diff --git a/Makefile b/Makefile
index e2c9bd6..85ad6e2 100644
--- a/Makefile
+++ b/Makefile
@@ -25,6 +25,7 @@ generate: root build
 
 	.root/bin/easyjson -all .root/src/$(PKG)/tests/data.go 
 	.root/bin/easyjson -all .root/src/$(PKG)/tests/nothing.go
+	.root/bin/easyjson -all .root/src/$(PKG)/tests/errors.go
 	.root/bin/easyjson -snake_case .root/src/$(PKG)/tests/snake.go
 	.root/bin/easyjson -omit_empty .root/src/$(PKG)/tests/omitempty.go
 	.root/bin/easyjson -build_tags=use_easyjson .root/src/$(PKG)/benchmark/data.go
diff --git a/jlexer/context.go b/jlexer/context.go
new file mode 100644
index 0000000..ec53902
--- /dev/null
+++ b/jlexer/context.go
@@ -0,0 +1,92 @@
+package jlexer
+
+import "io"
+
+type Walker interface {
+	OnEnterObject()
+	OnNextObjectKey(key string)
+	OnExitObject()
+
+	OnEnterArray()
+	OnNextArrayElement()
+	OnExitArray()
+}
+
+func (l *Lexer) WalkUpToPosition(w Walker) error {
+	l1 := &Lexer{}
+	l1.Data = l.Data
+
+	type StackItem int
+	const (
+		Object StackItem = iota
+		Array
+	)
+
+	var stack []StackItem
+	haveKey := false
+
+	for {
+		l1.fetchToken()
+		if l1.pos > l.pos || !l1.Ok() {
+			break
+		}
+		switch {
+		case l1.IsDelim('{'):
+			l1.Skip()
+
+			stack = append(stack, Object)
+			w.OnEnterObject()
+			haveKey = false
+
+		case l1.IsDelim('}'):
+			l1.Skip()
+
+			if len(stack) > 0 {
+				stack = stack[:len(stack)-1]
+				l1.WantComma()
+			}
+			w.OnExitObject()
+			haveKey = false
+
+		case l1.IsDelim('['):
+			l1.Skip()
+
+			stack = append(stack, Array)
+			w.OnEnterArray()
+			haveKey = false
+
+		case l1.IsDelim(']'):
+			l1.Skip()
+
+			if len(stack) > 0 {
+				stack = stack[:len(stack)-1]
+				l1.WantComma()
+			}
+			w.OnExitArray()
+			haveKey = false
+
+		case len(stack) > 0 && stack[len(stack)-1] == Object && !haveKey:
+			key := l1.UnsafeString()
+			w.OnNextObjectKey(key)
+
+			l1.WantColon()
+			haveKey = true
+
+		case len(stack) > 0 && stack[len(stack)-1] == Array:
+			w.OnNextArrayElement()
+			l1.Skip()
+			l1.WantComma()
+
+		default:
+			l1.Skip()
+			l1.WantComma()
+			haveKey = false
+		}
+
+	}
+
+	if l1.Error() == io.EOF {
+		return nil
+	}
+	return l1.Error()
+}
diff --git a/jlexer/context_test.go b/jlexer/context_test.go
new file mode 100644
index 0000000..3b7ee58
--- /dev/null
+++ b/jlexer/context_test.go
@@ -0,0 +1,85 @@
+package jlexer
+
+import (
+	"fmt"
+	"testing"
+)
+
+type TestWalker struct {
+	ErrorPrefix string
+	T           *testing.T
+	Items       []string
+}
+
+func (w *TestWalker) item(s string) {
+	if len(w.Items) == 0 {
+		w.T.Errorf("%sTestWalker(): no items left; want %q", w.ErrorPrefix, s)
+	} else if w.Items[0] != s {
+		w.T.Errorf("%sTestWalker(): got %q; want %q", w.ErrorPrefix, s, w.Items[0])
+		w.Items = w.Items[1:]
+	} else {
+		w.Items = w.Items[1:]
+	}
+}
+
+func (w *TestWalker) OnEnterObject()             { w.item("{") }
+func (w *TestWalker) OnExitObject()              { w.item("}") }
+func (w *TestWalker) OnNextObjectKey(key string) { w.item("e:" + key) }
+func (w *TestWalker) OnEnterArray()              { w.item("[") }
+func (w *TestWalker) OnNextArrayElement()        { w.item("e") }
+func (w *TestWalker) OnExitArray()               { w.item("]") }
+
+func TestWalkUpToPosition(t *testing.T) {
+	for i, test := range []struct {
+		JSON       string
+		Items      []string
+		Start, End int
+	}{
+		{
+			JSON:  ``,
+			Items: []string{},
+			End:   -1,
+		}, {
+			JSON:  `{"aaa": 5, "qqq": 10}`,
+			Items: []string{"{", "e:aaa", "e:qqq", "}"},
+			End:   -1,
+		}, {
+			JSON:  `{"aaa": 5, "qqq": {"\t\t": null}}`,
+			Items: []string{"{", "e:aaa", "e:qqq", "{", "e:\t\t", "}", "}"},
+			End:   -1,
+		}, {
+			JSON:  `{"aaa": 5, "qqq": 10}`,
+			End:   len(`{"aaa": 5, "qqq": `),
+			Items: []string{"{", "e:aaa", "e:qqq"},
+		}, {
+			JSON:  `{"aaa": 5, "qqq": 10}`,
+			End:   len(`{"aaa": 5, `),
+			Items: []string{"{", "e:aaa"},
+		}, {
+			JSON:  `[null, false, {"aaa": 5}]`,
+			Items: []string{"[", "e", "e", "{", "e:aaa", "}", "]"},
+			End:   -1,
+		}, {
+			JSON:  `[null, "aaa"]`,
+			Items: []string{"[", "e", "e", "]"},
+			End:   -1,
+		},
+	} {
+		l := &Lexer{Data: []byte(test.JSON)}
+
+		if test.End != -1 {
+			l.pos = test.End
+		} else {
+			l.pos = len(test.JSON)
+		}
+		w := &TestWalker{T: t, Items: test.Items, ErrorPrefix: fmt.Sprintf("[%d,%q] ", i, test.JSON)}
+
+		if err := l.WalkUpToPosition(w); err != nil {
+			t.Errorf("[%d,%q] WalkUpToPosition() error: %v", i, test.JSON, err)
+		}
+
+		if len(w.Items) > 0 {
+			t.Errorf("[%d,%q] WalkUpToPosition: items %q left", i, test.JSON, w.Items)
+		}
+	}
+}
diff --git a/jlexer/lexer.go b/jlexer/lexer.go
index eac6cf5..169105a 100644
--- a/jlexer/lexer.go
+++ b/jlexer/lexer.go
@@ -6,6 +6,7 @@ package jlexer
 
