diff --git a/refactor/lexical/lexical.go b/refactor/lexical/lexical.go
new file mode 100644
index 00000000..485aab5f
--- /dev/null
+++ b/refactor/lexical/lexical.go
@@ -0,0 +1,756 @@
+// Package lexical computes the structure of the lexical environment,
+// including the definition of and references to all universal,
+// package-level, file-level and function-local entities.  It does not
+// record qualified identifiers, labels, struct fields, or methods.
+//
+// It is intended for renaming and refactoring tools, which need a more
+// precise understanding of identifier resolution than is available from
+// the output of the type-checker alone.
+//
+// THIS INTERFACE IS EXPERIMENTAL AND MAY CHANGE OR BE REMOVED IN FUTURE.
+//
+package lexical
+
+// OVERVIEW
+//
+// As we traverse the AST, we build a "spaghetti stack" of Blocks,
+// i.e. a tree with parent edges pointing to the root.  Each time we
+// visit an identifier that's a reference into the lexical environment,
+// we create and save an Environment, which captures the current mapping
+// state of the Block; these are saved for the client.
+//
+// We don't bother recording non-lexical references.
+
+// TODO(adonovan):
+// - make it robust against syntax errors.  Audit all type assertions, etc.
+// - better still, after the Go 1.4 thaw, move this into go/types.
+//   I don't think it need be a big change since the visitor is already there;
+//   we just need to records Environments.  lexical.Block is analogous
+//   to types.Scope.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"os"
+	"strconv"
+
+	"code.google.com/p/go.tools/go/types"
+)
+
+const trace = false
+
+var logf = func(format string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, format, args...)
+}
+
+// A Block is a level of the lexical environment, a tree of blocks.
+// It maps names to objects.
+//
+type Block struct {
+	kind   string   // one of universe package file func block if switch typeswitch case for range
+	syntax ast.Node // syntax declaring the block (nil for universe and package) [needed?]
+
+	parent   Environment
+	bindings []types.Object // bindings in lexical order
+	index    map[string]int // maps a name to the index of its binding, for fast lookup
+}
+
+// An Environment is a snapshot of a Block taken at a certain lexical
+// position. It may contain bindings for fewer names than the
+// (completed) block, or different bindings for names that are
+// re-defined later in the block.
+//
+// For example, the lexical Block for the function f below contains a
+// binding for the local var x, but the Environments captured by at the
+// two print(x) calls differ: the first contains this binding, the
+// second does not.  The first Environment contains a different binding
+// for x: the string var defined in the package block, an ancestor.
+//
+//	var x string
+// 	func f() {
+//		print(x)
+//		x := 1
+//		print(x)
+//	}
+//
+type Environment struct {
+	block     *Block
+	nbindings int // length of prefix of block.bindings that's visible
+}
+
+// Depth returns the depth of this block in the block tree.
+// The universal block has depth 1, a package block 2, a file block 3, etc.
+func (b *Block) Depth() int {
+	if b == nil {
+		return 0
+	}
+	return 1 + b.parent.block.Depth()
+}
+
+// env returns an Environment that is a snapshot of b's current state.
+func (b *Block) env() Environment {
+	return Environment{b, len(b.bindings)}
+}
+
+// Lookup returns the definition of name in the environment specified by
+// env, and the Block that defines it, which may be an ancestor.
+func (env Environment) Lookup(name string) (types.Object, *Block) {
+	if env.block == nil {
+		return nil, nil
+	}
+	return lookup(env.block, name, env.nbindings)
+}
+
+// nbindings specifies what prefix of b.bindings should be considered visible.
+func lookup(b *Block, name string, nbindings int) (types.Object, *Block) {
+	if b == nil {
+		return nil, nil
+	}
+	if i, ok := b.index[name]; ok && i < nbindings {
+		return b.bindings[i], b
+	}
+
+	parent := b.parent
+	if parent.block == nil {
+		return nil, nil
+	}
+	return lookup(parent.block, name, parent.nbindings)
+}
+
+// Lookup returns the definition of name in the environment specified by
+// b, and the Block that defines it, which may be an ancestor.
+func (b *Block) Lookup(name string) (types.Object, *Block) {
+	return b.env().Lookup(name)
+}
+
+// Block returns the block of which this environment is a partial view.
+func (env Environment) Block() *Block {
+	return env.block
+}
+
+func (env Environment) String() string {
+	return fmt.Sprintf("%s:%d", env.block, env.nbindings)
+}
+
+func (b *Block) String() string {
+	var s string
+	if b.parent.block != nil {
+		s = b.parent.block.String()
+		s += "."
+	}
+	return s + b.kind
+}
+
+var universe = &Block{kind: "universe", index: make(map[string]int)}
+
+func init() {
+	for i, name := range types.Universe.Names() {
+		obj := types.Universe.Lookup(name)
+		universe.bindings = append(universe.bindings, obj)
+		universe.index[name] = i
+	}
+}
+
+// -- resolver ---------------------------------------------------------
+
+// A Reference provides the lexical environment for a given reference to
+// an object in lexical scope.
+type Reference struct {
+	Id  *ast.Ident
+	Env Environment
+}
+
+// resolver holds the state of the identifier resolution visitation:
+// the package information, the result, and the current block.
+type resolver struct {
+	fset    *token.FileSet
+	imports map[string]*types.Package
+	pkg     *types.Package
+	info    *types.Info
+
+	// visitor state
+	block *Block
+
+	result *Info
+}
+
+func (r *resolver) setBlock(kind string, syntax ast.Node) *Block {
+	b := &Block{
+		kind:   kind,
+		syntax: syntax,
+		parent: r.block.env(),
+		index:  make(map[string]int),
+	}
+	if syntax != nil {
+		r.result.Blocks[syntax] = b
+	}
+	r.block = b
+	return b
+}
+
+func (r *resolver) use(id *ast.Ident, env Environment) {
+	if id.Name == "_" {
+		return // an error
+	}
+	obj, _ := env.Lookup(id.Name)
+	if obj == nil {
+		logf("%s: lookup of %s failed\n", r.fset.Position(id.Pos()), id.Name)
+	} else if want := r.info.Uses[id]; obj != want {
+		// sanity check against go/types resolver
+		logf("%s: internal error: lookup of %s yielded wrong object: got %v (%s), want %v\n",
+			r.fset.Position(id.Pos()), id.Name, types.ObjectString(r.pkg, obj),
+			r.fset.Position(obj.Pos()),
+			want)
+	}
+	if trace {
+		logf("use %s = %v in %s\n", id.Name, types.ObjectString(r.pkg, obj), env)
+	}
+
+	r.result.Refs[obj] = append(r.result.Refs[obj], Reference{id, env})
+}
+
+func (r *resolver) define(b *Block, id *ast.Ident) {
+	obj := r.info.Defs[id]
+	if obj == nil {
+		logf("%s: internal error: not a defining ident: %s\n",
+			r.fset.Position(id.Pos()), id.Name)
+		panic(id)
+	}
+	r.defineObject(b, id.Name, obj)
+
+	// Objects (other than PkgName) defined at file scope
+	// are also defined in the enclosing package scope.
+	if _, ok := b.syntax.(*ast.File); ok {
+		switch obj.(type) {
+		default:
+			r.defineObject(b.parent.block, id.Name, obj)
+		case nil, *types.PkgName:
+		}
+	}
+}
+
+// Used for implicit objects created by some ImportSpecs and CaseClauses.
+func (r *resolver) defineImplicit(b *Block, n ast.Node, name string) {
+	obj := r.info.Implicits[n]
+	if obj == nil {
+		logf("%s: internal error: not an implicit definition: %T\n",
+			r.fset.Position(n.Pos()), n)
+	}
+	r.defineObject(b, name, obj)
+}
+
+func (r *resolver) defineObject(b *Block, name string, obj types.Object) {
+	if obj.Name() == "_" {
+		return
+	}
+	i := len(b.bindings)
+	b.bindings = append(b.bindings, obj)
+	b.index[name] = i
+	if trace {
+		logf("def %s = %s in %s\n", name, types.ObjectString(r.pkg, obj), b)
+	}
+	r.result.Defs[obj] = b
+}
+
+func (r *resolver) function(recv *ast.FieldList, typ *ast.FuncType, body *ast.BlockStmt, syntax ast.Node) {
+	// Use all signature types in enclosing block.
+	r.expr(typ)
+	r.fieldList(recv, false)
+
+	savedBlock := r.block // save
+	r.setBlock("func", syntax)
+
+	// Define all parameters/results, and visit the body, within the func block.
+	r.fieldList(typ.Params, true)
+	r.fieldList(typ.Results, true)
+	r.fieldList(recv, true)
+	if body != nil {
+		r.stmtList(body.List)
+	}
+
+	r.block = savedBlock // restore
+}
+
+func (r *resolver) fieldList(list *ast.FieldList, def bool) {
+	if list != nil {
+		for _, f := range list.List {
+			if def {
+				for _, id := range f.Names {
+					r.define(r.block, id)
+				}
+			} else {
+				r.expr(f.Type)
+			}
+		}
+	}
+}
+
+func (r *resolver) exprList(list []ast.Expr) {
+	for _, x := range list {
+		r.expr(x)
+	}
+}
+
+func (r *resolver) expr(n ast.Expr) {
+	switch n := n.(type) {
+	case *ast.BadExpr:
+	case *ast.BasicLit:
+		// no-op
+
+	case *ast.Ident:
+		r.use(n, r.block.env())
+
+	case *ast.Ellipsis:
+		if n.Elt != nil {
+			r.expr(n.Elt)
+		}
+
+	case *ast.FuncLit:
+		r.function(nil, n.Type, n.Body, n)
+
+	case *ast.CompositeLit:
+		if n.Type != nil {
+			r.expr(n.Type)
+		}
+		tv := r.info.Types[n]
+		if _, ok := deref(tv.Type).Underlying().(*types.Struct); ok {
+			for _, elt := range n.Elts {
+				if kv, ok := elt.(*ast.KeyValueExpr); ok {
+					r.expr(kv.Value)
+
+					// Also uses field kv.Key (non-lexical)
+					//  id := kv.Key.(*ast.Ident)
+					//  obj := r.info.Uses[id]
+					//  logf("use %s = %v (field)\n",
+					// 	id.Name, types.ObjectString(r.pkg, obj))
+					// TODO make a fake FieldVal selection?
+				} else {
+					r.expr(elt)
+				}
+			}
+		} else {
+			r.exprList(n.Elts)
+		}
+
+	case *ast.ParenExpr:
+		r.expr(n.X)
+
+	case *ast.SelectorExpr:
+		r.expr(n.X)
+
+		// Non-lexical reference to field/method, or qualified identifier.
+		// if sel, ok := r.info.Selections[n]; ok { // selection
+		// 	switch sel.Kind() {
+		// 	case types.FieldVal:
+		// 		logf("use %s = %v (field)\n",
+		// 			n.Sel.Name, types.ObjectString(r.pkg, sel.Obj()))
+		// 	case types.MethodExpr, types.MethodVal:
+		// 		logf("use %s = %v (method)\n",
+		// 			n.Sel.Name, types.ObjectString(r.pkg, sel.Obj()))
+		// 	}
+		// } else { // qualified identifier
+		// 	obj := r.info.Uses[n.Sel]
+		// 	logf("use %s = %v (qualified)\n", n.Sel.Name, obj)
+		// }
+
+	case *ast.IndexExpr:
+		r.expr(n.X)
+		r.expr(n.Index)
+
+	case *ast.SliceExpr:
+		r.expr(n.X)
+		if n.Low != nil {
+			r.expr(n.Low)
+		}
+		if n.High != nil {
+			r.expr(n.High)
+		}
+		if n.Max != nil {
+			r.expr(n.Max)
+		}
+
+	case *ast.TypeAssertExpr:
+		r.expr(n.X)
+		if n.Type != nil {
+			r.expr(n.Type)
+		}
+
+	case *ast.CallExpr:
+		r.expr(n.Fun)
+		r.exprList(n.Args)
+
+	case *ast.StarExpr:
+		r.expr(n.X)
+
+	case *ast.UnaryExpr:
+		r.expr(n.X)
+
+	case *ast.BinaryExpr:
+		r.expr(n.X)
+		r.expr(n.Y)
+
+	case *ast.KeyValueExpr:
+		r.expr(n.Key)
+		r.expr(n.Value)
+
+	case *ast.ArrayType:
+		if n.Len != nil {
+			r.expr(n.Len)
+		}
+		r.expr(n.Elt)
+
+	case *ast.StructType:
+		// Use all the type names, but don't define any fields.
