[release-branch.r58] reflect: disallow Interface method on Value obtained via unexported name

Also remove exp/datafmt that depends on the broken reflect behavior.

««« CL 5267049 / eeca0d4a91a3
reflect: disallow Interface method on Value obtained via unexported name

Had been allowing it for use by fmt, but it is too hard to lock down.
Fix other packages not to depend on it.

R=r, r
CC=golang-dev
https://golang.org/cl/5266054
»»»

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5297042
diff --git a/src/pkg/Makefile b/src/pkg/Makefile
index 2d6b3d0..5aa5856 100644
--- a/src/pkg/Makefile
+++ b/src/pkg/Makefile
@@ -76,7 +76,6 @@
 	encoding/hex\
 	encoding/pem\
 	exec\
-	exp/datafmt\
 	exp/eval\
 	exp/gui\
 	exp/gui/x11\
diff --git a/src/pkg/exp/datafmt/Makefile b/src/pkg/exp/datafmt/Makefile
deleted file mode 100644
index aa94538..0000000
--- a/src/pkg/exp/datafmt/Makefile
+++ /dev/null
@@ -1,12 +0,0 @@
-# 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.
-
-include ../../../Make.inc
-
-TARG=exp/datafmt
-GOFILES=\
-	datafmt.go\
-	parser.go\
-
-include ../../../Make.pkg
diff --git a/src/pkg/exp/datafmt/datafmt.go b/src/pkg/exp/datafmt/datafmt.go
deleted file mode 100644
index 10e4b54..0000000
--- a/src/pkg/exp/datafmt/datafmt.go
+++ /dev/null
@@ -1,731 +0,0 @@
-// 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.
-
-/*	Package datafmt implements syntax-directed, type-driven formatting
-	of arbitrary data structures. Formatting a data structure consists of
-	two phases: first, a parser reads a format specification and builds a
-	"compiled" format. Then, the format can be applied repeatedly to
-	arbitrary values. Applying a format to a value evaluates to a []byte
-	containing the formatted value bytes, or nil.
-
-	A format specification is a set of package declarations and format rules:
-
-		Format      = [ Entry { ";" Entry } [ ";" ] ] .
-		Entry       = PackageDecl | FormatRule .
-
-	(The syntax of a format specification is presented in the same EBNF
-	notation as used in the Go language specification. The syntax of white
-	space, comments, identifiers, and string literals is the same as in Go.)
-
-	A package declaration binds a package name (such as 'ast') to a
-	package import path (such as '"go/ast"'). Each package used (in
-	a type name, see below) must be declared once before use.
-
-		PackageDecl = PackageName ImportPath .
-		PackageName = identifier .
-		ImportPath  = string .
-
-	A format rule binds a rule name to a format expression. A rule name
-	may be a type name or one of the special names 'default' or '/'.
-	A type name may be the name of a predeclared type (for example, 'int',
-	'float32', etc.), the package-qualified name of a user-defined type
-	(for example, 'ast.MapType'), or an identifier indicating the structure
-	of unnamed composite types ('array', 'chan', 'func', 'interface', 'map',
-	or 'ptr'). Each rule must have a unique name; rules can be declared in
-	any order.
-
-		FormatRule  = RuleName "=" Expression .
-		RuleName    = TypeName | "default" | "/" .
-		TypeName    = [ PackageName "." ] identifier .
-
-	To format a value, the value's type name is used to select the format rule
-	(there is an override mechanism, see below). The format expression of the
-	selected rule specifies how the value is formatted. Each format expression,
-	when applied to a value, evaluates to a byte sequence or nil.
-
-	In its most general form, a format expression is a list of alternatives,
-	each of which is a sequence of operands:
-
-		Expression  = [ Sequence ] { "|" [ Sequence ] } .
-		Sequence    = Operand { Operand } .
-
-	The formatted result produced by an expression is the result of the first
-	alternative sequence that evaluates to a non-nil result; if there is no
-	such alternative, the expression evaluates to nil. The result produced by
-	an operand sequence is the concatenation of the results of its operands.
-	If any operand in the sequence evaluates to nil, the entire sequence
-	evaluates to nil.
-
-	There are five kinds of operands:
-
-		Operand     = Literal | Field | Group | Option | Repetition .
-
-	Literals evaluate to themselves, with two substitutions. First,
-	%-formats expand in the manner of fmt.Printf, with the current value
-	passed as the parameter. Second, the current indentation (see below)
-	is inserted after every newline or form feed character.
-
-		Literal     = string .
-
-	This table shows string literals applied to the value 42 and the
-	corresponding formatted result:
-
-		"foo"       foo
-		"%x"        2a
-		"x = %d"    x = 42
-		"%#x = %d"  0x2a = 42
-
-	A field operand is a field name optionally followed by an alternate
-	rule name. The field name may be an identifier or one of the special
-	names @ or *.
-
-		Field       = FieldName [ ":" RuleName ] .
-		FieldName   = identifier | "@" | "*" .
-
-	If the field name is an identifier, the current value must be a struct,
-	and there must be a field with that name in the struct. The same lookup
-	rules apply as in the Go language (for instance, the name of an anonymous
-	field is the unqualified type name). The field name denotes the field
-	value in the struct. If the field is not found, formatting is aborted
-	and an error message is returned. (TODO consider changing the semantics
-	such that if a field is not found, it evaluates to nil).
-
-	The special name '@' denotes the current value.
-
-	The meaning of the special name '*' depends on the type of the current
-	value:
-
-		array, slice types   array, slice element (inside {} only, see below)
-		interfaces           value stored in interface
-		pointers             value pointed to by pointer
-
-	(Implementation restriction: channel, function and map types are not
-	supported due to missing reflection support).
-
-	Fields are evaluated as follows: If the field value is nil, or an array
-	or slice element does not exist, the result is nil (see below for details
-	on array/slice elements). If the value is not nil the field value is
-	formatted (recursively) using the rule corresponding to its type name,
-	or the alternate rule name, if given.
-
-	The following example shows a complete format specification for a
-	struct 'myPackage.Point'. Assume the package
-
-		package myPackage  // in directory myDir/myPackage
-		type Point struct {
-			name string;
-			x, y int;
-		}
-
-	Applying the format specification
-
-		myPackage "myDir/myPackage";
-		int = "%d";
-		hexInt = "0x%x";
-		string = "---%s---";
-		myPackage.Point = name "{" x ", " y:hexInt "}";
-
-	to the value myPackage.Point{"foo", 3, 15} results in
-
-		---foo---{3, 0xf}
-
-	Finally, an operand may be a grouped, optional, or repeated expression.
-	A grouped expression ("group") groups a more complex expression (body)
-	so that it can be used in place of a single operand:
-
-		Group       = "(" [ Indentation ">>" ] Body ")" .
-		Indentation = Expression .
-		Body        = Expression .
-
-	A group body may be prefixed by an indentation expression followed by '>>'.
-	The indentation expression is applied to the current value like any other
-	expression and the result, if not nil, is appended to the current indentation
-	during the evaluation of the body (see also formatting state, below).
-
-	An optional expression ("option") is enclosed in '[]' brackets.
-
-		Option      = "[" Body "]" .
-
-	An option evaluates to its body, except that if the body evaluates to nil,
-	the option expression evaluates to an empty []byte. Thus an option's purpose
-	is to protect the expression containing the option from a nil operand.
-
-	A repeated expression ("repetition") is enclosed in '{}' braces.
-
-		Repetition  = "{" Body [ "/" Separator ] "}" .
-		Separator   = Expression .
-
-	A repeated expression is evaluated as follows: The body is evaluated
-	repeatedly and its results are concatenated until the body evaluates
-	to nil. The result of the repetition is the (possibly empty) concatenation,
-	but it is never nil. An implicit index is supplied for the evaluation of
-	the body: that index is used to address elements of arrays or slices. If
-	the corresponding elements do not exist, the field denoting the element
-	evaluates to nil (which in turn may terminate the repetition).
-
-	The body of a repetition may be followed by a '/' and a "separator"
-	expression. If the separator is present, it is invoked between repetitions
-	of the body.
-
-	The following example shows a complete format specification for formatting
-	a slice of unnamed type. Applying the specification
-
-		int = "%b";
-		array = { * / ", " };  // array is the type name for an unnamed slice
-
-	to the value '[]int{2, 3, 5, 7}' results in
-
-		10, 11, 101, 111
-
-	Default rule: If a format rule named 'default' is present, it is used for
-	formatting a value if no other rule was found. A common default rule is
-
-		default = "%v"
-
-	to provide default formatting for basic types without having to specify
-	a specific rule for each basic type.
-
-	Global separator rule: If a format rule named '/' is present, it is
-	invoked with the current value between literals. If the separator
-	expression evaluates to nil, it is ignored.
-
-	For instance, a global separator rule may be used to punctuate a sequence
-	of values with commas. The rules:
-
-		default = "%v";
-		/ = ", ";
-
-	will format an argument list by printing each one in its default format,
-	separated by a comma and a space.
-*/
-package datafmt
-
-import (
-	"bytes"
-	"fmt"
-	"go/token"
-	"io"
-	"os"
-	"reflect"
-	"runtime"
-)
-
-
-// ----------------------------------------------------------------------------
-// Format representation
-
-// Custom formatters implement the Formatter function type.
-// A formatter is invoked with the current formatting state, the
-// value to format, and the rule name under which the formatter
-// was installed (the same formatter function may be installed
-// under different names). The formatter may access the current state
-// to guide formatting and use State.Write to append to the state's
-// output.
-//
-// A formatter must return a boolean value indicating if it evaluated
