From fe2bc11e1fac672cc23e9ffd01673257a1330707 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Mon, 29 Sep 2014 13:32:14 -0700
Subject: [PATCH] cmd/yacc: fix handling of tokens that don't start with
 letters

CL 149110043 changed yacc to no longer keep a leading space
for quoted tokens.  That is OK by itself but unfortunately
yacc was relying on that leading space to notice which tokens
it should not output as const declarations.

Add a few such tokens to expr.y, although it won't make any
immediate difference as we seem to have no tests for yacc.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://golang.org/cl/152720043
---
 src/cmd/yacc/testdata/expr/expr.y |  2 ++
 src/cmd/yacc/yacc.go              | 14 +++++++++-----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/cmd/yacc/testdata/expr/expr.y b/src/cmd/yacc/testdata/expr/expr.y
index 09451949ff..721b1c9172 100644
--- a/src/cmd/yacc/testdata/expr/expr.y
+++ b/src/cmd/yacc/testdata/expr/expr.y
@@ -32,6 +32,8 @@ import (
 
 %type	<num>	expr expr1 expr2 expr3
 
+%token '+' '-' '*' '/' '(' ')'
+
 %token	<num>	NUM
 
 %%
diff --git a/src/cmd/yacc/yacc.go b/src/cmd/yacc/yacc.go
index 0761811cf4..4dba376fc2 100644
--- a/src/cmd/yacc/yacc.go
+++ b/src/cmd/yacc/yacc.go
@@ -195,8 +195,9 @@ type Item struct {
 }
 
 type Symb struct {
-	name  string
-	value int
+	name    string
+	noconst bool
+	value   int
 }
 
 type Wset struct {
@@ -509,8 +510,7 @@ outer:
 	// put out non-literal terminals
 	for i := TOKSTART; i <= ntokens; i++ {
 		// non-literals
-		c := tokset[i].name[0]
-		if c != ' ' && c != '$' {
+		if !tokset[i].noconst {
 			fmt.Fprintf(ftable, "const %v = %v\n", tokset[i].name, tokset[i].value)
 		}
 	}
@@ -734,7 +734,7 @@ func defin(nt int, s string) int {
 			copy(anontrst, nontrst)
 			nontrst = anontrst
 		}
-		nontrst[nnonter] = Symb{s, 0}
+		nontrst[nnonter] = Symb{name: s}
 		return NTBASE + nnonter
 	}
 
@@ -769,9 +769,13 @@ func defin(nt int, s string) int {
 		if val == 0 {
 			errorf("token value 0 is illegal")
 		}
+		tokset[ntokens].noconst = true
 	} else {
 		val = extval
 		extval++
+		if s[0] == '$' {
+			tokset[ntokens].noconst = true
+		}
 	}
 
 	tokset[ntokens].value = val
-- 
2.50.0