Known 2.3 Compilation/Decompilation Errors

[Jacky720]

This is a list of errors I have thus far encountered when reviewing compilation for Deltarune Chapter 1&2.

Crashes:

• Assignment to variables which share names with scripts (gml_Object_obj_CHAPTER_SELECT_Create_0)
• Local function recognition (gml_Object_obj_darkfountain_Draw_0)
• Something with decompilation of a local assignment yields var a += (gml_Object_obj_queen_bulletcontroller_Step_0)
• 8bf886f buffer_get_surface now should accept fewer arguments (gml_Object_obj_shapepuzzle_Draw_0)
• @@ functions (gml_Object_obj_tensionbar_Draw_0)
• Instance IDs with dot notation (several room start entries)
• e5ada74 Scripts. While I have made some progress on assembling these (hackalicious branch), the offsets in references still need to be adjusted.

Non-matching:

• setowner calls. Currently, I'm ignoring these, which really helps.
• Weird decompilation of a while loop as a while loop inside an identical if statement (gml_Object_DEVICE_CHOICE_ch1_Step_0)
• Code duplication in decompilation of breaks in loops. I think this has actually been around before 2.3; as I recall, Undertale narrowly avoids it using the profile system. (gml_Object_DEVICE_FAILURE_Step_0)
  There is a similar issue in some for loops, apparently without the break statement; this may indicate an undecompiled continue? (gml_Object_lang_sprite_layer_hider_Create_0)
• Array ++/-- calls do not compile correctly. (gml_Object_DEVICE_MENU_Step_0)
• Global array ++/-- calls do not decompile correctly. (gml_Object_obj_battlecontroller_Step_0)
• Several collision events are compiling with bf or b instructions shooting just short of instructions they should come after, including popenvs, popzs, and even bs (gml_Object_o_coaster_jama_Collision_o_coaster_hero)
• 5a6e45a room_speed is being popped as a Self variable, not a Builtin? (gml_Object_o_boxingcontroller_Create_0)
• Assigning other objects' alarms needs a conv (to variable) instruction in 2.3. (gml_Object_o_boxingqueen_Step_0)
• 5a6e45a Builtin arrays are incorrectly compiling as Self, including the -5/-1 bit that is still used in 2.3. (gml_Object_o_coaster_berdly_Step_0)
• Something is incorrect (maybe use of the bool type?) in compiling a complex if clause. (gml_Object_obj_alleyswitch_Step_0)
• instance_exists(self) should compile using @@This@@. Likewise with other. (gml_Object_obj_battle_cleanup_Alarm_0)
• Some apparently useless b instructions (going where the code was going anyway) are being dropped. (gml_Object_obj_battletester_Draw_64) This also seems to show up in profile-less Undertale.
• Ternaries with ? 1 : 0 are simplified in decompilation to use the condition directly. (gml_Object_obj_berdlyb2_enemy_Step_0)
• Anonymous script offsets are still not corrected, but this appears to only be an issue for exact 1:1 saving; the game runs with only minor tweaks after CheckDecompiler.
• Anything with multiple functions becomes a mess.
• return statements in ifs do not compile (gml_GlobalScript_scr_drawpart_crop).
• And more... Le sigh.

[Miepee]

Some of these have seperate issues. Might wanna collect them here.
The return statement in an if statement i.e. sounds like #900

[colinator27]

Most of these should be fixed by #2056, specifically aside from setowner/array owners not being implemented yet.