Correctly access ScalarPair fields during const eval

src/test/ui/const-eval/issue-51300.rs

@@ -0,0 +1,41 @@
+// 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.
+
+// compile-pass
+// https://github.com/rust-lang/rust/issues/51300
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+pub struct Stat {
+    pub id: u8,
+    pub index: usize,
+}
+
+impl Stat {
+    pub const STUDENT_HAPPINESS: Stat = Stat{
+        id: 0,
+        index: 0,
+    };
+    pub const STUDENT_HUNGER: Stat = Stat{
+        id: 0,
+        index: Self::STUDENT_HAPPINESS.index + 1,
+    };
+
+}
+
+pub fn from_index(id: u8, index: usize) -> Option<Stat> {
+    let stat = Stat{id, index};
+    match stat {
+        Stat::STUDENT_HAPPINESS => Some(Stat::STUDENT_HAPPINESS),
+        Stat::STUDENT_HUNGER => Some(Stat::STUDENT_HUNGER),
+        _ => None,
+    }
+}
+
+fn main() { }