Add support for typer coercion for invariant type arguments such as a…#6518
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Add support for typer coercion for invariant type arguments such as a…#6518
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…rray payloads. If type `t<'a>` is invariant in `'a` allow type coercion from `t<t1> ` to `t<t2>` if both `t1` can be coerced to `t2` and `t2` can be coerced to `t1`, which must imply that the runtime representations are the same.
cristianoc
commented
Dec 11, 2023
| newty2 t2.level (Ttuple[t2]), !univar_pairs) :: cstrs | ||
| (* Invariant type argument: check both ways *) | ||
| if | ||
| subtype_rec env ((t1, t2)::trace) t1 t2 [] = [] && |
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This is using the special case cstrs = []. Not sure if there's a good way to use existing constraints collected up to now.
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So good 😍 ! This is going to be crazy useful for our coercions and spreads. Maybe we should add a few tests that cases that shouldn't be allowed still isn't? |
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…rray payloads.
If type
t<'a>is invariant in'aallow type coercion fromt<t1>tot<t2>if botht1can be coerced tot2andt2can be coerced tot1, which must imply that the runtime representations are the same.