This executable is intended to be installed in the toolchain and act as
an executable compiler plugin just like other 'macro' plugins.
This plugin server has an optional method 'loadPluginLibrary' that
dynamically loads dylib plugins.
The compiler has a newly added option '-external-plugin-path'. This
option receives a pair of the plugin library search path (just like
'-plugin-path') and the corresponding "plugin server" path, separated
by '#'. i.e.
-external-plugin-path
<plugin library search path>#<plugin server executable path>
For exmaple, when there's a macro decl:
@freestanding(expression)
macro stringify<T>(T) -> (T, String) =
#externalMacro(module: "BasicMacro", type: "StringifyMacro")
The compiler look for 'libBasicMacro.dylib' in '-plugin-path' paths,
if not found, it falls back to '-external-plugin-path' and tries to find
'libBasicMacro.dylib' in them. If it's found, the "plugin server" path
is launched just like an executable plugin, then 'loadPluginLibrary'
method is invoked via IPC, which 'dlopen' the library path in the plugin
server. At the actual macro expansion, the mangled name for
'BasicMacro.StringifyMacro' is used to resolve the macro just like
dylib plugins in the compiler.
This is useful for
* Isolating the plugin process, so the plugin crashes doesn't result
the compiler crash
* Being able to use library plugins linked with other `swift-syntax`
versions
rdar://105104850
For future usage from other host libraries written in Swift
For CMake:
* Explicitly specify LINKER_LANGAGE to CXX in existing components so
that 'swiftc' is not used when linking with 'swiftASTGen'
* Add 'EMIT_MODULE' argument to 'add_pure_swift_host_library' to emit
.swiftmodule usable from other Swift libraries.
Add SourceManager that can keep track of multiple source file syntax
nodes along with their external representations. The source manager can
emit diagnostics into any of those files, including tracking any
explicitly "detached" syntax nodes used for macro expansion.
Make sure we detach syntax nodes before passing them to macro
implementations, so they cannot see more of the source file than they
are permitted. We hadn't been doing this before (by accident), and
doing so motivated the introduction of the SourceManager.
Additionally, perform operator folding on macro arguments as part of
detaching them. Macro clients shouldn't have to do this, and moreover,
when clients do this, they lose the ability to easily emit diagnostics
on the now-folded nodes.
Introduce an experimental option `BuiltinMacros` that takes the magic
literals (`#file`, `#line`, `#function`, etc.) after type checking and
processes the original source for the expression using the build
syntactic macro system in the swift-syntax library. At present, the
result of expansion is printed to standard output, but it's enough to
verify that we're able to find the corresponding syntax node based on
the C++ AST.
