diff options
Diffstat (limited to 'compiler/coreSyn/CoreUtils.hs')
| -rw-r--r-- | compiler/coreSyn/CoreUtils.hs | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/compiler/coreSyn/CoreUtils.hs b/compiler/coreSyn/CoreUtils.hs index 3c65072974..7635a6d66a 100644 --- a/compiler/coreSyn/CoreUtils.hs +++ b/compiler/coreSyn/CoreUtils.hs @@ -481,8 +481,15 @@ bindNonRec :: Id -> CoreExpr -> CoreExpr -> CoreExpr -- the simplifier deals with them perfectly well. See -- also 'MkCore.mkCoreLet' bindNonRec bndr rhs body - | needsCaseBinding (idType bndr) rhs = Case rhs bndr (exprType body) [(DEFAULT, [], body)] - | otherwise = Let (NonRec bndr rhs) body + | isTyVar bndr = let_bind + | isCoVar bndr = if isCoArg rhs then let_bind + {- See Note [Binding coercions] -} else case_bind + | isJoinId bndr = let_bind + | needsCaseBinding (idType bndr) rhs = case_bind + | otherwise = let_bind + where + case_bind = Case rhs bndr (exprType body) [(DEFAULT, [], body)] + let_bind = Let (NonRec bndr rhs) body -- | Tests whether we have to use a @case@ rather than @let@ binding for this expression -- as per the invariants of 'CoreExpr': see "CoreSyn#let_app_invariant" @@ -505,7 +512,12 @@ mkAltExpr (LitAlt lit) [] [] mkAltExpr (LitAlt _) _ _ = panic "mkAltExpr LitAlt" mkAltExpr DEFAULT _ _ = panic "mkAltExpr DEFAULT" -{- +{- Note [Binding coercions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider binding a CoVar, c = e. Then, we must atisfy +Note [CoreSyn type and coercion invariant] in CoreSyn, +which allows only (Coercion co) on the RHS. + ************************************************************************ * * Operations oer case alternatives |