# CMP0057

Support new `if()` IN_LIST operator.

CMake 3.3 adds support for the new IN_LIST operator.

The `OLD` behavior for this policy is to ignore the IN_LIST operator. The `NEW` behavior is to interpret the IN_LIST operator.

This policy was introduced in CMake version 3.3. CMake version 3.15.0-rc2 warns when the policy is not set and uses `OLD` behavior. Use the `cmake_policy()` command to set it to `OLD` or `NEW` explicitly.

Note

The `OLD` behavior of a policy is `deprecated by definition` and may be removed in a future version of CMake.