Add the notion of "constructor-like" Ids for rule-matching

This patch adds an optional CONLIKE modifier to INLINE/NOINLINE pragmas, 
   {-# NOINLINE CONLIKE [1] f #-}
The effect is to allow applications of 'f' to be expanded in a potential
rule match.  Example
  {-# RULE "r/f" forall v. r (f v) = f (v+1) #-}

Consider the term
     let x = f v in ..x...x...(r x)...
Normally the (r x) would not match the rule, because GHC would be scared
about duplicating the redex (f v). However the CONLIKE modifier says to
treat 'f' like a constructor in this situation, and "look through" the
unfolding for x.  So (r x) fires, yielding (f (v+1)).

The main changes are:
  - Syntax

  - The inlinePragInfo field of an IdInfo has a RuleMatchInfo
    component, which records whether or not the Id is CONLIKE.
    Of course, this needs to be serialised in interface files too.

  - The occurrence analyser (OccAnal) and simplifier (Simplify) treat
    CONLIKE thing like constructors, by ANF-ing them

  - New function coreUtils.exprIsExpandable is like exprIsCheap, but
    additionally spots applications of CONLIKE functions

  - A CoreUnfolding has a field that caches exprIsExpandable

  - The rule matcher consults this field.  See 
    Note [Expanding variables] in Rules.lhs.

On the way I fixed a lurking variable bug in the way variables are
expanded.  See Note [Do not expand locally-bound variables] in
Rule.lhs.  I also did a bit of reformatting and refactoring in
Rules.lhs, so the module has more lines changed than are really
different.

2 files changed, 6 insertions, 6 deletions

diff --git a/compiler/deSugar/DsBinds.lhs b/compiler/deSugar/DsBinds.lhs
index 4c144b8e50..80a7cf66ef 100644
--- a/compiler/deSugar/DsBinds.lhs
+++ b/compiler/deSugar/DsBinds.lhs
@@ -516,12 +516,12 @@ addInlinePrags prags bndr rhs
 	(inl:_) -> addInlineInfo inl bndr rhs
 
 addInlineInfo :: InlineSpec -> Id -> CoreExpr -> (Id,CoreExpr)
-addInlineInfo (Inline phase is_inline) bndr rhs
-  = (attach_phase bndr phase, wrap_inline is_inline rhs)
+addInlineInfo (Inline prag is_inline) bndr rhs
+  = (attach_pragma bndr prag, wrap_inline is_inline rhs)
   where
-    attach_phase bndr phase 
-	| isAlwaysActive phase = bndr	-- Default phase
-	| otherwise  	       = bndr `setInlinePragma` phase
+    attach_pragma bndr prag
+        | isDefaultInlinePragma prag = bndr
+        | otherwise                  = bndr `setInlinePragma` prag
 
     wrap_inline True  body = mkInlineMe body
     wrap_inline False body = body
diff --git a/compiler/deSugar/DsForeign.lhs b/compiler/deSugar/DsForeign.lhs
index 0c40318a1f..7071ab7ef4 100644
--- a/compiler/deSugar/DsForeign.lhs
+++ b/compiler/deSugar/DsForeign.lhs
@@ -387,7 +387,7 @@ dsFExportDynamic id cconv = do
                         , Lam stbl_value ccall_adj
                         ]
 
-        fed = (id `setInlinePragma` NeverActive, io_app)
+        fed = (id `setInlineActivation` NeverActive, io_app)
                -- Never inline the f.e.d. function, because the litlit
                -- might not be in scope in other modules.