-// to a non-nil value (true), or a nil value (false).
-//
-type Formatter func(state *State, value interface{}, ruleName string) bool
-
-
-// A FormatterMap is a set of custom formatters.
-// It maps a rule name to a formatter function.
-//
-type FormatterMap map[string]Formatter
-
-
-// A parsed format expression is built from the following nodes.
-//
-type (
-	expr interface{}
-
-	alternatives []expr // x | y | z
-
-	sequence []expr // x y z
-
-	literal [][]byte // a list of string segments, possibly starting with '%'
-
-	field struct {
-		fieldName string // including "@", "*"
-		ruleName  string // "" if no rule name specified
-	}
-
-	group struct {
-		indent, body expr // (indent >> body)
-	}
-
-	option struct {
-		body expr // [body]
-	}
-
-	repetition struct {
-		body, separator expr // {body / separator}
-	}
-
-	custom struct {
-		ruleName string
-		fun      Formatter
-	}
-)
-
-
-// A Format is the result of parsing a format specification.
-// The format may be applied repeatedly to format values.
-//
-type Format map[string]expr
-
-
-// ----------------------------------------------------------------------------
-// Formatting
-
-// An application-specific environment may be provided to Format.Apply;
-// the environment is available inside custom formatters via State.Env().
-// Environments must implement copying; the Copy method must return an
-// complete copy of the receiver. This is necessary so that the formatter
-// can save and restore an environment (in case of an absent expression).
-//
-// If the Environment doesn't change during formatting (this is under
-// control of the custom formatters), the Copy function can simply return
-// the receiver, and thus can be very light-weight.
-//
-type Environment interface {
-	Copy() Environment
-}
-
-
-// State represents the current formatting state.
-// It is provided as argument to custom formatters.
-//
-type State struct {
-	fmt       Format         // format in use
-	env       Environment    // user-supplied environment
-	errors    chan os.Error  // not chan *Error (errors <- nil would be wrong!)
-	hasOutput bool           // true after the first literal has been written
-	indent    bytes.Buffer   // current indentation
-	output    bytes.Buffer   // format output
-	linePos   token.Position // position of line beginning (Column == 0)
-	default_  expr           // possibly nil
-	separator expr           // possibly nil
-}
-
-
-func newState(fmt Format, env Environment, errors chan os.Error) *State {
-	s := new(State)
-	s.fmt = fmt
-	s.env = env
-	s.errors = errors
-	s.linePos = token.Position{Line: 1}
-
-	// if we have a default rule, cache it's expression for fast access
-	if x, found := fmt["default"]; found {
-		s.default_ = x
-	}
-
-	// if we have a global separator rule, cache it's expression for fast access
-	if x, found := fmt["/"]; found {
-		s.separator = x
-	}
-
-	return s
-}
-
-
-// Env returns the environment passed to Format.Apply.
-func (s *State) Env() interface{} { return s.env }
-
-
-// LinePos returns the position of the current line beginning
-// in the state's output buffer. Line numbers start at 1.
-//
-func (s *State) LinePos() token.Position { return s.linePos }
-
-
-// Pos returns the position of the next byte to be written to the
-// output buffer. Line numbers start at 1.
-//
-func (s *State) Pos() token.Position {
-	offs := s.output.Len()
-	return token.Position{Line: s.linePos.Line, Column: offs - s.linePos.Offset, Offset: offs}
-}
-
-
-// Write writes data to the output buffer, inserting the indentation
-// string after each newline or form feed character. It cannot return an error.
-//
-func (s *State) Write(data []byte) (int, os.Error) {
-	n := 0
-	i0 := 0
-	for i, ch := range data {
-		if ch == '\n' || ch == '\f' {
-			// write text segment and indentation
-			n1, _ := s.output.Write(data[i0 : i+1])
-			n2, _ := s.output.Write(s.indent.Bytes())
-			n += n1 + n2
-			i0 = i + 1
-			s.linePos.Offset = s.output.Len()
-			s.linePos.Line++
-		}
-	}
-	n3, _ := s.output.Write(data[i0:])
-	return n + n3, nil
-}
-
-
-type checkpoint struct {
-	env       Environment
-	hasOutput bool
-	outputLen int
-	linePos   token.Position
-}
-
-
-func (s *State) save() checkpoint {
-	saved := checkpoint{nil, s.hasOutput, s.output.Len(), s.linePos}
-	if s.env != nil {
-		saved.env = s.env.Copy()
-	}
-	return saved
-}
-
-
-func (s *State) restore(m checkpoint) {
-	s.env = m.env
-	s.output.Truncate(m.outputLen)
-}
-
-
-func (s *State) error(msg string) {
-	s.errors <- os.NewError(msg)
-	runtime.Goexit()
-}
-
-
-// TODO At the moment, unnamed types are simply mapped to the default
-//      names below. For instance, all unnamed arrays are mapped to
-//      'array' which is not really sufficient. Eventually one may want
-//      to be able to specify rules for say an unnamed slice of T.
-//
-
-func typename(typ reflect.Type) string {
-	switch typ.Kind() {
-	case reflect.Array:
-		return "array"
-	case reflect.Slice:
-		return "array"
-	case reflect.Chan:
-		return "chan"
-	case reflect.Func:
-		return "func"
-	case reflect.Interface:
-		return "interface"
-	case reflect.Map:
-		return "map"
-	case reflect.Ptr:
-		return "ptr"
-	}
-	return typ.String()
-}
-
-func (s *State) getFormat(name string) expr {
-	if fexpr, found := s.fmt[name]; found {
-		return fexpr
-	}
-
-	if s.default_ != nil {
-		return s.default_
-	}
-
-	s.error(fmt.Sprintf("no format rule for type: '%s'", name))
-	return nil
-}
-
-
-// eval applies a format expression fexpr to a value. If the expression
-// evaluates internally to a non-nil []byte, that slice is appended to
-// the state's output buffer and eval returns true. Otherwise, eval
-// returns false and the state remains unchanged.
-//
-func (s *State) eval(fexpr expr, value reflect.Value, index int) bool {
-	// an empty format expression always evaluates
-	// to a non-nil (but empty) []byte
-	if fexpr == nil {
-		return true
-	}
-
-	switch t := fexpr.(type) {
-	case alternatives:
-		// append the result of the first alternative that evaluates to
-		// a non-nil []byte to the state's output
-		mark := s.save()
-		for _, x := range t {
-			if s.eval(x, value, index) {
-				return true
-			}
-			s.restore(mark)
-		}
-		return false
-
-	case sequence:
-		// append the result of all operands to the state's output
-		// unless a nil result is encountered
-		mark := s.save()
-		for _, x := range t {
-			if !s.eval(x, value, index) {
-				s.restore(mark)
-				return false
-			}
-		}
-		return true
-
-	case literal:
-		// write separator, if any
-		if s.hasOutput {
-			// not the first literal
-			if s.separator != nil {
-				sep := s.separator // save current separator
-				s.separator = nil  // and disable it (avoid recursion)
-				mark := s.save()
-				if !s.eval(sep, value, index) {
-					s.restore(mark)
-				}
-				s.separator = sep // enable it again
-			}
-		}
-		s.hasOutput = true
-		// write literal segments
-		for _, lit := range t {
-			if len(lit) > 1 && lit[0] == '%' {
-				// segment contains a %-format at the beginning
-				if lit[1] == '%' {
-					// "%%" is printed as a single "%"
-					s.Write(lit[1:])
-				} else {
-					// use s instead of s.output to get indentation right
-					fmt.Fprintf(s, string(lit), value.Interface())
-				}
-			} else {
-				// segment contains no %-formats
-				s.Write(lit)
-			}
-		}
-		return true // a literal never evaluates to nil
-
-	case *field:
-		// determine field value
-		switch t.fieldName {
-		case "@":
-			// field value is current value
-
-		case "*":
-			// indirection: operation is type-specific
-			switch v := value; v.Kind() {
-			case reflect.Array:
-				if v.Len() <= index {
-					return false
-				}
-				value = v.Index(index)
-
-			case reflect.Slice:
-				if v.IsNil() || v.Len() <= index {
-					return false
-				}
-				value = v.Index(index)
-
-			case reflect.Map:
-				s.error("reflection support for maps incomplete")
-
-			case reflect.Ptr:
-				if v.IsNil() {
-					return false
-				}
-				value = v.Elem()
-
-			case reflect.Interface:
-				if v.IsNil() {
-					return false
-				}
-				value = v.Elem()
-
-			case reflect.Chan:
-				s.error("reflection support for chans incomplete")
-
-			case reflect.Func:
-				s.error("reflection support for funcs incomplete")
-
-			default:
-				s.error(fmt.Sprintf("error: * does not apply to `%s`", value.Type()))
-			}
-
-		default:
-			// value is value of named field
-			var field reflect.Value
-			if sval := value; sval.Kind() == reflect.Struct {
-				field = sval.FieldByName(t.fieldName)
-				if !field.IsValid() {
-					// TODO consider just returning false in this case
-					s.error(fmt.Sprintf("error: no field `%s` in `%s`", t.fieldName, value.Type()))
-				}
-			}
-			value = field
-		}
-
-		// determine rule
-		ruleName := t.ruleName
-		if ruleName == "" {
-			// no alternate rule name, value type determines rule
-			ruleName = typename(value.Type())
-		}
-		fexpr = s.getFormat(ruleName)
-
-		mark := s.save()
-		if !s.eval(fexpr, value, index) {
-			s.restore(mark)
-			return false
-		}
-		return true
-
-	case *group:
-		// remember current indentation
-		indentLen := s.indent.Len()
-
-		// update current indentation
-		mark := s.save()
-		s.eval(t.indent, value, index)
-		// if the indentation evaluates to nil, the state's output buffer
-		// didn't change - either way it's ok to append the difference to
-		// the current indentation
-		s.indent.Write(s.output.Bytes()[mark.outputLen:s.output.Len()])
-		s.restore(mark)
-
-		// format group body
-		mark = s.save()
-		b := true
-		if !s.eval(t.body, value, index) {
-			s.restore(mark)
-			b = false
-		}
-
-		// reset indentation
-		s.indent.Truncate(indentLen)
-		return b
-
-	case *option:
-		// evaluate the body and append the result to the state's output
-		// buffer unless the result is nil
-		mark := s.save()
-		if !s.eval(t.body, value, 0) { // TODO is 0 index correct?
-			s.restore(mark)
-		}
-		return true // an option never evaluates to nil
-
-	case *repetition:
-		// evaluate the body and append the result to the state's output
-		// buffer until a result is nil
-		for i := 0; ; i++ {
-			mark := s.save()
-			// write separator, if any
-			if i > 0 && t.separator != nil {
-				// nil result from separator is ignored
-				mark := s.save()
-				if !s.eval(t.separator, value, i) {
-					s.restore(mark)
-				}
-			}
-			if !s.eval(t.body, value, i) {
-				s.restore(mark)
-				break
-			}
-		}
-		return true // a repetition never evaluates to nil
-
-	case *custom:
-		// invoke the custom formatter to obtain the result
-		mark := s.save()
-		if !t.fun(s, value.Interface(), t.ruleName) {
-			s.restore(mark)
-			return false
-		}
-		return true
-	}
-
-	panic("unreachable")
-	return false
-}
-
-
-// Eval formats each argument according to the format
-// f and returns the resulting []byte and os.Error. If
-// an error occurred, the []byte contains the partially
-// formatted result. An environment env may be passed
-// in which is available in custom formatters through
-// the state parameter.
-//
-func (f Format) Eval(env Environment, args ...interface{}) ([]byte, os.Error) {
-	if f == nil {
-		return nil, os.NewError("format is nil")
-	}
-
-	errors := make(chan os.Error)
-	s := newState(f, env, errors)
-
-	go func() {
-		for _, v := range args {
-			fld := reflect.ValueOf(v)
-			if !fld.IsValid() {
-				errors <- os.NewError("nil argument")
-				return
-			}
-			mark := s.save()
-			if !s.eval(s.getFormat(typename(fld.Type())), fld, 0) { // TODO is 0 index correct?
-				s.restore(mark)
-			}
-		}
-		errors <- nil // no errors
-	}()
-
-	err := <-errors
-	return s.output.Bytes(), err
-}
-
-
-// ----------------------------------------------------------------------------
-// Convenience functions
-
-// Fprint formats each argument according to the format f
-// and writes to w. The result is the total number of bytes
-// written and an os.Error, if any.
-//
-func (f Format) Fprint(w io.Writer, env Environment, args ...interface{}) (int, os.Error) {
-	data, err := f.Eval(env, args...)
-	if err != nil {
-		// TODO should we print partial result in case of error?
-		return 0, err
-	}
-	return w.Write(data)
-}
-
-
-// Print formats each argument according to the format f
-// and writes to standard output. The result is the total
-// number of bytes written and an os.Error, if any.
-//
-func (f Format) Print(args ...interface{}) (int, os.Error) {
-	return f.Fprint(os.Stdout, nil, args...)
-}
-
-
-// Sprint formats each argument according to the format f
-// and returns the resulting string. If an error occurs
-// during formatting, the result string contains the
-// partially formatted result followed by an error message.
-//
-func (f Format) Sprint(args ...interface{}) string {
-	var buf bytes.Buffer
-	_, err := f.Fprint(&buf, nil, args...)
-	if err != nil {
-		var i interface{} = args
-		fmt.Fprintf(&buf, "--- Sprint(%s) failed: %v", fmt.Sprint(i), err)
-	}
-	return buf.String()
-}
diff --git a/src/pkg/exp/datafmt/datafmt_test.go b/src/pkg/exp/datafmt/datafmt_test.go
deleted file mode 100644
index d7c70b2..0000000
--- a/src/pkg/exp/datafmt/datafmt_test.go
+++ /dev/null
@@ -1,351 +0,0 @@
-// 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.
-
-package datafmt
-
-import (
-	"fmt"
-	"testing"
-	"go/token"
-)
-
-
-var fset = token.NewFileSet()
-
-
-func parse(t *testing.T, form string, fmap FormatterMap) Format {
-	f, err := Parse(fset, "", []byte(form), fmap)
-	if err != nil {
-		t.Errorf("Parse(%s): %v", form, err)
-		return nil
-	}
-	return f
-}
-
-
-func verify(t *testing.T, f Format, expected string, args ...interface{}) {
-	if f == nil {
-		return // allow other tests to run
-	}
-	result := f.Sprint(args...)
-	if result != expected {
-		t.Errorf(
-			"result  : `%s`\nexpected: `%s`\n\n",
-			result, expected)
-	}
-}
-
-
-func formatter(s *State, value interface{}, rule_name string) bool {
-	switch rule_name {
-	case "/":
-		fmt.Fprintf(s, "%d %d %d", s.Pos().Line, s.LinePos().Column, s.Pos().Column)
-		return true
-	case "blank":
-		s.Write([]byte{' '})
-		return true
-	case "int":
-		if value.(int)&1 == 0 {
-			fmt.Fprint(s, "even ")
-		} else {
-			fmt.Fprint(s, "odd ")
-		}
-		return true
-	case "nil":
-		return false
-	case "testing.T":
-		s.Write([]byte("testing.T"))
-		return true
-	}
-	panic("unreachable")
-	return false
-}
-
-
-func TestCustomFormatters(t *testing.T) {
-	fmap0 := FormatterMap{"/": formatter}
-	fmap1 := FormatterMap{"int": formatter, "blank": formatter, "nil": formatter}
-	fmap2 := FormatterMap{"testing.T": formatter}
-
-	f := parse(t, `int=`, fmap0)
-	verify(t, f, ``, 1, 2, 3)
-
-	f = parse(t, `int="#"`, nil)
-	verify(t, f, `###`, 1, 2, 3)
-
-	f = parse(t, `int="#";string="%s"`, fmap0)
-	verify(t, f, "#1 0 1#1 0 7#1 0 13\n2 0 0foo2 0 8\n", 1, 2, 3, "\n", "foo", "\n")
-
-	f = parse(t, ``, fmap1)
-	verify(t, f, `even odd even odd `, 0, 1, 2, 3)
-
-	f = parse(t, `/ =@:blank; float64="#"`, fmap1)
-	verify(t, f, `# # #`, 0.0, 1.0, 2.0)
-
-	f = parse(t, `float64=@:nil`, fmap1)
-	verify(t, f, ``, 0.0, 1.0, 2.0)
-
-	f = parse(t, `testing "testing"; ptr=*`, fmap2)
-	verify(t, f, `testing.T`, t)
-
-	// TODO needs more tests
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting of basic and simple composite types
-
-func check(t *testing.T, form, expected string, args ...interface{}) {
-	f := parse(t, form, nil)
-	if f == nil {
-		return // allow other tests to run
-	}
-	result := f.Sprint(args...)
-	if result != expected {
-		t.Errorf(
-			"format  : %s\nresult  : `%s`\nexpected: `%s`\n\n",
-			form, result, expected)
-	}
-}
-
-
-func TestBasicTypes(t *testing.T) {
-	check(t, ``, ``)
-	check(t, `bool=":%v"`, `:true:false`, true, false)
-	check(t, `int="%b %d %o 0x%x"`, `101010 42 52 0x2a`, 42)
-
-	check(t, `int="%"`, `%`, 42)
-	check(t, `int="%%"`, `%`, 42)
-	check(t, `int="**%%**"`, `**%**`, 42)
-	check(t, `int="%%%%%%"`, `%%%`, 42)
-	check(t, `int="%%%d%%"`, `%42%`, 42)
-
-	const i = -42
-	const is = `-42`
-	check(t, `int  ="%d"`, is, i)
-	check(t, `int8 ="%d"`, is, int8(i))
-	check(t, `int16="%d"`, is, int16(i))
-	check(t, `int32="%d"`, is, int32(i))
-	check(t, `int64="%d"`, is, int64(i))
-
-	const u = 42
-	const us = `42`
-	check(t, `uint  ="%d"`, us, uint(u))
-	check(t, `uint8 ="%d"`, us, uint8(u))
-	check(t, `uint16="%d"`, us, uint16(u))
-	check(t, `uint32="%d"`, us, uint32(u))
-	check(t, `uint64="%d"`, us, uint64(u))
-
-	const f = 3.141592
-	const fs = `3.141592`
-	check(t, `float64="%g"`, fs, f)
-	check(t, `float32="%g"`, fs, float32(f))
-	check(t, `float64="%g"`, fs, float64(f))
-}
-
-
-func TestArrayTypes(t *testing.T) {
-	var a0 [10]int
-	check(t, `array="array";`, `array`, a0)
-
-	a1 := [...]int{1, 2, 3}
-	check(t, `array="array";`, `array`, a1)
-	check(t, `array={*}; int="%d";`, `123`, a1)
-	check(t, `array={* / ", "}; int="%d";`, `1, 2, 3`, a1)
-	check(t, `array={* / *}; int="%d";`, `12233`, a1)
-
-	a2 := []interface{}{42, "foo", 3.14}
-	check(t, `array={* / ", "}; interface=*; string="bar"; default="%v";`, `42, bar, 3.14`, a2)
-}
-
-
-func TestChanTypes(t *testing.T) {
-	var c0 chan int
-	check(t, `chan="chan"`, `chan`, c0)
-
-	c1 := make(chan int)
-	go func() { c1 <- 42 }()
-	check(t, `chan="chan"`, `chan`, c1)
-	// check(t, `chan=*`, `42`, c1);  // reflection support for chans incomplete
-}
-
-
-func TestFuncTypes(t *testing.T) {
-	var f0 func() int
-	check(t, `func="func"`, `func`, f0)
-
-	f1 := func() int { return 42 }
-	check(t, `func="func"`, `func`, f1)
-	// check(t, `func=*`, `42`, f1);  // reflection support for funcs incomplete
-}
-
-
-func TestMapTypes(t *testing.T) {
-	var m0 map[string]int
-	check(t, `map="map"`, `map`, m0)
-
-	m1 := map[string]int{}
-	check(t, `map="map"`, `map`, m1)
-	// check(t, `map=*`, ``, m1);  // reflection support for maps incomplete
-}
-
-
-func TestPointerTypes(t *testing.T) {
-	var p0 *int
-	check(t, `ptr="ptr"`, `ptr`, p0)
-	check(t, `ptr=*`, ``, p0)
-	check(t, `ptr=*|"nil"`, `nil`, p0)
-
-	x := 99991
-	p1 := &x
-	check(t, `ptr="ptr"`, `ptr`, p1)
-	check(t, `ptr=*; int="%d"`, `99991`, p1)
-}
-
-
-func TestDefaultRule(t *testing.T) {
-	check(t, `default="%v"`, `42foo3.14`, 42, "foo", 3.14)
-	check(t, `default="%v"; int="%x"`, `abcdef`, 10, 11, 12, 13, 14, 15)
-	check(t, `default="%v"; int="%x"`, `ab**ef`, 10, 11, "**", 14, 15)
-	check(t, `default="%x"; int=@:default`, `abcdef`, 10, 11, 12, 13, 14, 15)
-}
-
-
-func TestGlobalSeparatorRule(t *testing.T) {
-	check(t, `int="%d"; / ="-"`, `1-2-3-4`, 1, 2, 3, 4)
-	check(t, `int="%x%x"; / ="*"`, `aa*aa`, 10, 10)
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting of a struct
-
-type T1 struct {
-	a int
-}
-
-const F1 = `datafmt "datafmt";` +
-	`int = "%d";` +
-	`datafmt.T1 = "<" a ">";`
-
-func TestStruct1(t *testing.T) { check(t, F1, "<42>", T1{42}) }
-
-
-// ----------------------------------------------------------------------------
-// Formatting of a struct with an optional field (ptr)
-
-type T2 struct {
-	s string
-	p *T1
-}
-
-const F2a = F1 +
-	`string = "%s";` +
-	`ptr = *;` +
-	`datafmt.T2 = s ["-" p "-"];`
-
-const F2b = F1 +
-	`string = "%s";` +
-	`ptr = *;` +
-	`datafmt.T2 = s ("-" p "-" | "empty");`
-
-func TestStruct2(t *testing.T) {
-	check(t, F2a, "foo", T2{"foo", nil})
-	check(t, F2a, "bar-<17>-", T2{"bar", &T1{17}})
-	check(t, F2b, "fooempty", T2{"foo", nil})
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting of a struct with a repetitive field (slice)
-
-type T3 struct {
-	s string
-	a []int
-}
-
-const F3a = `datafmt "datafmt";` +
-	`default = "%v";` +
-	`array = *;` +
-	`datafmt.T3 = s  {" " a a / ","};`
-
-const F3b = `datafmt "datafmt";` +
-	`int = "%d";` +
-	`string = "%s";` +
-	`array = *;` +
-	`nil = ;` +
-	`empty = *:nil;` +
-	`datafmt.T3 = s [a:empty ": " {a / "-"}]`
-
-func TestStruct3(t *testing.T) {
-	check(t, F3a, "foo", T3{"foo", nil})
-	check(t, F3a, "foo 00, 11, 22", T3{"foo", []int{0, 1, 2}})
-	check(t, F3b, "bar", T3{"bar", nil})
-	check(t, F3b, "bal: 2-3-5", T3{"bal", []int{2, 3, 5}})
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting of a struct with alternative field
-
-type T4 struct {
-	x *int
-	a []int
-}
-
-const F4a = `datafmt "datafmt";` +
-	`int = "%d";` +
-	`ptr = *;` +
-	`array = *;` +
-	`nil = ;` +
-	`empty = *:nil;` +
-	`datafmt.T4 = "<" (x:empty x | "-") ">" `
-
