2 files changed, 17 insertions, 5 deletions
diff --git a/src/encoding/xml/marshal_test.go b/src/encoding/xml/marshal_test.go
index fe8b16fe43..c0c6a0cd9f 100644
--- a/src/encoding/xml/marshal_test.go
+++ b/src/encoding/xml/marshal_test.go
@@ -317,6 +317,10 @@ func (m *MyMarshalerAttrTest) MarshalXMLAttr(name Name) (Attr, error) {
 	return Attr{name, "hello world"}, nil
 }
 
+func (m *MyMarshalerAttrTest) UnmarshalXMLAttr(attr Attr) error {
+	return nil
+}
+
 type MarshalerStruct struct {
 	Foo MyMarshalerAttrTest `xml:",attr"`
 }
@@ -1732,7 +1736,7 @@ func TestDecodeEncode(t *testing.T) {
 	in.WriteString(`<?xml version="1.0" encoding="UTF-8"?>
 <?Target Instruction?>
 <root>
-</root>	
+</root>
 `)
 	dec := NewDecoder(&in)
 	enc := NewEncoder(&out)
@@ -1823,3 +1827,14 @@ func TestSimpleUseOfEncodeToken(t *testing.T) {
 		t.Errorf("enc.EncodeToken: expected %q; got %q", want, buf.String())
 	}
 }
+
+// Issue 16158. Decoder.unmarshalAttr ignores the return value of copyValue.
+func TestIssue16158(t *testing.T) {
+	const data = `<foo b="HELLOWORLD"></foo>`
+	err := Unmarshal([]byte(data), &struct {
+		B byte `xml:"b,attr,omitempty"`
+	}{})
+	if err == nil {
+		t.Errorf("Unmarshal: expected error, got nil")
+	}
+}
diff --git a/src/encoding/xml/read.go b/src/encoding/xml/read.go
index 937432e3a7..53c15a2840 100644
--- a/src/encoding/xml/read.go
+++ b/src/encoding/xml/read.go
@@ -232,7 +232,6 @@ func (p *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
 		}
 		val = val.Elem()
 	}
-
 	if val.CanInterface() && val.Type().Implements(unmarshalerAttrType) {
 		// This is an unmarshaler with a non-pointer receiver,
 		// so it's likely to be incorrect, but we do what we're told.
@@ -257,9 +256,7 @@ func (p *Decoder) unmarshalAttr(val reflect.Value, attr Attr) error {
 			return pv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(attr.Value))
 		}
 	}
-
-	copyValue(val, []byte(attr.Value))
-	return nil
+	return copyValue(val, []byte(attr.Value))
 }
 
 var (