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.
This fixes:
* An issue where the diagnostic messages were leaked
* Diagnose at correct position inside the regex literal
To do this:
* Introduce 'Parse' SwiftCompiler module that is a bridging layer
between '_CompilerRegexParser' and C++ libParse
* Move libswiftParseRegexLiteral and libswiftLexRegexLiteral to 'Parse'
Also this change makes 'SwiftCompilerSources/Package.swift' be configured
by CMake so it can actually be built with 'swift-build'.
rdar://92187284
Currently, SwiftCompilerSources' inclusion of the regex parser depends on CMake flag `SWIFT_ENABLE_EXPERIMENTAL_STRING_PROCESSING`. However, in some scenarios we want to build the regex parser as part of the compiler _without_ building the runtime modules. This patch makes building the regex parser the default regardless of `SWIFT_ENABLE_EXPERIMENTAL_STRING_PROCESSING`. Only when the build environment is missing the string processing repo, we skip building the regex parser by setting `SWIFT_BUILD_REGEX_PARSER_IN_COMPILER` to false.
As the _MatchingEngine module no longer contains the matching engine, this patch renames this module to describe its role more accurately. Because this module primarily contains the AST and the regex parsing logic, I propose we rename it to "_RegexParser".
Also renames the ExperimentalRegex module in SwiftCompilerSources to _RegexParser for consistency. This would prevent errors if sources in _RegexParser used qualified lookup with the module name.
