compilers: annotate lang_suffixes

mesonbuild/compilers/compilers.py

@@ -51,7 +51,7 @@ lib_suffixes = {'a', 'lib', 'dll', 'dll.a', 'dylib', 'so', 'js'}
 # Mapping of language to suffixes of files that should always be in that language
 # This means we can't include .h headers here since they could be C, C++, ObjC, etc.
 # First suffix is the language's default.
-lang_suffixes = {
+lang_suffixes: T.Mapping[str, T.Tuple[str, ...]] = {
     'c': ('c',),
     'cpp': ('cpp', 'cppm', 'cc', 'cxx', 'c++', 'hh', 'hpp', 'ipp', 'hxx', 'ino', 'ixx', 'C', 'H'),
     'cuda': ('cu',),