-const F4b = `datafmt "datafmt";` +
-	`int = "%d";` +
-	`ptr = *;` +
-	`array = *;` +
-	`nil = ;` +
-	`empty = *:nil;` +
-	`datafmt.T4 = "<" (a:empty {a / ", "} | "-") ">" `
-
-func TestStruct4(t *testing.T) {
-	x := 7
-	check(t, F4a, "<->", T4{nil, nil})
-	check(t, F4a, "<7>", T4{&x, nil})
-	check(t, F4b, "<->", T4{nil, nil})
-	check(t, F4b, "<2, 3, 7>", T4{nil, []int{2, 3, 7}})
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting a struct (documentation example)
-
-type Point struct {
-	name string
-	x, y int
-}
-
-const FPoint = `datafmt "datafmt";` +
-	`int = "%d";` +
-	`hexInt = "0x%x";` +
-	`string = "---%s---";` +
-	`datafmt.Point = name "{" x ", " y:hexInt "}";`
-
-func TestStructPoint(t *testing.T) {
-	p := Point{"foo", 3, 15}
-	check(t, FPoint, "---foo---{3, 0xf}", p)
-}
-
-
-// ----------------------------------------------------------------------------
-// Formatting a slice (documentation example)
-
-const FSlice = `int = "%b";` +
-	`array = { * / ", " }`
-
-func TestSlice(t *testing.T) { check(t, FSlice, "10, 11, 101, 111", []int{2, 3, 5, 7}) }
-
-
-// TODO add more tests
diff --git a/src/pkg/exp/datafmt/parser.go b/src/pkg/exp/datafmt/parser.go
deleted file mode 100644
index 7dedb53..0000000
--- a/src/pkg/exp/datafmt/parser.go
+++ /dev/null
@@ -1,386 +0,0 @@
-// 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.
-
-package datafmt
-
-import (
-	"container/vector"
-	"go/scanner"
-	"go/token"
-	"os"
-	"strconv"
-	"strings"
-)
-
-// ----------------------------------------------------------------------------
-// Parsing
-
-type parser struct {
-	scanner.ErrorVector
-	scanner scanner.Scanner
-	file    *token.File
-	pos     token.Pos   // token position
-	tok     token.Token // one token look-ahead
-	lit     string      // token literal
-
-	packs map[string]string // PackageName -> ImportPath
-	rules map[string]expr   // RuleName -> Expression
-}
-
-
-func (p *parser) next() {
-	p.pos, p.tok, p.lit = p.scanner.Scan()
-	switch p.tok {
-	case token.CHAN, token.FUNC, token.INTERFACE, token.MAP, token.STRUCT:
-		// Go keywords for composite types are type names
-		// returned by reflect. Accept them as identifiers.
-		p.tok = token.IDENT // p.lit is already set correctly
-	}
-}
-
-
-func (p *parser) init(fset *token.FileSet, filename string, src []byte) {
-	p.ErrorVector.Reset()
-	p.file = fset.AddFile(filename, fset.Base(), len(src))
-	p.scanner.Init(p.file, src, p, scanner.AllowIllegalChars) // return '@' as token.ILLEGAL w/o error message
-	p.next()                                                  // initializes pos, tok, lit
-	p.packs = make(map[string]string)
-	p.rules = make(map[string]expr)
-}
-
-
-func (p *parser) error(pos token.Pos, msg string) {
-	p.Error(p.file.Position(pos), msg)
-}
-
-
-func (p *parser) errorExpected(pos token.Pos, msg string) {
-	msg = "expected " + msg
-	if pos == p.pos {
-		// the error happened at the current position;
-		// make the error message more specific
-		msg += ", found '" + p.tok.String() + "'"
-		if p.tok.IsLiteral() {
-			msg += " " + p.lit
-		}
-	}
-	p.error(pos, msg)
-}
-
-
-func (p *parser) expect(tok token.Token) token.Pos {
-	pos := p.pos
-	if p.tok != tok {
-		p.errorExpected(pos, "'"+tok.String()+"'")
-	}
-	p.next() // make progress in any case
-	return pos
-}
-
-
-func (p *parser) parseIdentifier() string {
-	name := p.lit
-	p.expect(token.IDENT)
-	return name
-}
-
-
-func (p *parser) parseTypeName() (string, bool) {
-	pos := p.pos
-	name, isIdent := p.parseIdentifier(), true
-	if p.tok == token.PERIOD {
-		// got a package name, lookup package
-		if importPath, found := p.packs[name]; found {
-			name = importPath
-		} else {
-			p.error(pos, "package not declared: "+name)
-		}
-		p.next()
-		name, isIdent = name+"."+p.parseIdentifier(), false
-	}
-	return name, isIdent
-}
-
-
-// Parses a rule name and returns it. If the rule name is
-// a package-qualified type name, the package name is resolved.
-// The 2nd result value is true iff the rule name consists of a
-// single identifier only (and thus could be a package name).
-//
-func (p *parser) parseRuleName() (string, bool) {
-	name, isIdent := "", false
-	switch p.tok {
-	case token.IDENT:
-		name, isIdent = p.parseTypeName()
-	case token.DEFAULT:
-		name = "default"
-		p.next()
-	case token.QUO:
-		name = "/"
-		p.next()
-	default:
-		p.errorExpected(p.pos, "rule name")
-		p.next() // make progress in any case
-	}
-	return name, isIdent
-}
-
-
-func (p *parser) parseString() string {
-	s := ""
-	if p.tok == token.STRING {
-		s, _ = strconv.Unquote(p.lit)
-		// Unquote may fail with an error, but only if the scanner found
-		// an illegal string in the first place. In this case the error
-		// has already been reported.
-		p.next()
-		return s
-	} else {
-		p.expect(token.STRING)
-	}
-	return s
-}
-
-
-func (p *parser) parseLiteral() literal {
-	s := []byte(p.parseString())
-
-	// A string literal may contain %-format specifiers. To simplify
-	// and speed up printing of the literal, split it into segments
-	// that start with "%" possibly followed by a last segment that
-	// starts with some other character.
-	var list vector.Vector
-	i0 := 0
-	for i := 0; i < len(s); i++ {
-		if s[i] == '%' && i+1 < len(s) {
-			// the next segment starts with a % format
-			if i0 < i {
-				// the current segment is not empty, split it off
-				list.Push(s[i0:i])
-				i0 = i
-			}
-			i++ // skip %; let loop skip over char after %
-		}
-	}
-	// the final segment may start with any character
-	// (it is empty iff the string is empty)
-	list.Push(s[i0:])
-
-	// convert list into a literal
-	lit := make(literal, list.Len())
-	for i := 0; i < list.Len(); i++ {
-		lit[i] = list.At(i).([]byte)
-	}
-
-	return lit
-}
-
-
-func (p *parser) parseField() expr {
-	var fname string
-	switch p.tok {
-	case token.ILLEGAL:
-		if p.lit != "@" {
-			return nil
-		}
-		fname = "@"
-		p.next()
-	case token.MUL:
-		fname = "*"
-		p.next()
-	case token.IDENT:
-		fname = p.parseIdentifier()
-	default:
-		return nil
-	}
-
-	var ruleName string
-	if p.tok == token.COLON {
-		p.next()
-		ruleName, _ = p.parseRuleName()
-	}
-
-	return &field{fname, ruleName}
-}
-
-
-func (p *parser) parseOperand() (x expr) {
-	switch p.tok {
-	case token.STRING:
-		x = p.parseLiteral()
-
-	case token.LPAREN:
-		p.next()
-		x = p.parseExpression()
-		if p.tok == token.SHR {
-			p.next()
-			x = &group{x, p.parseExpression()}
-		}
-		p.expect(token.RPAREN)
-
-	case token.LBRACK:
-		p.next()
-		x = &option{p.parseExpression()}
-		p.expect(token.RBRACK)
-
-	case token.LBRACE:
-		p.next()
-		x = p.parseExpression()
-		var div expr
-		if p.tok == token.QUO {
-			p.next()
-			div = p.parseExpression()
-		}
-		x = &repetition{x, div}
-		p.expect(token.RBRACE)
-
-	default:
-		x = p.parseField() // may be nil
-	}
-
-	return x
-}
-
-
-func (p *parser) parseSequence() expr {
-	var list vector.Vector
-
-	for x := p.parseOperand(); x != nil; x = p.parseOperand() {
-		list.Push(x)
-	}
-
-	// no need for a sequence if list.Len() < 2
-	switch list.Len() {
-	case 0:
-		return nil
-	case 1:
-		return list.At(0).(expr)
-	}
-
-	// convert list into a sequence
-	seq := make(sequence, list.Len())
-	for i := 0; i < list.Len(); i++ {
-		seq[i] = list.At(i).(expr)
-	}
-	return seq
-}
-
-
-func (p *parser) parseExpression() expr {
-	var list vector.Vector
-
-	for {
-		x := p.parseSequence()
-		if x != nil {
-			list.Push(x)
-		}
-		if p.tok != token.OR {
-			break
-		}
-		p.next()
-	}
-
-	// no need for an alternatives if list.Len() < 2
-	switch list.Len() {
-	case 0:
-		return nil
-	case 1:
-		return list.At(0).(expr)
-	}
-
-	// convert list into a alternatives
-	alt := make(alternatives, list.Len())
-	for i := 0; i < list.Len(); i++ {
-		alt[i] = list.At(i).(expr)
-	}
-	return alt
-}
-
-
-func (p *parser) parseFormat() {
-	for p.tok != token.EOF {
-		pos := p.pos
-
-		name, isIdent := p.parseRuleName()
-		switch p.tok {
-		case token.STRING:
-			// package declaration
-			importPath := p.parseString()
-
-			// add package declaration
-			if !isIdent {
-				p.error(pos, "illegal package name: "+name)
-			} else if _, found := p.packs[name]; !found {
-				p.packs[name] = importPath
-			} else {
-				p.error(pos, "package already declared: "+name)
-			}
-
-		case token.ASSIGN:
-			// format rule
-			p.next()
-			x := p.parseExpression()
-
-			// add rule
-			if _, found := p.rules[name]; !found {
-				p.rules[name] = x
-			} else {
-				p.error(pos, "format rule already declared: "+name)
-			}
-
-		default:
-			p.errorExpected(p.pos, "package declaration or format rule")
-			p.next() // make progress in any case
-		}
-
-		if p.tok == token.SEMICOLON {
-			p.next()
-		} else {
-			break
-		}
-	}
-	p.expect(token.EOF)
-}
-
-
-func remap(p *parser, name string) string {
-	i := strings.Index(name, ".")
-	if i >= 0 {
-		packageName, suffix := name[0:i], name[i:]
-		// lookup package
-		if importPath, found := p.packs[packageName]; found {
-			name = importPath + suffix
-		} else {
-			var invalidPos token.Position
-			p.Error(invalidPos, "package not declared: "+packageName)
-		}
-	}
-	return name
-}
-
-
-// Parse parses a set of format productions from source src. Custom
-// formatters may be provided via a map of formatter functions. If
-// there are no errors, the result is a Format and the error is nil.
-// Otherwise the format is nil and a non-empty ErrorList is returned.
-//
-func Parse(fset *token.FileSet, filename string, src []byte, fmap FormatterMap) (Format, os.Error) {
-	// parse source
-	var p parser
-	p.init(fset, filename, src)
-	p.parseFormat()
-
-	// add custom formatters, if any
-	for name, form := range fmap {
-		name = remap(&p, name)
-		if _, found := p.rules[name]; !found {
-			p.rules[name] = &custom{name, form}
-		} else {
-			var invalidPos token.Position
-			p.Error(invalidPos, "formatter already declared: "+name)
-		}
-	}
-
-	return p.rules, p.GetError(scanner.NoMultiples)
-}
diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index 122b951..1f059d4 100644
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -62,7 +62,7 @@
 func (i I) String() string { return Sprintf("<%d>", int(i)) }
 
