This patch changes the class template printer to disambiguate const-qualified template arguments by wrapping them with __cxxConst<>, rather than suffixing them with _const.
This is necessary to accommodate template arguments that aren't just identifiers (i.e., Foo<Int_const> is ok, but Foo<Bar<T>_const> and Foo<((Bar) -> Baz)_const> are not syntactically valid). With this patch, we would produce Foo<__cxxConst<Int>>, Foo<__cxxConst<Bar<T>>, and Foo<__cxxConst<((Bar) -> Baz)>> instead.
This patch also disambiguates volatile-qualified template arguments with __cxxVolatile<>, and changes the printing scheme for std::nullptr_t from nil to __cxxNullPtrT (since nil is not a syntactically valid type name).
rdar://143769901
When Swift imports C++ template class instantiations, it generates a human-readable Swift name for each instantiation.
Having name collisions causes multiple Swift type with the same name, which confuses the compiler.
`MyClass<int[]>` and `MyClass<long[]>` were both being imported as `MyClass<_>` into Swift. This patch fixes that:
* `MyClass<int[]>` is now imported as `MyClass<[CInt]>`
* `MyClass<int[123]>` is now imported as `MyClass<Vector<CInt, 123>>`
rdar://138921102
This change is necessary to differentiate between C++ const and non-const types in Swift.
For instance, `const int` and `int` would both be printed as `CInt` in Swift.
After this change, `const int` is stored as `CInt_const`
This makes sure we are printing more than one level of C++ template specializations when emitting a Swift struct name.
For instance, `std::__wrap_iter<char*>` and `std::__wrap_iter<const char*>` are currently imported with the same name in Swift. This means the mangled string will be the same for these specializations, despite them being distinct types. This causes mangling errors.
rdar://117485399
