Improve depth-cutoff for printing HsSyn in error messages

[ghc-hetmet.git] / compiler / utils / Outputable.lhs

diff --git a/compiler/utils/Outputable.lhs b/compiler/utils/Outputable.lhs
index 52262ec..4f8d320 100644 (file)
--- a/compiler/utils/Outputable.lhs
+++ b/compiler/utils/Outputable.lhs
@@ -1,10 +1,10 @@
 %
+% (c) The University of Glasgow 2006
 % (c) The GRASP Project, Glasgow University, 1992-1998
 %
-\section[Outputable]{Classes for pretty-printing}
 
-Defines classes for pretty-printing and forcing, both forms of
-``output.''
+Outputable: defines classes for pretty-printing and forcing, both
+forms of ``output.''
 
 \begin{code}
 
@@ -14,7 +14,8 @@ module Outputable (
        BindingSite(..),
 
        PprStyle, CodeStyle(..), PrintUnqualified, alwaysQualify,
-       getPprStyle, withPprStyle, withPprStyleDoc, pprDeeper, pprSetDepth,
+       getPprStyle, withPprStyle, withPprStyleDoc, 
+       pprDeeper, pprDeeperList, pprSetDepth,
        codeStyle, userStyle, debugStyle, dumpStyle, asmStyle,
        ifPprDebug, qualName, qualModule,
        mkErrStyle, defaultErrStyle, defaultDumpStyle, defaultUserStyle,
@@ -25,7 +26,7 @@ module Outputable (
        empty, nest,
        text, char, ftext, ptext,
        int, integer, float, double, rational,
-       parens, brackets, braces, quotes, doubleQuotes, angleBrackets,
+       parens, cparen, brackets, braces, quotes, doubleQuotes, angleBrackets,
        semi, comma, colon, dcolon, space, equals, dot, arrow,
        lparen, rparen, lbrack, rbrack, lbrace, rbrace, underscore,
        (<>), (<+>), hcat, hsep, 
@@ -62,10 +63,9 @@ import qualified Pretty
 import Pretty          ( Doc, Mode(..) )
 import Panic
 
-import DATA_WORD       ( Word32 )
-
-import IO              ( Handle, stderr, stdout, hFlush )
-import Char             ( ord )
+import Data.Word       ( Word32 )
+import System.IO       ( Handle, stderr, stdout, hFlush )
+import Data.Char        ( ord )
 \end{code}
 
 
@@ -76,6 +76,7 @@ import Char             ( ord )
 %************************************************************************
 
 \begin{code}
+
 data PprStyle
   = PprUser PrintUnqualified Depth
                -- Pretty-print in a way that will make sense to the
@@ -188,6 +189,19 @@ pprDeeper d (PprUser q (PartWay 0)) = Pretty.text "..."
 pprDeeper d (PprUser q (PartWay n)) = d (PprUser q (PartWay (n-1)))
 pprDeeper d other_sty              = d other_sty
 
+pprDeeperList :: ([SDoc] -> SDoc) -> [SDoc] -> SDoc
+-- Truncate a list that list that is longer than the current depth
+pprDeeperList f ds (PprUser q (PartWay n))
+  | n==0      = Pretty.text "..."
+  | otherwise = f (go 0 ds) (PprUser q (PartWay (n-1)))
+  where
+    go i [] = []
+    go i (d:ds) | i >= n    = [text "...."]
+               | otherwise = d : go (i+1) ds
+
+pprDeeperList f ds other_sty
+  = f ds other_sty
+
 pprSetDepth :: Int -> SDoc -> SDoc
 pprSetDepth n d (PprUser q _) = d (PprUser q (PartWay n))
 pprSetDepth n d other_sty     = d other_sty
@@ -311,6 +325,8 @@ brackets d sty     = Pretty.brackets (d sty)
 doubleQuotes d sty = Pretty.doubleQuotes (d sty)
 angleBrackets d    = char '<' <> d <> char '>'
 
+cparen b d sty       = Pretty.cparen b (d sty)
+
 -- quotes encloses something in single quotes...
 -- but it omits them if the thing ends in a single quote
 -- so that we don't get `foo''.  Instead we just have foo'.