there can never be too many tests

tests/compile-fail/invalid_enum_discriminant.rs

@@ -0,0 +1,14 @@
+#[repr(C)]
+pub enum Foo {
+    A, B, C, D
+}
+
+fn main() {
+    let f = unsafe { std::mem::transmute::<i32, Foo>(42) };
+    match f {
+        Foo::A => {}, //~ ERROR invalid enum discriminant value read
+        Foo::B => {},
+        Foo::C => {},
+        Foo::D => {},
+    }
+}