getDictClassTys, isTyVarDict,
instLoc, zonkInst, tidyInsts, tidyMoreInsts,
Inst, pprInsts, pprDictsInFull, pprInstInFull, tcGetInstEnvs,
- isIPDict, isInheritableInst, pprDFuns, pprDictsTheta
+ isInheritableInst, pprDFuns, pprDictsTheta
)
import TcEnv ( tcGetGlobalTyVars, tcLookupId, findGlobals )
import InstEnv ( lookupInstEnv, classInstances )
non_std_tyvars = unionVarSets (map tyVarsOfInst non_stds)
-- Collect together all the bad guys
- bad_guys = non_stds ++ concat std_bads
- (bad_ips, non_ips) = partition isIPDict bad_guys
- (no_insts, ambigs) = partition no_inst non_ips
- no_inst d = not (isTyVarDict d)
- -- Previously, there was a more elaborate no_inst definition:
+ bad_guys = non_stds ++ concat std_bads
+ (non_ips, bad_ips) = partition isClassDict bad_guys
+ (ambigs, no_insts) = partition is_ambig non_ips
+ is_ambig d = not (isEmptyVarSet (tyVarsOfInst d))
+ -- If the dict has free type variables, it's almost certainly ambiguous,
+ -- and that's the first thing to fix
+ -- Otherwise, addNoInstanceErrs does the right thing
+ -- [ Previously, there was a different no_inst definition:
-- no_inst d = not (isTyVarDict d) || tyVarsOfInst d `subVarSet` fixed_tvs
-- fixed_tvs = oclose (fdPredsOfInsts tidy_dicts) emptyVarSet
- -- But that seems over-elaborate to me; it only bites for class decls with
- -- fundeps like this: class C a b | -> b where ...
+ -- But that seems over-elaborate to me; it only bites for class decls with
+ -- fundeps like this: class C a b | -> b where ...]
in
-- Report definite errors
addNoInstanceErrs mb_what givens dicts
= -- Some of the dicts are here because there is no instances
-- and some because there are too many instances (overlap)
- -- The first thing we do is separate them
getDOpts `thenM` \ dflags ->
tcGetInstEnvs `thenM` \ inst_envs ->
let
| otherwise
= case lookupInstEnv dflags inst_envs clas tys of
-- The case of exactly one match and no unifiers means
- -- a successful lookup. That can't happen here.
+ -- a successful lookup. That can't happen here, becuase
+ -- dicts only end up here if they didn't match in Inst.lookupInst
#ifdef DEBUG
([m],[]) -> pprPanic "addNoInstanceErrs" (ppr dict)
#endif
in
-- Now generate a good message for the no-instance bunch
- mk_probable_fix tidy_env2 mb_what no_inst_dicts `thenM` \ (tidy_env3, probable_fix) ->
+ mk_probable_fix tidy_env2 no_inst_dicts `thenM` \ (tidy_env3, probable_fix) ->
let
no_inst_doc | null no_inst_dicts = empty
| otherwise = vcat [addInstLoc no_inst_dicts heading, probable_fix]
where
dfuns = [df | (_, (_,_,df)) <- matches]
- mk_probable_fix tidy_env Nothing dicts -- Top level
- = mkMonomorphismMsg tidy_env dicts
- mk_probable_fix tidy_env (Just what) dicts -- Nested (type signatures, instance decls)
- = returnM (tidy_env, sep [ptext SLIT("Probable fix:"), nest 2 fix1, nest 2 fix2])
+ mk_probable_fix tidy_env dicts
+ = returnM (tidy_env, sep [ptext SLIT("Probable fix:"), nest 2 (vcat fixes)])
where
- fix1 = sep [ptext SLIT("Add") <+> pprDictsTheta dicts,
- ptext SLIT("to the") <+> what]
+ fixes = add_ors (fix1 ++ fix2)
- fix2 | null instance_dicts = empty
- | otherwise = ptext SLIT("Or add an instance declaration for")
- <+> pprDictsTheta instance_dicts
+ fix1 = case mb_what of
+ Nothing -> [] -- Top level
+ Just what -> -- Nested (type signatures, instance decls)
+ [ sep [ ptext SLIT("add") <+> pprDictsTheta dicts,
+ ptext SLIT("to the") <+> what] ]
+
+ fix2 | null instance_dicts = []
+ | otherwise = [ ptext SLIT("add an instance declaration for")
+ <+> pprDictsTheta instance_dicts ]
instance_dicts = [d | d <- dicts, isClassDict d, not (isTyVarDict d)]
-- Insts for which it is worth suggesting an adding an instance declaration
-- Exclude implicit parameters, and tyvar dicts
+ add_ors :: [SDoc] -> [SDoc]
+ add_ors (f1:fs) = f1 : map (ptext SLIT("or") <+>) fs
addTopAmbigErrs dicts
-- Divide into groups that share a common set of ambiguous tyvars
report :: [(Inst,[TcTyVar])] -> TcM ()
report pairs@((inst,tvs) : _) -- The pairs share a common set of ambiguous tyvars
- = mkMonomorphismMsg tidy_env dicts `thenM` \ (tidy_env, mono_msg) ->
+ = mkMonomorphismMsg tidy_env tvs `thenM` \ (tidy_env, mono_msg) ->
setSrcSpan (instLocSrcSpan (instLoc inst)) $
-- the location of the first one will do for the err message
addErrTcM (tidy_env, msg $$ mono_msg)
where
dicts = map fst pairs
msg = sep [text "Ambiguous type variable" <> plural tvs <+>
- pprQuotedList tvs <+> in_msg,
+ pprQuotedList tvs <+> in_msg,
nest 2 (pprDictsInFull dicts)]
- in_msg | isSingleton dicts = text "in the top-level constraint:"
- | otherwise = text "in these top-level constraints:"
+ in_msg = text "in the constraint" <> plural dicts <> colon
-mkMonomorphismMsg :: TidyEnv -> [Inst] -> TcM (TidyEnv, Message)
+mkMonomorphismMsg :: TidyEnv -> [TcTyVar] -> TcM (TidyEnv, Message)
-- There's an error with these Insts; if they have free type variables
-- it's probably caused by the monomorphism restriction.
-- Try to identify the offending variable
-- ASSUMPTION: the Insts are fully zonked
-mkMonomorphismMsg tidy_env insts
- | isEmptyVarSet inst_tvs
- = returnM (tidy_env, empty)
- | otherwise
- = findGlobals inst_tvs tidy_env `thenM` \ (tidy_env, docs) ->
+mkMonomorphismMsg tidy_env inst_tvs
+ = findGlobals (mkVarSet inst_tvs) tidy_env `thenM` \ (tidy_env, docs) ->
returnM (tidy_env, mk_msg docs)
-
where
- inst_tvs = tyVarsOfInsts insts
-
- mk_msg [] = empty -- This happens in things like
- -- f x = show (read "foo")
- -- whre monomorphism doesn't play any role
+ mk_msg [] = ptext SLIT("Probable fix: add a type signature that fixes these type variable(s)")
+ -- This happens in things like
+ -- f x = show (read "foo")
+ -- whre monomorphism doesn't play any role
mk_msg docs = vcat [ptext SLIT("Possible cause: the monomorphism restriction applied to the following:"),
nest 2 (vcat docs),
ptext SLIT("Probable fix: give these definition(s) an explicit type signature")]
projects / ghc-hetmet.git / commitdiff