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| author | Max Bolingbroke <batterseapower@hotmail.com> | 2011-09-06 09:04:37 +0100 |
|---|---|---|
| committer | Max Bolingbroke <batterseapower@hotmail.com> | 2011-09-09 08:26:59 +0100 |
| commit | de8c8d68cabb5f24304fad2f03caa41fdf182b4f (patch) | |
| tree | 88e191e91aebad8ce2a2ef2bb467be73e0c4d063 /compiler/hsSyn | |
| parent | 967633d4175a1d5ce525fa3194f53c219b5e2f91 (diff) | |
| download | haskell-de8c8d68cabb5f24304fad2f03caa41fdf182b4f.tar.gz | |
Implement associated type defaults
Basically, now you can write:
class Cls a where
type Typ a
type Typ a = Just a
And now if an instance does not specify an explicit associated type
instance, one will be generated afresh based on that default. So for
example this instance:
instance Cls Int where
Will be equivalent to this one:
instance Cls Int where
type Typ Int = Just Int
Diffstat (limited to 'compiler/hsSyn')
| -rw-r--r-- | compiler/hsSyn/Convert.lhs | 2 | ||||
| -rw-r--r-- | compiler/hsSyn/HsDecls.lhs | 12 |
2 files changed, 9 insertions, 5 deletions
diff --git a/compiler/hsSyn/Convert.lhs b/compiler/hsSyn/Convert.lhs index f84776546a..90cf99d582 100644 --- a/compiler/hsSyn/Convert.lhs +++ b/compiler/hsSyn/Convert.lhs @@ -183,7 +183,7 @@ cvtDec (ClassD ctxt cl tvs fds decs) ; returnL $ TyClD $ ClassDecl { tcdCtxt = cxt', tcdLName = tc', tcdTyVars = tvs' , tcdFDs = fds', tcdSigs = sigs', tcdMeths = binds' - , tcdATs = ats', tcdDocs = [] } + , tcdATs = ats', tcdATDefs = [], tcdDocs = [] } -- no docs in TH ^^ } diff --git a/compiler/hsSyn/HsDecls.lhs b/compiler/hsSyn/HsDecls.lhs index 82f113c096..940e6a73c3 100644 --- a/compiler/hsSyn/HsDecls.lhs +++ b/compiler/hsSyn/HsDecls.lhs @@ -499,7 +499,9 @@ data TyClDecl name tcdSigs :: [LSig name], -- ^ Methods' signatures tcdMeths :: LHsBinds name, -- ^ Default methods tcdATs :: [LTyClDecl name], -- ^ Associated types; ie - -- only 'TyFamily' + -- only 'TyFamily' + tcdATDefs :: [LTyClDecl name], -- ^ Associated type defaults; ie + -- only 'TySynonym' tcdDocs :: [LDocDecl] -- ^ Haddock docs } deriving (Data, Typeable) @@ -646,14 +648,16 @@ instance OutputableBndr name ppr_sigx (Just kind) = dcolon <+> pprKind kind ppr (ClassDecl {tcdCtxt = context, tcdLName = lclas, tcdTyVars = tyvars, - tcdFDs = fds, - tcdSigs = sigs, tcdMeths = methods, tcdATs = ats}) - | null sigs && null ats -- No "where" part + tcdFDs = fds, + tcdSigs = sigs, tcdMeths = methods, + tcdATs = ats, tcdATDefs = at_defs}) + | null sigs && isEmptyBag methods && null ats && null at_defs -- No "where" part = top_matter | otherwise -- Laid out = vcat [ top_matter <+> ptext (sLit "where") , nest 2 $ pprDeclList (map ppr ats ++ + map ppr at_defs ++ pprLHsBindsForUser methods sigs) ] where top_matter = ptext (sLit "class") |