Commit 4417e97d authored by simonpj@microsoft.com's avatar simonpj@microsoft.com
Browse files

Improve error messsage when argument count varies

parent a0f8de19
......@@ -44,7 +44,7 @@ import Id ( idType, mkLocalId )
import TyCon ( TyCon )
import Util ( isSingleton )
import Outputable
import SrcLoc ( Located(..) )
import SrcLoc ( Located(..), getLoc )
import ErrUtils ( Message )
import List ( nub )
......@@ -74,7 +74,7 @@ tcMatchesFun fun_name matches exp_ty
-- sensible location. Note: we have to do this odd
-- ann-grabbing, because we don't always have annotations in
-- hand when we call tcMatchesFun...
checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches)
checkArgs fun_name matches
-- ToDo: Don't use "expected" stuff if there ain't a type signature
-- because inconsistency between branches
......@@ -489,18 +489,23 @@ tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside
number of args are used in each equation.
\begin{code}
sameNoOfArgs :: MatchGroup Name -> Bool
sameNoOfArgs (MatchGroup matches _)
= isSingleton (nub (map args_in_match matches))
checkArgs :: Name -> MatchGroup Name -> TcM ()
checkArgs fun (MatchGroup (match1:matches) _)
| null bad_matches = return ()
| otherwise
= failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+>
ptext SLIT("have different numbers of arguments"),
nest 2 (ppr (getLoc match1)),
nest 2 (ppr (getLoc (head bad_matches)))])
where
n_args1 = args_in_match match1
bad_matches = [m | m <- matches, args_in_match m /= n_args1]
args_in_match :: LMatch Name -> Int
args_in_match (L _ (Match pats _ _)) = length pats
\end{code}
\begin{code}
varyingArgsErr name matches
= sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
4 (pprMatch ctxt match)
......
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