Auto merge of #34172 - jseyfried:avoid_configuring_interpolated_ast, r=alexcrichton

Fix ICE regression caused by configuring interpolated AST

Fixes #34171.
r? @nrc

src/libsyntax/config.rs

@@ -14,6 +14,7 @@ use feature_gate::GatedCfgAttr;
 use fold::Folder;
 use {ast, fold, attr};
 use codemap::{Spanned, respan};
+use parse::token;
 use ptr::P;
 
 use util::small_vector::SmallVector;
@@ -247,6 +248,12 @@ impl<T: CfgFolder> fold::Folder for T {
         self.configure(item).map(|item| fold::noop_fold_trait_item(item, self))
                             .unwrap_or(SmallVector::zero())
     }
+
+    fn fold_interpolated(&mut self, nt: token::Nonterminal) -> token::Nonterminal {
+        // Don't configure interpolated AST (c.f. #34171).
+        // Interpolated AST will get configured once the surrounding tokens are parsed.
+        nt
+    }
 }
 
 fn fold_expr<F: CfgFolder>(folder: &mut F, expr: P<ast::Expr>) -> P<ast::Expr> {

src/test/compile-fail/issue-34171.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.
+
+#![feature(rustc_attrs)]
+
+macro_rules! null { ($i:tt) => {} }
+macro_rules! apply_null {
+    ($i:item) => { null! { $i } }
+}
+
+#[rustc_error]
+fn main() { //~ ERROR compilation successful
+    apply_null!(#[cfg(all())] fn f() {});
+}