Provisional API: This reference documents current compiler behavior. Compatibility is not yet promised.

src/components/protocol-adapters.x

Protocol adapters and Var descriptors.

Design notes

The compiler presents each resolved conformance whose forward converter the unit defines, and whose participant is not numeric, as a conform form. It has settled each member’s owner and storage, reported their collisions and missing conversions, and introduced the generated names:

(conform BASE PARTICIPANT FORWARD REVERSE BINDER DESCRIPTOR (ROW…))

FORWARD and REVERSE spell the participant’s converters to and from BASE, and BINDER is the protocol’s type variable. A ROW is (MEMBER STATUS SOURCE EXPECTED TEMPLATE PART...): STATUS is base-dflt, implmntd, or no-member, SOURCE the function that implements the member, EXPECTED its signature for the participant, and TEMPLATE its signature in the protocol. Each PART asks for one function NAME, a binding. (default NAME STORAGE) is the forwarding member PARTICIPANT_MEMBER, static when STORAGE is static, which calls SOURCE. (inherited NAME EXPECTED) is the prototype of that member, which another conformance defines with the signature EXPECTED. (thunk NAME ERASED) is the descriptor slot MEMBER’s function, whose signature ERASED types each protocol variable Var. DESCRIPTOR is (METHODS NAME VAR-TAG AREA [TAG]) for a Var participant with its own descriptor, and empty otherwise: the method table’s name, the registered type name and its Var tag, the unit-init area, and an explicit tag. A rule answers file-scope code for the unit’s support, or (seq) when it placed everything.

This rule places each function and the static method table among the unit’s support declarations, and the table’s assignment and the descriptor’s registration in the unit’s initialization. A forwarding member or thunk passes each parameter the protocol types BINDER through a converter: FORWARD for a forwarding member, REVERSE for a thunk. A thunk that prints a boxed struct or union, a copy that has an identity only before unboxing, guards its rendering path.

Each definition precedes the definitions that call it: the compiler settles whether a linked copy reaches a compile-time operation when the copy binds.