diff options
| author | Simon Peyton Jones <simonpj@microsoft.com> | 2015-02-19 20:53:55 +0000 |
|---|---|---|
| committer | Simon Peyton Jones <simonpj@microsoft.com> | 2015-02-19 20:53:55 +0000 |
| commit | ef391f88ecde6d66cae0fd216ba0d25956fec1fb (patch) | |
| tree | 561fc63b69451f81b516be3be21b4bc2e928a224 /compiler | |
| parent | e9d72cefeda243d5962d0615fe7ad22ff615d134 (diff) | |
| download | haskell-ef391f88ecde6d66cae0fd216ba0d25956fec1fb.tar.gz | |
Comments only
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/typecheck/TcBinds.hs | 2 | ||||
| -rw-r--r-- | compiler/typecheck/TcPat.hs | 37 |
2 files changed, 22 insertions, 17 deletions
diff --git a/compiler/typecheck/TcBinds.hs b/compiler/typecheck/TcBinds.hs index acdaf8f876..7b988daf2f 100644 --- a/compiler/typecheck/TcBinds.hs +++ b/compiler/typecheck/TcBinds.hs @@ -542,7 +542,7 @@ tcPolyCheck :: RecFlag -- Whether it's recursive after breaking -> TcM (LHsBinds TcId, [TcId], TopLevelFlag) -- There is just one binding, -- it binds a single variable, --- it has a signature, +-- it has a complete type signature, tcPolyCheck rec_tc prag_fn sig@(TcSigInfo { sig_name = name, sig_poly_id = Just poly_id , sig_tvs = tvs_w_scoped diff --git a/compiler/typecheck/TcPat.hs b/compiler/typecheck/TcPat.hs index 7856413612..9f37a56962 100644 --- a/compiler/typecheck/TcPat.hs +++ b/compiler/typecheck/TcPat.hs @@ -140,12 +140,16 @@ data TcSigInfo -- sig_id = Just id, then sig_name = idName id. sig_poly_id :: Maybe TcId, - -- Just <=> complete type signature of - -- which the polymorphic type is known. - -- Nothing <=> partial type signature of - -- which the type is not yet fully - -- known. - -- See Note [Complete and partial type signatures] + -- Just f <=> the type signature had no wildcards, so the precise, + -- complete polymorphic type is known. In that case, + -- f is the polymorphic Id, with that type + + -- Nothing <=> the type signature is partial (i.e. includes one or more + -- wildcards). In this case it doesn't make sense to give + -- the polymorphic Id, because we are going to /infer/ its + -- type, so we can't make the polymorphic Id ab-initio + -- + -- See Note [Complete and partial type signatures] sig_tvs :: [(Maybe Name, TcTyVar)], -- Instantiated type and kind variables @@ -154,16 +158,17 @@ data TcSigInfo sig_nwcs :: [(Name, TcTyVar)], -- Instantiated wildcard variables + -- If sig_poly_id = Just f, then sig_nwcs must be empty - sig_theta :: TcThetaType, -- Instantiated theta - - sig_extra_cts :: Maybe SrcSpan, -- Just loc <=> An extra-constraints - -- wildcard was present. Any extra - -- constraints inferred during - -- type-checking will be added to the - -- partial type signature. Stores the - -- location of the wildcard. + sig_extra_cts :: Maybe SrcSpan, + -- Just loc <=> An extra-constraints wildcard was present + -- at location loc + -- e.g. f :: (Eq a, _) => a -> a + -- Any extra constraints inferred during + -- type-checking will be added to the sig_theta. + -- If sig_poly_id = Just f, sig_extra_cts must be Nothing + sig_theta :: TcThetaType, -- Instantiated theta sig_tau :: TcSigmaType, -- Instantiated tau -- See Note [sig_tau may be polymorphic] @@ -288,8 +293,8 @@ res_ty free vars. Note [Complete and partial type signatures] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -A type signature is partial when it contains one or more wildcards. -The wildcard can either be: +A type signature is partial when it contains one or more wildcards +(= type holes). The wildcard can either be: * A (type) wildcard occurring in sig_theta or sig_tau. These are stored in sig_nwcs. f :: Bool -> _ |