diff options
Diffstat (limited to 'compiler/GHC/Tc/Solver/Canonical.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Canonical.hs | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/compiler/GHC/Tc/Solver/Canonical.hs b/compiler/GHC/Tc/Solver/Canonical.hs index 1a5aacdbe1..4df06c2fca 100644 --- a/compiler/GHC/Tc/Solver/Canonical.hs +++ b/compiler/GHC/Tc/Solver/Canonical.hs @@ -2378,8 +2378,9 @@ Now, clearly we don't want to unify alpha:=Int! Yet at the moment we process [G] alpha[1] ~ Int, we don't have any given-equalities in the inert set, and hence there are no given equalities to make alpha untouchable. -(NB: if it were alpha[2] ~ Int, this argument wouldn't hold. But that -almost never happens, and will never happen at all if we cure #18929.) +NB: if it were alpha[2] ~ Int, this argument wouldn't hold. But that +never happens: invariant (GivenInv) in Note [TcLevel invariants] +in GHC.Tc.Utils.TcType. Simple solution: never unify in Givens! -} |