This disables TBD validation when C++ interop is enabled, unless an explicit `-validate-tbd-against-ir=` flag was passed.
rdar://83405989 / https://github.com/apple/swift/issues/56458
`std::map` conformance to `CxxDictionary` is synthesized properly, only the `std::unordered_map` conformance is problematic.
Let's make sure we test the `std::map` conformance with libstdc++ on Linux.
This adds a protocol to the C++ standard library overlay which will improve the ergonomics of `std::map` and `std::unordered_map` when used from Swift code.
As of now, `CxxDictionary` adds a subscript with an optional return type that mimics the subscript of `Swift.Dictionary`.
Similar to https://github.com/apple/swift/pull/63244.
C++ iterator types are often templated, and sometimes declare `operator==` as a non-member templated function. In libc++, an example of this is `__wrap_iter` which is used as an iterator type for `std::vector` and `std::string`.
We don't currently import templated non-member operators into Swift, however, we still want to support common C++ iterator patterns.
This change adds logic to instantiate templated non-member `operator==` for types that define `iterator_category` and are therefore likely to be valid iterator types.
rdar://97915515
If an operator is declared as a method of a templated class, we were failing to look it up during auto-conformance to `UnsafeCxxInputIterator`.
This fixes `Interop/Cxx/stdlib/use-std-map.swift` on Ubuntu.
rdar://102420290
This fixes an error that occurred when trying to use the subscript on an instance `std::map`:
```
error: cannot assign through subscript: 'map' is immutable
```
This was happening even with a mutable `std::map` instance.
`std::map::operator[]` has two overloads:
* `T& operator[]( const Key& key )`
* `T& operator[]( Key&& key )`
The second one is imported with an `inout` parameter, and we picked it as an implementation of the subscript getter because it was the last of the two overloads to get imported.
Swift does not allow subscripts with `inout` parameters. This is checked at the AST level, and those checks do not run for synthesized Swift code. This caused Swift to produce a surprising error which actually indicated that the argument of the subscript, not the instance itself, must be mutable.
rdar://100529571
