Improve interaction between macros 2.0 and macro_rules!.

src/test/run-pass/hygiene/auxiliary/legacy_interaction.rs

@@ -0,0 +1,19 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-pretty pretty-printing is unhygienic
+
+#[macro_export]
+macro_rules! m {
+    () => {
+        fn f() {} // (2)
+        g(); // (1)
+    }
+}

src/test/run-pass/hygiene/legacy_interaction.rs

@@ -0,0 +1,50 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-pretty pretty-printing is unhygienic
+
+// aux-build:legacy_interaction.rs
+
+#![feature(decl_macro)]
+#[allow(unused)]
+
+extern crate legacy_interaction;
+// ^ defines
+// ```rust
+//  macro_rules! m {
+//     () => {
+//         fn f() // (1)
+//         g() // (2)
+//     }
+// }
+// ```rust
+
+mod def_site {
+    // Unless this macro opts out of hygiene, it should resolve the same wherever it is invoked.
+    pub macro m2() {
+        ::legacy_interaction::m!();
+        f(); // This should resolve to (1)
+        fn g() {} // We want (2) resolve to this, not to (4)
+    }
+}
+
+mod use_site {
+    fn test() {
+        fn f() -> bool { true } // (3)
+        fn g() -> bool { true } // (4)
+
+        ::def_site::m2!();
+
+        let _: bool = f(); // This should resolve to (3)
+        let _: bool = g(); // This should resolve to (4)
+    }
+}
+
+fn main() {}