The SILGen testsuite consists of valid Swift code covering most language
features. We use these tests to verify that no unknown nodes are in the
file's libSyntax tree. That way we will (hopefully) catch any future
changes or additions to the language which are not implemented in
libSyntax.
Rather than mangling the complete generic signature of a constrained
extension, only mangle the requirements not already satisfied by the
nominal type. For example, given:
extension Dictionary where Value: Equatable {
// OLD: _T0s10DictionaryV2t3s8HashableRzs9EquatableR_r0_lE3baryyF
// NEW: _T0s10DictionaryV2t3s9EquatableR_rlE3baryyF
public func bar() { }
}
In the existing mangling, we mangle the `Key: Hashable` requirement that’s
part of the generic signature. With this change, we only mangle the new
requirement (`Value: Equatable`).
This is a win for constrained extensions *except* in the case of a
constrained extension of a nominal type with a single, unconstrained
generic parameter:
extension Array where Element: Equatable {
// OLD: _T0Sa2t3s9EquatableRzlE3baryyF
// NEW would be: _T0Sa2t3s9EquatableRzrlE3baryyF
public func bar() { }
}
Check explicily for this shortcut mangling and fall back to the old
path, so this change is a strict improvement.
Recently I changed the ArchetypeBuilder is minimize requirements
in generic signatures. However substitution lists still contained
all recursively-expanded nested types.
With recursive conformances, this list becomes potentially
infinite, so we can't expand it out anymore. Also, it is just
a waste of time to have them there.
The existing code assumed that the _bridgeToObjectiveC witness would never come from a protocol extension. Generating the correct set of substitutions is a bit harder than it ought to be, due to inconsistencies in how Sema represents generic witnesses. Fixes rdar://problem/28279269.
