- checkDupRdrNames meth_names `thenM_`
- -- Check that the same method is not given twice in the
- -- same instance decl instance C T where
- -- f x = ...
- -- g y = ...
- -- f x = ...
- -- We must use checkDupRdrNames because the Name of the
- -- method is the Name of the class selector, whose SrcSpan
- -- points to the class declaration
-