1 files changed, 102 insertions, 0 deletions
diff --git a/src/test/ui/consts/const-eval/ub-enum.rs b/src/test/ui/consts/const-eval/ub-enum.rs
new file mode 100644
index 000000000..d8d2a499b
--- /dev/null
+++ b/src/test/ui/consts/const-eval/ub-enum.rs
@@ -0,0 +1,102 @@
+// stderr-per-bitwidth
+#![feature(never_type)]
+
+use std::mem;
+
+#[repr(transparent)]
+#[derive(Copy, Clone)]
+struct Wrap<T>(T);
+
+#[derive(Copy, Clone)]
+enum Never {}
+
+// # simple enum with discriminant 0
+
+#[repr(usize)]
+#[derive(Copy, Clone)]
+enum Enum {
+    A = 0,
+}
+
+const GOOD_ENUM: Enum = unsafe { mem::transmute(0usize) };
+
+const BAD_ENUM: Enum = unsafe { mem::transmute(1usize) };
+//~^ ERROR is undefined behavior
+
+const BAD_ENUM_PTR: Enum = unsafe { mem::transmute(&1) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+
+const BAD_ENUM_WRAPPED: Wrap<Enum> = unsafe { mem::transmute(&1) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+
+// # simple enum with discriminant 2
+
+// (Potentially) invalid enum discriminant
+#[repr(usize)]
+#[derive(Copy, Clone)]
+enum Enum2 {
+    A = 2,
+}
+
+const BAD_ENUM2: Enum2 = unsafe { mem::transmute(0usize) };
+//~^ ERROR is undefined behavior
+const BAD_ENUM2_PTR: Enum2 = unsafe { mem::transmute(&0) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+// something wrapping the enum so that we test layout first, not enum
+const BAD_ENUM2_WRAPPED: Wrap<Enum2> = unsafe { mem::transmute(&0) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+
+// Undef enum discriminant.
+#[repr(C)]
+union MaybeUninit<T: Copy> {
+    uninit: (),
+    init: T,
+}
+const BAD_ENUM2_UNDEF : Enum2 = unsafe { MaybeUninit { uninit: () }.init };
+//~^ ERROR is undefined behavior
+
+// Pointer value in an enum with a niche that is not just 0.
+const BAD_ENUM2_OPTION_PTR: Option<Enum2> = unsafe { mem::transmute(&0) };
+//~^ ERROR any use of this value will cause an error
+//~| WARN this was previously accepted by the compiler but is being phased out
+
+// # valid discriminant for uninhabited variant
+
+// An enum with 3 variants of which some are uninhabited -- so the uninhabited variants *do*
+// have a discriminant.
+enum UninhDiscriminant {
+    A,
+    B(!),
+    C,
+    D(Never),
+}
+
+const GOOD_INHABITED_VARIANT1: UninhDiscriminant = unsafe { mem::transmute(0u8) }; // variant A
+const GOOD_INHABITED_VARIANT2: UninhDiscriminant = unsafe { mem::transmute(2u8) }; // variant C
+
+const BAD_UNINHABITED_VARIANT1: UninhDiscriminant = unsafe { mem::transmute(1u8) };
+//~^ ERROR is undefined behavior
+const BAD_UNINHABITED_VARIANT2: UninhDiscriminant = unsafe { mem::transmute(3u8) };
+//~^ ERROR is undefined behavior
+
+// # other
+
+// Invalid enum field content (mostly to test printing of paths for enum tuple
+// variants and tuples).
+// Need to create something which does not clash with enum layout optimizations.
+const BAD_OPTION_CHAR: Option<(char, char)> = Some(('x', unsafe { mem::transmute(!0u32) }));
+//~^ ERROR is undefined behavior
+
+// All variants are uninhabited but also have data.
+// Use `0` as constant to make behavior endianess-independent.
+const BAD_UNINHABITED_WITH_DATA1: Result<(i32, Never), (i32, !)> = unsafe { mem::transmute(0u64) };
+//~^ ERROR evaluation of constant value failed
+const BAD_UNINHABITED_WITH_DATA2: Result<(i32, !), (i32, Never)> = unsafe { mem::transmute(0u64) };
+//~^ ERROR evaluation of constant value failed
+
+fn main() {
+}