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Simon Peyton Jones authored
-------------------------------------------- Fix another bug in the squash-newtypes story. -------------------------------------------- [This one was spotted by Marcin, and is now enshrined in test tc130.] The desugarer straddles the boundary between the type checker and Core, so it sometimes needs to look through newtypes/implicit parameters and sometimes not. This is really a bit painful, but I can't think of a better way to do it. The only simple way to fix things was to pass a bit more type information in the HsExpr type, from the type checker to the desugarer. That led to the non-local changes you can see. On the way I fixed one other thing. In various HsSyn constructors there is a Type that is bogus (bottom) before the type checker, and filled in with a real type by the type checker. In one place it was a (Maybe Type) which was Nothing before, and (Just ty) afterwards. I've defined a type synonym HsTypes.PostTcType for this, and a named bottom value HsTypes.placeHolderType to use when you want the bottom value.
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