Fix polymorphic kvar type variable mismatch and add regression tests#2651
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facundominguez merged 6 commits intodevelopfrom Apr 13, 2026
Merged
Fix polymorphic kvar type variable mismatch and add regression tests#2651facundominguez merged 6 commits intodevelopfrom
facundominguez merged 6 commits intodevelopfrom
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- Update PKVar constructor to 3 parameters across liquidhaskell-boot
(Expand.hs, Generate.hs, Parse.hs, Fresh.hs, RType.hs, Types.hs)
- Add regression test PolyKVar2649.hs exercising polymorphic kvars
where a function with kvar-inferred specs is called from a different
type variable context
In consEApp, after instantiating predicates during a type application,
traverse the result type and stamp every PKVar with the type variable
mapping {symbol(α) → sort(τ)}. This records how type variables are
instantiated, so the solver can apply correct sort substitutions when
the same kvar is used across different type variable contexts.
Fixes #2649.
Written with Copilot
PolyKVar2649a: simpler variant from the issue comments — a helper function with open kvar refinements called from a function requiring a concrete Set-based postcondition. PolyKVar2649b: original issue example — a local go function with a different type variable than the outer uniques function. Both tests verify the fix produces proper Liquid Type Mismatch errors rather than crashing with a sort mismatch in elaboration. Written with Copilot
Update all PKVar pattern matches in liquidhaskell-boot to match the new PKVar constructor order: tsu (TyVarSubst) before su (KVarSubst). Written with Copilot
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This PR fixes #2649.
It depends on ucsd-progsys/liquid-fixpoint#837
Now
liquidhaskellcan specify how type variables in kvar solutions should be instantiated. This is possible to discover when encountering type applications during constraint generation.liquid-fixpointwill then substitute the type variables when applying kvar solutions.