diff --git a/cmd/bundle/main.go b/cmd/bundle/main.go
index 5da7aa12..d1f5348e 100644
--- a/cmd/bundle/main.go
+++ b/cmd/bundle/main.go
@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !go1.8
-
 // Bundle creates a single-source-file version of a source package
 // suitable for inclusion in a particular target package.
 //
diff --git a/cmd/bundle/main18.go b/cmd/bundle/main18.go
deleted file mode 100644
index 9b44559a..00000000
--- a/cmd/bundle/main18.go
+++ /dev/null
@@ -1,388 +0,0 @@
-// Copyright 2015 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.
-
-// +build go1.8
-
-// Bundle creates a single-source-file version of a source package
-// suitable for inclusion in a particular target package.
-//
-// Usage:
-//
-//	bundle [-o file] [-dst path] [-pkg name] [-prefix p] [-import old=new] <src>
-//
-// The src argument specifies the import path of the package to bundle.
-// The bundling of a directory of source files into a single source file
-// necessarily imposes a number of constraints.
-// The package being bundled must not use cgo; must not use conditional
-// file compilation, whether with build tags or system-specific file names
-// like code_amd64.go; must not depend on any special comments, which
-// may not be preserved; must not use any assembly sources;
-// must not use renaming imports; and must not use reflection-based APIs
-// that depend on the specific names of types or struct fields.
-//
-// By default, bundle writes the bundled code to standard output.
-// If the -o argument is given, bundle writes to the named file
-// and also includes a ``//go:generate'' comment giving the exact
-// command line used, for regenerating the file with ``go generate.''
-//
-// Bundle customizes its output for inclusion in a particular package, the destination package.
-// By default bundle assumes the destination is the package in the current directory,
-// but the destination package can be specified explicitly using the -dst option,
-// which takes an import path as its argument.
-// If the source package imports the destination package, bundle will remove
-// those imports and rewrite any references to use direct references to the
-// corresponding symbols.
-// Bundle also must write a package declaration in the output and must
-// choose a name to use in that declaration.
-// If the -package option is given, bundle uses that name.
-// Otherwise, if the -dst option is given, bundle uses the last
-// element of the destination import path.
-// Otherwise, by default bundle uses the package name found in the
-// package sources in the current directory.
-//
-// To avoid collisions, bundle inserts a prefix at the beginning of
-// every package-level const, func, type, and var identifier in src's code,
-// updating references accordingly. The default prefix is the package name
-// of the source package followed by an underscore. The -prefix option
-// specifies an alternate prefix.
-//
-// Occasionally it is necessary to rewrite imports during the bundling
-// process. The -import option, which may be repeated, specifies that
-// an import of "old" should be rewritten to import "new" instead.
-//
-// Example
-//
-// Bundle archive/zip for inclusion in cmd/dist:
-//
-//	cd $GOROOT/src/cmd/dist
-//	bundle -o zip.go archive/zip
-//
-// Bundle golang.org/x/net/http2 for inclusion in net/http,
-// prefixing all identifiers by "http2" instead of "http2_",
-// and rewriting the import "golang.org/x/net/http2/hpack"
-// to "internal/golang.org/x/net/http2/hpack":
-//
-//	cd $GOROOT/src/net/http
-//	bundle -o h2_bundle.go \
-//		-prefix http2 \
-//		-import golang.org/x/net/http2/hpack=internal/golang.org/x/net/http2/hpack \
-//		golang.org/x/net/http2
-//
-// Two ways to update the http2 bundle:
-//
-//	go generate net/http
-//
-//	cd $GOROOT/src/net/http
-//	go generate
-//
-// Update both bundles, restricting ``go generate'' to running bundle commands:
-//
-//	go generate -run bundle cmd/dist net/http
-//
-package main
-
-import (
-	"bytes"
-	"flag"
-	"fmt"
-	"go/ast"
