From: Simon Peyton Jones <simonpj@microsoft.com>
Date: Wed, 4 May 2011 15:37:08 +0000 (+0100)
Subject: Merge branch monad-comp onto master
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=7028041739973c3dc17b23a98c65c892f41f0647

Merge branch monad-comp onto master

This patch implements monad comprehensions, Trac #4370.
Thanks to Nils Schweinsberg for doing most of the heavy lifting.

I did quite a lot of related refactoring as well.  Notably:

* Combined TransformStmt and GroupStmt into a single
  constructor TransStmt; they share a lot of code.
  I also made TransStmt into a record; it has a lot of fields.

* Remove the "result expression" field of HsDo, and instead
  implement LastStmt, which is expected to be at the end
  of a list of Stmts

* Generalise and tidy up the typechecking of monad comprehensions

* Do-notation in arrows is marked with HsStmtContext = ArrowExpr

* tcMDoStmt (which was only used for arrows) is moved
  to TcArrows, and renamed tcArrDoStmt

* Improved documentation in the user manual

* Lots of other minor changes
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7028041739973c3dc17b23a98c65c892f41f0647