GDScript: Fix subscript resolution on constant non-metatype GDScript base

modules/gdscript/tests/scripts/runtime/features/metatypes.gd

@@ -25,12 +25,24 @@ func test():
 		if str(property.name).begins_with("test_"):
 			print(Utils.get_property_signature(property))
 
+	print("---")
 	check_gdscript_native_class(test_native)
 	check_gdscript(test_script)
 	check_gdscript(test_class)
 	check_enum(test_enum)
 
+	print("---")
 	print(test_native.stringify([]))
 	print(test_script.TEST)
 	print(test_class.TEST)
 	print(test_enum.keys())
+
+	print("---")
+	# Some users add unnecessary type hints to `const`-`preload`, which removes metatypes.
+	# For **constant** `GDScript` we still check the class members, despite the wider type.
+	const ScriptNoMeta: GDScript = Other
+	const ClassNoMeta: GDScript = MyClass
+	var a := ScriptNoMeta.TEST
+	var b := ClassNoMeta.TEST
+	print(a)
+	print(b)

modules/gdscript/tests/scripts/runtime/features/metatypes.out

@@ -3,11 +3,16 @@ var test_native: GDScriptNativeClass
 var test_script: GDScript
 var test_class: GDScript
 var test_enum: Dictionary
+---
 GDScriptNativeClass
 GDScript
 GDScript
 { "A": 0, "B": 1, "C": 2 }
+---
 []
 100
 10
 ["A", "B", "C"]
+---
+100
+10