Add OAuth2 authentication

vendor/google.golang.org/appengine/cmd/aefix/fix.go

@@ -0,0 +1,848 @@
+// Copyright 2011 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.
+
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"os"
+	"path"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+type fix struct {
+	name string
+	date string // date that fix was introduced, in YYYY-MM-DD format
+	f    func(*ast.File) bool
+	desc string
+}
+
+// main runs sort.Sort(byName(fixes)) before printing list of fixes.
+type byName []fix
+
+func (f byName) Len() int           { return len(f) }
+func (f byName) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }
+func (f byName) Less(i, j int) bool { return f[i].name < f[j].name }
+
+// main runs sort.Sort(byDate(fixes)) before applying fixes.
+type byDate []fix
+
+func (f byDate) Len() int           { return len(f) }
+func (f byDate) Swap(i, j int)      { f[i], f[j] = f[j], f[i] }
+func (f byDate) Less(i, j int) bool { return f[i].date < f[j].date }
+
+var fixes []fix
+
+func register(f fix) {
+	fixes = append(fixes, f)
+}
+
+// walk traverses the AST x, calling visit(y) for each node y in the tree but
+// also with a pointer to each ast.Expr, ast.Stmt, and *ast.BlockStmt,
+// in a bottom-up traversal.
+func walk(x interface{}, visit func(interface{})) {
+	walkBeforeAfter(x, nop, visit)
+}
+
+func nop(interface{}) {}
+
+// walkBeforeAfter is like walk but calls before(x) before traversing
+// x's children and after(x) afterward.
+func walkBeforeAfter(x interface{}, before, after func(interface{})) {
+	before(x)
+
+	switch n := x.(type) {
+	default:
+		panic(fmt.Errorf("unexpected type %T in walkBeforeAfter", x))
+
+	case nil:
+
+	// pointers to interfaces
+	case *ast.Decl:
+		walkBeforeAfter(*n, before, after)
+	case *ast.Expr:
+		walkBeforeAfter(*n, before, after)
+	case *ast.Spec:
+		walkBeforeAfter(*n, before, after)
+	case *ast.Stmt:
+		walkBeforeAfter(*n, before, after)
+
+	// pointers to struct pointers
+	case **ast.BlockStmt:
+		walkBeforeAfter(*n, before, after)
+	case **ast.CallExpr:
+		walkBeforeAfter(*n, before, after)
+	case **ast.FieldList:
+		walkBeforeAfter(*n, before, after)
+	case **ast.FuncType:
+		walkBeforeAfter(*n, before, after)
+	case **ast.Ident:
+		walkBeforeAfter(*n, before, after)
+	case **ast.BasicLit:
+		walkBeforeAfter(*n, before, after)
+
+	// pointers to slices
+	case *[]ast.Decl:
+		walkBeforeAfter(*n, before, after)
+	case *[]ast.Expr:
+		walkBeforeAfter(*n, before, after)
+	case *[]*ast.File:
+		walkBeforeAfter(*n, before, after)
+	case *[]*ast.Ident:
+		walkBeforeAfter(*n, before, after)
+	case *[]ast.Spec:
+		walkBeforeAfter(*n, before, after)
+	case *[]ast.Stmt:
+		walkBeforeAfter(*n, before, after)
+
+	// These are ordered and grouped to match ../../pkg/go/ast/ast.go
+	case *ast.Field:
+		walkBeforeAfter(&n.Names, before, after)
+		walkBeforeAfter(&n.Type, before, after)
+		walkBeforeAfter(&n.Tag, before, after)
+	case *ast.FieldList:
+		for _, field := range n.List {
+			walkBeforeAfter(field, before, after)
+		}
+	case *ast.BadExpr:
+	case *ast.Ident:
+	case *ast.Ellipsis:
+		walkBeforeAfter(&n.Elt, before, after)
+	case *ast.BasicLit:
+	case *ast.FuncLit:
+		walkBeforeAfter(&n.Type, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.CompositeLit:
+		walkBeforeAfter(&n.Type, before, after)
+		walkBeforeAfter(&n.Elts, before, after)
+	case *ast.ParenExpr:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.SelectorExpr:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.IndexExpr:
+		walkBeforeAfter(&n.X, before, after)
+		walkBeforeAfter(&n.Index, before, after)
+	case *ast.SliceExpr:
+		walkBeforeAfter(&n.X, before, after)
+		if n.Low != nil {
+			walkBeforeAfter(&n.Low, before, after)
+		}
+		if n.High != nil {
+			walkBeforeAfter(&n.High, before, after)
+		}
+	case *ast.TypeAssertExpr:
+		walkBeforeAfter(&n.X, before, after)
+		walkBeforeAfter(&n.Type, before, after)
+	case *ast.CallExpr:
+		walkBeforeAfter(&n.Fun, before, after)
+		walkBeforeAfter(&n.Args, before, after)
