diff options
Diffstat (limited to 'compiler/typecheck/TcEvidence.hs')
| -rw-r--r-- | compiler/typecheck/TcEvidence.hs | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/compiler/typecheck/TcEvidence.hs b/compiler/typecheck/TcEvidence.hs index fa1908983a..1d6098dbf5 100644 --- a/compiler/typecheck/TcEvidence.hs +++ b/compiler/typecheck/TcEvidence.hs @@ -399,19 +399,16 @@ data EvBindsVar -- Some Given, some Wanted ebv_tcvs :: IORef CoVarSet - -- The free coercion vars of the (rhss of) the coercion bindings - -- All of these are Wanted - -- - -- Coercions don't actually have bindings - -- because we plug them in-place (via a mutable - -- variable); but we keep their free variables - -- so that we can report unused given constraints + -- The free Given coercion vars needed by Wanted coercions that + -- are solved by filling in their HoleDest in-place. Since they + -- don't appear in ebv_binds, we keep track of their free + -- variables so that we can report unused given constraints -- See Note [Tracking redundant constraints] in TcSimplify } | CoEvBindsVar { -- See Note [Coercion evidence only] - -- See above for comments on ebv_uniq, evb_tcvs + -- See above for comments on ebv_uniq, ebv_tcvs ebv_uniq :: Unique, ebv_tcvs :: IORef CoVarSet } @@ -834,6 +831,8 @@ evTermCoercion tm = case evTermCoercion_maybe tm of ********************************************************************* -} findNeededEvVars :: EvBindMap -> VarSet -> VarSet +-- Find all the Given evidence needed by seeds, +-- looking transitively through binds findNeededEvVars ev_binds seeds = transCloVarSet also_needs seeds where |