 import (
 	"encoding/base64"
+	"flag"
 	"fmt"
 	"io"
 	"reflect"
@@ -14,6 +15,8 @@ import (
 	"unsafe"
 )
 
+var UseSemanticErrors = flag.Bool("use_many_errors", true, "Allow lexer collect semantic errors")
+
 // tokenKind determines type of a token.
 type tokenKind byte
 
@@ -46,7 +49,8 @@ type Lexer struct {
 	firstElement bool // Whether current element is the first in array or an object.
 	wantSep      byte // A comma or a colon character, which need to occur before a token.
 
-	err error // Error encountered during lexing, if any.
+	fatalError     error   // Fatal error occured during lexing. It is usually a syntax error.
+	SemanticErrors []error // Semantic errors occured during lexing. Marshalling will be continued after finding this errors.
 }
 
 // fetchToken scans the input for the next token.
@@ -148,7 +152,7 @@ func (r *Lexer) fetchToken() {
 			return
 		}
 	}
-	r.err = io.EOF
+	r.fatalError = io.EOF
 	return
 }
 
@@ -369,7 +373,7 @@ func (r *Lexer) fetchString() {
 
 // scanToken scans the next token if no token is currently available in the lexer.
 func (r *Lexer) scanToken() {
-	if r.token.kind != tokenUndef || r.err != nil {
+	if r.token.kind != tokenUndef || r.fatalError != nil {
 		return
 	}
 
@@ -384,20 +388,20 @@ func (r *Lexer) consume() {
 
 // Ok returns true if no error (including io.EOF) was encountered during scanning.
 func (r *Lexer) Ok() bool {
-	return r.err == nil
+	return r.fatalError == nil
 }
 
 const maxErrorContextLen = 13
 
 func (r *Lexer) errParse(what string) {
-	if r.err == nil {
+	if r.fatalError == nil {
 		var str string
 		if len(r.Data)-r.pos <= maxErrorContextLen {
 			str = string(r.Data)
 		} else {
 			str = string(r.Data[r.pos:r.pos+maxErrorContextLen-3]) + "..."
 		}
-		r.err = &LexerError{
+		r.fatalError = &LexerError{
 			Reason: what,
 			Offset: r.pos,
 			Data:   str,
@@ -409,15 +413,23 @@ func (r *Lexer) errSyntax() {
 	r.errParse("syntax error")
 }
 
