Auto merge of #28672 - sanxiyn:const-eval-span, r=alexcrichton

Fix #28402.

src/test/compile-fail/const-eval-span.rs

@@ -0,0 +1,24 @@
+// 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.
+
+// Check that error in constant evaluation of enum discriminant
+// provides the context for what caused the evaluation.
+
+struct S(i32);
+
+const CONSTANT: S = S(0);
+//~^ ERROR: constant evaluation error: unsupported constant expr
+
+enum E {
+    V = CONSTANT,
+    //~^ NOTE: for enum discriminant here
+}
+
+fn main() {}