try to do better line number reporting

in the presence of yacc lookahead.
better but still not perfect

R=ken
OCL=33541
CL=33541

src/cmd/gc/dcl.c

@@ -146,6 +146,14 @@ testdclstack(void)
 	}
 }
 
+void
+redeclare(Sym *s, char *where)
+{
+	yyerror("%S redeclared %s\n"
+		"\tprevious declaration at %L",
+		s, where, s->lastlineno);
+}
+
 /*
  * declare individual names - var, typ, const
  */
@@ -153,7 +161,6 @@ void
 declare(Node *n, int ctxt)
 {
 	Sym *s;
-	char *what;
 	int gen;
 	static int typegen, vargen;
 
@@ -177,25 +184,11 @@ declare(Node *n, int ctxt)
 	if(ctxt == PAUTO)
 		n->xoffset = BADWIDTH;
 
-	if(s->block == block) {
-		what = "???";
-		switch(n->op) {
-		case ONAME:
-			what = "variable";
-			break;
-		case OLITERAL:
-			what = "constant";
-			break;
-		case OTYPE:
-			what = "type";
-			break;
-		}
+	if(s->block == block)
+		redeclare(s, "in this block");
 
-		yyerror("%s %S redeclared in this block %d", what, s, block);
-		print("\tprevious declaration at %L\n", s->lastlineno);
-	}
 	s->block = block;
-	s->lastlineno = lineno;
+	s->lastlineno = parserline();
 	s->def = n;
 	n->vargen = gen;
 	n->funcdepth = funcdepth;
@@ -731,10 +724,8 @@ typedcl2(Type *pt, Type *t)
 
 	if(pt->etype == TFORW)
 		goto ok;
-	if(!cvttype(pt, t)) {
-		yyerror("redeclaration of %T during imports", pt);
-		return;
-	}
+	if(!cvttype(pt, t))
+		yyerror("inconsistent definition for type %S during import\n\t%lT\n\t%lT", pt->sym, pt, t);
 	return;
 
 ok:
@@ -743,6 +734,7 @@ ok:
 	pt->method = nil;
 	pt->nod = n;
 	pt->sym = n->sym;
+	pt->sym->lastlineno = parserline();
 	declare(n, PEXTERN);
 
 	checkwidth(pt);

src/cmd/gc/export.c

@@ -258,15 +258,8 @@ dumpexport(void)
 Sym*
 importsym(Sym *s, int op)
 {
-	if(s->def != N && s->def->op != op) {
-		// Clumsy hack for
-		//	package parser
-		//	import "go/parser"	// defines type parser
-		if(s == lookup(package))
-			s->def = N;
-		else
-			yyerror("redeclaration of %lS during import", s, s->def->op, op);
-	}
+	if(s->def != N && s->def->op != op)
+		redeclare(s, "during import");
 
 	// mark the symbol so it is not reexported
 	if(s->def == N) {
@@ -349,7 +342,7 @@ importvar(Sym *s, Type *t, int ctxt)
 	if(s->def != N && s->def->op == ONAME) {
 		if(cvttype(t, s->def->type))
 			return;
-		warn("redeclare import var %S from %T to %T",
+		yyerror("inconsistent definition for var %S during import\n\t%T\n\t%T",
 			s, s->def->type, t);
 	}
 	n = newname(s);

src/cmd/gc/go.h

@@ -593,6 +593,7 @@ EXTERN	Dlist	dotlist[10];	// size is max depth of embeddeds
 
 EXTERN	Io	curio;
 EXTERN	Io	pushedio;
+EXTERN	int32	lexlineno;
 EXTERN	int32	lineno;
 EXTERN	int32	prevlineno;
 EXTERN	char*	pathname;
@@ -704,7 +705,6 @@ void	typeinit(void);
 void	lexinit(void);
 char*	lexname(int);
 int32	getr(void);
-int	getnsc(void);
 int	escchar(int, int*, vlong*);
 int	getc(void);
 void	ungetc(int);
@@ -782,6 +782,7 @@ Sym*	pkglookup(char*, char*);
 Sym*	restrictlookup(char*, char*);
 void	importdot(Sym*);
 void	yyerror(char*, ...);
+int	parserline(void);
 void	warn(char*, ...);
 void	fatal(char*, ...);
 void	linehist(char*, int32, int);
@@ -880,6 +881,8 @@ Type*	tounsigned(Type*);
 void	smagic(Magic*);
 void	umagic(Magic*);
 
+void	redeclare(Sym*, char*);
+
 /*
  *	dcl.c
  */

src/cmd/gc/go.y

@@ -43,7 +43,7 @@
 %token		LIGNORE LINC LLE LLSH LLT LNE LOROR LRSH
 %token		LSEMIBRACE
 
-%type	<lint>	lbrace
+%type	<lint>	lbrace import_here
 %type	<sym>	sym packname
 %type	<val>	oliteral
 
@@ -126,6 +126,7 @@ file:
 package:
 	%prec NotPackage
 	{
+		prevlineno = lineno;
 		yyerror("package statement must be first");
 		mkpackage("main");
 	}
@@ -158,7 +159,47 @@ import:
 |	LIMPORT '(' ')'
 
 import_stmt:
-	import_here import_package import_there import_done
+	import_here import_package import_there
+	{
+		Sym *import, *my;
+
+		import = pkgimportname;
+		my = pkgmyname;
+		pkgmyname = S;
+		pkgimportname = S;
+
+		if(import == S)
+			break;
+		if(my == S)
+			my = import;
+		if(my->name[0] == '.') {
+			importdot(import);
+			break;
+		}
+
+		// In order to allow multifile packages to use type names
+		// that are the same as the package name (i.e. go/parser
+		// is package parser and has a type called parser), we have
+		// to not bother trying to declare the package if it is our package.
+		// TODO(rsc): Is there a better way to tell if the package is ours?
+		if(my == import && strcmp(import->name, package) == 0)
+			break;
+
+		// TODO(rsc): this line is needed for a package
+		// which does bytes := in a function, which creates
+		// an ONONAME for bytes, but then a different file
+		// imports "bytes".  more generally we need to figure out
+		// what it means if one file imports "bytes" and another
+		// declares a top-level name.
+		if(my->def && my->def->op == ONONAME)
+			my->def = N;
+
+		my->def = nod(OPACK, N, N);
+		my->def->sym = import;
+		my->lastlineno = $1;
+		import->block = -1;	// above top level
+	}
+	
 
 import_stmt_list:
 	import_stmt
@@ -168,6 +209,7 @@ import_here:
 	LLITERAL
 	{
 		// import with original name
+		$$ = parserline();
 		pkgimportname = S;
 		pkgmyname = S;
 		importfile(&$1);
@@ -175,13 +217,17 @@ import_here:
 |	sym LLITERAL
 	{
 		// import with given name
+		$$ = parserline();
 		pkgimportname = S;
 		pkgmyname = $1;
+		if(pkgmyname->def)
+			redeclare(pkgmyname, "as imported package name");
 		importfile(&$2);
 	}
 |	'.' LLITERAL
 	{
 		// import into my name space
+		$$ = parserline();
 		pkgmyname = lookup(".");
 		importfile(&$2);
 	}
@@ -214,48 +260,6 @@ import_there:
 		checkimports();
 	}
 
-import_done:
-	{
-		Sym *import, *my;
-
-		import = pkgimportname;
-		my = pkgmyname;
-		pkgmyname = S;
-		pkgimportname = S;
-
-		if(import == S)
-			break;
-		if(my == S)
-			my = import;
-		if(my->name[0] == '.') {
-			importdot(import);
-			break;
-		}
-
-		// In order to allow multifile packages to use type names
-		// that are the same as the package name (i.e. go/parser
-		// is package parser and has a type called parser), we have
-		// to not bother trying to declare the package if it is our package.
-		// TODO(rsc): Is there a better way to tell if the package is ours?
-		if(my == import && strcmp(import->name, package) == 0)
-			break;
-
-		// TODO(rsc): this line is needed for a package
-		// which does bytes := in a function, which creates
-		// an ONONAME for bytes, but then a different file
-		// imports "bytes".  more generally we need to figure out
-		// what it means if one file imports "bytes" and another
-		// declares a top-level name.
-		if(my->def && my->def->op == ONONAME)
-			my->def = N;
-
-		if(my->def)
-			yyerror("redeclaration of %S by import\n\t%N", my, my->def);
-		my->def = nod(OPACK, N, N);
-		my->def->sym = import;
-		import->block = -1;	// above top level
-	}
-
 /*
  * declarations
  */

src/cmd/gc/lex.c

@@ -73,7 +73,7 @@ main(int argc, char *argv[])
 	blockgen = 1;
 	dclcontext = PEXTERN;
 	nerrors = 0;
-	lineno = 1;
+	lexlineno = 1;
 
 	for(i=0; i<argc; i++) {
 		if(i == 0)
@@ -369,7 +369,7 @@ unimportfile(void)
 		Bterm(curio.bin);
 		curio.bin = nil;
 	} else
-		lineno--;	// re correct sys.6 line number
+		lexlineno--;	// re correct sys.6 line number
 	curio = pushedio;
 	pushedio.bin = nil;
 	inimportsys = 0;
@@ -382,7 +382,7 @@ cannedimports(char *file, char *cp)
 	if(!debug['A'])
 		anysym->def = typenod(types[TANY]);
 
-	lineno++;		// if sys.6 is included on line 1,
+	lexlineno++;		// if sys.6 is included on line 1,
 	linehist(file, 0, 0);	// the debugger gets confused
 
 	pushedio = curio;
@@ -420,7 +420,6 @@ _yylex(void)
 	vlong v;
 	char *cp;
 	Rune rune;
-	int32 lno;
 	Sym *s;
 
 	prevlineno = lineno;
@@ -430,6 +429,8 @@ l0:
 	if(isspace(c))
 		goto l0;
 
