In C++, a primary base class that is placed in the beginning of the type's memory layout isn't always the type that is the first in the list of bases – the base types might be laid out in memory in a different order.
This makes sure that IRGen handles base types of C++ structs in the correct order.
This fixes an assertion in asserts-enabled compilers, and an out-of-memory error in asserts-disabled compilers. The issue was happening for both value types and foreign reference types. This change also includes a small refactoring to reuse the logic between the two code paths.
rdar://140848603
In C++, a field of a derived class might be placed into the tail padding of a base class. Swift was not handling this case correctly, causing an asserts-disabled compiler to run out of RAM, and an asserts-enabled compiler to fail with an assertion.
Fixes this IRGen assertion:
```
Assertion failed: (offset >= NextOffset && "adding fields out of order"), function addField, file GenStruct.cpp, line 1509.
```
rdar://138764929
Instead of adding opaque fields for the base subobjects this patch
introduces a recursive walk to add all the base fields to the generated
Swift struct.
rdar://126754931
This test would fail on windows when built with assertions as the
`CxxShim` module was not imported. Add the missing import which is
required to enable this test on Windows.
This commit adds very basic support for importing and calling base class methods, getting and setting base class fields, and using types inside of base classes.