-	"go/build"
-	"go/format"
-	"go/parser"
-	"go/token"
-	"go/types"
-	"io/ioutil"
-	"log"
-	"os"
-	"path"
-	"strconv"
-	"strings"
-
-	"golang.org/x/tools/go/loader"
-)
-
-var (
-	outputFile = flag.String("o", "", "write output to `file` (default standard output)")
-	dstPath    = flag.String("dst", "", "set destination import `path` (default taken from current directory)")
-	pkgName    = flag.String("pkg", "", "set destination package `name` (default taken from current directory)")
-	prefix     = flag.String("prefix", "", "set bundled identifier prefix to `p` (default source package name + \"_\")")
-	underscore = flag.Bool("underscore", false, "rewrite golang.org to golang_org in imports; temporary workaround for golang.org/issue/16333")
-
-	importMap = map[string]string{}
-)
-
-func init() {
-	flag.Var(flagFunc(addImportMap), "import", "rewrite import using `map`, of form old=new (can be repeated)")
-}
-
-func addImportMap(s string) {
-	if strings.Count(s, "=") != 1 {
-		log.Fatal("-import argument must be of the form old=new")
-	}
-	i := strings.Index(s, "=")
-	old, new := s[:i], s[i+1:]
-	if old == "" || new == "" {
-		log.Fatal("-import argument must be of the form old=new; old and new must be non-empty")
-	}
-	importMap[old] = new
-}
-
-func usage() {
-	fmt.Fprintf(os.Stderr, "Usage: bundle [options] <src>\n")
-	flag.PrintDefaults()
-}
-
-func main() {
-	log.SetPrefix("bundle: ")
-	log.SetFlags(0)
-
-	flag.Usage = usage
-	flag.Parse()
-	args := flag.Args()
-	if len(args) != 1 {
-		usage()
-		os.Exit(2)
-	}
-
-	if *dstPath != "" {
-		if *pkgName == "" {
-			*pkgName = path.Base(*dstPath)
-		}
-	} else {
-		wd, _ := os.Getwd()
-		pkg, err := build.ImportDir(wd, 0)
-		if err != nil {
-			log.Fatalf("cannot find package in current directory: %v", err)
-		}
-		*dstPath = pkg.ImportPath
-		if *pkgName == "" {
-			*pkgName = pkg.Name
-		}
-	}
-
-	code, err := bundle(args[0], *dstPath, *pkgName, *prefix)
-	if err != nil {
-		log.Fatal(err)
-	}
-	if *outputFile != "" {
-		err := ioutil.WriteFile(*outputFile, code, 0666)
-		if err != nil {
-			log.Fatal(err)
-		}
-	} else {
-		_, err := os.Stdout.Write(code)
-		if err != nil {
-			log.Fatal(err)
-		}
-	}
-}
-
-// isStandardImportPath is copied from cmd/go in the standard library.
-func isStandardImportPath(path string) bool {
-	i := strings.Index(path, "/")
-	if i < 0 {
-		i = len(path)
-	}
-	elem := path[:i]
-	return !strings.Contains(elem, ".")
-}
-
-var ctxt = &build.Default
-
-func bundle(src, dst, dstpkg, prefix string) ([]byte, error) {
-	// Load the initial package.
-	conf := loader.Config{ParserMode: parser.ParseComments, Build: ctxt}
-	conf.TypeCheckFuncBodies = func(p string) bool { return p == src }
-	conf.Import(src)
-
-	lprog, err := conf.Load()
-	if err != nil {
-		return nil, err
-	}
-
-	info := lprog.Package(src)
-	if prefix == "" {
-		pkgName := info.Files[0].Name.Name
-		prefix = pkgName + "_"
-	}
-
-	objsToUpdate := make(map[types.Object]bool)
-	var rename func(from types.Object)
-	rename = func(from types.Object) {
-		if !objsToUpdate[from] {
-			objsToUpdate[from] = true
-
-			// Renaming a type that is used as an embedded field
-			// requires renaming the field too. e.g.
-			// 	type T int // if we rename this to U..
-			// 	var s struct {T}
-			// 	print(s.T) // ...this must change too
-			if _, ok := from.(*types.TypeName); ok {
-				for id, obj := range info.Uses {
-					if obj == from {
-						if field := info.Defs[id]; field != nil {
-							rename(field)
-						}
-					}
-				}
-			}
-		}
-	}
-
-	// Rename each package-level object.
-	scope := info.Pkg.Scope()
-	for _, name := range scope.Names() {
-		rename(scope.Lookup(name))
-	}
-
-	var out bytes.Buffer
-
-	fmt.Fprintf(&out, "// Code generated by golang.org/x/tools/cmd/bundle.\n")
-	if *outputFile != "" {
-		fmt.Fprintf(&out, "//go:generate bundle %s\n", strings.Join(os.Args[1:], " "))
-	} else {
-		fmt.Fprintf(&out, "//   $ bundle %s\n", strings.Join(os.Args[1:], " "))
-	}
-	fmt.Fprintf(&out, "\n")
-
-	// Concatenate package comments from all files...
