Fix Trac #3259: expose 'lazy' only after generating interface files

[ghc-hetmet.git] / compiler / coreSyn / CorePrep.lhs

diff --git a/compiler/coreSyn/CorePrep.lhs b/compiler/coreSyn/CorePrep.lhs
index 908c90c..89ec98f 100644 (file)
--- a/compiler/coreSyn/CorePrep.lhs
+++ b/compiler/coreSyn/CorePrep.lhs
@@ -11,6 +11,7 @@ module CorePrep (
 
 #include "HsVersions.h"
 
+import PrelNames       ( lazyIdKey, hasKey )
 import CoreUtils
 import CoreArity
 import CoreFVs
@@ -89,6 +90,8 @@ The goal of this pass is to prepare for code generation.
     We want curried definitions for all of these in case they
     aren't inlined by some caller.
        
+9.  Replace (lazy e) by e.  See Note [lazyId magic] in MkId.lhs
+
 This is all done modulo type applications and abstractions, so that
 when type erasure is done for conversion to STG, we don't end up with
 any trivial or useless bindings.
@@ -341,9 +344,14 @@ cpeRhsE :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeRhs)
 
 cpeRhsE _env expr@(Type _) = return (emptyFloats, expr)
 cpeRhsE _env expr@(Lit _)  = return (emptyFloats, expr)
-cpeRhsE env expr@(App {})  = cpeApp env expr
 cpeRhsE env expr@(Var {})  = cpeApp env expr
 
+cpeRhsE env (Var f `App` _ `App` arg)
+  | f `hasKey` lazyIdKey         -- Replace (lazy a) by a
+  = cpeRhsE env arg              -- See Note [lazyId magic] in MkId
+
+cpeRhsE env expr@(App {}) = cpeApp env expr
+
 cpeRhsE env (Let bind expr)
   = do { (env', new_binds) <- cpeBind NotTopLevel env bind
        ; (floats, body) <- cpeRhsE env' expr
@@ -407,7 +415,7 @@ rhsToBodyNF rhs = do { (floats,body) <- rhsToBody rhs
 
 --------
 rhsToBody :: CpeRhs -> UniqSM (Floats, CpeBody)
--- Remove top level lambdas by let-bindinig
+-- Remove top level lambdas by let-binding
 
 rhsToBody (Note n expr)
         -- You can get things like
@@ -475,7 +483,7 @@ cpeApp env expr
 
     collect_args (App fun arg) depth
       = do { (fun',hd,fun_ty,floats,ss) <- collect_args fun (depth+1)
-           ; let
+          ; let
               (ss1, ss_rest)   = case ss of
                                    (ss1:ss_rest) -> (ss1,     ss_rest)
                                    []            -> (lazyDmd, [])
@@ -511,10 +519,10 @@ cpeApp env expr
       = collect_args fun depth  -- They aren't used by the code generator
 
        -- N-variable fun, better let-bind it
-       -- ToDo: perhaps we can case-bind rather than let-bind this closure,
-       -- since it is sure to be evaluated.
     collect_args fun depth
       = do { (fun_floats, fun') <- cpeArg env True fun ty
+                         -- The True says that it's sure to be evaluated,
+                         -- so we'll end up case-binding it
            ; return (fun', (fun', depth), ty, fun_floats, []) }
         where
          ty = exprType fun