To represent a type with code completion.
type? '.'? <code-completion-token>
This is "parser only" node which is not exposed to SwiftSyntax.
Using this, defer to set the parsed type to code-completion callbacks.
So that we can easily detect 'ParsedSyntaxNode' leaking. When it's
moved, the original node become "null" node. In the destructor of
'ParsedSyntaxNode', assert the node is not "recorded" node.
Instead of creating the AST directly in the parser (and libSyntax or
SwiftSyntax via SyntaxParsingContext), make Parser to explicitly create
a tree of ParsedSyntaxNodes. Their OpaqueSyntaxNodes can be either
libSyntax or SwiftSyntax. If AST is needed, it can be generated from the
libSyntax tree.
This eliminates the overhead of ParsedRawSyntaxNode needing to do memory management.
If ParsedRawSyntaxNode needs to point to some data the memory is allocated from a bump allocator.
There are also some improvements on how the ParsedSyntaxBuilders work.
Doing a "direct ParsedSyntaxRecorder::record[some syntax]" call from the parser is not a good idea due to possibility
of being in a backtracking context when the call is made. Replace them with "ParsedSyntaxRecorder::make[some syntax]"
which will implicitly check for backtracking and create a recorded or deferred node accordingly.
Instead of creating syntax nodes directly, modify the parser to invoke an abstract interface 'SyntaxParseActions' while it is parsing the source code.
This decouples the act of parsing from the act of forming a syntax tree representation.
'SyntaxTreeCreator' is an implementation of SyntaxParseActions that handles the logic of creating a syntax tree.
To enforce the layering separation of parsing and syntax tree creation, a static library swiftSyntaxParse is introduced to compose the two.
This decoupling is important for introducing a syntax parser library for SwiftSyntax to directly access parsing.
