[project @ 2001-04-23 19:34:57 by lewie]

Fix for infix decl w/ infix data constructor.
GHC was rejecting this:

    infix 2 |-
    ps  |-  q:qs = undefined

It parses the def as ((ps |- q) : qs), and doesn't have the fixity info
around at the point where it decides what is being defined.  Lacking
anything else to go on, it decides that `:' is being defined.

Fortunately, we don't really need fixity info to parse this correctly,
as a data constructor is always the wrong choice ;-)  The fix is to
dive into the left-hand-side until we find a non-data constructor.

This is naive - consider the case where `|-' has a high precedence.
Fortunately, someone clever put in a static check later on, presumably
at the point where we have all the fixity info, that rejects the definition
as bogus.  Yeah!

diff --git a/ghc/compiler/parser/ParseUtil.lhs b/ghc/compiler/parser/ParseUtil.lhs
index 969ca93..e444450 100644 (file)
--- a/ghc/compiler/parser/ParseUtil.lhs
+++ b/ghc/compiler/parser/ParseUtil.lhs
@@ -271,6 +271,11 @@ checkValSig other     ty loc = parseError "Type signature given for an expressio
 isFunLhs :: RdrNameHsExpr -> [RdrNameHsExpr] -> Maybe (RdrName, Bool, [RdrNameHsExpr])
 isFunLhs (OpApp l (HsVar op) fix r) es  | not (isRdrDataCon op)
                                = Just (op, True, (l:r:es))
+                                       | otherwise
+                               = case isFunLhs l es of
+                                   Just (op', True, j : k : es') ->
+                                     Just (op', True, j : OpApp k (HsVar op) fix r : es')
+                                   Nothing -> Nothing
 isFunLhs (HsVar f) es | not (isRdrDataCon f)
                                = Just (f,False,es)
 isFunLhs (HsApp f e) es        = isFunLhs f (e:es)