From 5a5799f613d802a52bc06207086af5425664038b Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Mon, 18 Jan 2010 16:26:40 -0800
Subject: [PATCH] gc: more precise handling of import .

Fixes #455.

R=ken2
CC=golang-dev
https://golang.org/cl/186212
---
 src/cmd/gc/dcl.c  | 11 ++++++++---
 src/cmd/gc/lex.c  |  6 +++---
 src/cmd/gc/subr.c |  1 +
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/cmd/gc/dcl.c b/src/cmd/gc/dcl.c
index c9fcb1204a..adf8da9bc0 100644
--- a/src/cmd/gc/dcl.c
+++ b/src/cmd/gc/dcl.c
@@ -149,9 +149,14 @@ testdclstack(void)
 void
 redeclare(Sym *s, char *where)
 {
-	yyerror("%S redeclared %s\n"
-		"\tprevious declaration at %L",
-		s, where, s->lastlineno);
+	if(s->lastlineno == 0)
+		yyerror("%S redeclared %s\n"
+			"\tprevious declaration during import",
+			s, where);
+	else
+		yyerror("%S redeclared %s\n"
+			"\tprevious declaration at %L",
+			s, where, s->lastlineno);
 }
 
 /*
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index d74cb096ad..c433c1ec9e 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -1470,9 +1470,9 @@ mkpackage(char* pkg)
 				if(s->def->op == OPACK) {
 					// throw away top-level package name leftover
 					// from previous file.
-					// TODO(rsc): remember that there was a package
-					// name, so that the name cannot be redeclared
-					// as a non-package in other files.
+					// leave s->block set to cause redeclaration
+					// errors if a conflicting top-level name is
+					// introduced by a different file.
 					if(!s->def->used && !nsyntaxerrors)
 						yyerrorl(s->def->lineno, "imported and not used: %s", s->def->sym->name);
 					s->def = N;
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index f38992b740..f7abc0357e 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -353,6 +353,7 @@ importdot(Sym *opkg, Node *pack)
 				continue;
 			}
 			s1->def = s->def;
+			s1->block = s->block;
 			s1->def->pack = pack;
 			n++;
 		}
-- 
2.48.1