Bug in opt_trans_rule in OptCoercion
The ForAllCo case in the definition of opt_trans_rule in OptCoercion is not right:
push_trans tv1 eta1 r1 tv2 eta2 r2
= fireTransRule "EtaAllTy" co1 co2 $
mkForAllCo tv1 (opt_trans is eta1 eta2) (opt_trans is' r1 r2')
where
is' = is `extendInScopeSet` tv1
r2' = substCoWithUnchecked [tv2] [TyVarTy tv1] r2 -- ill-kinded!
Given co1;co2
, where
co1 = \/ tv1 : eta1. r1
co2 = \/ tv2 : eta2. r2
We would like optimize the transitivity coercion. I think what we want is
\/tv1 : (eta1;eta2). (r1; r2[tv2 |-> tv1 |> eta1])
Namely it should be
r2' = substCoWithUnchecked [tv2] [mkCastTy (TyVarTy tv1) eta1] r2
If there is any program that could hit the bug it would be better, as we can add it to test cases.
Trac metadata
Trac field | Value |
---|---|
Version | 8.4.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |