* factor out common methods of AST Type/CanonicalType into a `TypeProperties` protocol.
* add more APIs to AST Type/CanoncialType.
* move `MetatypeRepresentation` from SIL.Type to AST.Type and implement it with a swift enum.
* let `Builder.createMetatype` get a CanonicalType as instance type, because the instance type must not be a lowered type.
`AvailabilityRange` is now being used as a currency type in more of the
compiler, and some of those uses are in permanent `ASTContext` allocations. The
class wraps the `VersionRange` utility, which is itself a wrapper around
`llvm::VersionTuple` with some additional storage for representing sentinel
values. Even though the two sentinel values can be be represented with just a
single bit of additional storage on top of the 16 bytes required to represent
`VersionTuple`, because of alignment requirements the sentinel values end up
bloating the layout of `VersionRange` by many bytes.
To make `AvailabilityRange` and `VersionRange` more efficient to store, we can
instead reserve two unlikely `llvm::VersionTuple` bit patterns as the sentinel
values instead. The values chosen are the same ones LLVM uses to represent
version tuple tombstones and empty keys in a `DenseMap`.
To pave the way for the new experimental feature which will operate on '@const' attribute and expand the scope of what's currently handled by '_const' without breaking compatibility, for now.
This will unblock parsing and type-checking availability queries that specify
custom availability domains, e.g.:
```
if #available(CustomDomain) {
// Use declarations protected by @available(CustomDomain)
}
```
Memory unsafety in the iteration part of the for-in loop (i.e., the part
that works on the iterator) can be covered by the "unsafe" effect on
the for..in loop, before the pattern.
It wraps an type-checked `AvailabilitySpec`, which guarantees that the spec has
a valid `AvailabilityDomain` associated with it. This will unblock moving
AvailabilitySpec domain resolution from parsing to sema.
Parse expanded buffer into dedicated syntax.
Also rename `BridgedGeneratedSourceFileKindAttribute` to
`BridgedGeneratedSourceFileKindAttributeFromClang` because C++ decl
(i.e. `GeneratedSourceInfo::Kind::AttributeFromClang`) was renamed a
while ago.
* Collect flag in `ParamDecl::setTypeRepr()`.
* [ASTGen] Separate `BridgedParamDecl.setTypeRepr(_:)` from
`BridgedParamDecl.createParsed(_:)` aligning with C++ API. The majority
of the creations don't set the typerepr.
* Update `ParamSpecifierRequest::evaluate` to handle non-implicit
`ParamDecl` without `TypeRepr` (i.e. untyped closure parameter), instead
of `setSpecifier(::Default)` manually in Parse.
Rework TypeAttribute bridging facilities.
Eliminate the _fake_ `swift::TypeAttributes`, but just use the normal
`BridgedArrayRef` for briding the attribute list. Introduce
`BridgedTypeOrCustomAttr` tagged pointer which resembles
`swift::TypeOrCustomAttr`.
* Instead of hoisting VarDecl in the bridging functions, do it in
ASTGen.
* Introduce `Decl::forEachDeclToHoist` to handle VarDecls in
PatternBindingDecl, and EnumElementDecl in EnumCaseDecl.
* Intorduce `withBridgedSwiftClosure(closure:call:)` as a callback
mechanism between Swift and C++
* In `generate(sourceFile:)`, instead of using `generate(codeBlockItem:)`
handle `CodeBlockItemSyntax.Item` manually to handle `TLCD` wrapping
and `VarDecl` hoisting.
* Make `generate(variableDecl:)` handle TLCD correctly.
