diff --git a/src/pkg/go/doc/doc_test.go b/src/pkg/go/doc/doc_test.go
index 9ffe72032c2..f957ede4abf 100644
--- a/src/pkg/go/doc/doc_test.go
+++ b/src/pkg/go/doc/doc_test.go
@@ -14,12 +14,14 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"testing"
 	"text/template"
 )
 
 var update = flag.Bool("update", false, "update golden (.out) files")
+var files = flag.String("files", "", "consider only Go test files matching this regular expression")
 
 const dataDir = "testdata"
 
@@ -66,14 +68,26 @@ type bundle struct {
 }
 
 func test(t *testing.T, mode Mode) {
-	// get all packages
+	// determine file filter
+	filter := isGoFile
+	if *files != "" {
+		rx, err := regexp.Compile(*files)
+		if err != nil {
+			t.Fatal(err)
+		}
+		filter = func(fi os.FileInfo) bool {
+			return isGoFile(fi) && rx.MatchString(fi.Name())
+		}
+	}
+
+	// get packages
 	fset := token.NewFileSet()
-	pkgs, err := parser.ParseDir(fset, dataDir, isGoFile, parser.ParseComments)
+	pkgs, err := parser.ParseDir(fset, dataDir, filter, parser.ParseComments)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	// test all packages
+	// test packages
 	for _, pkg := range pkgs {
 		importpath := dataDir + "/" + pkg.Name
 		doc := New(pkg, importpath, mode)
diff --git a/src/pkg/go/doc/exports.go b/src/pkg/go/doc/exports.go
index 68dd3841bed..146be5d8707 100644
--- a/src/pkg/go/doc/exports.go
+++ b/src/pkg/go/doc/exports.go
@@ -22,12 +22,38 @@ func filterIdentList(list []*ast.Ident) []*ast.Ident {
 	return list[0:j]
 }
 
+// removeErrorField removes anonymous fields named "error" from an interface.
+// This is called when "error" has been determined to be a local name,
+// not the predeclared type.
+//
+func removeErrorField(ityp *ast.InterfaceType) {
+	list := ityp.Methods.List // we know that ityp.Methods != nil
+	j := 0
+	for _, field := range list {
+		keepField := true
+		if n := len(field.Names); n == 0 {
+			// anonymous field
+			if fname, _ := baseTypeName(field.Type); fname == "error" {
+				keepField = false
+			}
+		}
+		if keepField {
+			list[j] = field
+			j++
+		}
+	}
+	if j < len(list) {
+		ityp.Incomplete = true
+	}
+	ityp.Methods.List = list[0:j]
+}
+
 // filterFieldList removes unexported fields (field names) from the field list
 // in place and returns true if fields were removed. Anonymous fields are
 // recorded with the parent type. filterType is called with the types of
 // all remaining fields.
 //
-func (r *reader) filterFieldList(parent *namedType, fields *ast.FieldList) (removedFields bool) {
+func (r *reader) filterFieldList(parent *namedType, fields *ast.FieldList, ityp *ast.InterfaceType) (removedFields bool) {
 	if fields == nil {
 		return
 	}
@@ -37,9 +63,15 @@ func (r *reader) filterFieldList(parent *namedType, fields *ast.FieldList) (remo
 		keepField := false
 		if n := len(field.Names); n == 0 {
 			// anonymous field
-			name := r.recordAnonymousField(parent, field.Type)
-			if ast.IsExported(name) {
+			fname := r.recordAnonymousField(parent, field.Type)
+			if ast.IsExported(fname) {
 				keepField = true
+			} else if ityp != nil && fname == "error" {
+				// possibly the predeclared error interface; keep
+				// it for now but remember this interface so that
+				// it can be fixed if error is also defined locally
+				keepField = true
+				r.remember(ityp)
 			}
 		} else {
 			field.Names = filterIdentList(field.Names)
@@ -86,14 +118,14 @@ func (r *reader) filterType(parent *namedType, typ ast.Expr) {
 	case *ast.ArrayType:
 		r.filterType(nil, t.Elt)
 	case *ast.StructType:
-		if r.filterFieldList(parent, t.Fields) {
+		if r.filterFieldList(parent, t.Fields, nil) {
 			t.Incomplete = true
 		}
 	case *ast.FuncType:
 		r.filterParamList(t.Params)
 		r.filterParamList(t.Results)
 	case *ast.InterfaceType:
-		if r.filterFieldList(parent, t.Methods) {
+		if r.filterFieldList(parent, t.Methods, t) {
 			t.Incomplete = true
 		}
 	case *ast.MapType:
@@ -116,9 +148,12 @@ func (r *reader) filterSpec(spec ast.Spec) bool {
 			return true
 		}
 	case *ast.TypeSpec:
-		if ast.IsExported(s.Name.Name) {
+		if name := s.Name.Name; ast.IsExported(name) {
 			r.filterType(r.lookupType(s.Name.Name), s.Type)
 			return true
+		} else if name == "error" {
+			// special case: remember that error is declared locally
+			r.errorDecl = true
 		}
 	}
 	return false
diff --git a/src/pkg/go/doc/reader.go b/src/pkg/go/doc/reader.go
index 5f0643caa33..bdfb294adb0 100644
--- a/src/pkg/go/doc/reader.go
+++ b/src/pkg/go/doc/reader.go
@@ -17,7 +17,7 @@ import (
 //
 // Internally, we treat functions like methods and collect them in method sets.
 