+		r.fieldList(n.Fields, false)
+
+	case *ast.FuncType:
+		// Use all the type names, but don't define any vars.
+		r.fieldList(n.Params, false)
+		r.fieldList(n.Results, false)
+
+	case *ast.InterfaceType:
+		// Use all the type names, but don't define any methods.
+		r.fieldList(n.Methods, false)
+
+	case *ast.MapType:
+		r.expr(n.Key)
+		r.expr(n.Value)
+
+	case *ast.ChanType:
+		r.expr(n.Value)
+
+	default:
+		panic(n)
+	}
+}
+
+func (r *resolver) stmtList(list []ast.Stmt) {
+	for _, s := range list {
+		r.stmt(s)
+	}
+}
+
+func (r *resolver) stmt(n ast.Stmt) {
+	switch n := n.(type) {
+	case *ast.BadStmt:
+	case *ast.EmptyStmt:
+		// nothing to do
+
+	case *ast.DeclStmt:
+		decl := n.Decl.(*ast.GenDecl)
+		for _, spec := range decl.Specs {
+			switch spec := spec.(type) {
+			case *ast.ValueSpec: // const or var
+				if spec.Type != nil {
+					r.expr(spec.Type)
+				}
+				r.exprList(spec.Values)
+				for _, name := range spec.Names {
+					r.define(r.block, name)
+				}
+
+			case *ast.TypeSpec:
+				r.define(r.block, spec.Name)
+				r.expr(spec.Type)
+			}
+		}
+
+	case *ast.LabeledStmt:
+		// Also defines label n.Label (non-lexical)
+		r.stmt(n.Stmt)
+
+	case *ast.ExprStmt:
+		r.expr(n.X)
+
+	case *ast.SendStmt:
+		r.expr(n.Chan)
+		r.expr(n.Value)
+
+	case *ast.IncDecStmt:
+		r.expr(n.X)
+
+	case *ast.AssignStmt:
+		if n.Tok == token.DEFINE {
+			r.exprList(n.Rhs)
+			for _, lhs := range n.Lhs {
+				id := lhs.(*ast.Ident)
+				if _, ok := r.info.Defs[id]; ok {
+					r.define(r.block, id)
+				} else {
+					r.use(id, r.block.env())
+				}
+			}
+		} else { // ASSIGN
+			r.exprList(n.Lhs)
+			r.exprList(n.Rhs)
+		}
+
+	case *ast.GoStmt:
+		r.expr(n.Call)
+
+	case *ast.DeferStmt:
+		r.expr(n.Call)
+
+	case *ast.ReturnStmt:
+		r.exprList(n.Results)
+
+	case *ast.BranchStmt:
+		if n.Label != nil {
+			// Also uses label n.Label (non-lexical)
+		}
+
+	case *ast.SelectStmt:
+		r.stmtList(n.Body.List)
+
+	case *ast.BlockStmt: // (explicit blocks only)
+		savedBlock := r.block // save
+		r.setBlock("block", n)
+		r.stmtList(n.List)
+		r.block = savedBlock // restore
+
+	case *ast.IfStmt:
+		savedBlock := r.block // save
+		r.setBlock("if", n)
+		if n.Init != nil {
+			r.stmt(n.Init)
+		}
+		r.expr(n.Cond)
+		r.stmt(n.Body) // new block
+		if n.Else != nil {
+			r.stmt(n.Else)
+		}
+		r.block = savedBlock // restore
+
+	case *ast.CaseClause:
+		savedBlock := r.block // save
+		r.setBlock("case", n)
+		if obj, ok := r.info.Implicits[n]; ok {
+			// e.g.
