solidity/test/libsolidity/syntaxTests/immutable/ctor_indirect_initialization.sol

contract C {
    uint immutable x;
    constructor() {
        initX();
    }

    function initX() internal {
        x = 3;
    }
}
// ----
// TypeError 1581: (119-120='x'): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.