Add tests for E0758
diff --git a/src/test/ui/unterminated-doc-comment.rs b/src/test/ui/unterminated-doc-comment.rs
new file mode 100644
index 0000000..82546fe
--- /dev/null
+++ b/src/test/ui/unterminated-doc-comment.rs
@@ -0,0 +1 @@
+/*! //~ ERROR E0758