cmd/yacc: remove go tool yacc

It is no longer used by Go.

It's now moved to golang.org/x/tools/cmd/goyacc for anybody who needs it.

Fixes #11229

Change-Id: Ia431d5a380c7ff784a2050dee2f5bc8acee015da
Reviewed-on: https://go-review.googlesource.com/27325
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

doc/articles/go_command.html

@@ -255,8 +255,7 @@ In particular, it does not have any facility for generating Go
 source files <em>during</em> a build, although it does provide
 <a href="/cmd/go/#hdr-Generate_Go_files_by_processing_source"><code>go</code>
 <code>generate</code></a>,
-which can automate the creation of Go files <em>before</em>
-the build, such as by running <code>yacc</code>.
+which can automate the creation of Go files <em>before</em> the build.
 For more advanced build setups, you may need to write a
 makefile (or a configuration file for the build tool of your choice)
 to run whatever tool creates the Go files and then check those generated source files

doc/go_faq.html

@@ -1670,8 +1670,7 @@ What compiler technology is used to build the compilers?</h3>
 
 <p>
 <code>Gccgo</code> has a front end written in C++, with a recursive descent parser coupled to the
-standard GCC back end. <code>Gc</code> is written in Go using
-<code>yacc</code>/<code>bison</code> for the parser
+standard GCC back end. <code>Gc</code> is written in Go with a recursive descent parser
 and uses a custom loader, also written in Go but
 based on the Plan 9 loader, to generate ELF/Mach-O/PE binaries.
 </p>

src/cmd/go/alldocs.go

@@ -367,7 +367,7 @@
 //
 // Generate runs commands described by directives within existing
 // files. Those commands can run any process but the intent is to
-// create or update Go source files, for instance by running yacc.
+// create or update Go source files.
 //
 // Go generate is never run automatically by go build, go get, go test,
 // and so on. It must be run explicitly.
@@ -430,10 +430,10 @@
 // can be used to create aliases or to handle multiword generators.
 // For example,
 //
-// 	//go:generate -command yacc go tool yacc
+// 	//go:generate -command foo go tool foo
 //
-// specifies that the command "yacc" represents the generator
-// "go tool yacc".
+// specifies that the command "foo" represents the generator
+// "go tool foo".
 //
 // Generate processes packages in the order given on the command line,
 // one at a time. If the command line lists .go files, they are treated

src/cmd/go/generate.go

@@ -25,7 +25,7 @@ var cmdGenerate = &Command{
 	Long: `
 Generate runs commands described by directives within existing
 files. Those commands can run any process but the intent is to
-create or update Go source files, for instance by running yacc.
+create or update Go source files.
 
 Go generate is never run automatically by go build, go get, go test,
 and so on. It must be run explicitly.
@@ -88,10 +88,10 @@ string xxx represents the command identified by the arguments. This
 can be used to create aliases or to handle multiword generators.
 For example,
 
-	//go:generate -command yacc go tool yacc
+	//go:generate -command foo go tool foo
 
-specifies that the command "yacc" represents the generator
-"go tool yacc".
+specifies that the command "foo" represents the generator
+"go tool foo".
 
 Generate processes packages in the order given on the command line,
 one at a time. If the command line lists .go files, they are treated

src/cmd/go/pkg.go

@@ -691,24 +691,23 @@ const (
 
 // goTools is a map of Go program import path to install target directory.
 var goTools = map[string]targetDir{
-	"cmd/addr2line":                        toTool,
-	"cmd/api":                              toTool,
-	"cmd/asm":                              toTool,
-	"cmd/compile":                          toTool,
-	"cmd/cgo":                              toTool,
-	"cmd/cover":                            toTool,
-	"cmd/dist":                             toTool,
-	"cmd/doc":                              toTool,
-	"cmd/fix":                              toTool,
-	"cmd/link":                             toTool,
-	"cmd/newlink":                          toTool,
-	"cmd/nm":                               toTool,
-	"cmd/objdump":                          toTool,
-	"cmd/pack":                             toTool,
-	"cmd/pprof":                            toTool,
-	"cmd/trace":                            toTool,
-	"cmd/vet":                              toTool,
-	"cmd/yacc":                             toTool,
+	"cmd/addr2line": toTool,
+	"cmd/api":       toTool,
+	"cmd/asm":       toTool,
+	"cmd/compile":   toTool,
+	"cmd/cgo":       toTool,
+	"cmd/cover":     toTool,
+	"cmd/dist":      toTool,
+	"cmd/doc":       toTool,
+	"cmd/fix":       toTool,
+	"cmd/link":      toTool,
+	"cmd/newlink":   toTool,
+	"cmd/nm":        toTool,
+	"cmd/objdump":   toTool,
+	"cmd/pack":      toTool,
+	"cmd/pprof":     toTool,
+	"cmd/trace":     toTool,
+	"cmd/vet":       toTool,
 	"code.google.com/p/go.tools/cmd/cover": stalePath,
 	"code.google.com/p/go.tools/cmd/godoc": stalePath,
 	"code.google.com/p/go.tools/cmd/vet":   stalePath,

