constify mem::discriminant

src/test/ui/consts/const_discriminant.rs

@@ -0,0 +1,22 @@
+// run-pass
+#![feature(const_discriminant)]
+
+use std::mem::{discriminant, Discriminant};
+
+enum Test {
+    A(u8),
+    B,
+    C { a: u8, b: u8 },
+}
+
+const TEST_A: Discriminant<Test> = discriminant(&Test::A(5));
+const TEST_A_OTHER: Discriminant<Test> = discriminant(&Test::A(17));
+const TEST_B: Discriminant<Test> = discriminant(&Test::B);
+
+fn main() {
+    assert_eq!(TEST_A, TEST_A_OTHER);
+    assert_eq!(TEST_A, discriminant(&Test::A(17)));
+    assert_eq!(TEST_B, discriminant(&Test::B));
+    assert_ne!(TEST_A, TEST_B);
+    assert_ne!(TEST_B, discriminant(&Test::C { a: 42, b: 7 }));
+}