- 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
- }
-
-tc_defaults decls@(DefaultDecl _ loc : _) =
- tcAddSrcLoc loc $
+tcDefaults []
+ = getDefaultTys -- No default declaration, so get the
+ -- default types from the envt;
+ -- i.e. use the curent ones
+ -- (the caller will put them back there)
+ -- It's important not to return defaultDefaultTys here (which
+ -- we used to do) because in a TH program, tcDefaults [] is called
+ -- repeatedly, once for each group of declarations between top-level
+ -- splices. We don't want to carefully set the default types in
+ -- one group, only for the next group to ignore them and install
+ -- defaultDefaultTys
+
+tcDefaults [L locn (DefaultDecl [])]
+ = returnM (Just []) -- Default declaration specifying no types
+
+tcDefaults [L locn (DefaultDecl mono_tys)]
+ = addSrcSpan locn $
+ addErrCtxt defaultDeclCtxt $
+ tcLookupClass numClassName `thenM` \ num_class ->
+ mappM tc_default_ty mono_tys `thenM` \ 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] `thenM_`
+
+ returnM (Just tau_tys)
+
+tcDefaults decls@(L locn (DefaultDecl _) : _) =
+ addSrcSpan locn $