 type B struct {
-	i I
+	I I
 	j int
 }
 
@@ -84,8 +84,8 @@
 }
 
 type S struct {
-	f F // a struct field that Formats
-	g G // a struct field that GoStrings
+	F F // a struct field that Formats
+	G G // a struct field that GoStrings
 }
 
 // A type with a String method with pointer receiver for testing %p
@@ -322,8 +322,8 @@
 	{"%+v", A{1, 2, "a", []int{1, 2}}, `{i:1 j:2 s:a x:[1 2]}`},
 
 	// +v on structs with Stringable items
-	{"%+v", B{1, 2}, `{i:<1> j:2}`},
-	{"%+v", C{1, B{2, 3}}, `{i:1 B:{i:<2> j:3}}`},
+	{"%+v", B{1, 2}, `{I:<1> j:2}`},
+	{"%+v", C{1, B{2, 3}}, `{i:1 B:{I:<2> j:3}}`},
 
 	// q on Stringable items
 	{"%s", I(23), `<23>`},
@@ -339,7 +339,7 @@
 	{"%#v", uint64(1<<64 - 1), "0xffffffffffffffff"},
 	{"%#v", 1000000000, "1000000000"},
 	{"%#v", map[string]int{"a": 1, "b": 2}, `map[string] int{"a":1, "b":2}`},
-	{"%#v", map[string]B{"a": {1, 2}, "b": {3, 4}}, `map[string] fmt_test.B{"a":fmt_test.B{i:1, j:2}, "b":fmt_test.B{i:3, j:4}}`},
+	{"%#v", map[string]B{"a": {1, 2}, "b": {3, 4}}, `map[string] fmt_test.B{"a":fmt_test.B{I:1, j:2}, "b":fmt_test.B{I:3, j:4}}`},
 	{"%#v", []string{"a", "b"}, `[]string{"a", "b"}`},
 
 	// slices with other formats
@@ -374,11 +374,11 @@
 	// Formatter
 	{"%x", F(1), "<x=F(1)>"},
 	{"%x", G(2), "2"},
-	{"%+v", S{F(4), G(5)}, "{f:<v=F(4)> g:5}"},
+	{"%+v", S{F(4), G(5)}, "{F:<v=F(4)> G:5}"},
 
 	// GoStringer
 	{"%#v", G(6), "GoString(6)"},
-	{"%#v", S{F(7), G(8)}, "fmt_test.S{f:<v=F(7)>, g:GoString(8)}"},
+	{"%#v", S{F(7), G(8)}, "fmt_test.S{F:<v=F(7)>, G:GoString(8)}"},
 