+	case *ast.StarExpr:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.UnaryExpr:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.BinaryExpr:
+		walkBeforeAfter(&n.X, before, after)
+		walkBeforeAfter(&n.Y, before, after)
+	case *ast.KeyValueExpr:
+		walkBeforeAfter(&n.Key, before, after)
+		walkBeforeAfter(&n.Value, before, after)
+
+	case *ast.ArrayType:
+		walkBeforeAfter(&n.Len, before, after)
+		walkBeforeAfter(&n.Elt, before, after)
+	case *ast.StructType:
+		walkBeforeAfter(&n.Fields, before, after)
+	case *ast.FuncType:
+		walkBeforeAfter(&n.Params, before, after)
+		if n.Results != nil {
+			walkBeforeAfter(&n.Results, before, after)
+		}
+	case *ast.InterfaceType:
+		walkBeforeAfter(&n.Methods, before, after)
+	case *ast.MapType:
+		walkBeforeAfter(&n.Key, before, after)
+		walkBeforeAfter(&n.Value, before, after)
+	case *ast.ChanType:
+		walkBeforeAfter(&n.Value, before, after)
+
+	case *ast.BadStmt:
+	case *ast.DeclStmt:
+		walkBeforeAfter(&n.Decl, before, after)
+	case *ast.EmptyStmt:
+	case *ast.LabeledStmt:
+		walkBeforeAfter(&n.Stmt, before, after)
+	case *ast.ExprStmt:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.SendStmt:
+		walkBeforeAfter(&n.Chan, before, after)
+		walkBeforeAfter(&n.Value, before, after)
+	case *ast.IncDecStmt:
+		walkBeforeAfter(&n.X, before, after)
+	case *ast.AssignStmt:
+		walkBeforeAfter(&n.Lhs, before, after)
+		walkBeforeAfter(&n.Rhs, before, after)
+	case *ast.GoStmt:
+		walkBeforeAfter(&n.Call, before, after)
+	case *ast.DeferStmt:
+		walkBeforeAfter(&n.Call, before, after)
+	case *ast.ReturnStmt:
+		walkBeforeAfter(&n.Results, before, after)
+	case *ast.BranchStmt:
+	case *ast.BlockStmt:
+		walkBeforeAfter(&n.List, before, after)
+	case *ast.IfStmt:
+		walkBeforeAfter(&n.Init, before, after)
+		walkBeforeAfter(&n.Cond, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+		walkBeforeAfter(&n.Else, before, after)
+	case *ast.CaseClause:
+		walkBeforeAfter(&n.List, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.SwitchStmt:
+		walkBeforeAfter(&n.Init, before, after)
+		walkBeforeAfter(&n.Tag, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.TypeSwitchStmt:
+		walkBeforeAfter(&n.Init, before, after)
+		walkBeforeAfter(&n.Assign, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.CommClause:
+		walkBeforeAfter(&n.Comm, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.SelectStmt:
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.ForStmt:
+		walkBeforeAfter(&n.Init, before, after)
+		walkBeforeAfter(&n.Cond, before, after)
+		walkBeforeAfter(&n.Post, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+	case *ast.RangeStmt:
+		walkBeforeAfter(&n.Key, before, after)
+		walkBeforeAfter(&n.Value, before, after)
+		walkBeforeAfter(&n.X, before, after)
+		walkBeforeAfter(&n.Body, before, after)
+
+	case *ast.ImportSpec:
+	case *ast.ValueSpec:
+		walkBeforeAfter(&n.Type, before, after)
+		walkBeforeAfter(&n.Values, before, after)
+		walkBeforeAfter(&n.Names, before, after)
+	case *ast.TypeSpec:
+		walkBeforeAfter(&n.Type, before, after)
+
+	case *ast.BadDecl:
+	case *ast.GenDecl:
+		walkBeforeAfter(&n.Specs, before, after)
+	case *ast.FuncDecl:
+		if n.Recv != nil {
+			walkBeforeAfter(&n.Recv, before, after)
+		}
+		walkBeforeAfter(&n.Type, before, after)
+		if n.Body != nil {
+			walkBeforeAfter(&n.Body, before, after)
+		}
+
+	case *ast.File:
+		walkBeforeAfter(&n.Decls, before, after)
+
+	case *ast.Package:
+		walkBeforeAfter(&n.Files, before, after)
+
+	case []*ast.File:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	case []ast.Decl:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	case []ast.Expr:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	case []*ast.Ident:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	case []ast.Stmt:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	case []ast.Spec:
+		for i := range n {
+			walkBeforeAfter(&n[i], before, after)
+		}
+	}
+	after(x)
+}
+
+// imports returns true if f imports path.
+func imports(f *ast.File, path string) bool {
+	return importSpec(f, path) != nil
+}
+
+// importSpec returns the import spec if f imports path,
+// or nil otherwise.
+func importSpec(f *ast.File, path string) *ast.ImportSpec {
+	for _, s := range f.Imports {
+		if importPath(s) == path {
+			return s
+		}
+	}
+	return nil
+}
+
+// importPath returns the unquoted import path of s,
+// or "" if the path is not properly quoted.
+func importPath(s *ast.ImportSpec) string {
+	t, err := strconv.Unquote(s.Path.Value)
+	if err == nil {
+		return t
+	}
+	return ""
+}
+
+// declImports reports whether gen contains an import of path.
+func declImports(gen *ast.GenDecl, path string) bool {
+	if gen.Tok != token.IMPORT {
+		return false
+	}
+	for _, spec := range gen.Specs {
+		impspec := spec.(*ast.ImportSpec)
+		if importPath(impspec) == path {
+			return true
+		}
+	}
+	return false
+}
+
+// isPkgDot returns true if t is the expression "pkg.name"
+// where pkg is an imported identifier.
+func isPkgDot(t ast.Expr, pkg, name string) bool {
+	sel, ok := t.(*ast.SelectorExpr)
+	return ok && isTopName(sel.X, pkg) && sel.Sel.String() == name
+}
+
+// isPtrPkgDot returns true if f is the expression "*pkg.name"
+// where pkg is an imported identifier.
+func isPtrPkgDot(t ast.Expr, pkg, name string) bool {
+	ptr, ok := t.(*ast.StarExpr)
+	return ok && isPkgDot(ptr.X, pkg, name)
+}
+
+// isTopName returns true if n is a top-level unresolved identifier with the given name.
+func isTopName(n ast.Expr, name string) bool {
+	id, ok := n.(*ast.Ident)
+	return ok && id.Name == name && id.Obj == nil
+}
+
+// isName returns true if n is an identifier with the given name.
+func isName(n ast.Expr, name string) bool {
+	id, ok := n.(*ast.Ident)
+	return ok && id.String() == name
+}
+
+// isCall returns true if t is a call to pkg.name.
+func isCall(t ast.Expr, pkg, name string) bool {
+	call, ok := t.(*ast.CallExpr)
+	return ok && isPkgDot(call.Fun, pkg, name)
+}
+
+// If n is an *ast.Ident, isIdent returns it; otherwise isIdent returns nil.
+func isIdent(n interface{}) *ast.Ident {
+	id, _ := n.(*ast.Ident)
+	return id
+}
+
+// refersTo returns true if n is a reference to the same object as x.
+func refersTo(n ast.Node, x *ast.Ident) bool {
+	id, ok := n.(*ast.Ident)
+	// The test of id.Name == x.Name handles top-level unresolved
+	// identifiers, which all have Obj == nil.
+	return ok && id.Obj == x.Obj && id.Name == x.Name
+}
+
+// isBlank returns true if n is the blank identifier.
+func isBlank(n ast.Expr) bool {
+	return isName(n, "_")
+}
+
+// isEmptyString returns true if n is an empty string literal.
+func isEmptyString(n ast.Expr) bool {
+	lit, ok := n.(*ast.BasicLit)
+	return ok && lit.Kind == token.STRING && len(lit.Value) == 2
+}
+
+func warn(pos token.Pos, msg string, args ...interface{}) {
+	if pos.IsValid() {
+		msg = "%s: " + msg
+		arg1 := []interface{}{fset.Position(pos).String()}
+		args = append(arg1, args...)
+	}
+	fmt.Fprintf(os.Stderr, msg+"\n", args...)
+}
+
+// countUses returns the number of uses of the identifier x in scope.
+func countUses(x *ast.Ident, scope []ast.Stmt) int {
+	count := 0
+	ff := func(n interface{}) {
+		if n, ok := n.(ast.Node); ok && refersTo(n, x) {
+			count++
+		}
+	}
+	for _, n := range scope {
+		walk(n, ff)
+	}
+	return count
+}
+
+// rewriteUses replaces all uses of the identifier x and !x in scope
+// with f(x.Pos()) and fnot(x.Pos()).
+func rewriteUses(x *ast.Ident, f, fnot func(token.Pos) ast.Expr, scope []ast.Stmt) {
+	var lastF ast.Expr
+	ff := func(n interface{}) {
+		ptr, ok := n.(*ast.Expr)
+		if !ok {
+			return
+		}
+		nn := *ptr
+
+		// The child node was just walked and possibly replaced.
+		// If it was replaced and this is a negation, replace with fnot(p).
+		not, ok := nn.(*ast.UnaryExpr)
+		if ok && not.Op == token.NOT && not.X == lastF {
+			*ptr = fnot(nn.Pos())
+			return
+		}
+		if refersTo(nn, x) {
+			lastF = f(nn.Pos())
+			*ptr = lastF
+		}
+	}
+	for _, n := range scope {
+		walk(n, ff)
+	}
+}
+
+// assignsTo returns true if any of the code in scope assigns to or takes the address of x.
+func assignsTo(x *ast.Ident, scope []ast.Stmt) bool {
+	assigned := false
+	ff := func(n interface{}) {
+		if assigned {
+			return
+		}
+		switch n := n.(type) {
+		case *ast.UnaryExpr:
+			// use of &x
+			if n.Op == token.AND && refersTo(n.X, x) {
+				assigned = true
+				return
+			}
+		case *ast.AssignStmt:
+			for _, l := range n.Lhs {
+				if refersTo(l, x) {
+					assigned = true
+					return
+				}
+			}
+		}
+	}
+	for _, n := range scope {
+		if assigned {
+			break
+		}
+		walk(n, ff)
+	}
+	return assigned
+}
+
+// newPkgDot returns an ast.Expr referring to "pkg.name" at position pos.
+func newPkgDot(pos token.Pos, pkg, name string) ast.Expr {
+	return &ast.SelectorExpr{
+		X: &ast.Ident{
+			NamePos: pos,
+			Name:    pkg,
+		},
+		Sel: &ast.Ident{
+			NamePos: pos,
+			Name:    name,
+		},
+	}
+}
+
+// renameTop renames all references to the top-level name old.
+// It returns true if it makes any changes.
+func renameTop(f *ast.File, old, new string) bool {
+	var fixed bool
+
+	// Rename any conflicting imports
+	// (assuming package name is last element of path).
+	for _, s := range f.Imports {
+		if s.Name != nil {
+			if s.Name.Name == old {
+				s.Name.Name = new
+				fixed = true
+			}
+		} else {
+			_, thisName := path.Split(importPath(s))
+			if thisName == old {
+				s.Name = ast.NewIdent(new)
+				fixed = true
+			}
+		}
+	}
+
+	// Rename any top-level declarations.
+	for _, d := range f.Decls {
+		switch d := d.(type) {
+		case *ast.FuncDecl:
+			if d.Recv == nil && d.Name.Name == old {
+				d.Name.Name = new
+				d.Name.Obj.Name = new
+				fixed = true
+			}
+		case *ast.GenDecl:
+			for _, s := range d.Specs {
+				switch s := s.(type) {
+				case *ast.TypeSpec:
+					if s.Name.Name == old {
+						s.Name.Name = new
+						s.Name.Obj.Name = new
+						fixed = true
+					}
+				case *ast.ValueSpec:
+					for _, n := range s.Names {
+						if n.Name == old {
+							n.Name = new
+							n.Obj.Name = new
+							fixed = true
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// Rename top-level old to new, both unresolved names
+	// (probably defined in another file) and names that resolve
+	// to a declaration we renamed.
+	walk(f, func(n interface{}) {
+		id, ok := n.(*ast.Ident)
+		if ok && isTopName(id, old) {
+			id.Name = new
+			fixed = true
+		}
+		if ok && id.Obj != nil && id.Name == old && id.Obj.Name == new {
+			id.Name = id.Obj.Name
+			fixed = true
+		}
+	})
+
+	return fixed
+}
+
+// matchLen returns the length of the longest prefix shared by x and y.
