ExprWithTySigOut

[Simon Peyton Jones]

Yes this is annoying.

The thing is that with the first constructor only we'd get
	(LHsSigWcType Id)
after type checking, but we don't have such a thing. `HsTypes` are typechecked to `Types`.  

Perhaps we could have
	(LHsSigWcType (StopAtRenamer d))

where
	type family StopAtRenamer a where
		StopAtRenamer Id = Name
		StopAtRenamer x = x

If this pattern happened a lot it might be worth it.  But I think this is the only occurrence.

Better ideas welcome.

Simon

|  -----Original Message-----
|  From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of Alan
|  & Kim Zimmerman
|  Sent: 19 December 2015 13:15
|  To: ghc-devs at haskell.org
|  Subject: ExprWithTySigOut
|  
|  At the moment HsExpr includes the following two constructors
|  
|    | ExprWithTySig
|                  (LHsExpr id)
|                  (LHsSigWcType id)
|  
|    | ExprWithTySigOut              -- Post typechecking
|                  (LHsExpr id)
|                  (LHsSigWcType Name)  -- Retain the signature,
|                                       -- as HsSigType Name, for
|                                       -- round-tripping purposes
|  
|  I do not understand why we need the second one, which hard-codes Name
|  instead of id.
|  
|  There are a couple of places where there is an XXXOut variant with
|  hard coded Name parameter, and these complicate creating any kind of
|  custom class intended to work on a parameterised AST as it ripples out
|  and forces Name instances of it everywhere.
|  
|  Perhaps we should introduce HsExprLR id id to cope with renaming?
|  
|  Alan
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