+	lineno = lexlineno;	/* start of token */
+
 	if(c >= Runeself) {
 		/* all multibyte runes are alpha */
 		cp = lexbuf;
@@ -504,11 +505,10 @@ l0:
 		clen = sizeof(int32);
 
 	casebq:
-		lno = lineno;
 		for(;;) {
 			c = getc();
 			if(c == EOF) {
-				yyerror("eof in string starting at line %L", lno);
+				yyerror("eof in string");
 				break;
 			}
 			if(c == '`')
@@ -791,7 +791,7 @@ l0:
 		goto lx;
 	case '{':
 		if(loophack == 1) {
-			DBG("%L lex: LBODY\n", lineno);
+			DBG("%L lex: LBODY\n", lexlineno);
 			loophack = 0;
 			return LBODY;
 		}
@@ -804,9 +804,9 @@ l0:
 
 lx:
 	if(c > 0xff)
-		DBG("%L lex: TOKEN %s\n", lineno, lexname(c));
+		DBG("%L lex: TOKEN %s\n", lexlineno, lexname(c));
 	else
-		DBG("%L lex: TOKEN '%c'\n", lineno, c);
+		DBG("%L lex: TOKEN '%c'\n", lexlineno, c);
 	if(isfrog(c)) {
 		yyerror("illegal character 0x%ux", c);
 		goto l0;
@@ -1044,7 +1044,7 @@ getc(void)
 		curio.peekc = curio.peekc1;
 		curio.peekc1 = 0;
 		if(c == '\n')
-			lineno++;
+			lexlineno++;
 		return c;
 	}
 
@@ -1063,7 +1063,7 @@ getc(void)
 		return EOF;
 
 	case '\n':
-		lineno++;
+		lexlineno++;
 		break;
 	}
 	return c;
@@ -1075,7 +1075,7 @@ ungetc(int c)
 	curio.peekc1 = curio.peekc;
 	curio.peekc = c;
 	if(c == '\n')
-		lineno--;
+		lexlineno--;
 }
 
 int32
@@ -1106,24 +1106,6 @@ loop:
 	return rune;
 }
 
-int
-getnsc(void)
-{
-	int c;
-
-	c = getc();
-	for(;;) {
-		if(!isspace(c))
-			return c;
-		if(c == '\n') {
-			lineno++;
-			return c;
-		}
-		c = getc();
-	}
-	return 0;
-}
-
 
 int
 escchar(int e, int *escflg, vlong *val)

src/cmd/gc/subr.c

@@ -14,23 +14,35 @@ errorexit(void)
 	exit(1);
 }
 
+extern int yychar;
+int
+parserline(void)
+{
+	if(yychar != 0 && yychar != -2)	// parser has one symbol lookahead
+		return prevlineno;
+	return lineno;
+}
+
 void
 yyerror(char *fmt, ...)
 {
 	va_list arg;
 
-	print("%L: ", lineno);
-	va_start(arg, fmt);
-	vfprint(1, fmt, arg);
-	va_end(arg);
 	if(strcmp(fmt, "syntax error") == 0) {
+		print("%L: syntax error near %s\n", lexlineno, lexbuf);
 		nsyntaxerrors++;
-		print(" near %s", lexbuf);
+		goto out;
 	}
+
+	print("%L: ", parserline());
+	va_start(arg, fmt);
+	vfprint(1, fmt, arg);
+	va_end(arg);
 	print("\n");
+
+out:
 	if(debug['h'])
 		*(int*)0 = 0;
-
 	nerrors++;
 	if(nerrors >= 10 && !debug['e'])
 		fatal("too many errors");
@@ -92,7 +104,7 @@ linehist(char *file, int32 off, int relative)
 
 	h = mal(sizeof(Hist));
 	h->name = file;
-	h->line = lineno;
+	h->line = lexlineno;
 	h->offset = off;
 	h->link = H;
 	if(ehist == H) {
@@ -245,7 +257,7 @@ importdot(Sym *opkg)
 				continue;
 			s1 = lookup(s->name);
 			if(s1->def != N) {
-				yyerror("redeclaration of %S during import", s1);
+				redeclare(s1, "during import");
 				continue;
 			}
 			s1->def = s->def;
@@ -310,7 +322,6 @@ remal(void *p, int32 on, int32 n)
 	return p;
 }
 
-extern int yychar;
 Node*
 nod(int op, Node *nleft, Node *nright)
 {
@@ -320,10 +331,7 @@ nod(int op, Node *nleft, Node *nright)
 	n->op = op;
 	n->left = nleft;
 	n->right = nright;
-	if(yychar <= 0)	// no lookahead
-		n->lineno = lineno;
-	else
-		n->lineno = prevlineno;
+	n->lineno = parserline();
 	n->xoffset = BADWIDTH;
 	return n;
 }

test/import1.go

@@ -8,7 +8,10 @@
 
 package main
 
+import "bufio"	// GCCGO_ERROR "previous"
+import bufio "os"	// ERROR "redeclared|redefinition|incompatible"
+
 import (
-	"bufio";	// GCCGO_ERROR "previous"
-	bufio "os";	// ERROR "redeclaration|redefinition|incompatible"
-)
+	"fmt";	// GCCGO_ERROR "previous"
+	fmt "math";	// ERROR "redeclared|redefinition|incompatible"
+)
\ No newline at end of file