- = tcLookupClassByKey_maybe numClassKey `thenNF_Tc` \ maybe_num ->
- case maybe_num of {
- Nothing -> -- Num has not been sucked in, so the defaults will
- -- never be used; so simply discard the default decl.
- -- This slightly benefits modules that don't use any
- -- numeric stuff at all, by avoid the necessity of
- -- always sucking in Num
- returnTc [] ;
-
- Just num -> -- The common case
-
- tcAddSrcLoc locn $
- mapTc tcHsType mono_tys `thenTc` \ tau_tys ->
-
- -- Check that all the types are instances of Num
- -- We only care about whether it worked or not
- tcAddErrCtxt defaultDeclCtxt $
- tcSimplifyCheckThetas
- [{- Nothing given -}]
- [ (num, [ty]) | ty <- tau_tys ] `thenTc_`
-
- returnTc tau_tys
- }
+ = tcLookupGlobal_maybe numClassName `thenNF_Tc` \ maybe_num ->
+ case maybe_num of
+ Just (AClass num_class) -> common_case num_class
+ other -> returnTc []
+ -- In the Nothing case, Num has not been sucked in, so the
+ -- defaults will never be used; so simply discard the default decl.
+ -- This slightly benefits modules that don't use any
+ -- numeric stuff at all, by avoid the necessity of
+ -- always sucking in Num
+ where
+ common_case num_class
+ = tcAddSrcLoc locn $
+ tcAddErrCtxt defaultDeclCtxt $
+ mapTc tc_default_ty mono_tys `thenTc` \ tau_tys ->
+
+ -- Check that all the types are instances of Num
+ -- We only care about whether it worked or not
+ tcSimplifyDefault [mkClassPred num_class [ty] | ty <- tau_tys] `thenTc_`
+
+ returnTc tau_tys