clang-tidy: IgnoreConversionFromTypes has no effect when set to 'long'

[jarledo]

In the following simple example clang-tidy will output a warning when the check cppcoreguidelines-narrowing-conversions is enabled.

int main() {
  long x = 123;
  int y = x;
}

$ clang-tidy --checks='cppcoreguidelines-narrowing-conversions' main.cpp
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "main.cpp"
No compilation database found in /home/user/programming_test or any parent directory
fixed-compilation-database: Error while opening fixed database: No such file or directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.
2 warnings generated.
/home/user/programming_test/main.cpp:3:7: warning: Value stored to 'y' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
  int y = x;
      ^   ~
/home/user/programming_test/main.cpp:3:7: note: Value stored to 'y' during its initialization is never read
  int y = x;
      ^   ~
/home/user/programming_test/main.cpp:3:11: warning: narrowing conversion from 'long' to signed type 'int' is implementation-defined [cppcoreguidelines-narrowing-conversions]
  int y = x;
          ^

This is as expected. However, if I run the same check but with IgnoreConversionFromTypes set to 'long' it still outputs the same warning:

$ clang-tidy --checks='cppcoreguidelines-narrowing-conversions' -config="{CheckOptions: [ {key: cppcoreguidelines-narrowing-conversions.IgnoreConversionFromTypes, value: 'long'} ]}" main.cpp
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "main.cpp"
No compilation database found in /home/user/programming_test or any parent directory
fixed-compilation-database: Error while opening fixed database: No such file or directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.
2 warnings generated.
/home/user/programming_test/main.cpp:3:7: warning: Value stored to 'y' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
  int y = x;
      ^   ~
/home/user/programming_test/main.cpp:3:7: note: Value stored to 'y' during its initialization is never read
  int y = x;
      ^   ~
/home/user/programming_test/main.cpp:3:11: warning: narrowing conversion from 'long' to signed type 'int' is implementation-defined [cppcoreguidelines-narrowing-conversions]
  int y = x;
          ^

It seems to only happen with the type long, if I run the same example but replace long x = 123; with size_t x = 123; then it works to set IgnoreConversionFromTypes to 'size_t'.

This is running Ubuntu 22.04 with clang-tidy installed with apt install:

$ clang-tidy --version
Ubuntu LLVM version 14.0.0

  Optimized build.
  Default target: x86_64-pc-linux-gnu
  Host CPU: skylake

[llvmbot]

@llvm/issue-subscribers-clang-tidy