patch applied (ghc-6.6/ghc): Do not filter the type envt after each GHCi stmt

[Ian Lynagh]

Tue Oct 10 07:32:25 PDT 2006  simonpj at microsoft.com
  * Do not filter the type envt after each GHCi stmt
  
  Fixes Trac #925
  
  A new comment in TcRnDriver in tcRnStmt reads thus: 
  
  At one stage I removed any shadowed bindings from the type_env;
  they are inaccessible but might, I suppose, cause a space leak if we leave them there.
  However, with Template Haskell they aren't necessarily inaccessible.  Consider this
  GHCi session
  	 Prelude> let f n = n * 2 :: Int
  	 Prelude> fName <- runQ [| f |]
  	 Prelude> $(return $ AppE fName (LitE (IntegerL 7)))
  	 14
  	 Prelude> let f n = n * 3 :: Int
  	 Prelude> $(return $ AppE fName (LitE (IntegerL 7)))
  In the last line we use 'fName', which resolves to the *first* 'f'
  in scope. If we delete it from the type env, GHCi crashes because
  it doesn't expect that.
  
  

    M ./compiler/typecheck/TcRnDriver.lhs -5 +19