[project @ 1999-06-01 16:40:41 by simonmar]

This commit replaces the old yacc parser with a Happy-generated one.
Notes:

	- The generated .hs file is *big*.  Best to use a recent
	  version of Happy, and even better to add the -c flag
	  to use unsafeCoerce# with ghc (versions 4.02+ please).

	- The lexer has grown all sorts of unsightly growths and
	  should be put down as soon as possible.

	- Parse errors may result in strange diagnostics.  I'm looking
	  into this.

	- HsSyn now contains a few extra constructors due to the way
	  patterns are parsed as expressions in the parser.

	- The layout rule is implemented according to the Haskell
	  report.  I found a couple of places in the libraries where
	  we previously weren't adhering to this - in particular the
	  rule about "nested contexts must be more indented than
	  outer contexts".  The rule is necessary to disambiguate
	  in the presence of empty declaration lists.

1 files changed, 11 insertions, 0 deletions

diff --git a/ghc/compiler/hsSyn/HsExpr.lhs b/ghc/compiler/hsSyn/HsExpr.lhs
index 24ab616694..caa8a6ba84 100644
--- a/ghc/compiler/hsSyn/HsExpr.lhs
+++ b/ghc/compiler/hsSyn/HsExpr.lhs
@@ -153,6 +153,17 @@ data HsExpr id pat
 		(HsExpr id pat) -- expr whose cost is to be measured
 \end{code}
 
+These constructors only appear temporarily in the parser.
+
+\begin{code}
+  | EWildPat			-- wildcard
+
+  | EAsPat	id		-- as pattern
+		(HsExpr id pat)
+
+  | ELazyPat	(HsExpr id pat) -- ~ pattern
+\end{code}
+
 Everything from here on appears only in typechecker output.
 
 \begin{code}