-// methodSet describes a set of methods. Entries where Decl == nil are conflict
+// A methodSet describes a set of methods. Entries where Decl == nil are conflict
 // entries (more then one method with the same name at the same embedding level).
 //
 type methodSet map[string]*Func
@@ -110,6 +110,9 @@ func baseTypeName(x ast.Expr) (name string, imported bool) {
 	return
 }
 
+// An embeddedSet describes a set of embedded types.
+type embeddedSet map[*namedType]bool
+
 // A namedType represents a named unqualified (package local, or possibly
 // predeclared) type. The namedType for a type name is always found via
 // reader.lookupType.
@@ -119,9 +122,9 @@ type namedType struct {
 	name string       // type name
 	decl *ast.GenDecl // nil if declaration hasn't been seen yet
 
-	isEmbedded bool                // true if this type is embedded
-	isStruct   bool                // true if this type is a struct
-	embedded   map[*namedType]bool // true if the embedded type is a pointer
+	isEmbedded bool        // true if this type is embedded
+	isStruct   bool        // true if this type is a struct
+	embedded   embeddedSet // true if the embedded type is a pointer
 
 	// associated declarations
 	values  []*Value // consts and vars
@@ -152,6 +155,10 @@ type reader struct {
 	values  []*Value // consts and vars
 	types   map[string]*namedType
 	funcs   methodSet
+
+	// support for package-local error type declarations
+	errorDecl bool                 // if set, type "error" was declared locally
+	fixlist   []*ast.InterfaceType // list of interfaces containing anonymous field "error"
 }
 
 func (r *reader) isVisible(name string) bool {
@@ -173,7 +180,7 @@ func (r *reader) lookupType(name string) *namedType {
 	// type not found - add one without declaration
 	typ := &namedType{
 		name:     name,
-		embedded: make(map[*namedType]bool),
+		embedded: make(embeddedSet),
 		funcs:    make(methodSet),
 		methods:  make(methodSet),
 	}
@@ -210,6 +217,10 @@ func (r *reader) readDoc(comment *ast.CommentGroup) {
 	r.doc += "\n" + text
 }
 
+func (r *reader) remember(typ *ast.InterfaceType) {
+	r.fixlist = append(r.fixlist, typ)
+}
+
 func specNames(specs []ast.Spec) []string {
 	names := make([]string, 0, len(specs)) // reasonable estimate
 	for _, s := range specs {
@@ -315,7 +326,7 @@ func (r *reader) readType(decl *ast.GenDecl, spec *ast.TypeSpec) {
 		return // no name or blank name - ignore the type
 	}
 
-	// A type should be added at most once, so info.decl
+	// A type should be added at most once, so typ.decl
 	// should be nil - if it is not, simply overwrite it.
 	typ.decl = decl
 
