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

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

    modifier initX() {
        _; x = 23;
    }
}
// ----
// TypeError 1581: (102-103='x'): Cannot write to immutable here: Immutable variables can only be initialized inline or assigned directly in the constructor.