ENH: Improve argument parsing error messages

Previously error messages produced by parsing of command argument
variable references, such as bad $KEY{VAR} syntax or a bad escape
sequence, did not provide good context information.  Errors parsing
arguments inside macro invocations gave no context at all.  Furthermore,
some errors such as a missing close curly "${VAR" would be reported but
build files would still be generated.

These changes teach CMake to report errors with good context information
for all command argument parsing problems.  Policy CMP0010 is introduced
so that existing projects that built despite such errors will continue
to work.

1 files changed, 1 insertions, 0 deletions

diff --git a/Source/cmPolicies.h b/Source/cmPolicies.h
index 06079b0..02f7276 100644
--- a/Source/cmPolicies.h
+++ b/Source/cmPolicies.h
@@ -50,6 +50,7 @@ public:
     CMP0007, // list command handling of empty elements
     CMP0008, // Full-path libraries must be a valid library file name
     CMP0009, // GLOB_RECURSE should not follow symlinks by default
+    CMP0010, // Bad variable reference syntax is an error
 
     // Always the last entry.  Useful mostly to avoid adding a comma
     // the last policy when adding a new one.