+func (r *Lexer) errSemantic() { // TODO: add error data.
+	r.AddSemanticError(&LexerError{
+		Reason: "syntax error",
+		Offset: r.pos,
+		Data:   "error occured", // TODO: fix this.
+	})
+}
+
 func (r *Lexer) errInvalidToken(expected string) {
-	if r.err == nil {
+	if r.fatalError == nil {
 		var str string
 		if len(r.token.byteValue) <= maxErrorContextLen {
 			str = string(r.token.byteValue)
 		} else {
 			str = string(r.token.byteValue[:maxErrorContextLen-3]) + "..."
 		}
-		r.err = &LexerError{
+		r.fatalError = &LexerError{
 			Reason: fmt.Sprintf("expected %s", expected),
 			Offset: r.pos,
 			Data:   str,
@@ -516,7 +528,7 @@ func (r *Lexer) SkipRecursive() {
 		wasEscape = false
 	}
 	r.pos = len(r.Data)
-	r.err = &LexerError{
+	r.fatalError = &LexerError{
 		Reason: "EOF reached while skipping array/object or token",
 		Offset: r.pos,
 		Data:   string(r.Data[r.pos:]),
@@ -547,7 +559,7 @@ func (r *Lexer) Consumed() {
 
 	for _, c := range r.Data[r.pos:] {
 		if c != ' ' && c != '\t' && c != '\r' && c != '\n' {
-			r.err = &LexerError{
+			r.fatalError = &LexerError{
 				Reason: "invalid character '" + string(c) + "' after top-level value",
 				Offset: r.pos,
 				Data:   string(r.Data[r.pos:]),
@@ -605,7 +617,7 @@ func (r *Lexer) Bytes() []byte {
 	ret := make([]byte, base64.StdEncoding.DecodedLen(len(r.token.byteValue)))
 	len, err := base64.StdEncoding.Decode(ret, r.token.byteValue)
 	if err != nil {
-		r.err = &LexerError{
+		r.fatalError = &LexerError{
 			Reason: err.Error(),
 		}
 		return nil
@@ -621,9 +633,13 @@ func (r *Lexer) Bool() bool {
 		r.fetchToken()
 	}
 	if !r.Ok() || r.token.kind != tokenBool {
+		if *UseSemanticErrors { // FIXME: remove copypaste from all methods.
+			r.errSemantic()
+			r.SkipRecursive() // FIXME:
+			return false
+		}
 		r.errInvalidToken("bool")
 		return false
-
 	}
 	ret := r.token.boolValue
 	r.consume()
@@ -635,9 +651,13 @@ func (r *Lexer) number() string {
 		r.fetchToken()
 	}
 	if !r.Ok() || r.token.kind != tokenNumber {
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+			return ""
+		}
 		r.errInvalidToken("number")
 		return ""
-
 	}
 	ret := bytesToStr(r.token.byteValue)
 	r.consume()
@@ -652,8 +672,13 @@ func (r *Lexer) Uint8() uint8 {
 
 	n, err := strconv.ParseUint(s, 10, 8)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint8(n)
@@ -667,8 +692,13 @@ func (r *Lexer) Uint16() uint16 {
 
 	n, err := strconv.ParseUint(s, 10, 16)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint16(n)
@@ -682,8 +712,13 @@ func (r *Lexer) Uint32() uint32 {
 
 	n, err := strconv.ParseUint(s, 10, 32)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint32(n)
@@ -697,8 +732,13 @@ func (r *Lexer) Uint64() uint64 {
 
 	n, err := strconv.ParseUint(s, 10, 64)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return n
@@ -716,8 +756,13 @@ func (r *Lexer) Int8() int8 {
 
 	n, err := strconv.ParseInt(s, 10, 8)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int8(n)
@@ -731,8 +776,13 @@ func (r *Lexer) Int16() int16 {
 
 	n, err := strconv.ParseInt(s, 10, 16)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int16(n)
@@ -746,8 +796,13 @@ func (r *Lexer) Int32() int32 {
 
 	n, err := strconv.ParseInt(s, 10, 32)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int32(n)
@@ -761,8 +816,13 @@ func (r *Lexer) Int64() int64 {
 
 	n, err := strconv.ParseInt(s, 10, 64)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return n
@@ -780,8 +840,13 @@ func (r *Lexer) Uint8Str() uint8 {
 
 	n, err := strconv.ParseUint(s, 10, 8)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint8(n)
@@ -795,8 +860,13 @@ func (r *Lexer) Uint16Str() uint16 {
 
 	n, err := strconv.ParseUint(s, 10, 16)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint16(n)
@@ -810,8 +880,13 @@ func (r *Lexer) Uint32Str() uint32 {
 
 	n, err := strconv.ParseUint(s, 10, 32)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return uint32(n)
@@ -825,8 +900,13 @@ func (r *Lexer) Uint64Str() uint64 {
 
