Fix converting fixed bytes to string

(cherry picked from commit a89e988)

Author: sobolev-igor

accounts/abi/unpack.go

@@ -426,14 +426,14 @@ func toString(index int, t Type, output []byte) (interface{}, error) {
 		if err != nil {
 			return nil, fmt.Errorf("abi: cannot convert value as fixed bytes array: %v", returnOutput)
 		}
-		return common.Bytes2HexWithPrefix(b.([]byte)), nil
+		return common.Bytes2HexWithPrefix(fixedBytesToSlice(b)), nil
 	case FunctionTy:
-		var f interface{}
-		f, err = ReadFixedBytes(t, returnOutput)
+		var b interface{}
+		b, err = ReadFixedBytes(t, returnOutput)
 		if err != nil {
 			return nil, fmt.Errorf("abi: cannot convert value as function: %v", returnOutput)
 		}
-		return common.Bytes2HexWithPrefix(f.([]byte)), nil
+		return common.Bytes2HexWithPrefix(fixedBytesToSlice(b)), nil
 	default:
 		return nil, fmt.Errorf("abi: unknown type %v", t.T)
 	}
@@ -482,3 +482,14 @@ func tuplePointsTo(index int, output []byte) (start int, err error) {
 	}
 	return int(offset.Uint64()), nil
 }
+
+func fixedBytesToSlice(b interface{}) (res []byte) {
+	arr := reflect.ValueOf(b)
+	length := arr.Len()
+	res = make([]byte, length)
+	for i := 0; i < length; i++ {
+		res[i] = arr.Index(i).Interface().(byte)
+	}
+
+	return res
+}

accounts/abi/unpack_test.go

@@ -243,6 +243,15 @@ var unpackTests = []unpackTest{
 			IntOne *big.Int
 		}{big.NewInt(1)},
 	},
+	{
+		def: `[{"name":"one","type":"string"},{"name":"two","type":"bytes32"},{"name":"three","type":"bytes"}]`,
+		enc: "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",
+		want: struct {
+			One   string
+			Two   [32]uint8
+			Three []uint8
+		}{"e0521376-a321-4f37-91ac-317c0b7e5085", [32]uint8{151, 46, 214, 224, 104, 205, 102, 217, 169, 11, 14, 48, 12, 207, 20, 45, 167, 83, 166, 143, 156, 117, 200, 91, 26, 255, 91, 133, 204, 224, 156, 62}, []uint8{67, 65, 176, 125, 173, 85, 142, 145, 16, 74, 192, 141, 62, 147, 155, 115, 234, 141, 114, 62, 156, 251, 142, 185, 220, 124, 83, 33, 84, 219, 181, 223, 46, 94, 147, 81, 67, 56, 236, 248, 197, 18, 186, 135, 84, 98, 56, 53, 63, 244, 210, 131, 102, 187, 93, 145, 226, 147, 139, 105, 44, 231, 37, 207, 28}},
+	},
 	{
 		def:  `[{"type":"bool"}]`,
 		enc:  "",