 	// %T
 	{"%T", (4 - 3i), "complex128"},
diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index c18a8ea..1042315 100644
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -259,10 +259,8 @@
 // the thing inside the interface, not the interface itself.
 func getField(v reflect.Value, i int) reflect.Value {
 	val := v.Field(i)
-	if i := val; i.Kind() == reflect.Interface {
-		if inter := i.Interface(); inter != nil {
-			return reflect.ValueOf(inter)
-		}
+	if val.Kind() == reflect.Interface && !val.IsNil() {
+		val = val.Elem()
 	}
 	return val
 }
@@ -289,27 +287,32 @@
 	p.buf.WriteByte('?')
 }
 
-func (p *pp) badVerb(verb int, val interface{}) {
+func (p *pp) badVerb(verb int, val interface{}, val1 reflect.Value) {
 	p.add('%')
 	p.add('!')
 	p.add(verb)
 	p.add('(')
-	if val == nil {
-		p.buf.Write(nilAngleBytes)
-	} else {
+	switch {
+	case val != nil:
 		p.buf.WriteString(reflect.TypeOf(val).String())
 		p.add('=')
 		p.printField(val, 'v', false, false, 0)
+	case val1.IsValid():
+		p.buf.WriteString(val1.Type().String())
+		p.add('=')
+		p.printValue(val1, 'v', false, false, 0)
+	default:
+		p.buf.Write(nilAngleBytes)
 	}
 	p.add(')')
 }
 
-func (p *pp) fmtBool(v bool, verb int, value interface{}) {
+func (p *pp) fmtBool(v bool, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 't', 'v':
 		p.fmt.fmt_boolean(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
@@ -323,7 +326,7 @@
 	p.fmt.pad(p.runeBuf[0:w])
 }
 
-func (p *pp) fmtInt64(v int64, verb int, value interface{}) {
+func (p *pp) fmtInt64(v int64, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'b':
 		p.fmt.integer(v, 2, signed, ldigits)
@@ -337,7 +340,7 @@
 		if 0 <= v && v <= unicode.MaxRune {
 			p.fmt.fmt_qc(v)
 		} else {
-			p.badVerb(verb, value)
+			p.badVerb(verb, value, value1)
 		}
 	case 'x':
 		p.fmt.integer(v, 16, signed, ldigits)
@@ -346,7 +349,7 @@
 	case 'X':
 		p.fmt.integer(v, 16, signed, udigits)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
@@ -376,7 +379,7 @@
 	p.fmt.precPresent = precPresent
 }
 
-func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}) {
+func (p *pp) fmtUint64(v uint64, verb int, goSyntax bool, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'b':
 		p.fmt.integer(int64(v), 2, unsigned, ldigits)
@@ -396,7 +399,7 @@
 		if 0 <= v && v <= unicode.MaxRune {
 			p.fmt.fmt_qc(int64(v))
 		} else {
-			p.badVerb(verb, value)
+			p.badVerb(verb, value, value1)
 		}
 	case 'x':
 		p.fmt.integer(int64(v), 16, unsigned, ldigits)
@@ -405,11 +408,11 @@
 	case 'U':
 		p.fmtUnicode(int64(v))
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtFloat32(v float32, verb int, value interface{}) {
+func (p *pp) fmtFloat32(v float32, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'b':
 		p.fmt.fmt_fb32(v)
@@ -424,11 +427,11 @@
 	case 'G':
 		p.fmt.fmt_G32(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtFloat64(v float64, verb int, value interface{}) {
+func (p *pp) fmtFloat64(v float64, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'b':
 		p.fmt.fmt_fb64(v)
@@ -443,33 +446,33 @@
 	case 'G':
 		p.fmt.fmt_G64(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtComplex64(v complex64, verb int, value interface{}) {
+func (p *pp) fmtComplex64(v complex64, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'e', 'E', 'f', 'F', 'g', 'G':
 		p.fmt.fmt_c64(v, verb)
 	case 'v':
 		p.fmt.fmt_c64(v, 'g')
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtComplex128(v complex128, verb int, value interface{}) {
+func (p *pp) fmtComplex128(v complex128, verb int, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'e', 'E', 'f', 'F', 'g', 'G':
 		p.fmt.fmt_c128(v, verb)
 	case 'v':
 		p.fmt.fmt_c128(v, 'g')
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtString(v string, verb int, goSyntax bool, value interface{}) {
+func (p *pp) fmtString(v string, verb int, goSyntax bool, value interface{}, value1 reflect.Value) {
 	switch verb {
 	case 'v':
 		if goSyntax {
@@ -486,11 +489,11 @@
 	case 'q':
 		p.fmt.fmt_q(v)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
-func (p *pp) fmtBytes(v []byte, verb int, goSyntax bool, depth int, value interface{}) {
+func (p *pp) fmtBytes(v []byte, verb int, goSyntax bool, depth int, value interface{}, value1 reflect.Value) {
 	if verb == 'v' || verb == 'd' {
 		if goSyntax {
 			p.buf.Write(bytesBytes)
@@ -525,7 +528,7 @@
 	case 'q':
 		p.fmt.fmt_q(s)
 	default:
-		p.badVerb(verb, value)
+		p.badVerb(verb, value, value1)
 	}
 }
 
@@ -535,12 +538,12 @@
 	case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
 		u = value.Pointer()
 	default:
-		p.badVerb(verb, field)
+		p.badVerb(verb, field, value)
 		return
 	}
 	if goSyntax {
 		p.add('(')
-		p.buf.WriteString(reflect.TypeOf(field).String())
+		p.buf.WriteString(value.Type().String())
 		p.add(')')
 		p.add('(')
 		if u == 0 {
@@ -561,12 +564,48 @@
 	uintptrBits = reflect.TypeOf(uintptr(0)).Bits()
 )
 
+func (p *pp) handleMethods(field interface{}, verb int, plus, goSyntax bool, depth int) (wasString, handled bool) {
+	// Is it a Formatter?
+	if formatter, ok := field.(Formatter); ok {
+		handled = true
+		wasString = false
+		formatter.Format(p, verb)
+		return
+	}
+	// Must not touch flags before Formatter looks at them.
+	if plus {
+		p.fmt.plus = false
+	}
+
+	// If we're doing Go syntax and the field knows how to supply it, take care of it now.
+	if goSyntax {
+		p.fmt.sharp = false
+		if stringer, ok := field.(GoStringer); ok {
+			wasString = false
+			handled = true
+			// Print the result of GoString unadorned.
+			p.fmtString(stringer.GoString(), 's', false, field, reflect.Value{})
+			return
+		}
+	} else {
+		// Is it a Stringer?
+		if stringer, ok := field.(Stringer); ok {
+			wasString = false
+			handled = true
+			p.printField(stringer.String(), verb, plus, false, depth)
+			return
+		}
+	}
+	handled = false
+	return
+}
+
 func (p *pp) printField(field interface{}, verb int, plus, goSyntax bool, depth int) (wasString bool) {
 	if field == nil {
 		if verb == 'T' || verb == 'v' {
 			p.buf.Write(nilAngleBytes)
 		} else {
-			p.badVerb(verb, field)
+			p.badVerb(verb, field, reflect.Value{})
 		}
 		return false
 	}
@@ -581,115 +620,133 @@
 		p.fmtPointer(field, reflect.ValueOf(field), verb, goSyntax)
 		return false
 	}
-	// Is it a Formatter?
-	if formatter, ok := field.(Formatter); ok {
-		formatter.Format(p, verb)
-		return false // this value is not a string
 
-	}
-	// Must not touch flags before Formatter looks at them.
-	if plus {
-		p.fmt.plus = false
-	}
-	// If we're doing Go syntax and the field knows how to supply it, take care of it now.
-	if goSyntax {
-		p.fmt.sharp = false
-		if stringer, ok := field.(GoStringer); ok {
-			// Print the result of GoString unadorned.
-			p.fmtString(stringer.GoString(), 's', false, field)
-			return false // this value is not a string
-		}
-	} else {
-		// Is it a Stringer?
-		if stringer, ok := field.(Stringer); ok {
-			p.printField(stringer.String(), verb, plus, false, depth)
-			return false // this value is not a string
-		}
+	if wasString, handled := p.handleMethods(field, verb, plus, goSyntax, depth); handled {
+		return wasString
 	}
 