+			//   switch y := x.(type) {
+			//   case T: // we declare an implicit 'var y T' in this block
+			//   }
+			r.defineImplicit(r.block, n, obj.Name())
+		}
+		r.exprList(n.List)
+		r.stmtList(n.Body)
+		r.block = savedBlock // restore
+
+	case *ast.SwitchStmt:
+		savedBlock := r.block // save
+		r.setBlock("switch", n)
+		if n.Init != nil {
+			r.stmt(n.Init)
+		}
+		if n.Tag != nil {
+			r.expr(n.Tag)
+		}
+		r.stmtList(n.Body.List)
+		r.block = savedBlock // restore
+
+	case *ast.TypeSwitchStmt:
+		savedBlock := r.block // save
+		r.setBlock("typeswitch", n)
+		if n.Init != nil {
+			r.stmt(n.Init)
+		}
+		if assign, ok := n.Assign.(*ast.AssignStmt); ok { // y := x.(type)
+			r.expr(assign.Rhs[0]) // skip y: not a defining ident
+		} else {
+			r.stmt(n.Assign)
+		}
+		r.stmtList(n.Body.List)
+		r.block = savedBlock // restore
+
+	case *ast.CommClause:
+		savedBlock := r.block // save
+		r.setBlock("case", n)
+		if n.Comm != nil {
+			r.stmt(n.Comm)
+		}
+		r.stmtList(n.Body)
+		r.block = savedBlock // restore
+
+	case *ast.ForStmt:
+		savedBlock := r.block // save
+		r.setBlock("for", n)
+		if n.Init != nil {
+			r.stmt(n.Init)
+		}
+		if n.Cond != nil {
+			r.expr(n.Cond)
+		}
+		if n.Post != nil {
+			r.stmt(n.Post)
+		}
+		r.stmt(n.Body)
+		r.block = savedBlock // restore
+
+	case *ast.RangeStmt:
+		r.expr(n.X)
+		savedBlock := r.block // save
+		r.setBlock("range", n)
+		if n.Tok == token.DEFINE {
+			if n.Key != nil {
+				r.define(r.block, n.Key.(*ast.Ident))
+			}
+			if n.Value != nil {
+				r.define(r.block, n.Value.(*ast.Ident))
+			}
+		} else {
+			if n.Key != nil {
+				r.expr(n.Key)
+			}
+			if n.Value != nil {
+				r.expr(n.Value)
+			}
+		}
+		r.stmt(n.Body)
+		r.block = savedBlock // restore
+
+	default:
+		panic(n)
+	}
+}
+
+func (r *resolver) doImport(s *ast.ImportSpec, fileBlock *Block) {
+	path, _ := strconv.Unquote(s.Path.Value)
+	pkg := r.imports[path]
+	if s.Name == nil { // normal
+		r.defineImplicit(fileBlock, s, pkg.Name())
+	} else if s.Name.Name == "." { // dot import
+		for _, name := range pkg.Scope().Names() {
+			if ast.IsExported(name) {
+				obj := pkg.Scope().Lookup(name)
+				r.defineObject(fileBlock, name, obj)
+			}
+		}
+	} else { // renaming import
+		r.define(fileBlock, s.Name)
+	}
+}
+
+func (r *resolver) doPackage(pkg *types.Package, files []*ast.File) {
+	r.block = universe
+	r.result.Blocks[nil] = universe
+
+	r.result.PackageBlock = r.setBlock("package", nil)
+
+	var fileBlocks []*Block
+
+	// 1. Insert all package-level objects into file and package blocks.
+	//    (PkgName objects are only inserted into file blocks.)
+	for _, f := range files {
+		r.block = r.result.PackageBlock
+		fileBlock := r.setBlock("file", f) // package is not yet visible to file
+		fileBlocks = append(fileBlocks, fileBlock)
+
+		for _, d := range f.Decls {
+			switch d := d.(type) {
+			case *ast.GenDecl:
+				for _, s := range d.Specs {
+					switch s := s.(type) {
+					case *ast.ImportSpec:
+						r.doImport(s, fileBlock)
+
+					case *ast.ValueSpec: // const or var
+						for _, name := range s.Names {
+							r.define(r.result.PackageBlock, name)
+						}
+
+					case *ast.TypeSpec:
+						r.define(r.result.PackageBlock, s.Name)
+					}
+				}
+
+			case *ast.FuncDecl:
+				if d.Recv == nil { // function
+					if d.Name.Name != "init" {
+						r.define(r.result.PackageBlock, d.Name)
+					}
+				}
+			}
+		}
+	}
+
+	// 2. Now resolve bodies of GenDecls and FuncDecls.
