CMP0111: Clarify that the new error is on a missing property setting

The previous wording could be confused with the file missing on disk.

1 files changed, 10 insertions, 3 deletions

diff --git a/Help/policy/CMP0111.rst b/Help/policy/CMP0111.rst
index 37e5ad5..e327583 100644
--- a/Help/policy/CMP0111.rst
+++ b/Help/policy/CMP0111.rst
@@ -3,10 +3,17 @@ CMP0111
 
 .. versionadded:: 3.19
 
-An imported target with a missing location fails during generation.
+An imported target missing its location property fails during generation.
 
-Prior to this the location would be generated as ``<TARGET_NAME>-NOTFOUND``,
-which would result in build failures.
+:ref:`Imported Targets` for library files and executables require that
+their location on disk is specified in a target property such as
+:prop_tgt:`IMPORTED_LOCATION`, :prop_tgt:`IMPORTED_IMPLIB`, or a
+per-configuration equivalent.  If a needed location property is not set,
+CMake 3.18 and below generate the string ``<TARGET_NAME>-NOTFOUND`` in
+its place, which results in failures of the corresponding rules at build
+time.  CMake 3.19 and above prefer instead to raise an error during
+generation.  This policy provides compatibility for projects that have
+not been updated to expect the new behavior.
 
 The ``OLD`` behavior of this policy is to generate the location of an imported
 unknown, static or shared library target as ``<TARGET_NAME>-NOTFOUND`` if not