 	// Some types can be done without reflection.
 	switch f := field.(type) {
 	case bool:
-		p.fmtBool(f, verb, field)
+		p.fmtBool(f, verb, field, reflect.Value{})
 		return false
 	case float32:
-		p.fmtFloat32(f, verb, field)
+		p.fmtFloat32(f, verb, field, reflect.Value{})
 		return false
 	case float64:
-		p.fmtFloat64(f, verb, field)
+		p.fmtFloat64(f, verb, field, reflect.Value{})
 		return false
 	case complex64:
-		p.fmtComplex64(complex64(f), verb, field)
+		p.fmtComplex64(complex64(f), verb, field, reflect.Value{})
 		return false
 	case complex128:
-		p.fmtComplex128(f, verb, field)
+		p.fmtComplex128(f, verb, field, reflect.Value{})
 		return false
 	case int:
-		p.fmtInt64(int64(f), verb, field)
+		p.fmtInt64(int64(f), verb, field, reflect.Value{})
 		return false
 	case int8:
-		p.fmtInt64(int64(f), verb, field)
+		p.fmtInt64(int64(f), verb, field, reflect.Value{})
 		return false
 	case int16:
-		p.fmtInt64(int64(f), verb, field)
+		p.fmtInt64(int64(f), verb, field, reflect.Value{})
 		return false
 	case int32:
-		p.fmtInt64(int64(f), verb, field)
+		p.fmtInt64(int64(f), verb, field, reflect.Value{})
 		return false
 	case int64:
-		p.fmtInt64(f, verb, field)
+		p.fmtInt64(f, verb, field, reflect.Value{})
 		return false
 	case uint:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
+		p.fmtUint64(uint64(f), verb, goSyntax, field, reflect.Value{})
 		return false
 	case uint8:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
+		p.fmtUint64(uint64(f), verb, goSyntax, field, reflect.Value{})
 		return false
 	case uint16:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
+		p.fmtUint64(uint64(f), verb, goSyntax, field, reflect.Value{})
 		return false
 	case uint32:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
+		p.fmtUint64(uint64(f), verb, goSyntax, field, reflect.Value{})
 		return false
 	case uint64:
-		p.fmtUint64(f, verb, goSyntax, field)
+		p.fmtUint64(f, verb, goSyntax, field, reflect.Value{})
 		return false
 	case uintptr:
-		p.fmtUint64(uint64(f), verb, goSyntax, field)
+		p.fmtUint64(uint64(f), verb, goSyntax, field, reflect.Value{})
 		return false
 	case string:
-		p.fmtString(f, verb, goSyntax, field)
+		p.fmtString(f, verb, goSyntax, field, reflect.Value{})
 		return verb == 's' || verb == 'v'
 	case []byte:
-		p.fmtBytes(f, verb, goSyntax, depth, field)
+		p.fmtBytes(f, verb, goSyntax, depth, field, reflect.Value{})
 		return verb == 's'
 	}
 
 	// Need to use reflection
-	value := reflect.ValueOf(field)
+	return p.printReflectValue(reflect.ValueOf(field), verb, plus, goSyntax, depth)
+}
 
+// printValue is like printField but starts with a reflect value, not an interface{} value.
+func (p *pp) printValue(value reflect.Value, verb int, plus, goSyntax bool, depth int) (wasString bool) {
+	if !value.IsValid() {
+		if verb == 'T' || verb == 'v' {
+			p.buf.Write(nilAngleBytes)
+		} else {
+			p.badVerb(verb, nil, value)
+		}
+		return false
+	}
+
+	// Special processing considerations.
+	// %T (the value's type) and %p (its address) are special; we always do them first.
+	switch verb {
+	case 'T':
+		p.printField(value.Type().String(), 's', false, false, 0)
+		return false
+	case 'p':
+		p.fmtPointer(nil, value, verb, goSyntax)
+		return false
+	}
+
+	// Handle values with special methods.
+	// Call always, even when field == nil, because handleMethods clears p.fmt.plus for us.
+	var field interface{}
+	if value.CanInterface() {
+		field = value.Interface()
+	}
+	if wasString, handled := p.handleMethods(field, verb, plus, goSyntax, depth); handled {
+		return wasString
+	}
+
+	return p.printReflectValue(value, verb, plus, goSyntax, depth)
+}
+
+// printReflectValue is the fallback for both printField and printValue.
+// It uses reflect to print the value.
+func (p *pp) printReflectValue(value reflect.Value, verb int, plus, goSyntax bool, depth int) (wasString bool) {
 BigSwitch:
 	switch f := value; f.Kind() {
 	case reflect.Bool:
-		p.fmtBool(f.Bool(), verb, field)
+		p.fmtBool(f.Bool(), verb, nil, value)
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		p.fmtInt64(f.Int(), verb, field)
+		p.fmtInt64(f.Int(), verb, nil, value)
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		p.fmtUint64(uint64(f.Uint()), verb, goSyntax, field)
+		p.fmtUint64(uint64(f.Uint()), verb, goSyntax, nil, value)
 	case reflect.Float32, reflect.Float64:
 		if f.Type().Size() == 4 {
-			p.fmtFloat32(float32(f.Float()), verb, field)
+			p.fmtFloat32(float32(f.Float()), verb, nil, value)
 		} else {
-			p.fmtFloat64(float64(f.Float()), verb, field)
+			p.fmtFloat64(float64(f.Float()), verb, nil, value)
 		}
 	case reflect.Complex64, reflect.Complex128:
 		if f.Type().Size() == 8 {
-			p.fmtComplex64(complex64(f.Complex()), verb, field)
+			p.fmtComplex64(complex64(f.Complex()), verb, nil, value)
 		} else {
-			p.fmtComplex128(complex128(f.Complex()), verb, field)
+			p.fmtComplex128(complex128(f.Complex()), verb, nil, value)
 		}
 	case reflect.String:
-		p.fmtString(f.String(), verb, goSyntax, field)
+		p.fmtString(f.String(), verb, goSyntax, nil, value)
 	case reflect.Map:
 		if goSyntax {
 			p.buf.WriteString(f.Type().String())
@@ -706,9 +763,9 @@
 					p.buf.WriteByte(' ')
 				}
 			}
-			p.printField(key.Interface(), verb, plus, goSyntax, depth+1)
+			p.printValue(key, verb, plus, goSyntax, depth+1)
 			p.buf.WriteByte(':')
-			p.printField(f.MapIndex(key).Interface(), verb, plus, goSyntax, depth+1)
+			p.printValue(f.MapIndex(key), verb, plus, goSyntax, depth+1)
 		}
 		if goSyntax {
 			p.buf.WriteByte('}')
@@ -717,7 +774,7 @@
 		}
 	case reflect.Struct:
 		if goSyntax {
-			p.buf.WriteString(reflect.TypeOf(field).String())
+			p.buf.WriteString(value.Type().String())
 		}
 		p.add('{')
 		v := f
@@ -736,20 +793,20 @@
 					p.buf.WriteByte(':')
 				}
 			}
-			p.printField(getField(v, i).Interface(), verb, plus, goSyntax, depth+1)
+			p.printValue(getField(v, i), verb, plus, goSyntax, depth+1)
 		}
 		p.buf.WriteByte('}')
 	case reflect.Interface:
 		value := f.Elem()
 		if !value.IsValid() {
 			if goSyntax {
-				p.buf.WriteString(reflect.TypeOf(field).String())
+				p.buf.WriteString(value.Type().String())
 				p.buf.Write(nilParenBytes)
 			} else {
 				p.buf.Write(nilAngleBytes)
 			}
 		} else {
-			return p.printField(value.Interface(), verb, plus, goSyntax, depth+1)
+			return p.printValue(value, verb, plus, goSyntax, depth+1)
 		}
 	case reflect.Array, reflect.Slice:
 		// Byte slices are special.
@@ -765,11 +822,11 @@
 			for i := range bytes {
 				bytes[i] = byte(f.Index(i).Uint())
 			}
-			p.fmtBytes(bytes, verb, goSyntax, depth, field)
+			p.fmtBytes(bytes, verb, goSyntax, depth, nil, value)
 			return verb == 's'
 		}
 		if goSyntax {
-			p.buf.WriteString(reflect.TypeOf(field).String())
+			p.buf.WriteString(value.Type().String())
 			p.buf.WriteByte('{')
 		} else {
 			p.buf.WriteByte('[')
@@ -782,7 +839,7 @@
 					p.buf.WriteByte(' ')
 				}
 			}
-			p.printField(f.Index(i).Interface(), verb, plus, goSyntax, depth+1)
+			p.printValue(f.Index(i), verb, plus, goSyntax, depth+1)
 		}
 		if goSyntax {
 			p.buf.WriteByte('}')
@@ -797,17 +854,17 @@
 			switch a := f.Elem(); a.Kind() {
 			case reflect.Array, reflect.Slice:
 				p.buf.WriteByte('&')
-				p.printField(a.Interface(), verb, plus, goSyntax, depth+1)
+				p.printValue(a, verb, plus, goSyntax, depth+1)
 				break BigSwitch
 			case reflect.Struct:
 				p.buf.WriteByte('&')
-				p.printField(a.Interface(), verb, plus, goSyntax, depth+1)
+				p.printValue(a, verb, plus, goSyntax, depth+1)
 				break BigSwitch
 			}
 		}
 		if goSyntax {
 			p.buf.WriteByte('(')
-			p.buf.WriteString(reflect.TypeOf(field).String())
+			p.buf.WriteString(value.Type().String())
 			p.buf.WriteByte(')')
 			p.buf.WriteByte('(')
 			if v == 0 {
@@ -824,7 +881,7 @@
 		}
 		p.fmt0x64(uint64(v), true)
 	case reflect.Chan, reflect.Func, reflect.UnsafePointer:
-		p.fmtPointer(field, value, verb, goSyntax)
+		p.fmtPointer(nil, value, verb, goSyntax)
 	default:
 		p.unknownType(f)
 	}
diff --git a/src/pkg/reflect/all_test.go b/src/pkg/reflect/all_test.go
index c83a9b7..7a72ef8 100644
--- a/src/pkg/reflect/all_test.go
+++ b/src/pkg/reflect/all_test.go
@@ -855,13 +855,13 @@
 
 func TestInterfaceExtraction(t *testing.T) {
 	var s struct {
-		w io.Writer
+		W io.Writer
 	}
 
-	s.w = os.Stdout
+	s.W = os.Stdout
 	v := Indirect(ValueOf(&s)).Field(0).Interface()
-	if v != s.w.(interface{}) {
-		t.Error("Interface() on interface: ", v, s.w)
+	if v != s.W.(interface{}) {
+		t.Error("Interface() on interface: ", v, s.W)
 	}
 }
 