-	for _, f := range info.Files {
-		if doc := f.Doc.Text(); strings.TrimSpace(doc) != "" {
-			for _, line := range strings.Split(doc, "\n") {
-				fmt.Fprintf(&out, "// %s\n", line)
-			}
-		}
-	}
-	// ...but don't let them become the actual package comment.
-	fmt.Fprintln(&out)
-
-	fmt.Fprintf(&out, "package %s\n\n", dstpkg)
-
-	// BUG(adonovan,shurcooL): bundle may generate incorrect code
-	// due to shadowing between identifiers and imported package names.
-	//
-	// The generated code will either fail to compile or
-	// (unlikely) compile successfully but have different behavior
-	// than the original package. The risk of this happening is higher
-	// when the original package has renamed imports (they're typically
-	// renamed in order to resolve a shadow inside that particular .go file).
-
-	// TODO(adonovan,shurcooL):
-	// - detect shadowing issues, and either return error or resolve them
-	// - preserve comments from the original import declarations.
-
-	// pkgStd and pkgExt are sets of printed import specs. This is done
-	// to deduplicate instances of the same import name and path.
-	var pkgStd = make(map[string]bool)
-	var pkgExt = make(map[string]bool)
-	for _, f := range info.Files {
-		for _, imp := range f.Imports {
-			path, err := strconv.Unquote(imp.Path.Value)
-			if err != nil {
-				log.Fatalf("invalid import path string: %v", err) // Shouldn't happen here since conf.Load succeeded.
-			}
-			if path == dst {
-				continue
-			}
-			if newPath, ok := importMap[path]; ok {
-				path = newPath
-			}
-
-			var name string
-			if imp.Name != nil {
-				name = imp.Name.Name
-			}
-			spec := fmt.Sprintf("%s %q", name, path)
-			if isStandardImportPath(path) {
-				pkgStd[spec] = true
-			} else {
-				if *underscore {
-					spec = strings.Replace(spec, "golang.org/", "golang_org/", 1)
-				}
-				pkgExt[spec] = true
-			}
-		}
-	}
-
-	// Print a single declaration that imports all necessary packages.
-	fmt.Fprintln(&out, "import (")
-	for p := range pkgStd {
-		fmt.Fprintf(&out, "\t%s\n", p)
-	}
-	if len(pkgExt) > 0 {
-		fmt.Fprintln(&out)
-	}
-	for p := range pkgExt {
-		fmt.Fprintf(&out, "\t%s\n", p)
-	}
-	fmt.Fprint(&out, ")\n\n")
-
-	// Modify and print each file.
-	for _, f := range info.Files {
-		// Update renamed identifiers.
-		for id, obj := range info.Defs {
-			if objsToUpdate[obj] {
-				id.Name = prefix + obj.Name()
-			}
-		}
-		for id, obj := range info.Uses {
-			if objsToUpdate[obj] {
-				id.Name = prefix + obj.Name()
-			}
-		}
-
-		// For each qualified identifier that refers to the
-		// destination package, remove the qualifier.
-		// The "@@@." strings are removed in postprocessing.
-		ast.Inspect(f, func(n ast.Node) bool {
-			if sel, ok := n.(*ast.SelectorExpr); ok {
-				if id, ok := sel.X.(*ast.Ident); ok {
-					if obj, ok := info.Uses[id].(*types.PkgName); ok {
-						if obj.Imported().Path() == dst {
-							id.Name = "@@@"
-						}
-					}
-				}
-			}
-			return true
-		})
-
-		// Pretty-print package-level declarations.
-		// but no package or import declarations.
-		//
-		// TODO(adonovan): this may cause loss of comments
-		// preceding or associated with the package or import
-		// declarations or not associated with any declaration.
-		// Check.
-		var buf bytes.Buffer
-		for _, decl := range f.Decls {
-			if decl, ok := decl.(*ast.GenDecl); ok && decl.Tok == token.IMPORT {
-				continue
-			}
-			buf.Reset()
-			format.Node(&buf, lprog.Fset, decl)
-			// Remove each "@@@." in the output.
-			// TODO(adonovan): not hygienic.
-			out.Write(bytes.Replace(buf.Bytes(), []byte("@@@."), nil, -1))
-			out.WriteString("\n\n")
-		}
-	}
-
-	// Now format the entire thing.
-	result, err := format.Source(out.Bytes())
-	if err != nil {
-		log.Fatalf("formatting failed: %v", err)
-	}
-
-	return result, nil
-}
-
-type flagFunc func(string)
-
-func (f flagFunc) Set(s string) error {
-	f(s)
-	return nil
-}
-
-func (f flagFunc) String() string { return "" }