* move it from the SIL to the AST module (where it belongs)
* change the signature of `diagnose` from `diagnose(location, .some_error)` to `diagnose(.some_error, at: location)`
* add an overload to allow passing a `SIL.Location` directly to `diagnose`
* add a `Diagnostic : Error` utility struct which allows throwing a `Diagnostic`
As the optimizer uses more and more AST stuff, it's now time to create an "AST" module.
Initially it defines following AST datastructures:
* declarations: `Decl` + derived classes
* `Conformance`
* `SubstitutionMap`
* `Type` and `CanonicalType`
Some of those were already defined in the SIL module and are now moved to the AST module.
This change also cleans up a few things:
* proper definition of `NominalTypeDecl`-related APIs in `SIL.Type`
* rename `ProtocolConformance` to `Conformance`
* use `AST.Type`/`AST.CanonicalType` instead of `BridgedASTType` in SIL and the Optimizer
ASTGen always builds with the host Swift compiler, without requiring
bootstrapping, and is enabled in more places. Move the regex literal
parsing logic there so it is enabled in more host environments, and
makes use of CMake's Swift support. Enable all of the regex literal
tests when ASTGen is built, to ensure everything is working.
Remove the "AST" and "Parse" Swift modules from SwiftCompilerSources,
because they are no longer needed.
To use _RegexParser from SwiftSyntax.
* Create 'libswiftCompilerModules_SwiftSyntax.a' which is a subset of
'libswiftCompilerModules.a'
* Link 'lib_InternalSwiftSyntaxParser' to
'libswiftCompilerModules_SwiftSyntax.a'
* Factor out swift runtime linking logic in CMake so that dynamic
libraries can link to Swift runtime, in addition to executables
* Link 'lib_InternalSwiftSyntaxParser' to swift runtime
