[erlc] "internal consistency check failed" with some optimizations disabled

[RobinMorisset]

Describe the bug
Running erlc with +no_copt +no_bool_opt +no_ssa_opt on the following code:

f() ->
    [0 || (X = (true or (X = is_port(node()))))].

results in the following error:

type_conflict:1: function f/0+10:
  Internal consistency check failed - please report this bug.
  Instruction: {select_val,{x,1},
                           {f,7},
                           {list,[{atom,false},{f,8},{atom,true},{f,9}]}}
  Error:       {type_conflict,{t_atom,[false]},{t_atom,[false]}}:

I have not managed to reproduce this bug with default options for erlc, but I am reporting it anyway in case it is revealing a more serious problem.

Expected behavior
From the name of the options, I expected them to only affect optimizations, and not transformations that are required for correctness.

Affected versions

• master
• master + beam_ssa_type: Track substitutions on a per-block basis #6619 (checked to make sure that this is not yet another duplicate of [erlc] internal consistency check failed: "illegal_branch, try_handler" #6599)

[jhogberg]

Thanks for your report, the type inference in the validator was a bit weaker than it should have been. I've fixed it in #6964