avm2: Throw TypeError when 'astype' receives a null/undefined class

core/src/avm2/activation.rs

@@ -2901,17 +2901,23 @@ impl<'a, 'gc> Activation<'a, 'gc> {
         let class = self
             .pop_stack()
             .as_object()
-            .and_then(|c| c.as_class_object())
-            .ok_or("Cannot coerce a value to a type that is null, undefined, or not a class")?;
+            .and_then(|c| c.as_class_object());
         let value = self.pop_stack();
 
+        if let Some(class) = class {
             if value.is_of_type(self, class) {
                 self.push_stack(value);
             } else {
                 self.push_stack(Value::Null);
             }
-
             Ok(FrameControl::Continue)
+        } else {
+            return Err(Error::AvmError(type_error(
+                self,
+                "Error #1009: Cannot access a property or method of a null object reference.",
+                1009,
+            )?));
+        }
     }
 
     fn op_instance_of(&mut self) -> Result<FrameControl<'gc>, Error<'gc>> {

tests/tests/swfs/avm2/astype_missing_class/Test.as

@@ -0,0 +1,25 @@
+package {
+	import flash.display.MovieClip;
+	public class Test {
+		public function Test() {
+			tryCast("Hello", null);
+			tryCast("Hello", undefined);
+			tryCast("Hello", Class);
+			tryCast(Object, null);
+			tryCast(Object, undefined);
+			tryCast(Object, Class);
+			tryCast(null, null);
+			tryCast(null, undefined);
+			tryCast(undefined, null);
+			tryCast(undefined, undefined);
+		}
+	
+		private function tryCast(val: *, klass: Class) {
+			try {
+				trace(val + " as " + klass + ": " + (val as klass));
+			} catch(e) {
+				trace("Caught error from `" + val + " as " + klass + "`: " + e);
+			}
+		}
+	}
+}

tests/tests/swfs/avm2/astype_missing_class/output.txt

@@ -0,0 +1,10 @@
+Caught error from `Hello as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Caught error from `Hello as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Hello as [class Class]: null
+Caught error from `[class Object] as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Caught error from `[class Object] as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+[class Object] as [class Class]: [class Object]
+Caught error from `null as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Caught error from `null as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Caught error from `undefined as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.
+Caught error from `undefined as null`: TypeError: Error #1009: Cannot access a property or method of a null object reference.

tests/tests/swfs/avm2/astype_missing_class/test.toml

@@ -0,0 +1 @@
+num_frames = 1