[mingxwa]

Motivation

• A dispatch type defined by PRO_DEF_MEM_DISPATCH, PRO_DEF_FREE_DISPATCH or PRO_DEF_FREE_AS_MEM_DISPATCH carries an accessor, so the function it calls also fixes the name and kind of the function exposed on a proxy. Providing same-name access by default is the v4 design that v5 removes.
• Calling one function and exposing it under another name, or as a member instead of a free function, required a hand-written dispatch type.

Design

• member_dispatch<"name"> calls the member function name, and free_dispatch<"name"> calls the free function name. member_access<"name"> defines the member function name on proxy, and free_access<"name"> defines the hidden friend name.
• A convention selects its dispatch type and its access type independently. The dispatch types carry no accessor, and no access type is selected for them implicitly.
• PRO_ENABLE_MEMBER(name) and PRO_ENABLE_FREE(name) define the dispatch and access specializations for name at global namespace scope. Each name is enabled at most once per translation unit for each macro.
• free_dispatch performs ordinary lookup from its own scope, then the namespace pro::inline v5, the namespace pro and its inline namespaces, and finally the global namespace. Argument-dependent lookup happens at instantiation.

Changes

• Added the class templates member_dispatch, member_access, free_dispatch and free_access, declared next to operator_dispatch so that proxy_macros.h stays a macro-only header, and exported them from the proxy.v5 module.
• Added PRO_ENABLE_MEMBER and PRO_ENABLE_FREE with their version-qualified forms and the ambiguity diagnostics of the other version-less macros.
• Added PRO5D_DEF_FREE_ACCESSOR for access types that define hidden friends.
• Added specification pages for the four class templates and the two macros, covering the accessor of each descriptor, the lookup rules of free_dispatch and module usage.
• Moved the free-as-member test, the weak member dispatch of ResourceDictionary, the reflection traits tests and the module test onto the new types.
• Replaced the shared reflection access test with a facade whose member access type combines a direct convention and a reflection and whose free access type exposes the same reflection.