rustdoc: add test case for email that looks like intra-doc link

Author: notriddle

src/test/rustdoc/intra-doc/email-address.rs

@@ -1,8 +1,10 @@
-#![allow(rustdoc::broken_intra_doc_links)]
+#![forbid(rustdoc::broken_intra_doc_links)]
 
 //! Email me at <hello@example.com>.
 //! Email me at <hello-world@example.com>.
-//! Email me at <hello@localhost> (this warns but will still become a link).
+//! Email me at <hello@localhost>.
+//! Email me at <prim@i32>.
 // @has email_address/index.html '//a[@href="mailto:hello@example.com"]' 'hello@example.com'
 // @has email_address/index.html '//a[@href="mailto:hello-world@example.com"]' 'hello-world@example.com'
 // @has email_address/index.html '//a[@href="mailto:hello@localhost"]' 'hello@localhost'
+// @has email_address/index.html '//a[@href="mailto:prim@i32"]' 'prim@i32'