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Simplify unification with uninhabited tags to happen anytime tags are uninhabited

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I believe this is safe! No need to gate it behind a mode.
This commit is contained in:
Ayaz Hafiz 2022-09-20 14:13:55 -05:00
parent 16e8a07e27
commit b0598ef817
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2 changed files with 34 additions and 39 deletions
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9
crates/compiler/solve/src/solve.rs
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@ -1357,14 +1357,17 @@ fn solve(
let snapshot = subs.snapshot();
let unify_cond_and_patterns_outcome = {
// When unifying the cond type with what the branches expect, allow the
// When unifying the cond type with what the branches expect, we'll want the
// branches to gain constructors that are uninabited; that way, we can permit
// unification of things like
// [Ok Str] ~ [Ok Str, Result []]
// which we want here, because `Result []` need not be matched - it is
// impossible to construct!
let mode = Mode::EQ_WITH_EXTENSION_BY_UNINHABITED_TYPES;
unify(&mut UEnv::new(subs), branches_var, real_var, mode)
//
// The order of variables is important here - to do such a unification, the
// unifier expects the branch variable on the left, and the condition variable
// (containing uninhabited variants to grow by) on the right.
unify(&mut UEnv::new(subs), branches_var, real_var, Mode::EQ)
};
let should_check_exhaustiveness;