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fix triple (or more) mutualy recursive type aliases

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Folkert 2020-06-30 14:25:47 +02:00
parent 5483ec819f
commit c589be43c6
3 changed files with 47 additions and 9 deletions
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4
compiler/unify/src/unify.rs
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@ -573,11 +573,11 @@ fn unify_shared_tags(
// with uniqueness inference). Thus we must expand the recursive tag union to
// unify if with the non-recursive one. Thus:
// replace the rvar with ctx.second in expected
// replace the rvar with ctx.second (the whole recursive tag union) in expected
subs.explicit_substitute(rvar, ctx.second, expected);
// but, by the `is_structure` condition above, only if we're unifying with a structure!
// when `actual` is just a flex/rigid variable, the substitution will expand a
// when `actual` is just a flex/rigid variable, the substitution would expand a
// recursive tag union infinitely!
unify_pool(subs, pool, actual, expected)