@@ -543,7 +554,7 @@ func customizeRecv(f *Func, recvTypeName string, embeddedIsPtr bool, level int)
 
 // collectEmbeddedMethods collects the embedded methods of typ in mset.
 //
-func (r *reader) collectEmbeddedMethods(mset methodSet, typ *namedType, recvTypeName string, embeddedIsPtr bool, level int, visited map[*namedType]bool) {
+func (r *reader) collectEmbeddedMethods(mset methodSet, typ *namedType, recvTypeName string, embeddedIsPtr bool, level int, visited embeddedSet) {
 	visited[typ] = true
 	for embedded, isPtr := range typ.embedded {
 		// Once an embedded type is embedded as a pointer type
@@ -572,12 +583,19 @@ func (r *reader) computeMethodSets() {
 		// collect embedded methods for t
 		if t.isStruct {
 			// struct
-			r.collectEmbeddedMethods(t.methods, t, t.name, false, 1, make(map[*namedType]bool))
+			r.collectEmbeddedMethods(t.methods, t, t.name, false, 1, make(embeddedSet))
 		} else {
 			// interface
 			// TODO(gri) fix this
 		}
 	}
+
+	// if error was declared locally, don't treat it as exported field anymore
+	if r.errorDecl {
+		for _, ityp := range r.fixlist {
+			removeErrorField(ityp)
+		}
+	}
 }
 
 // cleanupTypes removes the association of functions and methods with
diff --git a/src/pkg/go/doc/testdata/e.go b/src/pkg/go/doc/testdata/e.go
index 62a1a40fd71..19dd138cf40 100644
--- a/src/pkg/go/doc/testdata/e.go
+++ b/src/pkg/go/doc/testdata/e.go
@@ -1,4 +1,4 @@
-// Copyright 2011 The Go Authors. All rights reserved.
+// Copyright 2012 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.
 
