diff options
Diffstat (limited to 'compiler/prelude')
| -rw-r--r-- | compiler/prelude/PrelRules.hs | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/compiler/prelude/PrelRules.hs b/compiler/prelude/PrelRules.hs index 810fd2ba60..8838c4aaff 100644 --- a/compiler/prelude/PrelRules.hs +++ b/compiler/prelude/PrelRules.hs @@ -897,21 +897,22 @@ tagToEnumRule = do _ -> WARN( True, text "tagToEnum# on non-enumeration type" <+> ppr ty ) return $ mkRuntimeErrorApp rUNTIME_ERROR_ID ty "tagToEnum# on non-enumeration type" -{- -For dataToTag#, we can reduce if either - - (a) the argument is a constructor - (b) the argument is a variable whose unfolding is a known constructor --} - +------------------------------ dataToTagRule :: RuleM CoreExpr +-- Rules for dataToTag# dataToTagRule = a `mplus` b where + -- dataToTag (tagToEnum x) ==> x a = do [Type ty1, Var tag_to_enum `App` Type ty2 `App` tag] <- getArgs guard $ tag_to_enum `hasKey` tagToEnumKey guard $ ty1 `eqType` ty2 - return tag -- dataToTag (tagToEnum x) ==> x + return tag + + -- dataToTag (K e1 e2) ==> tag-of K + -- This also works (via exprIsConApp_maybe) for + -- dataToTag x + -- where x's unfolding is a constructor application b = do dflags <- getDynFlags [_, val_arg] <- getArgs |