modes. @xref{Setting Hooks}.
@item pure
-This property is used internally to mark certain named functions for
-byte compiler optimization. Do not set it.
+If the value is non-@code{nil}, the named function is considered to be
+side-effect free. Calls with constant arguments can be evaluated at
+compile time. This may shift run time errors to compile time.
@item risky-local-variable
If the value is non-@code{nil}, the named variable is considered risky