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Commit e7d9f816 authored by Matthew Dempsky's avatar Matthew Dempsky
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cmd/internal/gc, cmd/yacc: implement "expecting" syntax error messages 

Bison includes suggestions about what tokens are expected in the
current state when there's only four or fewer of them.  For example:

  syntax error: unexpected literal 2.01, expecting semicolon or newline or }

This CL adds the same functionality to cmd/yacc, which fully restores
the previous error message behavior from Go 1.4.

Updates #9968.

Change-Id: I2c1a1677c6d829a829d812c05e8813aa8829d09c
Reviewed-on: https://go-review.googlesource.com/8494
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: 's avatarRuss Cox <rsc@golang.org>
parent ee54d571
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Inline Side-by-side
Showing with 125 additions and 154 deletions
src/cmd/internal/gc/subr.go
View file @ e7d9f816
......@@ -162,18 +162,13 @@ func Yyerror(format string, args ...interface{}) {
return
}
// TODO(mdempsky): Extend cmd/yacc's verbose error
// messages to suggest expected tokens like Bison:
// "syntax error: unexpected literal 2.01, expecting semicolon or newline or }"
if false {
// The grammar has { and LBRACE but both show up as {.
// Rewrite syntax error referring to "{ or {" to say just "{".
// The grammar has ? and @ but only for reading imports.
// Silence them in ordinary errors.
msg = strings.Replace(msg, "{ or {", "{", -1)
msg = strings.Replace(msg, " or ?", "", -1)
msg = strings.Replace(msg, " or @", "", -1)
}
// The grammar has { and LBRACE but both show up as {.
// Rewrite syntax error referring to "{ or {" to say just "{".
// The grammar has ? and @ but only for reading imports.
// Silence them in ordinary errors.
msg = strings.Replace(msg, "{ or {", "{", -1)
msg = strings.Replace(msg, " or ?", "", -1)
msg = strings.Replace(msg, " or @", "", -1)
msg = strings.Replace(msg, "LLITERAL", litbuf, -1)
......
src/cmd/internal/gc/y.go
View file @ e7d9f816
......@@ -912,6 +912,63 @@ func yyStatname(s int) string {
return __yyfmt__.Sprintf("state-%v", s)
}
func yyErrorMessage(state, lookAhead int) string {
const TOKSTART = 4
if !yyErrorVerbose {
return "syntax error"
}
res := "syntax error: unexpected " + yyTokname(lookAhead)
// To match Bison, suggest at most four expected tokens.
expected := make([]int, 0, 4)
// Look for shiftable tokens.
base := yyPact[state]
for tok := TOKSTART; tok-1 < len(yyToknames); tok++ {
if n := base + tok; n >= 0 && n < yyLast && yyChk[yyAct[n]] == tok {
if len(expected) == cap(expected) {
return res
}
expected = append(expected, tok)
}
}
if yyDef[state] == -2 {
i := 0
for yyExca[i] != -1 || yyExca[i+1] != state {
i += 2
}
// Look for tokens that we accept or reduce.
for i += 2; yyExca[i] >= 0; i += 2 {
tok := yyExca[i]
if tok < TOKSTART || yyExca[i+1] == 0 {
continue
}
if len(expected) == cap(expected) {
return res
}
expected = append(expected, tok)
}
// If the default action is to accept or reduce, give up.
if yyExca[i+1] != 0 {
return res
}
}
for i, tok := range expected {
if i == 0 {
res += ", expecting "
} else {
res += " or "
}
res += yyTokname(tok)
}
return res
}
func yylex1(lex yyLexer, lval *yySymType) (char, token int) {
token = 0
char = lex.Lex(lval)
......@@ -1050,11 +1107,7 @@ yydefault:
/* error ... attempt to resume parsing */
switch Errflag {
case 0: /* brand new error */
yyErrMsg := "syntax error"
if yyErrorVerbose {
yyErrMsg += ": unexpected " + yyTokname(yytoken)
}
yylex.Error(yyErrMsg)
yylex.Error(yyErrorMessage(yystate, yytoken))
Nerrs++
if yyDebug >= 1 {
__yyfmt__.Printf("%s", yyStatname(yystate))
......@@ -1292,8 +1345,6 @@ yydefault:
Yyerror("empty top-level declaration")
yyVAL.list = nil
}
case 24:
yyVAL.list = yyS[yypt-0].list
case 25:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:292
......@@ -1416,8 +1467,6 @@ yydefault:
{
yyVAL.list = constiter(yyDollar[1].list, nil, yyDollar[3].list)
}
case 44:
yyVAL.list = yyS[yypt-0].list
case 45:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:387
......@@ -1717,8 +1766,6 @@ yydefault:
yyVAL.node = Nod(OFOR, nil, nil)
yyVAL.node.Ntest = yyDollar[1].node
}
case 72:
yyVAL.node = yyS[yypt-0].node
case 73:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:654
......@@ -1880,8 +1927,6 @@ yydefault:
yyVAL.node.List = yyDollar[4].list
typesw = typesw.Left
}
case 93:
yyVAL.node = yyS[yypt-0].node
case 94:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:796
......@@ -2002,8 +2047,6 @@ yydefault:
{
yyVAL.node = Nod(OSEND, yyDollar[1].node, yyDollar[3].node)
}
case 114:
yyVAL.node = yyS[yypt-0].node
case 115:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:880
......@@ -2087,8 +2130,6 @@ yydefault:
{
yyVAL.node = nodlit(yyDollar[1].val)
}
case 127:
yyVAL.node = yyS[yypt-0].node
case 128:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:948
......@@ -2138,8 +2179,6 @@ yydefault:
}
yyVAL.node = Nod(OSLICE3, yyDollar[1].node, Nod(OKEY, yyDollar[3].node, Nod(OKEY, yyDollar[5].node, yyDollar[7].node)))
}
case 134:
yyVAL.node = yyS[yypt-0].node
case 135:
yyDollar = yyS[yypt-5 : yypt+1]
//line go.y:986
......@@ -2174,8 +2213,6 @@ yydefault:
yyVAL.node.Right = yyDollar[2].node
yyVAL.node.List = yyDollar[6].list
}
case 139:
yyVAL.node = yyS[yypt-0].node
case 140:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1014
......@@ -2212,8 +2249,6 @@ yydefault:
yyVAL.node = yyDollar[2].node
yyVAL.node.List = yyDollar[3].list
}
case 144:
yyVAL.node = yyS[yypt-0].node
case 145:
yyDollar = yyS[yypt-4 : yypt+1]
//line go.y:1049
......@@ -2221,8 +2256,6 @@ yydefault:
yyVAL.node = yyDollar[2].node
yyVAL.node.List = yyDollar[3].list
}
case 146:
yyVAL.node = yyS[yypt-0].node
case 147:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1057
......@@ -2237,12 +2270,6 @@ yydefault:
yyVAL.node = Nod(OPAREN, yyVAL.node, nil)
}
}
case 148:
yyVAL.node = yyS[yypt-0].node
case 149:
yyVAL.node = yyS[yypt-0].node
case 150:
yyVAL.node = yyS[yypt-0].node
case 151:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1078
......@@ -2277,8 +2304,6 @@ yydefault:
{
yyVAL.node = nil
}
case 156:
yyVAL.node = yyS[yypt-0].node
case 157:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1115
......@@ -2289,8 +2314,6 @@ yydefault:
yyVAL.sym = Pkglookup(yyDollar[1].sym.Name, builtinpkg)
}
}
case 158:
yyVAL.sym = yyS[yypt-0].sym
case 159:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1124
......@@ -2338,8 +2361,6 @@ yydefault:
yyVAL.node.Pack.Used = true
}
}
case 163:
yyVAL.node = yyS[yypt-0].node
case 164:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1181
......@@ -2353,66 +2374,24 @@ yydefault:
{
yyVAL.node = Nod(ODDD, yyDollar[2].node, nil)
}
case 166:
yyVAL.node = yyS[yypt-0].node
case 167:
yyVAL.node = yyS[yypt-0].node
case 168:
yyVAL.node = yyS[yypt-0].node
case 169:
yyVAL.node = yyS[yypt-0].node
case 170:
yyVAL.node = yyS[yypt-0].node
case 171:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1197
{
yyVAL.node = yyDollar[2].node
}
case 172:
yyVAL.node = yyS[yypt-0].node
case 173:
yyVAL.node = yyS[yypt-0].node
case 174:
yyVAL.node = yyS[yypt-0].node
case 175:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:1206
{
yyVAL.node = Nod(OIND, yyDollar[2].node, nil)
}
case 176:
yyVAL.node = yyS[yypt-0].node
case 177:
yyVAL.node = yyS[yypt-0].node
case 178:
yyVAL.node = yyS[yypt-0].node
case 179:
yyVAL.node = yyS[yypt-0].node
case 180:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1216
{
yyVAL.node = yyDollar[2].node
}
case 181:
yyVAL.node = yyS[yypt-0].node
case 182:
yyVAL.node = yyS[yypt-0].node
case 183:
yyVAL.node = yyS[yypt-0].node
case 184:
yyVAL.node = yyS[yypt-0].node
case 185:
yyVAL.node = yyS[yypt-0].node
case 186:
yyVAL.node = yyS[yypt-0].node
case 187:
yyVAL.node = yyS[yypt-0].node
case 188:
yyVAL.node = yyS[yypt-0].node
case 189:
yyVAL.node = yyS[yypt-0].node
case 190:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1237
......@@ -2459,10 +2438,6 @@ yydefault:
{
yyVAL.node = Nod(OTMAP, yyDollar[3].node, yyDollar[5].node)
}
case 196:
yyVAL.node = yyS[yypt-0].node
case 197:
yyVAL.node = yyS[yypt-0].node
case 198:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:1277
......@@ -2721,16 +2696,12 @@ yydefault:
nosplit = false
nowritebarrier = false
}
case 220:
yyVAL.list = yyS[yypt-0].list
case 221:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1526
{
yyVAL.list = concat(yyDollar[1].list, yyDollar[3].list)
}
case 222:
yyVAL.list = yyS[yypt-0].list
case 223:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1533
......@@ -2749,8 +2720,6 @@ yydefault:
{
yyVAL.list = list(yyDollar[1].list, yyDollar[3].node)
}
case 226:
yyVAL.list = yyS[yypt-0].list
case 227:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:1550
......@@ -2899,8 +2868,6 @@ yydefault:
yyVAL.node.List = yyDollar[2].list
yyVAL.node.Rlist = yyDollar[4].list
}
case 243:
yyVAL.node = yyS[yypt-0].node
case 244:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:1684
......@@ -2917,8 +2884,6 @@ yydefault:
yyVAL.node.Sym = yyDollar[1].sym
yyVAL.node = Nod(OKEY, yyVAL.node, yyDollar[2].node)
}
case 246:
yyVAL.node = yyS[yypt-0].node
case 247:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1699
......@@ -2949,32 +2914,18 @@ yydefault:
{
yyVAL.node = nil
}
case 252:
yyVAL.node = yyS[yypt-0].node
case 253:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1725
{
yyVAL.node = liststmt(yyDollar[1].list)
}
case 254:
yyVAL.node = yyS[yypt-0].node
case 255:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:1730
{
yyVAL.node = nil
}
case 256:
yyVAL.node = yyS[yypt-0].node
case 257:
yyVAL.node = yyS[yypt-0].node
case 258:
yyVAL.node = yyS[yypt-0].node
case 259:
yyVAL.node = yyS[yypt-0].node
case 260:
yyVAL.node = yyS[yypt-0].node
case 261:
yyDollar = yyS[yypt-2 : yypt+1]
//line go.y:1741
......@@ -3164,56 +3115,42 @@ yydefault:
{
yyVAL.node = nil
}
case 291:
yyVAL.node = yyS[yypt-0].node
case 292:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1906
{
yyVAL.list = nil
}
case 293:
yyVAL.list = yyS[yypt-0].list
case 294:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1912
{
yyVAL.node = nil
}
case 295:
yyVAL.node = yyS[yypt-0].node
case 296:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1918
{
yyVAL.list = nil
}
case 297:
yyVAL.list = yyS[yypt-0].list
case 298:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1924
{
yyVAL.list = nil
}
case 299:
yyVAL.list = yyS[yypt-0].list
case 300:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1930
{
yyVAL.list = nil
}
case 301:
yyVAL.list = yyS[yypt-0].list
case 302:
yyDollar = yyS[yypt-0 : yypt+1]
//line go.y:1936
{
yyVAL.val.Ctype = CTxxx
}
case 303:
yyVAL.val = yyS[yypt-0].val
case 304:
yyDollar = yyS[yypt-4 : yypt+1]
//line go.y:1946
......@@ -3279,16 +3216,6 @@ yydefault:
yyVAL.typ = pkgtype(yyDollar[1].sym)
importsym(yyDollar[1].sym, OTYPE)
}
case 312:
yyVAL.typ = yyS[yypt-0].typ
case 313:
yyVAL.typ = yyS[yypt-0].typ
case 314:
yyVAL.typ = yyS[yypt-0].typ
case 315:
yyVAL.typ = yyS[yypt-0].typ
case 316:
yyVAL.typ = yyS[yypt-0].typ
case 317:
yyDollar = yyS[yypt-1 : yypt+1]
//line go.y:2014
......@@ -3451,8 +3378,6 @@ yydefault:
{
yyVAL.list = nil
}
case 336:
yyVAL.list = yyS[yypt-0].list
case 337:
yyDollar = yyS[yypt-3 : yypt+1]
//line go.y:2152
......@@ -3500,8 +3425,6 @@ yydefault:
Yyerror("bad constant %v", Sconv(yyVAL.node.Sym, 0))
}
}
case 342:
yyVAL.node = yyS[yypt-0].node
case 343:
yyDollar = yyS[yypt-5 : yypt+1]
//line go.y:2198
......
src/cmd/yacc/yacc.go
View file @ e7d9f816
......@@ -3212,7 +3212,7 @@ type $$Parser interface {
type $$ParserImpl struct {
lookahead func() int
state func() int
state func() int
}
func (p *$$ParserImpl) Lookahead() int {
......@@ -3222,7 +3222,7 @@ func (p *$$ParserImpl) Lookahead() int {
func $$NewParser() $$Parser {
p := &$$ParserImpl{
lookahead: func() int { return -1 },
state: func() int { return -1 },
state: func() int { return -1 },
}
return p
}
......@@ -3247,6 +3247,63 @@ func $$Statname(s int) string {
return __yyfmt__.Sprintf("state-%v", s)
}
func $$ErrorMessage(state, lookAhead int) string {
const TOKSTART = 4
if !$$ErrorVerbose {
return "syntax error"
}
res := "syntax error: unexpected " + $$Tokname(lookAhead)
// To match Bison, suggest at most four expected tokens.
expected := make([]int, 0, 4)
// Look for shiftable tokens.
base := $$Pact[state]
for tok := TOKSTART; tok-1 < len($$Toknames); tok++ {
if n := base + tok; n >= 0 && n < $$Last && $$Chk[$$Act[n]] == tok {
if len(expected) == cap(expected) {
return res
}
expected = append(expected, tok)
}
}
if $$Def[state] == -2 {
i := 0
for $$Exca[i] != -1 || $$Exca[i+1] != state {
i += 2
}
// Look for tokens that we accept or reduce.
for i += 2; $$Exca[i] >= 0; i += 2 {
tok := $$Exca[i]
if tok < TOKSTART || $$Exca[i+1] == 0 {
continue
}
if len(expected) == cap(expected) {
return res
}
expected = append(expected, tok)
}
// If the default action is to accept or reduce, give up.
if $$Exca[i+1] != 0 {
return res
}
}
for i, tok := range expected {
if i == 0 {
res += ", expecting "
} else {
res += " or "
}
res += $$Tokname(tok)
}
return res
}
func $$lex1(lex $$Lexer, lval *$$SymType) (char, token int) {
token = 0
char = lex.Lex(lval)
......@@ -3385,11 +3442,7 @@ $$default:
/* error ... attempt to resume parsing */
switch Errflag {
case 0: /* brand new error */
$$ErrMsg := "syntax error"
if $$ErrorVerbose {
$$ErrMsg += ": unexpected " + $$Tokname($$token)
}
$$lex.Error($$ErrMsg)
$$lex.Error($$ErrorMessage($$state, $$token))
Nerrs++
if $$Debug >= 1 {
__yyfmt__.Printf("%s", $$Statname($$state))
......
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