lack of warnings/errors for unwanted latches

[astrollo]

Consider the following trivial (and buggy) code:

module test1 (input logic a, b, output logic y);
always_comb begin
  if (a)
    y = b;
end
endmodule

read_slang does not give any error or warning, and a muliplexer with output connected to in_0 is synthesized. read_verilog -sv followed by: proc gives correctly the following message and exit: ERROR: Latch inferred for signal \test1.\y from always_comb process Similar problems occur for casestatement, with case values incompletely covered (no default)

[povik]

Thanks, that needs addressing

[povik]

Actually I am not sure it needs addressing, this will emit a combinational loop which will be caught in a subsequent check call. To me a combinational loop is not an invalid reading of the input code when always_comb prohibits inference of latches.

We could detect this in the frontend and emit a warning/error, but there's risk of false positives depending on how we do the detection. In any case I reclassify this as an enhancement.

[phsauter]

I think the way it is currently handled in yosys-slang itself is fine (ie check catching the loop).
What would be more interesting would be a warning (or just info) in Slang itself that warns of incomplete cases.
-Wcase-gen-dup and -Wcase-gen-none show that something like that is probably possible.