[lldb] Reimplement and implement GetPointerType

[kastiglione]

Reimplement SwiftASTContext::GetPointerType to return the given type wrapped in UnsafePointer<T>. Also implement TypeSystemSwiftTypeRef::GetPointerType with a matching demangle-based implementation that also wraps in UnsafePointer.

Given a variable x: Int, here is some output:

(lldb) script print(lldb.frame.vars["x"][0].AddressOf())
(UnsafePointer<Int>) &x = 0x7ffeefbff728 {
  [0] = 23
}
(lldb) script print(lldb.frame.vars["x"][0].AddressOf().type)
@frozen struct UnsafePointer<Pointee> : Swift._Pointer {
...

rdar://68171356

[kastiglione]

I removed the unused Demangler parameter.

[kastiglione]

@swift-ci test

[kastiglione]

A follow up will be to fix the following:

(lldb) sc print(lldb.frame.vars["x"][0].AddressOf().Dereference())
No value

[kastiglione]

Looking closer at this output:

(lldb) sc print(lldb.frame.vars["x"][0].AddressOf())
(UnsafePointer<Int>) &x = 0x7ffeefbff728 {
  [0] = 23
}

1. Do we expect/like the output of (UnsafePointer<Int>) &x = <addr>?
2. Do we expect/like the fact that it's formatted as a single element array?

[adrian-prantl]

Apart from some stylistic nitpicks inline, this looks good!

[adrian-prantl]

Looking closer at this output:

(lldb) sc print(lldb.frame.vars["x"][0].AddressOf())
(UnsafePointer<Int>) &x = 0x7ffeefbff728 {
  [0] = 23
}

1. Do we expect/like the output of (UnsafePointer<Int>) &x = <addr>?
2. Do we expect/like the fact that it's formatted as a single element array?

I guess that is coming from a C-centric view that arrays and pointers are interchangeable. It does make much less sense in Swift.

[adrian-prantl]

... but that's a separate problem that presumably affects all pointer types.

[kastiglione]

@swift-ci test

[adrian-prantl]

Nice!