src/cmd/yacc/doc.go

-// Copyright 2009 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.
-
-/*
-
-Yacc is a version of yacc for Go.
-It is written in Go and generates parsers written in Go.
-
-Usage:
-
-	go tool yacc args...
-
-It is largely transliterated from the Inferno version written in Limbo
-which in turn was largely transliterated from the Plan 9 version
-written in C and documented at
-
-	https://9p.io/magic/man2html/1/yacc
-
-Adepts of the original yacc will have no trouble adapting to this
-form of the tool.
-
-The directory $GOROOT/src/cmd/yacc/testdata/expr is a yacc program
-for a very simple expression parser. See expr.y and main.go in that
-directory for examples of how to write and build yacc programs.
-
-The generated parser is reentrant. The parsing function yyParse expects
-to be given an argument that conforms to the following interface:
-
-	type yyLexer interface {
-		Lex(lval *yySymType) int
-		Error(e string)
-	}
-
-Lex should return the token identifier, and place other token
-information in lval (which replaces the usual yylval).
-Error is equivalent to yyerror in the original yacc.
-
-Code inside the grammar actions may refer to the variable yylex,
-which holds the yyLexer passed to yyParse.
-
-Clients that need to understand more about the parser state can
-create the parser separately from invoking it. The function yyNewParser
-returns a yyParser conforming to the following interface:
-
-	type yyParser interface {
-		Parse(yyLex) int
-		Lookahead() int
-	}
-
-Parse runs the parser; the top-level call yyParse(yylex) is equivalent
-to yyNewParser().Parse(yylex).
-
-Lookahead can be called during grammar actions to read (but not consume)
-the value of the current lookahead token, as returned by yylex.Lex.
-If there is no current lookahead token (because the parser has not called Lex
-or has consumed the token returned by the most recent call to Lex),
-Lookahead returns -1. Calling Lookahead is equivalent to reading
-yychar from within in a grammar action.
-
-Multiple grammars compiled into a single program should be placed in
-distinct packages.  If that is impossible, the "-p prefix" flag to
-yacc sets the prefix, by default yy, that begins the names of
-symbols, including types, the parser, and the lexer, generated and
-referenced by yacc's generated code.  Setting it to distinct values
-allows multiple grammars to be placed in a single package.
-
-*/
-package main

src/cmd/yacc/testdata/expr/README

-This directory contains a simple program demonstrating how to use
-the Go version of yacc.
-
-To build it:
-
-	$ go generate
-	$ go build
-
-or
-
-	$ go generate
-	$ go run expr.go
-
-The file main.go contains the "go generate" command to run yacc to
-create expr.go from expr.y. It also has the package doc comment,
-as godoc will not scan the .y file.
-
-The actual implementation is in expr.y.
-
-The program is not installed in the binary distributions of Go.

