if: Implement new IN_LIST operator

3 files changed, 19 insertions, 1 deletions

diff --git a/Help/command/if.rst b/Help/command/if.rst
index d50b14c8a2..396becfaa6 100644
--- a/Help/command/if.rst
+++ b/Help/command/if.rst
@@ -134,6 +134,9 @@ Possible expressions are:
  Component-wise integer version number comparison (version format is
  ``major[.minor[.patch[.tweak]]]``).
 
+``if(<variable|string> IN_LIST <variable>)``
+ True if the given element is contained in the named list variable.
+
 ``if(DEFINED <variable>)``
  True if the given variable is defined.  It does not matter if the
  variable is true or false just if it has been set.  (Note macro
diff --git a/Help/policy/CMP0057.rst b/Help/policy/CMP0057.rst
index 377f22d3fe..1298a16311 100644
--- a/Help/policy/CMP0057.rst
+++ b/Help/policy/CMP0057.rst
@@ -1,4 +1,14 @@
 CMP0057
 -------
 
-This policy is reserved for future use.
+Support new :command:`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 |release| warns when the policy is not set and uses
+``OLD`` behavior.  Use the :command:`cmake_policy` command to set
+it to ``OLD`` or ``NEW`` explicitly.
diff --git a/Help/release/dev/if-IN_LIST.rst b/Help/release/dev/if-IN_LIST.rst
new file mode 100644
index 0000000000..9dd07253d7
--- /dev/null
+++ b/Help/release/dev/if-IN_LIST.rst
@@ -0,0 +1,5 @@
+if-IN_LIST
+----------
+
+* Add a new IN_LIST operator to if() that evaluates true
+  if a given element is contained in a named list.