Better disambiguation between subscript-expression and compound-statement

This error tolerance case needs some special handling.

class A {
    function b() {
        if ($expression {
            $a = 3;
            $b = "hello";
        }
        echo "hi";
    }
    
    public function c() {
    }
}

In this case, the if statement is missing a close paren. However, rather than getting parsed as an if-statement missing a close paren, it gets parsed as a subscript-expression (which is defined as follows, according to the PHP language spec.

subscript-expression:
  dereferencable-expression   [   expressionopt   ]
  dereferencable-expression   {   expression   }   <b>[Deprecated form]</b>

This results in the first close brace getting treated as a close brace for the method, rather than the if statement. Then the next close brace gets eaten by the Class node (which terminates the class), so c() ends up being a function, rather than a method.

Reproduce the PHP snippet and inspect the parser rules or entry points handling subscript-expression, if statements, and compound statements. Confirm the corrected parse keeps the missing-parenthesis error associated with the if statement and preserves c() as a method of class A.