macros: Do not match on "complex" nonterminals requiring AST comparisons

2 files changed, 47 insertions, 0 deletions

diff --git a/src/test/ui/macros/nonterminal-matching.rs b/src/test/ui/macros/nonterminal-matching.rs
new file mode 100644
index 00000000000..4dcb8afa94e
--- /dev/null
+++ b/src/test/ui/macros/nonterminal-matching.rs
@@ -0,0 +1,36 @@
+// Copyright 2018 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.
+
+// Check that we are refusing to match on complex nonterminals for which tokens are
+// unavailable and we'd have to go through AST comparisons.
+
+#![feature(decl_macro, macro_lifetime_matcher)]
+
+macro simple_nonterminal($nt_ident: ident, $nt_lifetime: lifetime, $nt_tt: tt) {
+    macro n(a $nt_ident b $nt_lifetime c $nt_tt d) {
+        struct S;
+    }
+
+    n!(a $nt_ident b $nt_lifetime c $nt_tt d);
+}
+
+macro complex_nonterminal($nt_item: item) {
+    macro n(a $nt_item b) {
+        struct S;
+    }
+
+    n!(a $nt_item b); //~ ERROR no rules expected the token `enum E { }`
+}
+
+simple_nonterminal!(a, 'a, (x, y, z)); // OK
+
+complex_nonterminal!(enum E {});
+
+fn main() {}
diff --git a/src/test/ui/macros/nonterminal-matching.stderr b/src/test/ui/macros/nonterminal-matching.stderr
new file mode 100644
index 00000000000..bf2221d52a4
--- /dev/null
+++ b/src/test/ui/macros/nonterminal-matching.stderr
@@ -0,0 +1,11 @@
+error: no rules expected the token `enum E { }`
+  --> $DIR/nonterminal-matching.rs:29:10
+   |
+LL |     n!(a $nt_item b); //~ ERROR no rules expected the token `enum E { }`
+   |          ^^^^^^^^
+...
+LL | complex_nonterminal!(enum E {});
+   | -------------------------------- in this macro invocation
+
+error: aborting due to previous error
+