dart:ffi resolve outstanding design decisions

[dcharkes]

Make decisions on open design decisions:

• dart:ffi canonical representation of C null pointer in Dart #35756 representation of C null
• dart:ffi Uint64 load/store values which cannot be represented in Dart int #35757 Uint64 store/load
• [vm/ffi] Allow subclassing Pointer? #35782 signature allocate/fromAddress
• dart:ffi int8 etc truncate and sign extend vs exceptions #35787 int8 etc truncate vs exception
• Re-design struct API to facilitate reference semantics #35840 struct representation
• dart:ffi break up Pointer API into const/indexable/castable #35841 const / indexable / castable Pointers
• dart:ffi hide or restrict Pointer.address and fromAddress #35844 restrict fromAddress and address
• dart:ffi Void size one byte or unknown #35879 void size
• [vm/ffi] DynamicLibrary extends Struct #35881 Library extends Pointer
• dart:ffi remove Pointer.offsetBy #35883 remove Pointer.offsetBy
• dart:ffi asFunction / lookupFunction static function vs instance method #35903 asFunction static vs instance method
• [vm/ffi] int, long, size_t, uintptr_t, wchar_t, etc #36140 support int, long, etc?

[dcharkes]

Closing this issue because we have adopted the "type-design" label for ffi design decisions.

[sensuikan1973]

"type-design" label for ffi design decisions.

⇒ https://github.com/dart-lang/sdk/projects/13?card_filter_query=label%3Atype-design