@@ -1156,18 +1156,18 @@
 }
 
 type S0 struct {
-	a, b, c int
+	A, B, C int
 	D1
 	D2
 }
 
 type S1 struct {
-	b int
+	B int
 	S0
 }
 
 type S2 struct {
-	a int
+	A int
 	*S1
 }
 
@@ -1182,36 +1182,36 @@
 type S3 struct {
 	S1x
 	S2
-	d, e int
+	D, E int
 	*S1y
 }
 
 type S4 struct {
 	*S4
-	a int
+	A int
 }
 
 var fieldTests = []FTest{
 	{struct{}{}, "", nil, 0},
-	{struct{}{}, "foo", nil, 0},
-	{S0{a: 'a'}, "a", []int{0}, 'a'},
-	{S0{}, "d", nil, 0},
-	{S1{S0: S0{a: 'a'}}, "a", []int{1, 0}, 'a'},
-	{S1{b: 'b'}, "b", []int{0}, 'b'},
+	{struct{}{}, "Foo", nil, 0},
+	{S0{A: 'a'}, "A", []int{0}, 'a'},
+	{S0{}, "D", nil, 0},
+	{S1{S0: S0{A: 'a'}}, "A", []int{1, 0}, 'a'},
+	{S1{B: 'b'}, "B", []int{0}, 'b'},
 	{S1{}, "S0", []int{1}, 0},
-	{S1{S0: S0{c: 'c'}}, "c", []int{1, 2}, 'c'},
-	{S2{a: 'a'}, "a", []int{0}, 'a'},
+	{S1{S0: S0{C: 'c'}}, "C", []int{1, 2}, 'c'},
+	{S2{A: 'a'}, "A", []int{0}, 'a'},
 	{S2{}, "S1", []int{1}, 0},
-	{S2{S1: &S1{b: 'b'}}, "b", []int{1, 0}, 'b'},
-	{S2{S1: &S1{S0: S0{c: 'c'}}}, "c", []int{1, 1, 2}, 'c'},
-	{S2{}, "d", nil, 0},
+	{S2{S1: &S1{B: 'b'}}, "B", []int{1, 0}, 'b'},
+	{S2{S1: &S1{S0: S0{C: 'c'}}}, "C", []int{1, 1, 2}, 'c'},
+	{S2{}, "D", nil, 0},
 	{S3{}, "S1", nil, 0},
-	{S3{S2: S2{a: 'a'}}, "a", []int{1, 0}, 'a'},
-	{S3{}, "b", nil, 0},
-	{S3{d: 'd'}, "d", []int{2}, 0},
-	{S3{e: 'e'}, "e", []int{3}, 'e'},
-	{S4{a: 'a'}, "a", []int{1}, 'a'},
-	{S4{}, "b", nil, 0},
+	{S3{S2: S2{A: 'a'}}, "A", []int{1, 0}, 'a'},
+	{S3{}, "B", nil, 0},
+	{S3{D: 'd'}, "D", []int{2}, 0},
+	{S3{E: 'e'}, "E", []int{3}, 'e'},
+	{S4{A: 'a'}, "A", []int{1}, 'a'},
+	{S4{}, "B", nil, 0},
 }
 
 func TestFieldByIndex(t *testing.T) {
@@ -1508,3 +1508,68 @@
 		t.Errorf("after Fprintf CallSlice: %q != %q", b.String(), "hello 42 world")
 	}
 }
+
+type Private struct {
+	x int
+	y **int
+}
+
+func (p *Private) m() {
+}
+
+type Public struct {
+	X int
+	Y **int
+}
+
+func (p *Public) M() {
+}
+
+func TestUnexported(t *testing.T) {
+	var pub Public
+	v := ValueOf(&pub)
+	isValid(v.Elem().Field(0))
+	isValid(v.Elem().Field(1))
+	isValid(v.Elem().FieldByName("X"))
+	isValid(v.Elem().FieldByName("Y"))
+	isValid(v.Type().Method(0).Func)
+	isNonNil(v.Elem().Field(0).Interface())
+	isNonNil(v.Elem().Field(1).Interface())
+	isNonNil(v.Elem().FieldByName("X").Interface())
+	isNonNil(v.Elem().FieldByName("Y").Interface())
+	isNonNil(v.Type().Method(0).Func.Interface())
+
+	var priv Private
+	v = ValueOf(&priv)
+	isValid(v.Elem().Field(0))
+	isValid(v.Elem().Field(1))
+	isValid(v.Elem().FieldByName("x"))
+	isValid(v.Elem().FieldByName("y"))
+	isValid(v.Type().Method(0).Func)
+	shouldPanic(func() { v.Elem().Field(0).Interface() })
+	shouldPanic(func() { v.Elem().Field(1).Interface() })
+	shouldPanic(func() { v.Elem().FieldByName("x").Interface() })
+	shouldPanic(func() { v.Elem().FieldByName("y").Interface() })
+	shouldPanic(func() { v.Type().Method(0).Func.Interface() })
+}
+
+func shouldPanic(f func()) {
+	defer func() {
+		if recover() == nil {
+			panic("did not panic")
+		}
+	}()
+	f()
+}
+
+func isNonNil(x interface{}) {
+	if x == nil {
+		panic("nil interface")
+	}
+}
+
+func isValid(v Value) {
+	if !v.IsValid() {
+		panic("zero Value")
+	}
+}
diff --git a/src/pkg/reflect/deepequal.go b/src/pkg/reflect/deepequal.go
index a483135..63c28fe 100644
--- a/src/pkg/reflect/deepequal.go
+++ b/src/pkg/reflect/deepequal.go
@@ -104,7 +104,7 @@
 		return true
 	default:
 		// Normal equality suffices
-		return v1.Interface() == v2.Interface()
+		return valueInterface(v1, false) == valueInterface(v2, false)
 	}
 
 	panic("Not reached")
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go
index 3abe13e..9ece67f 100644
--- a/src/pkg/reflect/value.go
+++ b/src/pkg/reflect/value.go
@@ -841,14 +841,7 @@
 	if iv.kind == Invalid {
 		panic(&ValueError{"reflect.Value.CanInterface", iv.kind})
 	}
-	// TODO(rsc): Check flagRO too.  Decide what to do about asking for
-	// interface for a value obtained via an unexported field.
-	// If the field were of a known type, say chan int or *sync.Mutex,
-	// the caller could interfere with the data after getting the
-	// interface.  But fmt.Print depends on being able to look.
-	// Now that reflect is more efficient the special cases in fmt
-	// might be less important.
-	return v.InternalMethod == 0
+	return v.InternalMethod == 0 && iv.flag&flagRO == 0
 }
 
 // Interface returns v's value as an interface{}.
@@ -856,19 +849,25 @@
 // (as opposed to Type.Method), Interface cannot return an
 // interface value, so it panics.
 func (v Value) Interface() interface{} {
-	return v.internal().Interface()
+	return valueInterface(v, true)
 }
 
-func (iv internalValue) Interface() interface{} {
+func valueInterface(v Value, safe bool) interface{} {
+	iv := v.internal()
+	return iv.valueInterface(safe)
+}
+
+func (iv internalValue) valueInterface(safe bool) interface{} {
 	if iv.method {
 		panic("reflect.Value.Interface: cannot create interface value for method with bound receiver")
 	}
-	/*
-		if v.flag()&noExport != 0 {
-			panic("reflect.Value.Interface: cannot return value obtained from unexported struct field")
-		}
-	*/
 
+	if safe && iv.flag&flagRO != 0 {
+		// Do not allow access to unexported values via Interface,
+		// because they might be pointers that should not be 
+		// writable or methods or function that should not be callable.
+		panic("reflect.Value.Interface: cannot return value obtained from unexported field or method")
+	}
 	if iv.kind == Interface {
 		// Special case: return the element inside the interface.
 		// Won't recurse further because an interface cannot contain an interface.
@@ -1669,7 +1668,7 @@
 		if addr == nil {
 			addr = unsafe.Pointer(new(interface{}))
 		}
-		x := iv.Interface()
+		x := iv.valueInterface(false)
 		if dst.NumMethod() == 0 {
 			*(*interface{})(addr) = x
 		} else {
diff --git a/test/interface/fake.go b/test/interface/fake.go
index bdc5b90..ddb8325 100644
--- a/test/interface/fake.go
+++ b/test/interface/fake.go
@@ -12,20 +12,20 @@
 import "reflect"
 
 type T struct {
-	f float32
-	g float32
+	F float32
+	G float32
 
-	s string
-	t string
+	S string
+	T string
 
-	u uint32
-	v uint32
+	U uint32
+	V uint32
 
-	w uint32
-	x uint32
+	W uint32
+	X uint32
 
-	y uint32
-	z uint32
+	Y uint32
+	Z uint32
 }
 
 func add(s, t string) string {
@@ -40,16 +40,16 @@
 
 func main() {
 	var x T
-	x.f = 1.0
-	x.g = x.f
-	x.s = add("abc", "def")
-	x.t = add("abc", "def")
-	x.u = 1
-	x.v = 2
-	x.w = 1 << 28
-	x.x = 2 << 28
-	x.y = 0x12345678
-	x.z = x.y
+	x.F = 1.0
+	x.G = x.F
+	x.S = add("abc", "def")
+	x.T = add("abc", "def")
+	x.U = 1
+	x.V = 2
+	x.W = 1 << 28
+	x.X = 2 << 28
+	x.Y = 0x12345678
+	x.Z = x.Y
 
 	// check mem and string
 	v := reflect.ValueOf(x)