Tests/GeneratorExpression/check-common.cmake - third_party/cmake - Git at Google

 function(check var val)
   if(NOT "${${var}}" STREQUAL "${val}")
     message(SEND_ERROR "${var} is \"${${var}}\", not \"${val}\"")
   endif()
 endfunction()
	function(check var val)
	if(NOT "${${var}}" STREQUAL "${val}")
	message(SEND_ERROR "${var} is \"${${var}}\", not \"${val}\"")
	endif()
	endfunction()