For the most part, this moves 3/4 tests to 4/5 tests. There are
some interesting changes here because API notes for 4 also apply
to 3 unless otherwise specified, and 4.2 is the next version after
4 rather than 5, but everything should still be correct and testing
useful stuff.
ClangImporter::lookupTypeDecl allows a Clang type declaration to be
imported by Clang name instead of by Swift name. Now that we're using
Clang names in mangled names, that's exactly what we need to
reconstruct an AST type from a mangled name.
Also:
- Handle @compatibility_alias in ClangImporter::lookupTypeDecl
- Print errors when type reconstruction fails in swift-ide-test
- Add an extra test for RemoteAST
This means all cross-module references and all mangled names will
consistently use the Swift 4 name (the canonical type), no special
handling required.
The main thing we lose here is that the Swift 4 names of imported
types become usable in Swift 3 mode without any diagnostics, similar
to how most language features introduced in Swift 4 are available in
Swift 3 mode. It also implies that the Swift 4 name will show up in
demangled names.
rdar://problem/31616162
