:r#if) => {};
+} //~^ ERROR: invalid fragment specifier `r#if`
+
+fn main() {}

tests/ui/macros/invalid-fragment-specifier.stderr

@@ -0,0 +1,18 @@
+error: invalid fragment specifier `id`
+  --> $DIR/invalid-fragment-specifier.rs:2:6
+   |
+LL |     ($wrong:id) => {};
+   |      ^^^^^^^^^
+   |
+   = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis`
+
+error: invalid fragment specifier `r#if`
+  --> $DIR/invalid-fragment-specifier.rs:7:6
+   |
+LL |     ($wrong:r#if) => {};
+   |      ^^^^^^^^^^^
+   |
+   = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis`
+
+error: aborting due to 2 previous errors
+

tests/ui/macros/macro-invalid-fragment-spec.rs

@@ -1,8 +0,0 @@
-macro_rules! foo(
-    ($x:foo) => ()
-    //~^ ERROR invalid fragment specifier
-);
-
-fn main() {
-    foo!(foo);
-}

tests/ui/macros/macro-invalid-fragment-spec.stderr

@@ -1,10 +0,0 @@
-error: invalid fragment specifier `foo`
-  --> $DIR/macro-invalid-fragment-spec.rs:2:6
-   |
-LL |     ($x:foo) => ()
-   |      ^^^^^^
-   |
-   = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, `literal`, `path`, `meta`, `tt`, `item` and `vis`
-
-error: aborting due to 1 previous error
-