gc: fix line number at EOF

Fixes #1474.

R=ken2
CC=golang-dev
https://golang.org/cl/4432061

src/cmd/gc/go.h

@@ -582,6 +582,7 @@ struct	Io
 	Biobuf*	bin;
 	int32	ilineno;
 	int	nlsemi;
+	int	eofnl;
 	int	peekc;
 	int	peekc1;	// second peekc for ...
 	char*	cp;	// used for content when bin==nil

src/cmd/gc/lex.c

@@ -1310,7 +1310,7 @@ getc(void)
 			lexlineno++;
 		return c;
 	}
-
+	
 	if(curio.bin == nil) {
 		c = *curio.cp & 0xff;
 		if(c != 0)
@@ -1325,8 +1325,11 @@ getc(void)
 			break;
 		}
 	case EOF:
-		return EOF;
-
+		// insert \n at EOF
+		if(curio.eofnl)
+			return EOF;
+		curio.eofnl = 1;
+		c = '\n';
 	case '\n':
 		if(pushedio.bin == nil)
 			lexlineno++;

test/fixedbugs/bug332.go

+// errchk $G $D/$F.go
+
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// type T int
+
+func main() {}
+
+// issue 1474
+
+// important: no newline on end of next line.
+// 6g used to print <epoch> instead of bug332.go:111 
+func (t *T) F() {} // ERROR "bug332"
\ No newline at end of file