Use information from reflection section of the binary to lookup
type field info such as name and it's type and return it using
new `swift_getFieldAt` method based on nominal type and field index.
The old-style mirrors were the basis for non-custom, reflection based Mirrors. As part of removing old-style mirrors, reflection based Mirrors are reimplemented without them. Reflection.mm is deleted and replaced with ReflectionMirror.mm, which borrows a chunk of the old code but presents a simpler API to the Swift side. ReflectionMirror.swift then uses that API to implement a reflection-based Mirror init.
rdar://problem/20356017
@objc protocols don't have witness tables. However, both type metadata
(in the nominal type descriptors) and the runtime code to demangle
type names into metadata weren't acknowledging this. Fix type metadata
emission to not count an "extra argument" for @objc protocol
conformance requirements, and teach the runtime code to properly look
for conformances to @objc protocols (through the Objective-C runtime)
and not record witness tables for them.
This makes resolving mangled names to nominal types in the same module more efficient, and for eventual secrecy improvements, also allows types in the same module to be referenced from mangled typerefs without encoding any source-level name information about them.
Given any heap object, this method dumps:
* The pointer address of the heap object.
* The pointer address of the heap metadata of the object.
* The strong reference count.
* The unowned reference count.
* The weak reference count.
* Whether or not the value is in the deinit state.
* Whether or not the heap object uses swift_retain or objc_retain.
* The address of the object's side table if one exists.
This makes it really easy when debugging quickly to get all of the information
that you could possibly need from a HeapObject.
`_typeByMangledName` could encounter types which have ownership attributes
associated with them which are not representable by the metadata object
but nevertheless are important, so such ownership information should be
returned along with metadata itself from the call.
When evaluating whether a given type conforms to a protocol, evaluate the
conditional requirements and pass the results to the witness table
accessor function. This provides the ability to query conditional
conformances at runtime, and is the last major part of implementing
SE-0143.
The newly-added unlock/lock dance in the conformance lookup code is a
temporary stub. We have some ideas to do this better.
Fixes rdar://problem/34944655.
