I did see that some uses in LLVM seem like people are writing

struct MyVec : std::vector<int> {};

simply as a kind of "mangling firewall," where the "natural" thing to write (in the absence of any external constraints) would have been simply:

using MyVec = std::vector<int>;

In the latter case the mangled symbol names would have contained "std::__1::vector<int, std::__1::allocator<int>>"; in the former case they'll simply contain "MyVec", which is (1) shorter, (2) easier to read in the debugger, and (3) more stable in case this is a long-lived shared-library ABI boundary.

Maybe we should be able to specify a specific mangled name:

typedef std::vector<int> MyVec _MangleAs("MyVec");

and maybe we should be able to use 'typedef' for forward declarations much in the same way we use 'class' for forward declarations. So the header file would have:

typedef ? MyVec _MangleAs("MyVec");

An alternative syntax might be to play around with extern C, maybe something like:

extern "C" "MyVec" typedef std::vector<int> MyVec;

I'm sure ChatGPT could suggest another dozen possible syntaxes.