src/cmd/yacc/testdata/expr/expr.y

-// Copyright 2013 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.
-
-// This is an example of a goyacc program.
-// To build it:
-// go tool yacc -p "expr" expr.y (produces y.go)
-// go build -o expr y.go
-// expr
-// > <type an expression>
-
-%{
-
-package main
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"io"
-	"log"
-	"math/big"
-	"os"
-	"unicode/utf8"
-)
-
-%}
-
-%union {
-	num *big.Rat
-}
-
-%type	<num>	expr expr1 expr2 expr3
-
-%token '+' '-' '*' '/' '(' ')'
-
-%token	<num>	NUM
-
-%%
-
-top:
-	expr
-	{
-		if $1.IsInt() {
-			fmt.Println($1.Num().String())
-		} else {
-			fmt.Println($1.String())
-		}
-	}
-
-expr:
-	expr1
-|	'+' expr
-	{
-		$$ = $2
-	}
-|	'-' expr
-	{
-		$$ = $2.Neg($2)
-	}
-
-expr1:
-	expr2
-|	expr1 '+' expr2
-	{
-		$$ = $1.Add($1, $3)
-	}
-|	expr1 '-' expr2
-	{
-		$$ = $1.Sub($1, $3)
-	}
-
-expr2:
-	expr3
-|	expr2 '*' expr3
-	{
-		$$ = $1.Mul($1, $3)
-	}
-|	expr2 '/' expr3
-	{
-		$$ = $1.Quo($1, $3)
-	}
-
-expr3:
-	NUM
-|	'(' expr ')'
-	{
-		$$ = $2
-	}
-
-
-%%
-
-// The parser expects the lexer to return 0 on EOF.  Give it a name
-// for clarity.
-const eof = 0
-
-// The parser uses the type <prefix>Lex as a lexer. It must provide
-// the methods Lex(*<prefix>SymType) int and Error(string).
-type exprLex struct {
-	line []byte
-	peek rune
-}
-
-// The parser calls this method to get each new token. This
-// implementation returns operators and NUM.
-func (x *exprLex) Lex(yylval *exprSymType) int {
-	for {
-		c := x.next()
-		switch c {
-		case eof:
-			return eof
-		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
-			return x.num(c, yylval)
-		case '+', '-', '*', '/', '(', ')':
-			return int(c)
-
-		// Recognize Unicode multiplication and division
-		// symbols, returning what the parser expects.
-		case '×':
-			return '*'
-		case '÷':
-			return '/'
-
-		case ' ', '\t', '\n', '\r':
-		default:
-			log.Printf("unrecognized character %q", c)
-		}
-	}
-}
-
-// Lex a number.
-func (x *exprLex) num(c rune, yylval *exprSymType) int {
-	add := func(b *bytes.Buffer, c rune) {
-		if _, err := b.WriteRune(c); err != nil {
-			log.Fatalf("WriteRune: %s", err)
-		}
-	}
-	var b bytes.Buffer
-	add(&b, c)
-	L: for {
-		c = x.next()
-		switch c {
-		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.', 'e', 'E':
-			add(&b, c)
-		default:
-			break L
-		}
-	}
-	if c != eof {
-		x.peek = c
-	}
-	yylval.num = &big.Rat{}
-	_, ok := yylval.num.SetString(b.String())
-	if !ok {
-		log.Printf("bad number %q", b.String())
-		return eof
-	}
-	return NUM
-}
-
-// Return the next rune for the lexer.
-func (x *exprLex) next() rune {
-	if x.peek != eof {
-		r := x.peek
-		x.peek = eof
-		return r
-	}
-	if len(x.line) == 0 {
-		return eof
-	}
-	c, size := utf8.DecodeRune(x.line)
-	x.line = x.line[size:]
-	if c == utf8.RuneError && size == 1 {
-		log.Print("invalid utf8")
-		return x.next()
-	}
-	return c
-}
-
-// The parser calls this method on a parse error.
-func (x *exprLex) Error(s string) {
-	log.Printf("parse error: %s", s)
-}
-
-func main() {
-	in := bufio.NewReader(os.Stdin)
-	for {
-		if _, err := os.Stdout.WriteString("> "); err != nil {
-			log.Fatalf("WriteString: %s", err)
-		}
-		line, err := in.ReadBytes('\n')
-		if err == io.EOF {
-			return
-		}
-		if err != nil {
-			log.Fatalf("ReadBytes: %s", err)
-		}
-
-		exprParse(&exprLex{line: line})
-	}
-}

src/cmd/yacc/testdata/expr/main.go

-// Copyright 2014 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.
-
-// This file holds the go generate command to run yacc on the grammar in expr.y.
-// To build expr:
-//	% go generate
-//	% go build
-
-//go:generate -command yacc go tool yacc
-//go:generate yacc -o expr.go -p "expr" expr.y
-
-// Expr is a simple expression evaluator that serves as a working example of
-// how to use Go's yacc implementation.
-package main