Commit 884b0a57 authored by simonpj@microsoft.com's avatar simonpj@microsoft.com
Browse files

Improve error message (Trac #1446)

parent 858a055d
......@@ -2716,11 +2716,11 @@ report_no_instances tidy_env mb_what insts
(clas,tys) = getDictClassTys wanted
mk_overlap_msg dict (matches, unifiers)
= vcat [ addInstLoc [dict] ((ptext SLIT("Overlapping instances for")
= ASSERT( not (null matches) )
vcat [ addInstLoc [dict] ((ptext SLIT("Overlapping instances for")
<+> pprPred (dictPred dict))),
sep [ptext SLIT("Matching instances") <> colon,
nest 2 (vcat [pprInstances ispecs, pprInstances unifiers])],
ASSERT( not (null matches) )
if not (isSingleton matches)
then -- Two or more matches
empty
......@@ -2728,7 +2728,8 @@ report_no_instances tidy_env mb_what insts
ASSERT( not (null unifiers) )
parens (vcat [ptext SLIT("The choice depends on the instantiation of") <+>
quotes (pprWithCommas ppr (varSetElems (tyVarsOfInst dict))),
ptext SLIT("Use -fallow-incoherent-instances to use the first choice above")])]
ptext SLIT("To pick the first instance above, use -fallow-incoherent-instances"),
ptext SLIT("when compiling the other instances")])]
where
ispecs = [ispec | (ispec, _) <- matches]
......
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