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Make sure records don't de-generalize function types, fixing ability let-generalization

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Closes #3641
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Ayaz Hafiz 2022-07-26 13:08:07 -04:00
parent ce8c8f7264
commit f145f29b1b
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2 changed files with 11 additions and 16 deletions
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10
crates/compiler/solve/src/solve.rs
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@ -3141,9 +3141,17 @@ fn adjust_rank_content(
EmptyRecord => {
// from elm-compiler: THEORY: an empty record never needs to get generalized
Rank::toplevel()
//
// But for us, that theory does not hold, because there might be type variables hidden
// inside a lambda set but not on the left or right of an arrow, and records should not
// force de-generalization in such cases.
//
// See https://github.com/rtfeldman/roc/issues/3641 for a longer discussion and
// example.
group_rank
}
// THEORY: an empty tag never needs to get generalized
EmptyTagUnion => Rank::toplevel(),
Record(fields, ext_var) => {