 a data type used for storing the data of the
new data category; the name of this type is the name of the data category with
"Ty" appended. For <tt>REGISTER_TRAIT_WITH_PROGRAMSTATE</tt>, this will simply
be passed data type; for the other three macros, this will be a specialized
version of the <a
href="http://llvm.org/doxygen/classllvm_1_1ImmutableList.html">llvm::ImmutableList</a>,
<a
href="http://llvm.org/doxygen/classllvm_1_1ImmutableSet.html">llvm::ImmutableSet</a>,
or <a
href="http://llvm.org/doxygen/c