Fix AttrSystemInitialValue on overridden properties

Summary:
If its set on the parent prop, but not on the child, we need to
explicitly clear it on the child's property.

Reviewed By: ricklavoie

Differential Revision: D13084126

fbshipit-source-id: 3de06f6239f770efe60a3da582060c5fbab6d4dc

hphp/runtime/vm/class.cpp

@@ -2594,9 +2594,9 @@ void Class::setProperties() {
        if (preProp->attrs() & AttrNoImplicitNullable) {
          prop.attrs |= AttrNoImplicitNullable;
        }
        if (preProp->attrs() & AttrSystemInitialValue) {
          prop.attrs |= AttrSystemInitialValue;
        }
        attrSetter(prop.attrs,
                   preProp->attrs() & AttrSystemInitialValue,
                   AttrSystemInitialValue);
        if (preProp->attrs() & AttrInitialSatisfiesTC) {
          prop.attrs |= AttrInitialSatisfiesTC;
        }
@@ -2651,9 +2651,9 @@ void Class::setProperties() {
        if (preProp->attrs() & AttrNoImplicitNullable) {
          prop.attrs |= AttrNoImplicitNullable;
        }
        if (preProp->attrs() & AttrSystemInitialValue) {
          prop.attrs |= AttrSystemInitialValue;
        }
        attrSetter(prop.attrs,
                   preProp->attrs() & AttrSystemInitialValue,
                   AttrSystemInitialValue);
        if (preProp->attrs() & AttrInitialSatisfiesTC) {
          prop.attrs |= AttrInitialSatisfiesTC;
        }

hphp/test/slow/object_property/system_initial_value.php

@@ -0,0 +1,36 @@
<?hh

class Y {
  const A = 'a';
}

class A {
  public ImmMap $pub;
  protected ImmMap $prot;
}

class X extends A {
  public ImmMap $pub = ImmMap {
    Y::A => 42,
  };
  protected ImmMap $prot = ImmMap {
    Y::A => 24,
  };

  function getPub() { return $this->pub; }
  function getProt() { return $this->prot; }
}

function test() {
  return new X;
}

function main() {
  for ($i = 1; $i < 100; $i++) {
    test();
  }
  $x = test();
  var_dump($x->getPub(), $x->getProt());
}

main();

hphp/test/slow/object_property/system_initial_value.php.expect

@@ -0,0 +1,8 @@
object(HH\ImmMap)#202 (1) {
  ["a"]=>
  int(42)
}
object(HH\ImmMap)#203 (1) {
  ["a"]=>
  int(24)
}