Auto merge of #37506 - jseyfried:improve_shadowing_checks, r=nrc

macros: improve shadowing checks

This PR improves macro-expanded shadowing checks to work with out-of-(pre)order expansion.

Out-of-order expansion became possible in #37084, so this technically a [breaking-change] for nightly.
The regression test from this PR is an example of code that would break.

r? @nrc

2 files changed, 37 insertions, 0 deletions

diff --git a/src/test/compile-fail/auxiliary/define_macro.rs b/src/test/compile-fail/auxiliary/define_macro.rs
new file mode 100644
index 00000000000..6b6b14a896b
--- /dev/null
+++ b/src/test/compile-fail/auxiliary/define_macro.rs
@@ -0,0 +1,16 @@
+// Copyright 2016 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.
+
+#[macro_export]
+macro_rules! define_macro {
+    ($i:ident) => {
+        macro_rules! $i { () => {} }
+    }
+}
diff --git a/src/test/compile-fail/out-of-order-shadowing.rs b/src/test/compile-fail/out-of-order-shadowing.rs
new file mode 100644
index 00000000000..1fafaf85112
--- /dev/null
+++ b/src/test/compile-fail/out-of-order-shadowing.rs
@@ -0,0 +1,21 @@
+// Copyright 2016 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.
+
+// aux-build:define_macro.rs
+// error-pattern: `bar` is already in scope
+
+macro_rules! bar { () => {} }
+define_macro!(bar);
+bar!();
+
+macro_rules! m { () => { #[macro_use] extern crate define_macro; } }
+m!();
+
+fn main() {}