interfaces can't have PHP4 constructors

Summary:
Don't raise errors for them

fixes #8121

Reviewed By: markw65

Differential Revision: D7418115

hphp/runtime/vm/class.cpp

@@ -1466,7 +1466,7 @@ void Class::setSpecial() {
     return;
   }
 
-  if (!(attrs() & AttrTrait)) {
+  if (!(attrs() & (AttrTrait | AttrInterface))) {
     // Look for Foo::Foo() (old style constructor) declared in this class
     // and deprecate warning if we are in PHP 7 mode
     if (matchedClassOrIsTrait(m_preClass->name())) {

hphp/test/slow/php7_bcbreak/php4-constructors.php

@@ -0,0 +1,28 @@
+<?php
+
+error_reporting(E_ALL | E_STRICT | E_DEPRECATED);
+
+// No PHP4 constructor
+interface foo {
+  public function foo();
+}
+
+// No PHP4 constructor
+class bar implements foo {
+  public function foo() {}
+}
+
+// No PHP4 constructor
+trait herp {
+  public function derp() {}
+}
+
+// PHP4 constructor via trait
+class derp {
+  use herp;
+}
+
+// direct PHP4 constructor
+class MyClass {
+  public function MyClass() {}
+}

hphp/test/slow/php7_bcbreak/php4-constructors.php.expectf

@@ -0,0 +1,3 @@
+Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; MyClass has a deprecated constructor in %s/test/slow/php7_bcbreak/php4-constructors.php on line 26
+
+Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; derp has a deprecated constructor in %s/test/slow/php7_bcbreak/php4-constructors.php on line 21

hphp/test/slow/php7_bcbreak/php4-constructors.php.ini

@@ -0,0 +1 @@
+hhvm.php7.all=1