Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master
http://hackage.haskell.org/trac/ghc/changeset/156d30d76c87230d1bb5374ccec4aa73387fec9a >--------------------------------------------------------------- commit 156d30d76c87230d1bb5374ccec4aa73387fec9a Author: Simon Peyton Jones <simo...@microsoft.com> Date: Tue Dec 4 10:58:36 2012 +0000 Fix buglet in -ddump-minimal-imports (Trac #7476) We were mixing up the *implicit* import of Prelude with a user-written import declaration >--------------------------------------------------------------- compiler/rename/RnNames.lhs | 40 +++++++++++++++++++++++++++------------- 1 files changed, 27 insertions(+), 13 deletions(-) diff --git a/compiler/rename/RnNames.lhs b/compiler/rename/RnNames.lhs index 03f9a2a..ca78368 100644 --- a/compiler/rename/RnNames.lhs +++ b/compiler/rename/RnNames.lhs @@ -1321,23 +1321,35 @@ warnUnusedImportDecls gbl_env -- it just doesn't seem worth it \end{code} + +Note [The ImportMap] +~~~~~~~~~~~~~~~~~~~~ +The ImportMap is a short-lived intermediate data struture records, for +each import declaration, what stuff brought into scope by that +declaration is actually used in the module. + +The SrcLoc is the location of the END of a particular 'import' +declaration. Why *END*? Becuase we don't want to get confused +by the implicit Prelude import. Consider (Trac #7476) the module + import Foo( foo ) + main = print foo +There is an implicit 'import Prelude(print)', and it gets a SrcSpan +of line 1:1 (just the point, not a span). If we use the *START* of +the SrcSpan to identify the import decl, we'll confuse the implicit +import Prelude with the explicit 'import Foo'. So we use the END. +It's just a cheap hack; we could equally well use the Span too. + +The AvailInfos are the things imported from that decl (just a list, +not normalised). + \begin{code} +type ImportMap = Map SrcLoc [AvailInfo] -- See [The ImportMap] + findImportUsage :: [LImportDecl Name] -> GlobalRdrEnv -> [RdrName] -> [ImportDeclUsage] -type ImportMap = Map SrcLoc [AvailInfo] --- The intermediate data struture records, for each import --- declaration, what stuff brought into scope by that --- declaration is actually used in the module. >--------------------------------------------------------------- --- The SrcLoc is the location of the start --- of a particular 'import' declaration >--------------------------------------------------------------- --- The AvailInfos are the things imported from that decl --- (just a list, not normalised) - findImportUsage imports rdr_env rdrs = map unused_decl imports where @@ -1347,7 +1359,8 @@ findImportUsage imports rdr_env rdrs unused_decl decl@(L loc (ImportDecl { ideclHiding = imps })) = (decl, nubAvails used_avails, unused_imps) where - used_avails = Map.lookup (srcSpanStart loc) import_usage `orElse` [] + used_avails = Map.lookup (srcSpanEnd loc) import_usage `orElse` [] + -- srcSpanEnd: see Note [The ImportMap] dont_report_as_unused = foldr add emptyNameSet used_avails add (Avail n) s = s `addOneToNameSet` n add (AvailTC n ns) s = s `addListToNameSet` (n:ns) @@ -1380,7 +1393,8 @@ extendImportMap rdr_env rdr imp_map = Map.insertWith add decl_loc [avail] imp_map where add _ avails = avail : avails -- add is really just a specialised (++) - decl_loc = srcSpanStart (is_dloc imp_decl_spec) + decl_loc = srcSpanEnd (is_dloc imp_decl_spec) + -- For srcSpanEnd see Note [The ImportMap] name = gre_name gre avail = case gre_par gre of ParentIs p -> AvailTC p [name] _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
