| otherwise
= do { meta_details <- readMutVar ref;
- ; WARN( not (isFlexi meta_details),
- hang (text "Double update of meta tyvar")
+ ; ASSERT2( isFlexi meta_details,
+ hang (text "Double update of meta tyvar")
2 (ppr tyvar $$ ppr meta_details) )
traceTc "writeMetaTyVar" (ppr tyvar <+> text ":=" <+> ppr ty)