swift函数的调用约定

• The convention of the function, indicated by the

  attribute. This is similar to the language-level @convention attribute, though SIL extends the set of supported conventions with additional distinctions not exposed at the language level:

  • @convention(thin) indicates a "thin" function reference, which uses the Swift calling convention with no special "self" or "context" parameters.
  • @convention(thick) indicates a "thick" function reference, which uses the Swift calling convention and carries a reference-counted context object used to represent captures or other state required by the function. This attribute is implied by @callee_owned or @callee_guaranteed.
  • @convention(block) indicates an Objective-C compatible block reference. The function value is represented as a reference to the block object, which is an id-compatible Objective-C object that embeds its invocation function within the object. The invocation function uses the C calling convention.
  • @convention(c) indicates a C function reference. The function value carries no context and uses the C calling convention.
  • @convention(objc_method) indicates an Objective-C method implementation. The function uses the C calling convention, with the SIL-level self parameter (by SIL convention mapped to the final formal parameter) mapped to the self and _cmd arguments of the implementation.
  • @convention(method) indicates a Swift instance method implementation. The function uses the Swift calling convention, using the special self parameter.
  • @convention(witness_method) indicates a Swift protocol method implementation. The function's polymorphic convention is emitted in such a way as to guarantee that it is polymorphic across all possible implementors of the protocol.

https://github.com/apple/swift/blob/master/docs/SIL.rst#properties-of-types