+func matchLen(x, y string) int {
+	i := 0
+	for i < len(x) && i < len(y) && x[i] == y[i] {
+		i++
+	}
+	return i
+}
+
+// addImport adds the import path to the file f, if absent.
+func addImport(f *ast.File, ipath string) (added bool) {
+	if imports(f, ipath) {
+		return false
+	}
+
+	// Determine name of import.
+	// Assume added imports follow convention of using last element.
+	_, name := path.Split(ipath)
+
+	// Rename any conflicting top-level references from name to name_.
+	renameTop(f, name, name+"_")
+
+	newImport := &ast.ImportSpec{
+		Path: &ast.BasicLit{
+			Kind:  token.STRING,
+			Value: strconv.Quote(ipath),
+		},
+	}
+
+	// Find an import decl to add to.
+	var (
+		bestMatch  = -1
+		lastImport = -1
+		impDecl    *ast.GenDecl
+		impIndex   = -1
+	)
+	for i, decl := range f.Decls {
+		gen, ok := decl.(*ast.GenDecl)
+		if ok && gen.Tok == token.IMPORT {
+			lastImport = i
+			// Do not add to import "C", to avoid disrupting the
+			// association with its doc comment, breaking cgo.
+			if declImports(gen, "C") {
+				continue
+			}
+
+			// Compute longest shared prefix with imports in this block.
+			for j, spec := range gen.Specs {
+				impspec := spec.(*ast.ImportSpec)
+				n := matchLen(importPath(impspec), ipath)
+				if n > bestMatch {
+					bestMatch = n
+					impDecl = gen
+					impIndex = j
+				}
+			}
+		}
+	}
+
+	// If no import decl found, add one after the last import.
+	if impDecl == nil {
+		impDecl = &ast.GenDecl{
+			Tok: token.IMPORT,
+		}
+		f.Decls = append(f.Decls, nil)
+		copy(f.Decls[lastImport+2:], f.Decls[lastImport+1:])
+		f.Decls[lastImport+1] = impDecl
+	}
+
+	// Ensure the import decl has parentheses, if needed.
+	if len(impDecl.Specs) > 0 && !impDecl.Lparen.IsValid() {
+		impDecl.Lparen = impDecl.Pos()
+	}
+
+	insertAt := impIndex + 1
+	if insertAt == 0 {
+		insertAt = len(impDecl.Specs)
+	}
+	impDecl.Specs = append(impDecl.Specs, nil)
+	copy(impDecl.Specs[insertAt+1:], impDecl.Specs[insertAt:])
+	impDecl.Specs[insertAt] = newImport
+	if insertAt > 0 {
+		// Assign same position as the previous import,
+		// so that the sorter sees it as being in the same block.
+		prev := impDecl.Specs[insertAt-1]
+		newImport.Path.ValuePos = prev.Pos()
+		newImport.EndPos = prev.Pos()
+	}
+
+	f.Imports = append(f.Imports, newImport)
+	return true
+}
+
+// deleteImport deletes the import path from the file f, if present.
+func deleteImport(f *ast.File, path string) (deleted bool) {
+	oldImport := importSpec(f, path)
+
+	// Find the import node that imports path, if any.
+	for i, decl := range f.Decls {
+		gen, ok := decl.(*ast.GenDecl)
+		if !ok || gen.Tok != token.IMPORT {
+			continue
+		}
+		for j, spec := range gen.Specs {
+			impspec := spec.(*ast.ImportSpec)
+			if oldImport != impspec {
+				continue
+			}
+
+			// We found an import spec that imports path.
+			// Delete it.
+			deleted = true
+			copy(gen.Specs[j:], gen.Specs[j+1:])
+			gen.Specs = gen.Specs[:len(gen.Specs)-1]
+
+			// If this was the last import spec in this decl,
+			// delete the decl, too.
+			if len(gen.Specs) == 0 {
+				copy(f.Decls[i:], f.Decls[i+1:])
+				f.Decls = f.Decls[:len(f.Decls)-1]
+			} else if len(gen.Specs) == 1 {
+				gen.Lparen = token.NoPos // drop parens
+			}
+			if j > 0 {
+				// We deleted an entry but now there will be
+				// a blank line-sized hole where the import was.
+				// Close the hole by making the previous
+				// import appear to "end" where this one did.
+				gen.Specs[j-1].(*ast.ImportSpec).EndPos = impspec.End()
+			}
+			break
+		}
+	}
+
+	// Delete it from f.Imports.