diff --git a/src/pkg/go/doc/testdata/error1.0.golden b/src/pkg/go/doc/testdata/error1.0.golden
new file mode 100644
index 00000000000..6c6fe5d49bd
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error1.0.golden
@@ -0,0 +1,30 @@
+// 
+PACKAGE error1
+
+IMPORTPATH
+	testdata/error1
+
+FILENAMES
+	testdata/error1.go
+
+TYPES
+	// 
+	type I0 interface {
+		// When embedded, the predeclared error interface
+		// must remain visible in interface types.
+		error
+	}
+
+	// 
+	type S0 struct {
+		// contains filtered or unexported fields
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// error should be visible
+			error
+		}
+	}
+
diff --git a/src/pkg/go/doc/testdata/error1.1.golden b/src/pkg/go/doc/testdata/error1.1.golden
new file mode 100644
index 00000000000..a8dc2e71dc3
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error1.1.golden
@@ -0,0 +1,32 @@
+// 
+PACKAGE error1
+
+IMPORTPATH
+	testdata/error1
+
+FILENAMES
+	testdata/error1.go
+
+TYPES
+	// 
+	type I0 interface {
+		// When embedded, the predeclared error interface
+		// must remain visible in interface types.
+		error
+	}
+
+	// 
+	type S0 struct {
+		// In struct types, an embedded error must only be visible
+		// if AllDecls is set.
+		error
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// error should be visible
+			error
+		}
+	}
+
diff --git a/src/pkg/go/doc/testdata/error1.2.golden b/src/pkg/go/doc/testdata/error1.2.golden
new file mode 100644
index 00000000000..6c6fe5d49bd
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error1.2.golden
@@ -0,0 +1,30 @@
+// 
+PACKAGE error1
+
+IMPORTPATH
+	testdata/error1
+
+FILENAMES
+	testdata/error1.go
+
+TYPES
+	// 
+	type I0 interface {
+		// When embedded, the predeclared error interface
+		// must remain visible in interface types.
+		error
+	}
+
+	// 
+	type S0 struct {
+		// contains filtered or unexported fields
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// error should be visible
+			error
+		}
+	}
+
diff --git a/src/pkg/go/doc/testdata/error1.go b/src/pkg/go/doc/testdata/error1.go
new file mode 100644
index 00000000000..3c777a78005
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error1.go
@@ -0,0 +1,24 @@
+// Copyright 2012 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 error1
+
+type I0 interface {
+	// When embedded, the predeclared error interface
+	// must remain visible in interface types.
+	error
+}
+
+type T0 struct {
+	ExportedField interface {
+		// error should be visible
+		error
+	}
+}
+
+type S0 struct {
+	// In struct types, an embedded error must only be visible
+	// if AllDecls is set.
+	error
+}
diff --git a/src/pkg/go/doc/testdata/error2.0.golden b/src/pkg/go/doc/testdata/error2.0.golden
new file mode 100644
index 00000000000..dedfe412a0f
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error2.0.golden
@@ -0,0 +1,27 @@
+// 
+PACKAGE error2
+
+IMPORTPATH
+	testdata/error2
+
+FILENAMES
+	testdata/error2.go
+
+TYPES
+	// 
+	type I0 interface {
+		// contains filtered or unexported methods
+	}
+
+	// 
+	type S0 struct {
+		// contains filtered or unexported fields
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// contains filtered or unexported methods
+		}
+	}
+
diff --git a/src/pkg/go/doc/testdata/error2.1.golden b/src/pkg/go/doc/testdata/error2.1.golden
new file mode 100644
index 00000000000..776bd1b3e40
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error2.1.golden
@@ -0,0 +1,37 @@
+// 
+PACKAGE error2
+
+IMPORTPATH
+	testdata/error2
+
+FILENAMES
+	testdata/error2.go
+
+TYPES
+	// 
+	type I0 interface {
+		// When embedded, the the locally declared error interface
+		// is only visible if all declarations are shown.
+		error
+	}
+
+	// 
+	type S0 struct {
+		// In struct types, an embedded error must only be visible
+		// if AllDecls is set.
+		error
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// error should not be visible
+			error
+		}
+	}
+
+	// This error declaration shadows the predeclared error type. 
+	type error interface {
+		Error() string
+	}
+
diff --git a/src/pkg/go/doc/testdata/error2.2.golden b/src/pkg/go/doc/testdata/error2.2.golden
new file mode 100644
index 00000000000..dedfe412a0f
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error2.2.golden
@@ -0,0 +1,27 @@
+// 
+PACKAGE error2
+
+IMPORTPATH
+	testdata/error2
+
+FILENAMES
+	testdata/error2.go
+
+TYPES
+	// 
+	type I0 interface {
+		// contains filtered or unexported methods
+	}
+
+	// 
+	type S0 struct {
+		// contains filtered or unexported fields
+	}
+
+	// 
+	type T0 struct {
+		ExportedField interface {
+			// contains filtered or unexported methods
+		}
+	}
+
diff --git a/src/pkg/go/doc/testdata/error2.go b/src/pkg/go/doc/testdata/error2.go
new file mode 100644
index 00000000000..6cc36feef3e
--- /dev/null
+++ b/src/pkg/go/doc/testdata/error2.go
@@ -0,0 +1,29 @@
+// Copyright 2012 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 error2
+
+type I0 interface {
+	// When embedded, the the locally declared error interface
+	// is only visible if all declarations are shown.
+	error
+}
+
+type T0 struct {
+	ExportedField interface {
+		// error should not be visible
+		error
+	}
+}
+
+type S0 struct {
+	// In struct types, an embedded error must only be visible
+	// if AllDecls is set.
+	error
+}
+
+// This error declaration shadows the predeclared error type.
+type error interface {
+	Error() string
+}
diff --git a/src/pkg/go/doc/testdata/f.go b/src/pkg/go/doc/testdata/f.go
index a3051e1fb3b..7e9add90784 100644
--- a/src/pkg/go/doc/testdata/f.go
+++ b/src/pkg/go/doc/testdata/f.go
@@ -1,4 +1,4 @@
-// Copyright 2011 The Go Authors. All rights reserved.
+// Copyright 2012 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.