Methods cannot be readonly
-----
<?php class A { readonly function foo() {} }
-----
!!php7
Method foo() cannot be readonly from 1:17 to 1:24
array(
    0: Stmt_Class(
        attrGroups: array(
        )
        flags: 0
        name: Identifier(
            name: A
        )
        extends: null
        implements: array(
        )
        stmts: array(
            0: Stmt_ClassMethod(
                attrGroups: array(
                )
                flags: MODIFIER_READONLY (64)
                byRef: false
                name: Identifier(
                    name: foo
                )
                params: array(
                )
                returnType: null
                stmts: array(
                )
            )
        )
    )
)