[Asar2] Three letter variable names are not accepted anymore

[hellow554]

The following code won't get accepted anymore:

A = $23
AB = $23
ABC = $23
ABCD = $23

a.asm:3: error: (Einvalid_number): Invalid number.
    in block: [ABC = $23]

Commit that introduces this bug: baac3ffc0f8c511238c67e04a25b0d784a527c0b Ping @p4plus2 : Can you take a look at it, please?

It was originally detected because of this code:

common/labels.asm:28: error: (Einvalid_number): Invalid number.
    in block: [M7A = $00211B]
common/labels.asm:29: error: (Einvalid_number): Invalid number.
    in block: [M7B = $00211C]
common/labels.asm:30: error: (Einvalid_number): Invalid number.
    in block: [M7C = $00211D]
common/labels.asm:31: error: (Einvalid_number): Invalid number.
    in block: [M7D = $00211E]
common/labels.asm:32: error: (Einvalid_number): Invalid number.
    in block: [M7X = $00211F]
common/labels.asm:33: error: (Einvalid_number): Invalid number.
    in block: [M7Y = $002120]
common/labels.asm:39: error: (Einvalid_number): Invalid number.
    in block: [WH0 = $002126]
common/labels.asm:40: error: (Einvalid_number): Invalid number.
    in block: [WH1 = $002127]
common/labels.asm:41: error: (Einvalid_number): Invalid number.
    in block: [WH2 = $002128]
common/labels.asm:42: error: (Einvalid_number): Invalid number.
    in block: [WH3 = $002129]
common/labels.asm:47: error: (Einvalid_number): Invalid number.
    in block: [TMW = $00212E]
common/labels.asm:48: error: (Einvalid_number): Invalid number.
    in block: [TSW = $00212F]

[p4plus2]

[randomdude999]

fixed an asar_2_beta now (for any 3-letter labels that are not valid instructions). however, lda = 123 still gives an invalid number error (this used to work in 1.9). i'm not sure whether this should be allowed, given that this creates somewhat nasty ambiguities, especially if we want to make asar even less whitespace-sensitive in the future. and well, this might look somewhat misleading anyways. so i'm currently leaning towards keeping this banned.

[hellow554]

Yes, that would be a good idea. Maybe reporting an error like: "can't redefine opcode lda" or similar.

[randomdude999]

well it's not redefining an opcode, it's creating a label called "lda". you can still do that like this:

lda:
lda lda

which is still valid. whether you should do that is a different question, but i don't think banning label names from coinciding with any instruction names is a good idea either, especially since the set of valid mnemonics depends on the current architecture, and spc700 and superfx include instructions like "stop", "sleep", or "loop", which i could totally see as being valid label names.

[randomdude999]

none of the other devs seemed to object to lda = 123 being an error, so closing this as completed.