This patch also refactors the structure of function signature node so
that closure signature can re-use parts of function signature. For
instance, we group arrow and return type to be "ReturnClause". And we
group parenthesized parameter list to be "ParamClause".
This structure of closure signature also calls for a good way to
represent either-or node in libSyntax APIs, since we've two ways to
specify parameters in closure: one is as regular function parameter and
the other is dot-separated simple names.
To construct struct syntax, this patch first specialized type
inheritance clause. For protocol's class requirement, we currently
treat it as an unknown type.
This patch also teaches SyntaxParsingContext to collect syntax nodes
from back in place. This is useful to squash multiple decl modifiers
for declarations like function. This is not used for struct declaration
because only accessibility modifier is allowed.
* Create Swift libSyntax API
This patch is an initial implementation of the Swift libSyntax API. It
aims to provide all features of the C++ API but exposed to Swift.
It currently resides in SwiftExperimental and will likely exist in a
molten state for a while.
* Only build SwiftSyntax on macOS
* Generate libSyntax API
This patch removes the hand-rolled libSyntax API and replaces it with an
API that's entirely automatically generated. This means the API is
guaranteed to be internally stylistically and functionally consistent.
