View patterns, record wildcards, and record puns

[ghc-hetmet.git] / compiler / deSugar / DsUtils.lhs

diff --git a/compiler/deSugar/DsUtils.lhs b/compiler/deSugar/DsUtils.lhs
index 209b017..9d787ad 100644 (file)
--- a/compiler/deSugar/DsUtils.lhs
+++ b/compiler/deSugar/DsUtils.lhs
@@ -12,7 +12,7 @@ This module exports some utility functions of no great interest.
 -- The above warning supression flag is a temporary kludge.
 -- While working on this module you are encouraged to remove it and fix
 -- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module DsUtils (
@@ -25,7 +25,7 @@ module DsUtils (
        cantFailMatchResult, alwaysFailMatchResult,
        extractMatchResult, combineMatchResults, 
        adjustMatchResult,  adjustMatchResultDs,
-       mkCoLetMatchResult, mkGuardedMatchResult, 
+       mkCoLetMatchResult, mkViewMatchResult, mkGuardedMatchResult, 
        matchCanFail, mkEvalMatchResult,
        mkCoPrimCaseMatchResult, mkCoAlgCaseMatchResult,
        wrapBind, wrapBinds,
@@ -319,6 +319,12 @@ seqVar var body = Case (Var var) var (exprType body)
 mkCoLetMatchResult :: CoreBind -> MatchResult -> MatchResult
 mkCoLetMatchResult bind = adjustMatchResult (mkDsLet bind)
 
+-- (mkViewMatchResult var' viewExpr var mr) makes the expression
+-- let var' = viewExpr var in mr
+mkViewMatchResult :: Id -> CoreExpr -> Id -> MatchResult -> MatchResult
+mkViewMatchResult var' viewExpr var = 
+    adjustMatchResult (mkDsLet (NonRec var' (mkDsApp viewExpr (Var var))))
+
 mkEvalMatchResult :: Id -> Type -> MatchResult -> MatchResult
 mkEvalMatchResult var ty
   = adjustMatchResult (\e -> Case (Var var) var ty [(DEFAULT, [], e)])