Assertion failure on itype declaration in macro

[mattmccutchen-cci]

Running 3c on the following code:

#define PARAM_DECL_WITH_ITYPE int *p : itype(_Ptr<int>)

void foo(PARAM_DECL_WITH_ITYPE);

produces:

3c: /home/matt/3c-2.wt/clang/lib/3C/ConstraintVariables.cpp:292: PointerVariableConstraint::PointerVariableConstraint(const clang::QualType&, clang::DeclaratorDecl*, std::string, ProgramInfo&, const clang::ASTContext&, std::string*, int, bool, clang::TypeSourceInfo*, const clang::QualType&): Assertion `ItypeStr.size() > 0' failed.

This is caused by the same problem with retrieval of the original source of a program element inside a macro that I partially worked around in #436; I added a note about this remaining case to clang/test/3C/params_in_macro.c. I decided to file an issue now because the problem came up in some of my manual tests related to #581. I guess we haven't run into this problem in real work yet because we don't tend to write Checked-C-specific constructs inside macros.

I don't have a good enough understanding of the code to know whether we can just remove the assertion or we might need to make other changes.