C++
clang HEAD 12.0.0 (https://github.com/llvm/llvm-project.git 344a3d0bc0fb0868b519c3342b4982d6121eece3)
$ clang++ prog.cc -Wall -Wextra -I/opt/wandbox/boost-1.73.0/clang-head/include -std=c++2a -Wsign-conversionprog.cc:6:18: warning: implicit conversion changes signedness: 'const int' to 'unsigned int' [-Wsign-conversion]
unsigned int j = i; // C4245
~ ^
prog.cc:12:18: warning: implicit conversion changes signedness: 'int' to 'unsigned int' [-Wsign-conversion]
unsigned int n = m; // okay
~ ^
prog.cc:14:18: warning: unused parameter 'i' [-Wunused-parameter]
void Test(size_t i) {}
^
prog.cc:17:10: warning: implicit conversion changes signedness: 'int' to 'size_t' (aka 'unsigned long') [-Wsign-conversion]
Test( -19 ); // C4245
~~~~ ^~~
4 warnings generated.