fix #40294 obligation cause.body_id is not always a NodeExpr

src/test/ui/resolve/issue-40294.rs

@@ -0,0 +1,23 @@
+// 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.
+
+trait Foo: Sized {
+    fn foo(self);
+}
+
+fn foo<'a,'b,T>(x: &'a T, y: &'b T)
+    where &'a T : Foo,
+          &'b T : Foo
+{
+    x.foo();
+    y.foo();
+}
+
+fn main() { }

src/test/ui/resolve/issue-40294.stderr

@@ -0,0 +1,15 @@
+error[E0282]: type annotations needed
+  --> $DIR/issue-40294.rs:15:1
+   |
+15 |   fn foo<'a,'b,T>(x: &'a T, y: &'b T)
+   |  _^ starting here...
+16 | |     where &'a T : Foo,
+17 | |           &'b T : Foo
+18 | | {
+19 | |     x.foo();
+20 | |     y.foo();
+21 | | }
+   | |_^ ...ending here: cannot infer type for `&'a T`
+
+error: aborting due to previous error
+