add missing test: expected paren or brace in macro

tests/ui/macros/paren-or-brace-expected.rs

@@ -0,0 +1,9 @@
+macro_rules! foo {
+    ( $( $i:ident ),* ) => {
+        $[count($i)]
+        //~^ ERROR expected `(` or `{`, found `[`
+        //~| ERROR
+    };
+}
+
+fn main() {}

tests/ui/macros/paren-or-brace-expected.stderr

@@ -0,0 +1,14 @@
+error: expected `(` or `{`, found `[`
+  --> $DIR/paren-or-brace-expected.rs:3:10
+   |
+LL |         $[count($i)]
+   |          ^^^^^^^^^^^
+
+error: expected one of: `*`, `+`, or `?`
+  --> $DIR/paren-or-brace-expected.rs:3:10
+   |
+LL |         $[count($i)]
+   |          ^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+