9be6519f5a
Builds on 36eae9d4f6 to emit a message instead of just trapping
when a switch over a non-frozen enum ends up not matching anything.
If the enum is known to be an @objc enum, the message is
unexpected enum case 'MyEnum(rawValue: -42)'
and if it's anything else (a Swift enum, a tuple containing enums,
whatever), it's a more opaque
unexpected enum case while switching on value of type 'MyEnum'
The reason for this is to avoid calling String(describing:) or
String(reflecting:) an arbitrary value when the enum might conform to
CustomStringConvertible and therefore /itself/ have a switch that's
going to fall off the end. By handling plain @objc enums (using a
bitcast), we've at least covered the 90% case.
rdar://problem/37728359
Resilient Library Evolution Tests
This directory tests for the correctness of resilience, which is a
broad term for Swift maximizing binary compatibility of a dependency
while maintaining the freedom to do things that would normally break
clients in other languages, such as changing the layout of nominal
types. The detailed explanation of resilience is out of scope of this
little readme and can be found in docs/LibraryEvolution.rst.
Each main test file should compile against "before" and "after" versions of the corresponding library file. The old and new versions are selected via the BEFORE or AFTER preprocessor variables.
In the library, going from BEFORE to AFTER must be an ABI-compatible change, as documented in the library evolution specification.
In the main program, going from BEFORE to AFTER does not have to be backward compatible.
In the main file, use your test library's getVersion helper function
to know which version of the library to expect at runtime.
There are four valid combinations for each test:
- Main file compiled against old library, linked against old library a.k.a. "before before"
- Main file compiled against old library, linked against new library, a.k.a. "before after"
- Main file compiled against new library, linked against old library, a.k.a. "after before"
- Main file compiled against new library, linked against new library, a.k.a. "after after"
The version of the library available at compile time determines which serialized declarations and transparent function bodies are visible.
When adding a new test, see the boilerplate at the top of each file for
the general pattern for this kind of test. Use the StdlibUnittest
library for assertions.