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| author | simonpj@microsoft.com <unknown> | 2006-08-08 13:59:10 +0000 |
|---|---|---|
| committer | simonpj@microsoft.com <unknown> | 2006-08-08 13:59:10 +0000 |
| commit | c295ee8ac9d7afb4d660dc3b63c10cca0a0b26e7 (patch) | |
| tree | d251eb52e9817085e8ba573033f1b2afb0d7254c /compiler | |
| parent | 1dc5c28c2370cc8254f024c5734f76d7e5827cd6 (diff) | |
| download | haskell-c295ee8ac9d7afb4d660dc3b63c10cca0a0b26e7.tar.gz | |
Check that lazy patterns are for lifted types
A lazy pattern match must be for a lifted type. This is illegal:
f x = case g x of
~(# x,y #) -> ...
This commit fixes the problem. Trac #845, test is tcfail159
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/typecheck/TcPat.lhs | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs index 3c1c3bacdc..ee33d4ac8f 100644 --- a/compiler/typecheck/TcPat.lhs +++ b/compiler/typecheck/TcPat.lhs @@ -278,7 +278,7 @@ tc_pat pstate (BangPat pat) pat_ty thing_inside = do { (pat', tvs, res) <- tc_lpat pstate pat pat_ty thing_inside ; return (BangPat pat', tvs, res) } --- There's a wrinkle with irrefuatable patterns, namely that we +-- There's a wrinkle with irrefutable patterns, namely that we -- must not propagate type refinement from them. For example -- data T a where { T1 :: Int -> T Int; ... } -- f :: T a -> Int -> a @@ -293,8 +293,14 @@ tc_pat pstate lpat@(LazyPat pat) pat_ty thing_inside thing_inside pstate -- Ignore refined pstate', -- revert to pstate + -- Check no existentials ; if (null pat_tvs) then return () else lazyPatErr lpat pat_tvs + + -- Check that the pattern has a lifted type + ; pat_tv <- newBoxyTyVar liftedTypeKind + ; boxyUnify pat_ty (mkTyVarTy pat_tv) + ; return (LazyPat pat', [], res) } tc_pat pstate (WildPat _) pat_ty thing_inside |