The compiler derived implementations of `Codable` conformances for enums did
not take enum element unavailability into account. This could result in
unavailable values being instantiated at runtime, leading to a general
violation of the invariant that unavailable code is unreachable at runtime.
This problem is possible because synthesized code is not type checked; had the
conformances been hand-written, they would have been rejected for referencing
unavailable declarations inside of available declarations.
This change specifically alters derivation for the following declarations:
- `Decodable.init(from:)`
- `Encodable.encode(to:)`
- `CodingKey.init(stringValue:)`
Resolves rdar://110098469
Covers a missing case in codable synthesis for enums with argument
payloads that have internal and external labels. When the name of the
var decl is used, the internal name of the parameter becomes the key
instead of the API name. In this case, this causes an invalid reference
to an enum case with the internal name as an argument to be synthesized
in the derived Decodable conformance which (hopefully) crashes
downstream.
rdar://86339848
* [Sema]: Add Codable synthesis for enums with associated values
* Incorporate review feedback for enum Codable synthesis
* Implement enum specific versions of existing Codable tests
* Encode parameterless enum cases as
* Add test for overloaded case identifiers
* Align code generation with latest proposal revision
* Put enum codable derivation behind flag
* clang-format sources
* Address review feedback and fix tests
* Add diagnostic for conflicting parameter identifiers
* Restructure code after rebase
