diff options
Diffstat (limited to 'compiler/GHC/HsToCore/Match/Constructor.hs')
| -rw-r--r-- | compiler/GHC/HsToCore/Match/Constructor.hs | 34 |
1 files changed, 30 insertions, 4 deletions
diff --git a/compiler/GHC/HsToCore/Match/Constructor.hs b/compiler/GHC/HsToCore/Match/Constructor.hs index 50127f9fe3..9ab8913099 100644 --- a/compiler/GHC/HsToCore/Match/Constructor.hs +++ b/compiler/GHC/HsToCore/Match/Constructor.hs @@ -93,17 +93,36 @@ have-we-used-all-the-constructors? question; the local function @match_cons_used@ does all the real work. -} +-- | Turn group of equations for a single constructor into a case expression? +-- +-- Example: +-- +-- data T = C Int Int | D Bool +-- +-- ROMES: Doesn't seem quite right, perhaps each group can only have 1 expr it's deconstructing? +-- let C a b = <expr> +-- D c = <expr> -- not sure about this second one, I think it's wrong here, just adding it bc I'm unsure. +-- in ... +-- +-- ==> +-- +-- case <expr> of +-- C a b -> ... +-- D c -> ... -- not sure about this second constructor being correct +-- +-- Relevant notes seem to be [Match Ids] and [Localise pattern binders] matchConFamily :: HasCallStack => NonEmpty Id -> Type -> NonEmpty (NonEmpty EquationInfo) -> DsM (MatchResult CoreExpr) -- Each group of eqns is for a single constructor matchConFamily (var :| vars) ty groups - = do let mult = idMult var + = pprTrace "matchConFamily" (ppr var <+> hsep (map ppr vars) $$ ppr (map idBinding (var:vars)) $$ ppr groups) $ + do let !mult = idMult var -- Each variable in the argument list correspond to one column in the -- pattern matching equations. Its multiplicity is the context -- multiplicity of the pattern. We extract that multiplicity, so that - -- 'matchOneconLike' knows the context multiplicity, in case it needs + -- 'matchOneConLike' knows the context multiplicity, in case it needs -- to come up with new variables. alts <- mapM (fmap toRealAlt . matchOneConLike vars ty mult) groups return (mkCoAlgCaseMatchResult var ty alts) @@ -198,9 +217,16 @@ matchOneConLike vars ty mult (eqn1 :| eqns) -- All eqns for a single construct -- necessarily correct, as it may come from a variable which was -- originally let bound and will now be lambda bound. -- See comments in dsUnliftedBind too. - ; let arg_vars' = map (`setIdBinding` (LambdaBound ManyTy)) arg_vars -- ROMES:TODO: Not ManyTy!! It depends on the constructor! + -- + -- ROMES:TODO:No,! We should only set LambdaBound x if we have a + -- LetBound var, otherwise it already has a multiplicity? Or should we + -- simply recompute it completely here? + -- + -- What if the only case putting us here really is dsUnliftedBind? Try to make the change there. + -- ; let arg_vars' = map (`setIdBinding` (LambdaBound ManyTy)) arg_vars -- ROMES:TODO: Not ManyTy!! It depends on the constructor! Don't always overwrite? + -- ...these arg_vars sometimes contain variables that were originally let bound, when do we make the change passing let bound variables to matchEquations? Should we always discern it here? ; return $ MkCaseAlt{ alt_pat = con1, - alt_bndrs = tvs1 ++ dicts1 ++ arg_vars', -- these arg_vars contain variables that were originally let bound + alt_bndrs = tvs1 ++ dicts1 ++ arg_vars, alt_wrapper = wrapper1, alt_result = foldr1 combineMatchResults match_results } } where |