Auto merge of #25209 - llogiq:master, r=eddyb

According to @eddyb – and my tests – the following gets rid of the ICE in issue #25180.

Author: bors

src/librustc/middle/check_const.rs

@@ -251,9 +251,10 @@ impl<'a, 'tcx, 'v> Visitor<'v> for CheckCrateVisitor<'a, 'tcx> {
                 b: &'v ast::Block,
                 s: Span,
                 fn_id: ast::NodeId) {
-        assert!(self.mode == Mode::Var);
-        self.with_euv(Some(fn_id), |euv| euv.walk_fn(fd, b));
-        visit::walk_fn(self, fk, fd, b, s);
+        self.with_mode(Mode::Var, |v| {
+            v.with_euv(Some(fn_id), |euv| euv.walk_fn(fd, b));
+            visit::walk_fn(v, fk, fd, b, s);
+        })
     }
 
     fn visit_pat(&mut self, p: &ast::Pat) {

src/test/run-pass/issue-25180.rs

@@ -0,0 +1,30 @@
+// Copyright 2015 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.
+
+// pretty-expanded FIXME #25180
+
+const EMPTY: &'static Fn() = &|| println!("ICE here");
+
+const ONE_ARGUMENT: &'static Fn(u32) = &|y| println!("{}", y);
+
+const PLUS_21: &'static (Fn(u32) -> u32) = &|y| y + 21;
+
+const MULTI_AND_LOCAL: &'static (Fn(u32, u32) -> u32) = &|x, y| {
+    let tmp = x + y;
+    tmp * 2
+};
+
+pub fn main() {
+    EMPTY();
+    ONE_ARGUMENT(42);
+    assert!(PLUS_21(21) == 42);
+    assert!(MULTI_AND_LOCAL(1, 2) == 6);
+}
+