cmake – Flex / Bison目标不存在

cmake_minimum_required(VERSION 2.8)

project(leaf)

add_subdirectory(leafc)

并在目录leafc中：

find_package(BISON)
find_package(FLEX)

BISON_TARGET(LeafParser ${CMAKE_CURRENT_SOURCE_DIR}/parser.y ${CMAKE_CURRENT_BINARY_DIR}/parser.cpp)
FLEX_TARGET(LeafScanner ${CMAKE_CURRENT_SOURCE_DIR}/lexer.l  ${CMAKE_CURRENT_BIANRY_DIR}/lexer.cpp)
ADD_FLEX_BISON_DEPENDENCY(LeafParser LeafScanner)

include_directories(${CMAKE_CURRENT_BINARY_DIR})
add_executable(leafc main.cpp ${BISON_LeafParser_OUTPUTS} ${FLEX_LeafScanner_OUTPUTS})

但是在尝试cmake时我遇到了这个错误.

CMake Error at /usr/share/cmake-2.8/Modules/FindFLEX.cmake:132 (MESSAGE):
  Flex target `LeafParser' does not exists.
Call Stack (most recent call first):
  leafc/CMakeLists.txt:6 (ADD_FLEX_BISON_DEPENDENCY)

CMake Error at /usr/share/cmake-2.8/Modules/FindFLEX.cmake:136 (MESSAGE):
  Bison target `LeafScanner' does not exists.
Call Stack (most recent call first):
  leafc/CMakeLists.txt:6 (ADD_FLEX_BISON_DEPENDENCY)

CMake Error at /usr/share/cmake-2.8/Modules/FindFLEX.cmake:139 (SET_SOURCE_FILES_PROPERTIES):
  set_source_files_properties called with incorrect number of arguments.
Call Stack (most recent call first):
  leafc/CMakeLists.txt:6 (ADD_FLEX_BISON_DEPENDENCY)

-- Configuring incomplete,errors occurred!

文件在那里：

├── CMakeLists.txt
├── leafc
│?? ├── CMakeLists.txt
│?? ├── lexer.l
│?? ├── main.cpp
│?? └── parser.y
└── README

那我做错了什么？