Deprecate unbinding $this from non-static closure

Author: nikic

Zend/tests/closure_041.phpt

@@ -80,6 +80,8 @@ scoped to A: bool(false)
 bound: no
 scoped to A: bool(true)
 bound: no
+
+Deprecated: Unbinding $this of closure is deprecated in %s on line %d
 scoped to A: bool(true)
 bound: no
 After binding, with same-class instance for the bound ones

Zend/tests/closure_044.phpt

@@ -38,7 +38,7 @@ $d = $nonstaticUnscoped->bindTo(new A, 'A'); $d(); echo "\n";
 $d = $nonstaticScoped->bindTo(new A, 'A'); $d(); echo "\n";
 
 echo "Done.\n";
---EXPECT--
+--EXPECTF--
 Before binding
 bool(false)
 bool(false)
@@ -50,6 +50,8 @@ After binding, null scope, no instance
 bool(false)
 bool(false)
 
+
+Deprecated: Unbinding $this of closure is deprecated in %s on line %d
 bool(false)
 bool(false)
 
@@ -64,6 +66,8 @@ After binding, with scope, no instance
 bool(true)
 bool(false)
 
+
+Deprecated: Unbinding $this of closure is deprecated in %s on line %d
 bool(true)
 bool(false)
 

Zend/tests/closure_046.phpt

@@ -38,7 +38,7 @@ echo "After binding, with different instance for the bound one", "\n";
 $d = $nonstaticScoped->bindTo(new B, "static"); $d(); echo "\n";
 
 echo "Done.\n";
---EXPECT--
+--EXPECTF--
 Before binding
 bool(false)
 bool(false)
@@ -50,6 +50,8 @@ After binding, no instance
 bool(false)
 bool(false)
 
+
+Deprecated: Unbinding $this of closure is deprecated in %s on line %d
 bool(true)
 bool(false)
 

Zend/tests/no_class_const_propagation_in_closures.phpt

@@ -18,7 +18,7 @@ class B {
 }
 
 $f = (new A)->f();
-var_dump($f->bindTo(null, 'B')());
+var_dump($f->bindTo(new B, 'B')());
 
 ?>
 --EXPECT--

Zend/zend_closures.c

@@ -90,6 +90,9 @@ static zend_bool zend_valid_closure_binding(
 		} else {
 			zend_error(E_DEPRECATED, "Unbinding $this of a method is deprecated");
 		}
+	} else if (!is_fake_closure && !Z_ISUNDEF(closure->this_ptr)) {
+		// TODO: Only deprecate if it had $this *originally*?
+		zend_error(E_DEPRECATED, "Unbinding $this of closure is deprecated");
 	}
 
 	if (scope && scope != func->common.scope && scope->type == ZEND_INTERNAL_CLASS) {