'export var' infers the wrong type of preload()

[lapspider45]

Godot version

v3.5.rc3.official.af8a02dda

System information

Linux

Issue description

export var example := preload("ExampleNode.tscn") results in this error message:

 built-in:3 - Parse Error: The export hint's type (Object) doesn't match the variable's type (PackedScene).
 modules/gdscript/gdscript.cpp:597 - Method failed. Returning: ERR_PARSE_ERROR

I'm getting the same parser error on 3.5 rc2 and 3.4.4 stable. Haven't tested other versions.

Steps to reproduce

extends Node

export var example := preload("ExampleNode.tscn") # parse error

export var example2 : PackedScene = preload("ExampleNode.tscn") # no error
var example3 := preload("ExampleNode.tscn") # no error

Minimal reproduction project

MRP_export_PackedScene.zip
(same code as in the steps to reproduce)

[KoBeWi]

No error in 4.0.

[ArshPanesar]

Godot version

v3.5.rc3.official.af8a02dda

EDIT: Fixed the issue by setting class_name for export property in _parse_class(), now correct datatype is inferred.

Made new fix, different fix in this comment is irrelevent

Not sure if this small fix would work but it removed the error in my fork:
ArshPanesar@08ae732

### Explanation
I ran the minimal project through a debugger and found that this export hint check in gdscript_parser.cpp (line: 7093) was causing the error:
// Check export hint if (v.data_type.has_type && v._export.type != Variant::NIL) { DataType export_type = _type_from_property(v._export); if (!_is_type_compatible(v.data_type, export_type, true)) { _set_error("The export hint's type (" + export_type.to_string() + ") doesn't match the variable's type (" + v.data_type.to_string() + ").",v.line); return; } }

The _is_type_compatible(v.data_type, export_type, true) returns false for the statement: export var example := preload("ExampleNode.tscn") when it should be true (Both are of NATIVE Kind and have builtin type as Object)
I was able to fix this by swapping the first two parameters: _is_type_compatible(export_type, v.data_type, true)

This worked because further down in this function _is_type_compatible(const DataType &p_container, const DataType &p_expression,...), if both DataType are of NATIVE Kind, it is checked whether p_container's native type inherits p_expression's native type, and a bool value is returned. This is done through is_parent_class(expr_native, container_native) function (line: 6295) in gdscript_parser.cpp. v.data_type's and export_type's native type is "Object" and "PackedScene" respectively. And the check is done in order as "Does Object Inherit PackedScene?", which is false and thus a parse error occured in the script.

### Unsure about the Fix
Although the swap fixed it, I dont know if I should open a PR as I'm not sure if this small fix would work. It would be very helpful if someone experienced with the parser could see if this fix would work or not.

Sorry for the long explanation, this is my second time contributing to a github repo and I really like Godot 😅