| add_library(foo STATIC) | |
| target_sources(foo PRIVATE FILE_SET sources TYPE SOURCES FILES foo.c) | |
| set_property(FILE_SET sources TARGET foo PROPERTY LANGUAGE CXX) | |
| get_property(language FILE_SET sources TARGET foo PROPERTY LANGUAGE) | |
| if(NOT language STREQUAL "CXX") | |
| message(SEND_ERROR "wrong language: '${language}' instead of 'CXX'") | |
| endif() |