From: simonpj@microsoft.com <unknown>
Date: Thu, 11 Jan 2007 13:10:29 +0000 (+0000)
Subject: Avoid duplicate defns of 'main' in module Main
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=b991caa149dd65f04ad4723b51571ded76bb2c76

Avoid duplicate defns of 'main' in module Main
---

diff --git a/compiler/iface/MkIface.lhs b/compiler/iface/MkIface.lhs
index 0fc3972..a9b9f03 100644
--- a/compiler/iface/MkIface.lhs
+++ b/compiler/iface/MkIface.lhs
@@ -257,11 +257,13 @@ mkIface hsc_env maybe_old_iface
 	; let	{ entities = typeEnvElts type_env ;
                   decls  = [ tyThingToIfaceDecl entity
 			   | entity <- entities,
-                             not (isImplicitTyThing entity
-                                  || isWiredInName (getName entity)) ]
-                        -- Don't put implicit Ids and class tycons in
-                        -- the interface file, Nor wired-in things; the
-                        -- compiler knows about them anyhow
+			     let name = getName entity,
+                             not (isImplicitTyThing entity),
+	                        -- No implicit Ids and class tycons in the interface file
+			     not (isWiredInName name),
+	                        -- Nor wired-in things; the compiler knows about them anyhow
+			     nameIsLocalOrFrom this_mod name  ]
+				-- Sigh: see Note [Root-main Id] in TcRnDriver
 
 		; fixities    = [(occ,fix) | FixItem occ fix _ <- nameEnvElts fix_env]
 		; deprecs     = mkIfaceDeprec src_deprecs
diff --git a/compiler/typecheck/TcRnDriver.lhs b/compiler/typecheck/TcRnDriver.lhs
index eabd3bc..6c4a35f 100644
--- a/compiler/typecheck/TcRnDriver.lhs
+++ b/compiler/typecheck/TcRnDriver.lhs
@@ -726,18 +726,7 @@ check_main ghc_mode tcg_env main_mod main_fn
 	; (main_expr, ty) <- setSrcSpan (srcLocSpan (getSrcLoc main_name)) $
 			     tcInferRho rhs
 
-	-- The function that the RTS invokes is always :Main.main,
-	-- which we call root_main_id.  
-	-- (Because GHC allows the user to have a module not called 
-	-- Main as the main module, we can't rely on the main function
-	-- being called "Main.main".  That's why root_main_id has a fixed
-	-- module ":Main".)
-	-- We also make root_main_id an implicit Id, by making main_name
-	-- its parent (hence (Just main_name)).  That has the effect
-	-- of preventing its type and unfolding from getting out into
-	-- the interface file. Otherwise we can end up with two defns
-	-- for 'main' in the interface file!
-
+		-- See Note [Root-main Id]
 	; let { root_main_name =  mkExternalName rootMainKey rOOT_MAIN 
 				   (mkVarOccFS FSLIT("main")) 
 				   (getSrcLoc main_name)
@@ -766,6 +755,19 @@ check_main ghc_mode tcg_env main_mod main_fn
 		<+> ptext SLIT("is not defined in module") <+> quotes (ppr main_mod)
 \end{code}
 
+Note [Root-main Id]
+~~~~~~~~~~~~~~~~~~~
+The function that the RTS invokes is always :Main.main, which we call
+root_main_id.  (Because GHC allows the user to have a module not
+called Main as the main module, we can't rely on the main function
+being called "Main.main".  That's why root_main_id has a fixed module
+":Main".)  
+
+This is unusual: it's a LocalId whose Name has a Module from another
+module.  Tiresomely, we must filter it out again in MkIface, les we
+get two defns for 'main' in the interface file!
+
+
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