+	for i, imp := range f.Imports {
+		if imp == oldImport {
+			copy(f.Imports[i:], f.Imports[i+1:])
+			f.Imports = f.Imports[:len(f.Imports)-1]
+			break
+		}
+	}
+
+	return
+}
+
+// rewriteImport rewrites any import of path oldPath to path newPath.
+func rewriteImport(f *ast.File, oldPath, newPath string) (rewrote bool) {
+	for _, imp := range f.Imports {
+		if importPath(imp) == oldPath {
+			rewrote = true
+			// record old End, because the default is to compute
+			// it using the length of imp.Path.Value.
+			imp.EndPos = imp.End()
+			imp.Path.Value = strconv.Quote(newPath)
+		}
+	}
+	return
+}
+
+func usesImport(f *ast.File, path string) (used bool) {
+	spec := importSpec(f, path)
+	if spec == nil {
+		return
+	}
+
+	name := spec.Name.String()
+	switch name {
+	case "<nil>":
+		// If the package name is not explicitly specified,
+		// make an educated guess. This is not guaranteed to be correct.
+		lastSlash := strings.LastIndex(path, "/")
+		if lastSlash == -1 {
+			name = path
+		} else {
+			name = path[lastSlash+1:]
+		}
+	case "_", ".":
+		// Not sure if this import is used - err on the side of caution.
+		return true
+	}
+
+	walk(f, func(n interface{}) {
+		sel, ok := n.(*ast.SelectorExpr)
+		if ok && isTopName(sel.X, name) {
+			used = true
+		}
+	})
+
+	return
+}
+
+func expr(s string) ast.Expr {
+	x, err := parser.ParseExpr(s)
+	if err != nil {
+		panic("parsing " + s + ": " + err.Error())
+	}
+	// Remove position information to avoid spurious newlines.
+	killPos(reflect.ValueOf(x))
+	return x
+}
+
+var posType = reflect.TypeOf(token.Pos(0))
+
+func killPos(v reflect.Value) {
+	switch v.Kind() {
+	case reflect.Ptr, reflect.Interface:
+		if !v.IsNil() {
+			killPos(v.Elem())
+		}
+	case reflect.Slice:
+		n := v.Len()
+		for i := 0; i < n; i++ {
+			killPos(v.Index(i))
+		}
+	case reflect.Struct:
+		n := v.NumField()
+		for i := 0; i < n; i++ {
+			f := v.Field(i)
+			if f.Type() == posType {
+				f.SetInt(0)
+				continue
+			}
+			killPos(f)
+		}
+	}
+}
+
+// A Rename describes a single renaming.
+type rename struct {
+	OldImport string // only apply rename if this import is present
+	NewImport string // add this import during rewrite
+	Old       string // old name: p.T or *p.T
+	New       string // new name: p.T or *p.T
+}
+
+func renameFix(tab []rename) func(*ast.File) bool {
+	return func(f *ast.File) bool {
+		return renameFixTab(f, tab)
+	}
+}
+
+func parseName(s string) (ptr bool, pkg, nam string) {
+	i := strings.Index(s, ".")
+	if i < 0 {
+		panic("parseName: invalid name " + s)
+	}
+	if strings.HasPrefix(s, "*") {
+		ptr = true
+		s = s[1:]
+		i--
+	}
+	pkg = s[:i]
+	nam = s[i+1:]
+	return
+}
+
+func renameFixTab(f *ast.File, tab []rename) bool {
+	fixed := false
+	added := map[string]bool{}
+	check := map[string]bool{}
+	for _, t := range tab {
+		if !imports(f, t.OldImport) {
+			continue
+		}
+		optr, opkg, onam := parseName(t.Old)
+		walk(f, func(n interface{}) {
+			np, ok := n.(*ast.Expr)
+			if !ok {
+				return
+			}
+			x := *np
+			if optr {
+				p, ok := x.(*ast.StarExpr)
+				if !ok {
+					return
+				}
+				x = p.X
+			}
+			if !isPkgDot(x, opkg, onam) {
+				return
+			}
+			if t.NewImport != "" && !added[t.NewImport] {
+				addImport(f, t.NewImport)
+				added[t.NewImport] = true
+			}
+			*np = expr(t.New)
+			check[t.OldImport] = true
+			fixed = true
+		})
+	}
+
+	for ipath := range check {
+		if !usesImport(f, ipath) {
+			deleteImport(f, ipath)
+		}
+	}
+	return fixed
+}