* let `SIL.Type` conform to `TypeProperties` to share the implementation of common type properties between the AST types and `SIL.Type`
* call references to an `AST.Type` `rawType` (instead of just `type`)
* remove unneeded stuff
* add comments
When creating a specialized witness table, we need to get the right specialized conformance.
In IRGen don't emit associated conformance witness table entries if the protocol is not a class protocol.
In this case the associated type can never be used to create an existential. Therefore such a witness table entry is never used at runtime in embedded swift.
Fixes a compiler crash
rdar://146448091
* fix a false error if a derived class has different generic parameters than its base class
* fix a similar problem if a non-generic class derives from a generic class
* fix a compiler crash for calling a class method on a class metatype
rdar://137692055
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
MandatoryPerformanceOptimizations already did most of the vtable specialization work.
So it makes sense to remove the VTableSpecializerPass completely and do everything in MandatoryPerformanceOptimizations.
