From cc02bb851921a07a83006988c5bc19b72a3f9049 Mon Sep 17 00:00:00 2001
From: simonmar <unknown>
Date: Wed, 30 Jun 1999 11:29:53 +0000
Subject: [PATCH] [project @ 1999-06-30 11:29:53 by simonmar] Allow the
following (not strictly H98) construct:
do
blah
e $ do
blah
This doesn't break any existing code, just allows more programs
through. Only the semantics for layout after a 'do' have changed.
---
ghc/compiler/parser/Lex.lhs | 18 +++++++++++++++---
ghc/compiler/parser/Parser.y | 9 +++++----
2 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/ghc/compiler/parser/Lex.lhs b/ghc/compiler/parser/Lex.lhs
index d705043da6bd..efcda1b6d46c 100644
--- a/ghc/compiler/parser/Lex.lhs
+++ b/ghc/compiler/parser/Lex.lhs
@@ -1198,13 +1198,25 @@ h = h
- we still need to insert another '}' followed by a ';',
hence the atbol trick.
+There's also a special hack in here to deal with
+
+ do
+ ....
+ e $ do
+ blah
+
+i.e. the inner context is at the same indentation level as the outer
+context. This is strictly illegal according to Haskell 98, but
+there's a lot of existing code using this style and it doesn't make
+any sense to disallow it, since empty 'do' lists don't make sense.
-}
-layoutOn :: P ()
-layoutOn buf s@(PState{ bol = bol, context = ctx }) =
+layoutOn :: Bool -> P ()
+layoutOn strict buf s@(PState{ bol = bol, context = ctx }) =
let offset = lexemeIndex buf -# bol in
case ctx of
- Layout prev_off : _ | prev_off >=# offset ->
+ Layout prev_off : _
+ | if strict then prev_off >=# offset else prev_off ># offset ->
--trace ("layout on, column: " ++ show (I# offset)) $
POk s{ context = Layout (offset +# 1#) : ctx, atbol = 1# } ()
other ->
diff --git a/ghc/compiler/parser/Parser.y b/ghc/compiler/parser/Parser.y
index 3348da9d3cdd..ef83b5e29531 100644
--- a/ghc/compiler/parser/Parser.y
+++ b/ghc/compiler/parser/Parser.y
@@ -1,6 +1,6 @@
{-
-----------------------------------------------------------------------------
-$Id: Parser.y,v 1.9 1999/06/28 16:42:23 simonmar Exp $
+$Id: Parser.y,v 1.10 1999/06/30 11:29:53 simonmar Exp $
Haskell grammar.
@@ -760,8 +760,8 @@ gdpat :: { RdrNameGRHS }
-- Statement sequences
stmtlist :: { [RdrNameStmt] }
- : '{' stmts '}' { reverse $2 }
- | layout_on stmts close { reverse $2 }
+ : '{' stmts '}' { reverse $2 }
+ | layout_on_for_do stmts close { reverse $2 }
stmts :: { [RdrNameStmt] }
: ';' stmts1 { $2 }
@@ -949,7 +949,8 @@ close :: { () }
: vccurly { () } -- context popped in lexer.
| error {% popContext }
-layout_on :: { () } : {% layoutOn }
+layout_on :: { () } : {% layoutOn True{-strict-} }
+layout_on_for_do :: { () } : {% layoutOn False }
-----------------------------------------------------------------------------
-- Miscellaneous (mostly renamings)
--
GitLab