Range error in constant

dasm special-cases negative immediates in, for example...

VAL = -1
  lda #VAL. ; assembles OK

Although numbers are stored internally as 32 bits, and by rights this would be equivalent to...

  lda #$FFFFFFFF

... it assembles OK with dasm using the low bye ($FF) of the internal 32-byte number.
All good so far. It's detecting that the two's complement negative can be expressed as a single byte.

However, long ago when I was "fixing" things, and as a result we were required to write ...

VAL = -1
    lda #VAL&$FF. ; nobody liked this

... well the "fix" was reverted/fixed, and we could once again write just ``lda #-1"
The rationale being that dasm would range-check (I am guessing) to detect if the operand was in the correct (signed or unsigned) range. And now to my point...

The valid signed range is of course 8 bits (2's complement). That is from $80 (-128 signed) to $FF (unsigned).
We should be able to use any value in that range without error. But not outside it.

It seems, however, that dasm is restricting the range to -$FF to +$FF, which is incorrect.
The correct range, as noted, is -$80 to +$FF.

As an example, the following assembles - and it should not...

  lda #-130.  ; whoops!  Range should be -128 to 255 inclusive.

Start by reproducing the issue with the lda #-130. example and locate the immediate-operand range-checking path in the assembler. Verify the accepted boundary values, ensuring -128 through 255 assemble while values outside that range are rejected.