API triggers unerasable-optional-argument warning in OCaml 4.12.0

[jmid]

@tmcgilchrist reported how the API triggers unerasable-optional-argument errors/warnings in OCaml 4.12.0
here #2 (comment)

File "src/qCSTM.ml", line 94, characters 25-35:
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94 |   let consistency_test ?(count=1000) ~name =
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                              ^^^^^^^^^^
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Error (warning 16 [unerasable-optional-argument]): this optional argument cannot be erased.
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File "src/qCSTM.ml", line 120, characters 19-29:
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120 |   let agree_test ?(count=1000) ~name =
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                         ^^^^^^^^^^
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Error (warning 16 [unerasable-optional-argument]): this optional argument cannot be erased.

One potential fix is to swap both count and name to both be labelled arguments (#2 (review)):

Edit: as for the unerasable-optional-argument and OCaml 4.12, I think the API should just make count labelled like name, but that change is probably also best handled separately...

@tmcgilchrist suggests another option of letting the functions take a unit as the last parameter (#2 (comment)):

@jmid one option for fixing 4.12 is adding unit to the functions see
tmcgilchrist/qcstm@fb226ad

I haven't used this enough to tell whether making ~count a label, requiring the user to supply a value, vs appending () is more ergonomic.

I suppose a third option is to disable the error/warning (-w -16?)... 😅