 	n, err := strconv.ParseUint(s, 10, 64)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return n
@@ -844,8 +924,13 @@ func (r *Lexer) Int8Str() int8 {
 
 	n, err := strconv.ParseInt(s, 10, 8)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int8(n)
@@ -859,8 +944,13 @@ func (r *Lexer) Int16Str() int16 {
 
 	n, err := strconv.ParseInt(s, 10, 16)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int16(n)
@@ -874,8 +964,13 @@ func (r *Lexer) Int32Str() int32 {
 
 	n, err := strconv.ParseInt(s, 10, 32)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return int32(n)
@@ -889,8 +984,13 @@ func (r *Lexer) Int64Str() int64 {
 
 	n, err := strconv.ParseInt(s, 10, 64)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return n
@@ -908,8 +1008,13 @@ func (r *Lexer) Float32() float32 {
 
 	n, err := strconv.ParseFloat(s, 32)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return float32(n)
@@ -923,23 +1028,32 @@ func (r *Lexer) Float64() float64 {
 
 	n, err := strconv.ParseFloat(s, 64)
 	if err != nil {
-		r.err = &LexerError{
-			Reason: err.Error(),
+		if *UseSemanticErrors {
+			r.errSemantic()
+			r.SkipRecursive()
+		} else {
+			r.fatalError = &LexerError{
+				Reason: err.Error(),
+			}
 		}
 	}
 	return n
 }
 
 func (r *Lexer) Error() error {
-	return r.err
+	return r.fatalError
 }
 
 func (r *Lexer) AddError(e error) {
-	if r.err == nil {
-		r.err = e
+	if r.fatalError == nil {
+		r.fatalError = e
 	}
 }
 
+func (r *Lexer) AddSemanticError(err error) {
+	r.SemanticErrors = append(r.SemanticErrors, err)
+}
+
 // Interface fetches an interface{} analogous to the 'encoding/json' package.
 func (r *Lexer) Interface() interface{} {
 	if r.token.kind == tokenUndef && r.Ok() {
diff --git a/jlexer/lexer_test.go b/jlexer/lexer_test.go
index e3add8c..f8ec84a 100644
--- a/jlexer/lexer_test.go
+++ b/jlexer/lexer_test.go
@@ -95,6 +95,9 @@ func TestNumber(t *testing.T) {
 			t.Errorf("[%d, %q] number() = %v; want %v", i, test.toParse, got, test.want)
 		}
 		err := l.Error()
+		if err == nil && len(l.SemanticErrors) != 0 {
+			err = l.SemanticErrors[0]
+		}
 		if err != nil && !test.wantError {
 			t.Errorf("[%d, %q] number() error: %v", i, test.toParse, err)
 		} else if err == nil && test.wantError {
@@ -125,6 +128,9 @@ func TestBool(t *testing.T) {
 			t.Errorf("[%d, %q] Bool() = %v; want %v", i, test.toParse, got, test.want)
 		}
 		err := l.Error()
+		if err == nil && len(l.SemanticErrors) != 0 {
+			err = l.SemanticErrors[0]
+		}
 		if err != nil && !test.wantError {
 			t.Errorf("[%d, %q] Bool() error: %v", i, test.toParse, err)
 		} else if err == nil && test.wantError {
diff --git a/tests/basic_test.go b/tests/basic_test.go
index 25b1bfc..34961ab 100644
--- a/tests/basic_test.go
+++ b/tests/basic_test.go
@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 
 	"github.com/mailru/easyjson"
+	"github.com/mailru/easyjson/jlexer"
 	"github.com/mailru/easyjson/jwriter"
 )
 
@@ -206,3 +207,25 @@ func TestNestedEasyJsonMarshal(t *testing.T) {
 		}
 	}
 }
+
+func TestSemanticErrors(t *testing.T) {
+	for i, test := range []struct {
+		Data     []byte
+		ErrorNum int
+	}{
+		{
+			Data:     []byte(`[1, 2, 3, "4", "5"]`),
+			ErrorNum: 2,
+		},
+	} {
+		l := jlexer.Lexer{Data: test.Data}
+
+		var v ErrorIntSlice
+
+		v.UnmarshalEasyJSON(&l)
+
+		if len(l.SemanticErrors) != test.ErrorNum {
+			t.Errorf("[%d] TestSemanticErrors(): errornum: want: %d, got %d", i, test.ErrorNum, len(l.SemanticErrors))
+		}
+	}
+}
diff --git a/tests/errors.go b/tests/errors.go
new file mode 100644
index 0000000..cc4eb93
--- /dev/null
+++ b/tests/errors.go
@@ -0,0 +1,4 @@
+package tests
+
+//easyjson:json
+type ErrorIntSlice []int