Commit 831297f1 authored by simonpj's avatar simonpj
Browse files

[project @ 1999-03-16 12:31:55 by simonpj]

Make it only a warning if you have a type like this:

	forall a. Int -> Int

These show up in interface files occasionally, just because
the simplifier is a bit blase about adding type arguments.

But it's an error to have

	forall a. Eq a => Int -> Int

The flag -fwarn-unused-matches reports a warning for these
redundant for-alls.
parent ce55bf9c
......@@ -48,8 +48,10 @@ import PrelInfo ( derivingOccurrences, numClass_RDR,
bindIO_NAME
)
import Bag ( bagToList )
import List ( partition )
import Outputable
import SrcLoc ( SrcLoc )
import CmdLineOpts ( opt_WarnUnusedMatches ) -- Warn of unused for-all'd tyvars
import UniqFM ( lookupUFM )
import Maybes ( maybeToBool, catMaybes )
import Util
......@@ -540,12 +542,19 @@ rnHsType doc (HsForAllTy (Just forall_tyvars) ctxt ty)
-- Explicit quantification.
-- Check that the forall'd tyvars are a subset of the
-- free tyvars in the tau-type part
-- That's only a warning... unless the tyvar is constrained by a
-- context in which case it's an error
= let
mentioned_tyvars = extractHsTyVars ty
bad_guys = filter (`notElem` mentioned_tyvars) forall_tyvar_names
forall_tyvar_names = map getTyVarName forall_tyvars
mentioned_tyvars = extractHsTyVars ty
constrained_tyvars = [tv | (_,tys) <- ctxt,
ty <- tys,
tv <- extractHsTyVars ty]
dubious_guys = filter (`notElem` mentioned_tyvars) forall_tyvar_names
(bad_guys, warn_guys) = partition (`elem` constrained_tyvars) dubious_guys
forall_tyvar_names = map getTyVarName forall_tyvars
in
mapRn (forAllErr doc ty) bad_guys `thenRn_`
mapRn (forAllErr doc ty) bad_guys `thenRn_`
mapRn (forAllWarn doc ty) warn_guys `thenRn_`
checkConstraints True doc forall_tyvar_names ctxt ty `thenRn` \ ctxt' ->
rnForAll doc forall_tyvars ctxt' ty
......@@ -791,9 +800,18 @@ dupClassAssertWarn ctxt (assertion : dups)
badDataCon name
= hsep [ptext SLIT("Illegal data constructor name"), quotes (ppr name)]
forAllWarn doc ty tyvar
| not opt_WarnUnusedMatches = returnRn ()
| otherwise
= addWarnRn (
sep [ptext SLIT("The universally quantified type variable") <+> quotes (ppr tyvar),
nest 4 (ptext SLIT("does not appear in the type") <+> quotes (ppr ty))]
$$
(ptext SLIT("In") <+> doc))
forAllErr doc ty tyvar
= addErrRn (
sep [ptext SLIT("The universally quantified type variable") <+> quotes (ppr tyvar),
sep [ptext SLIT("The constrained type variable") <+> quotes (ppr tyvar),
nest 4 (ptext SLIT("does not appear in the type") <+> quotes (ppr ty))]
$$
(ptext SLIT("In") <+> doc))
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment