Assignment of user-defined type causes compilation crash.

[Subway2023]

Version: v0.3.3: Atlantis

type U8 is uint8;
using {add as +} for U8 global;

function add(U8 x, U8 y) pure returns (U8 z) {
    assembly {
        z := add(div(x, 256), div(x, 256))
    }
}

contract C {
    function testBinary() external pure returns (U8, U8) {
        U8 a;
        U8 b;
        return (a + b, add(a, b));
    }
}

solang compile --target solana  test.sol

hread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: ()', src/codegen/yul/builtin.rs:471:10
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace