config: return to the go1.5 generated lang/y.go

It has improvements to error messaging that we want.

We'll use this occasion begin developing / building with Go 1.5 from
here on out. Build times will be slower, but we have core development
plans that will help mitigate that.

/cc @hashicorp/terraform-committers

config/lang/y.go

@@ -30,7 +30,10 @@ const INTEGER = 57355
 const FLOAT = 57356
 const STRING = 57357
 
-var parserToknames = []string{
+var parserToknames = [...]string{
+	"$end",
+	"error",
+	"$unk",
 	"PROGRAM_BRACKET_LEFT",
 	"PROGRAM_BRACKET_RIGHT",
 	"PROGRAM_STRING_START",
@@ -44,7 +47,7 @@ var parserToknames = []string{
 	"FLOAT",
 	"STRING",
 }
-var parserStatenames = []string{}
+var parserStatenames = [...]string{}
 
 const parserEofCode = 1
 const parserErrCode = 2
@@ -53,7 +56,7 @@ const parserMaxDepth = 200
 //line lang.y:165
 
 //line yacctab:1
-var parserExca = []int{
+var parserExca = [...]int{
 	-1, 1,
 	1, -1,
 	-2, 0,
@@ -67,75 +70,103 @@ var parserStates []string
 
 const parserLast = 30
 
-var parserAct = []int{
+var parserAct = [...]int{
 
 	9, 20, 16, 16, 7, 7, 3, 18, 10, 8,
 	1, 17, 14, 12, 13, 6, 6, 19, 8, 22,
 	15, 23, 24, 11, 2, 25, 16, 21, 4, 5,
 }
-var parserPact = []int{
+var parserPact = [...]int{
 
 	1, -1000, 1, -1000, -1000, -1000, -1000, 0, -1000, 15,
 	0, 1, -1000, -1000, -1, -1000, 0, -8, 0, -1000,
 	-1000, 12, -9, -1000, 0, -9,
 }
-var parserPgo = []int{
+var parserPgo = [...]int{
 
 	0, 0, 29, 28, 23, 6, 27, 10,
 }
-var parserR1 = []int{
+var parserR1 = [...]int{
 
 	0, 7, 7, 4, 4, 5, 5, 2, 1, 1,
 	1, 1, 1, 1, 1, 6, 6, 6, 3,
 }
-var parserR2 = []int{
+var parserR2 = [...]int{
 
 	0, 0, 1, 1, 2, 1, 1, 3, 3, 1,
 	1, 1, 3, 1, 4, 0, 3, 1, 1,
 }
-var parserChk = []int{
+var parserChk = [...]int{
 
 	-1000, -7, -4, -5, -3, -2, 15, 4, -5, -1,
 	8, -4, 13, 14, 12, 5, 11, -1, 8, -1,
 	9, -6, -1, 9, 10, -1,
 }
-var parserDef = []int{
+var parserDef = [...]int{
 
 	1, -2, 2, 3, 5, 6, 18, 0, 4, 0,
 	0, 9, 10, 11, 13, 7, 0, 0, 15, 12,
 	8, 0, 17, 14, 0, 16,
 }
-var parserTok1 = []int{
+var parserTok1 = [...]int{
 
 	1,
 }
-var parserTok2 = []int{
+var parserTok2 = [...]int{
 
 	2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
 	12, 13, 14, 15,
 }
-var parserTok3 = []int{
+var parserTok3 = [...]int{
 	0,
 }
 
+var parserErrorMessages = [...]struct {
+	state int
+	token int
+	msg   string
+}{}
+
 //line yaccpar:1
 
 /*	parser for yacc output	*/
 
-var parserDebug = 0
+var (
+	parserDebug        = 0
+	parserErrorVerbose = false
+)
 
 type parserLexer interface {
 	Lex(lval *parserSymType) int
 	Error(s string)
 }
 
+type parserParser interface {
+	Parse(parserLexer) int
+	Lookahead() int
+}
+
+type parserParserImpl struct {
+	lookahead func() int
+}
+
+func (p *parserParserImpl) Lookahead() int {
+	return p.lookahead()
+}
+
+func parserNewParser() parserParser {
+	p := &parserParserImpl{
+		lookahead: func() int { return -1 },
+	}
+	return p
+}
+
 const parserFlag = -1000
 
 func parserTokname(c int) string {
-	// 4 is TOKSTART above
+	if c >= 1 && c-1 < len(parserToknames) {
-	if c >= 4 && c-4 < len(parserToknames) {
+		if parserToknames[c-1] != "" {
-		if parserToknames[c-4] != "" {
+			return parserToknames[c-1]
-			return parserToknames[c-4]
 		}
 	}
 	return __yyfmt__.Sprintf("tok-%v", c)
@@ -150,51 +181,129 @@ func parserStatname(s int) string {
 	return __yyfmt__.Sprintf("state-%v", s)
 }
 
-func parserlex1(lex parserLexer, lval *parserSymType) int {
+func parserErrorMessage(state, lookAhead int) string {
-	c := 0
+	const TOKSTART = 4
-	char := lex.Lex(lval)
+
+	if !parserErrorVerbose {
+		return "syntax error"
+	}
+
+	for _, e := range parserErrorMessages {
+		if e.state == state && e.token == lookAhead {
+			return "syntax error: " + e.msg
+		}
+	}
+
+	res := "syntax error: unexpected " + parserTokname(lookAhead)
+
+	// To match Bison, suggest at most four expected tokens.
+	expected := make([]int, 0, 4)
+
+	// Look for shiftable tokens.
+	base := parserPact[state]
+	for tok := TOKSTART; tok-1 < len(parserToknames); tok++ {
+		if n := base + tok; n >= 0 && n < parserLast && parserChk[parserAct[n]] == tok {
+			if len(expected) == cap(expected) {
+				return res
+			}
+			expected = append(expected, tok)
+		}
+	}
+
+	if parserDef[state] == -2 {
+		i := 0
+		for parserExca[i] != -1 || parserExca[i+1] != state {
+			i += 2
+		}
+
+		// Look for tokens that we accept or reduce.
+		for i += 2; parserExca[i] >= 0; i += 2 {
+			tok := parserExca[i]
+			if tok < TOKSTART || parserExca[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 parserExca[i+1] != 0 {
+			return res
+		}
+	}
+
+	for i, tok := range expected {
+		if i == 0 {
+			res += ", expecting "
+		} else {
+			res += " or "
+		}
+		res += parserTokname(tok)
+	}
+	return res
+}
+
+func parserlex1(lex parserLexer, lval *parserSymType) (char, token int) {
+	token = 0
+	char = lex.Lex(lval)
 	if char <= 0 {
-		c = parserTok1[0]
+		token = parserTok1[0]
 		goto out
 	}
 	if char < len(parserTok1) {
-		c = parserTok1[char]
+		token = parserTok1[char]
 		goto out
 	}
 	if char >= parserPrivate {
 		if char < parserPrivate+len(parserTok2) {
-			c = parserTok2[char-parserPrivate]
+			token = parserTok2[char-parserPrivate]
 			goto out
 		}
 	}
 	for i := 0; i < len(parserTok3); i += 2 {
-		c = parserTok3[i+0]
+		token = parserTok3[i+0]
-		if c == char {
+		if token == char {
-			c = parserTok3[i+1]
+			token = parserTok3[i+1]
 			goto out
 		}
 	}
 
 out:
-	if c == 0 {
+	if token == 0 {
-		c = parserTok2[1] /* unknown char */
+		token = parserTok2[1] /* unknown char */
 	}
 	if parserDebug >= 3 {
-		__yyfmt__.Printf("lex %s(%d)\n", parserTokname(c), uint(char))
+		__yyfmt__.Printf("lex %s(%d)\n", parserTokname(token), uint(char))
 	}
-	return c
+	return char, token
 }
 
 func parserParse(parserlex parserLexer) int {
+	return parserNewParser().Parse(parserlex)
+}
+
+func (parserrcvr *parserParserImpl) Parse(parserlex parserLexer) int {
 	var parsern int
 	var parserlval parserSymType
 	var parserVAL parserSymType
+	var parserDollar []parserSymType
+	_ = parserDollar // silence set and not used
 	parserS := make([]parserSymType, parserMaxDepth)
 
 	Nerrs := 0   /* number of errors */
 	Errflag := 0 /* error recovery flag */
 	parserstate := 0
 	parserchar := -1
+	parsertoken := -1 // parserchar translated into internal numbering
+	parserrcvr.lookahead = func() int { return parserchar }
+	defer func() {
+		// Make sure we report no lookahead when not parsing.
+		parserstate = -1
+		parserchar = -1
+		parsertoken = -1
+	}()
 	parserp := -1
 	goto parserstack
 
@@ -207,7 +316,7 @@ ret1:
 parserstack:
 	/* put a state and value onto the stack */
 	if parserDebug >= 4 {
-		__yyfmt__.Printf("char %v in %v\n", parserTokname(parserchar), parserStatname(parserstate))
+		__yyfmt__.Printf("char %v in %v\n", parserTokname(parsertoken), parserStatname(parserstate))
 	}
 
 	parserp++
@@ -225,15 +334,16 @@ parsernewstate:
 		goto parserdefault /* simple state */
 	}
 	if parserchar < 0 {
-		parserchar = parserlex1(parserlex, &parserlval)
+		parserchar, parsertoken = parserlex1(parserlex, &parserlval)
 	}
-	parsern += parserchar
+	parsern += parsertoken
 	if parsern < 0 || parsern >= parserLast {
 		goto parserdefault
 	}
 	parsern = parserAct[parsern]
-	if parserChk[parsern] == parserchar { /* valid shift */
+	if parserChk[parsern] == parsertoken { /* valid shift */
 		parserchar = -1
+		parsertoken = -1
 		parserVAL = parserlval
 		parserstate = parsern
 		if Errflag > 0 {
@@ -247,7 +357,7 @@ parserdefault:
 	parsern = parserDef[parserstate]
 	if parsern == -2 {
 		if parserchar < 0 {
-			parserchar = parserlex1(parserlex, &parserlval)
+			parserchar, parsertoken = parserlex1(parserlex, &parserlval)
 		}
 
 		/* look through exception table */
@@ -260,7 +370,7 @@ parserdefault:
 		}
 		for xi += 2; ; xi += 2 {
 			parsern = parserExca[xi+0]
-			if parsern < 0 || parsern == parserchar {
+			if parsern < 0 || parsern == parsertoken {
 				break
 			}
 		}
@@ -273,11 +383,11 @@ parserdefault:
 		/* error ... attempt to resume parsing */
 		switch Errflag {
 		case 0: /* brand new error */
-			parserlex.Error("syntax error")
+			parserlex.Error(parserErrorMessage(parserstate, parsertoken))
 			Nerrs++
 			if parserDebug >= 1 {
 				__yyfmt__.Printf("%s", parserStatname(parserstate))
-				__yyfmt__.Printf(" saw %s\n", parserTokname(parserchar))
+				__yyfmt__.Printf(" saw %s\n", parserTokname(parsertoken))
 			}
 			fallthrough
 
@@ -305,12 +415,13 @@ parserdefault:
 
 		case 3: /* no shift yet; clobber input char */
 			if parserDebug >= 2 {
-				__yyfmt__.Printf("error recovery discards %s\n", parserTokname(parserchar))
+				__yyfmt__.Printf("error recovery discards %s\n", parserTokname(parsertoken))
 			}
-			if parserchar == parserEofCode {
+			if parsertoken == parserEofCode {
 				goto ret1
 			}
 			parserchar = -1
+			parsertoken = -1
 			goto parsernewstate /* try again in the same state */
 		}
 	}
@@ -325,6 +436,13 @@ parserdefault:
 	_ = parserpt // guard against "declared and not used"
 
 	parserp -= parserR2[parsern]
+	// parserp is now the index of $0. Perform the default action. Iff the
+	// reduced production is ε, $1 is possibly out of range.
+	if parserp+1 >= len(parserS) {
+		nyys := make([]parserSymType, len(parserS)*2)
+		copy(nyys, parserS)
+		parserS = nyys
+	}
 	parserVAL = parserS[parserp+1]
 
 	/* consult goto table to find next state */
@@ -344,6 +462,7 @@ parserdefault:
 	switch parsernt {
 
 	case 1:
+		parserDollar = parserS[parserpt-0 : parserpt+1]
 		//line lang.y:35
 		{
 			parserResult = &ast.LiteralNode{
@@ -353,9 +472,10 @@ parserdefault:
 			}
 		}
 	case 2:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:43
 		{
-			parserResult = parserS[parserpt-0].node
+			parserResult = parserDollar[1].node
 
 			// We want to make sure that the top value is always a Concat
 			// so that the return value is always a string type from an
@@ -365,28 +485,30 @@ parserdefault:
 			// because functionally the AST is the same, but we do that because
 			// it makes for an easy literal check later (to check if a string
 			// has any interpolations).
-			if _, ok := parserS[parserpt-0].node.(*ast.Concat); !ok {
+			if _, ok := parserDollar[1].node.(*ast.Concat); !ok {
-				if n, ok := parserS[parserpt-0].node.(*ast.LiteralNode); !ok || n.Typex != ast.TypeString {
+				if n, ok := parserDollar[1].node.(*ast.LiteralNode); !ok || n.Typex != ast.TypeString {
 					parserResult = &ast.Concat{
-						Exprs: []ast.Node{parserS[parserpt-0].node},
+						Exprs: []ast.Node{parserDollar[1].node},
-						Posx:  parserS[parserpt-0].node.Pos(),
+						Posx:  parserDollar[1].node.Pos(),
 					}
 				}
 			}
 		}
 	case 3:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:66
 		{
-			parserVAL.node = parserS[parserpt-0].node
+			parserVAL.node = parserDollar[1].node
 		}
 	case 4:
+		parserDollar = parserS[parserpt-2 : parserpt+1]
 		//line lang.y:70
 		{
 			var result []ast.Node
-			if c, ok := parserS[parserpt-1].node.(*ast.Concat); ok {
+			if c, ok := parserDollar[1].node.(*ast.Concat); ok {
-				result = append(c.Exprs, parserS[parserpt-0].node)
+				result = append(c.Exprs, parserDollar[2].node)
 			} else {
-				result = []ast.Node{parserS[parserpt-1].node, parserS[parserpt-0].node}
+				result = []ast.Node{parserDollar[1].node, parserDollar[2].node}
 			}
 
 			parserVAL.node = &ast.Concat{
@@ -395,89 +517,103 @@ parserdefault:
 			}
 		}
 	case 5:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:86
 		{
-			parserVAL.node = parserS[parserpt-0].node
+			parserVAL.node = parserDollar[1].node
 		}
 	case 6:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:90
 		{
-			parserVAL.node = parserS[parserpt-0].node
+			parserVAL.node = parserDollar[1].node
 		}
 	case 7:
+		parserDollar = parserS[parserpt-3 : parserpt+1]
 		//line lang.y:96
 		{
-			parserVAL.node = parserS[parserpt-1].node
+			parserVAL.node = parserDollar[2].node
 		}
 	case 8:
+		parserDollar = parserS[parserpt-3 : parserpt+1]
 		//line lang.y:102
 		{
-			parserVAL.node = parserS[parserpt-1].node
+			parserVAL.node = parserDollar[2].node
 		}
 	case 9:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:106
 		{
-			parserVAL.node = parserS[parserpt-0].node
+			parserVAL.node = parserDollar[1].node
 		}
 	case 10:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:110
 		{
 			parserVAL.node = &ast.LiteralNode{
-				Value: parserS[parserpt-0].token.Value.(int),
+				Value: parserDollar[1].token.Value.(int),
 				Typex: ast.TypeInt,
-				Posx:  parserS[parserpt-0].token.Pos,
+				Posx:  parserDollar[1].token.Pos,
 			}
 		}
 	case 11:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:118
 		{
 			parserVAL.node = &ast.LiteralNode{
-				Value: parserS[parserpt-0].token.Value.(float64),
+				Value: parserDollar[1].token.Value.(float64),
 				Typex: ast.TypeFloat,
-				Posx:  parserS[parserpt-0].token.Pos,
+				Posx:  parserDollar[1].token.Pos,
 			}
 		}
 	case 12:
+		parserDollar = parserS[parserpt-3 : parserpt+1]
 		//line lang.y:126
 		{
 			parserVAL.node = &ast.Arithmetic{
-				Op:    parserS[parserpt-1].token.Value.(ast.ArithmeticOp),
+				Op:    parserDollar[2].token.Value.(ast.ArithmeticOp),
-				Exprs: []ast.Node{parserS[parserpt-2].node, parserS[parserpt-0].node},
+				Exprs: []ast.Node{parserDollar[1].node, parserDollar[3].node},
-				Posx:  parserS[parserpt-2].node.Pos(),
+				Posx:  parserDollar[1].node.Pos(),
 			}
 		}
 	case 13:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:134
 		{
-			parserVAL.node = &ast.VariableAccess{Name: parserS[parserpt-0].token.Value.(string), Posx: parserS[parserpt-0].token.Pos}
+			parserVAL.node = &ast.VariableAccess{Name: parserDollar[1].token.Value.(string), Posx: parserDollar[1].token.Pos}
 		}
 	case 14:
+		parserDollar = parserS[parserpt-4 : parserpt+1]
 		//line lang.y:138
 		{
-			parserVAL.node = &ast.Call{Func: parserS[parserpt-3].token.Value.(string), Args: parserS[parserpt-1].nodeList, Posx: parserS[parserpt-3].token.Pos}
+			parserVAL.node = &ast.Call{Func: parserDollar[1].token.Value.(string), Args: parserDollar[3].nodeList, Posx: parserDollar[1].token.Pos}
 		}
 	case 15:
+		parserDollar = parserS[parserpt-0 : parserpt+1]
 		//line lang.y:143
 		{
 			parserVAL.nodeList = nil
 		}
 	case 16:
+		parserDollar = parserS[parserpt-3 : parserpt+1]
 		//line lang.y:147
 		{
-			parserVAL.nodeList = append(parserS[parserpt-2].nodeList, parserS[parserpt-0].node)
+			parserVAL.nodeList = append(parserDollar[1].nodeList, parserDollar[3].node)
 		}
 	case 17:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:151
 		{
-			parserVAL.nodeList = append(parserVAL.nodeList, parserS[parserpt-0].node)
+			parserVAL.nodeList = append(parserVAL.nodeList, parserDollar[1].node)
 		}
 	case 18:
+		parserDollar = parserS[parserpt-1 : parserpt+1]
 		//line lang.y:157
 		{
 			parserVAL.node = &ast.LiteralNode{
-				Value: parserS[parserpt-0].token.Value.(string),
+				Value: parserDollar[1].token.Value.(string),
 				Typex: ast.TypeString,
-				Posx:  parserS[parserpt-0].token.Pos,
+				Posx:  parserDollar[1].token.Pos,
 			}
 		}
 	}