Implement an ASTGen operation to bridge swift-syntax diagnostics, as
produced by the parser, operator folding, and macros, over to the C++
diagnostic engine infrastructure. Use this to wire up macro expansion
diagnostics.
The API provided by macro evaluation has changed a bit. Adapt ASTGen to
the new API, and use this as an opportunity to start moving more tests
to using the shared libraries built into the toolchain.
A macro declaration contains the external module and type name of the
macro's implementation. Use that information to find the macro type
(via its type metadata accessor) in a loaded plugin, so we no longer
require the "allMacros" array. Instead, each macro implementation type
must be a public struct.
Since we are now fully dependent on the macro declaration for
everything about a macro except its kind, remove most of the query
infrastructure for compiler plugins.
Replace the macro registration scheme based on the allMacros array with
The macro signature can depend on both the owning module and any
supplemental signature modules. Create import declarations for each of these
prior to import resolution of the macro signature buffer.
Allow more than one macro plugin to introduce a macro with the same
name, and let the constraint solver figure out which one to call. Also
eliminates a potential use-after-free if we somehow find additional
compiler plugins to load after having expanded a macro.
Plumb the information about the owning module and supplemental
signature modules through to the Macro data structure, for both
built-in and plugin macros.
We're resolving the given module names into module declarations, but
otherwise performing no checking and not emitting any diagnostics.
This information is not yet used.
Type check user-defined macros plugins with user-provided type signatures.
Also, load plugin libraries with `RTLD_LOCAL` instead of `RTLD_GLOBAL` to prevent symbol collision between plugins. `llvm::sys::DynamicLibrary` only supports `RTLD_GLOBAL` so we use the plain `dlopen` instead. This does not work on Windows and needs to be fixed.
Friend PR: apple/swift-syntax#1042
Allow user-defined macros to be loaded from dynamic libraries and evaluated.
- Introduce a _CompilerPluginSupport module installed into the toolchain. Its `_CompilerPlugin` protocol acts as a stable interface between the compiler and user-defined macros.
- Introduce a `-load-plugin-library <path>` attribute which allows users to specify dynamic libraries to be loaded into the compiler.
A macro library must declare a public top-level computed property `public var allMacros: [Any.Type]` and be compiled to a dynamic library. The compiler will call the getter of this property to obtain and register all macros.
Known issues:
- We current do not have a way to strip out unnecessary symbols from the plugin dylib, i.e. produce a plugin library that does not contain SwiftSyntax symbols that will collide with the compiler itself.
- `MacroExpansionExpr`'s type is hard-coded as `(Int, String)`. It should instead be specified by the macro via protocol requirements such as `signature` and `genericSignature`. We need more protocol requirements in `_CompilerPlugin` to handle this.
- `dlopen` is not secure and is only for prototyping use here.
Friend PR: apple/swift-syntax#1022
