error[E0080]: it is undefined behavior to use this value --> $DIR/ub-enum.rs:24:1 | LL | const BAD_ENUM: Enum = unsafe { mem::transmute(1usize) }; | ^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .: encountered 0x00000001, but expected a valid enum tag | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 4, align: 4) { 01 00 00 00 │ .... } error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:27:1 | LL | const BAD_ENUM_PTR: Enum = unsafe { mem::transmute(&1) }; | ^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes | = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:30:1 | LL | const BAD_ENUM_WRAPPED: Wrap = unsafe { mem::transmute(&1) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes | = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported error[E0080]: it is undefined behavior to use this value --> $DIR/ub-enum.rs:42:1 | LL | const BAD_ENUM2: Enum2 = unsafe { mem::transmute(0usize) }; | ^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at .: encountered 0x00000000, but expected a valid enum tag | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 4, align: 4) { 00 00 00 00 │ .... } error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:44:1 | LL | const BAD_ENUM2_PTR: Enum2 = unsafe { mem::transmute(&0) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes | = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:47:1 | LL | const BAD_ENUM2_WRAPPED: Wrap = unsafe { mem::transmute(&0) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes | = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:56:42 | LL | const BAD_ENUM2_UNDEF : Enum2 = unsafe { MaybeUninit { uninit: () }.init }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ using uninitialized data, but this operation requires initialized memory error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:61:1 | LL | const BAD_ENUM2_OPTION_PTR: Option = unsafe { mem::transmute(&0) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unable to turn pointer into raw bytes | = help: this code performed an operation that depends on the underlying bytes representing a pointer = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported error[E0080]: it is undefined behavior to use this value --> $DIR/ub-enum.rs:78:1 | LL | const BAD_UNINHABITED_VARIANT1: UninhDiscriminant = unsafe { mem::transmute(1u8) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at ..0: encountered a value of the never type `!` | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 1, align: 1) { 01 │ . } error[E0080]: it is undefined behavior to use this value --> $DIR/ub-enum.rs:80:1 | LL | const BAD_UNINHABITED_VARIANT2: UninhDiscriminant = unsafe { mem::transmute(3u8) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at ..0: encountered a value of uninhabited type Never | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 1, align: 1) { 03 │ . } error[E0080]: it is undefined behavior to use this value --> $DIR/ub-enum.rs:88:1 | LL | const BAD_OPTION_CHAR: Option<(char, char)> = Some(('x', unsafe { mem::transmute(!0u32) })); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value at ..0.1: encountered 0xffffffff, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`) | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 8, align: 4) { 78 00 00 00 ff ff ff ff │ x....... } error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:93:77 | LL | const BAD_UNINHABITED_WITH_DATA1: Result<(i32, Never), (i32, !)> = unsafe { mem::transmute(0u64) }; | ^^^^^^^^^^^^^^^^^^^^ transmuting to uninhabited type error[E0080]: evaluation of constant value failed --> $DIR/ub-enum.rs:95:77 | LL | const BAD_UNINHABITED_WITH_DATA2: Result<(i32, !), (i32, Never)> = unsafe { mem::transmute(0u64) }; | ^^^^^^^^^^^^^^^^^^^^ transmuting to uninhabited type error: aborting due to 13 previous errors For more information about this error, try `rustc --explain E0080`.