+	for i, f := range files {
+		fileBlock := fileBlocks[i]
+		fileBlock.parent = r.result.PackageBlock.env() // make entire package visible to this file
+
+		for _, d := range f.Decls {
+			r.block = fileBlock
+
+			switch d := d.(type) {
+			case *ast.GenDecl:
+				for _, s := range d.Specs {
+					switch s := s.(type) {
+					case *ast.ValueSpec: // const or var
+						if s.Type != nil {
+							r.expr(s.Type)
+						}
+						r.exprList(s.Values)
+
+					case *ast.TypeSpec:
+						r.expr(s.Type)
+					}
+				}
+
+			case *ast.FuncDecl:
+				r.function(d.Recv, d.Type, d.Body, d)
+			}
+		}
+	}
+
+	r.block = nil
+}
+
+// An Info contains the lexical reference structure of a package.
+type Info struct {
+	Defs         map[types.Object]*Block      // maps each object to its defining lexical block
+	Refs         map[types.Object][]Reference // maps each object to the set of references to it
+	Blocks       map[ast.Node]*Block          // maps declaring syntax to block; nil => universe
+	PackageBlock *Block                       // the package-level lexical block
+}
+
+// Structure computes the structure of the lexical environment of the
+// package specified by (pkg, info, files).
+//
+// The info.{Types,Defs,Uses,Implicits} maps must have been populated
+// by the type-checker
+//
+// fset is used for logging.
+//
+func Structure(fset *token.FileSet, pkg *types.Package, info *types.Info, files []*ast.File) *Info {
+	r := resolver{
+		fset:    fset,
+		imports: make(map[string]*types.Package),
+		result: &Info{
+			Defs:   make(map[types.Object]*Block),
+			Refs:   make(map[types.Object][]Reference),
+			Blocks: make(map[ast.Node]*Block),
+		},
+		pkg:  pkg,
+		info: info,
+	}
+
+	// Build import map for just this package.
+	r.imports["unsafe"] = types.Unsafe
+	for _, imp := range pkg.Imports() {
+		r.imports[imp.Path()] = imp
+	}
+
+	r.doPackage(pkg, files)
+
+	return r.result
+}
+
+// -- Plundered from code.google.com/p/go.tools/go/ssa -----------------
+
+// deref returns a pointer's element type; otherwise it returns typ.
+func deref(typ types.Type) types.Type {
+	if p, ok := typ.Underlying().(*types.Pointer); ok {
+		return p.Elem()
+	}
+	return typ
+}
diff --git a/refactor/lexical/lexical_test.go b/refactor/lexical/lexical_test.go
new file mode 100644
index 00000000..56feb1d1
--- /dev/null
+++ b/refactor/lexical/lexical_test.go
@@ -0,0 +1,55 @@
+// 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.
+
+package lexical
+
+import (
+	"go/build"
+	"testing"
+
+	"code.google.com/p/go.tools/go/buildutil"
+	"code.google.com/p/go.tools/go/loader"
+)
+
+func TestStdlib(t *testing.T) {
+	defer func(saved func(format string, args ...interface{})) {
+		logf = saved
+	}(logf)
+	logf = t.Errorf
+
+	ctxt := build.Default // copy
+
+	// Enumerate $GOROOT packages.
+	saved := ctxt.GOPATH
+	ctxt.GOPATH = "" // disable GOPATH during AllPackages
+	pkgs := buildutil.AllPackages(&ctxt)
+	ctxt.GOPATH = saved
+
+	// Throw in a number of go.tools packages too.
+	pkgs = append(pkgs,
+		"code.google.com/p/go.tools/cmd/godoc",
+		"code.google.com/p/go.tools/refactor/lexical")
+
+	// Load, parse and type-check the program.
+	conf := loader.Config{
+		Build:         &ctxt,
+		SourceImports: true,
+	}
+	for _, path := range pkgs {
+		if err := conf.ImportWithTests(path); err != nil {
+			t.Error(err)
+		}
+	}
+
+	iprog, err := conf.Load()
+	if err != nil {
+		t.Fatalf("Load failed: %v", err)
+	}
+
+	// This test ensures that Structure doesn't panic and that
+	// its internal sanity-checks against go/types don't fail.
+	for pkg, info := range iprog.AllPackages {
+		_ = Structure(iprog.Fset, pkg, &info.Info, info.Files)
+	}
+}