State variables cannot have external visibility

[bitbart]

State variables can have visibility public, private or internal (default):

https://docs.soliditylang.org/en/latest/contracts.html#state-variable-visibility

The following contract should either not be parsable or should not pass typechecking:

contract C {
    int external x;
    constructor() { x = 1; }
    function f() external view returns (int) { return(x); }
}