[swift-dev] The proper way to get all visible protocols in a decl context

[Douglas Gregor]

> On Feb 29, 2016, at 3:00 PM, Haichuan Wang via swift-dev <swift-dev at swift.org> wrote:
> 
> Hi,
> 
> I'm using Swift to do some language feature research. One feature I'm testing is automatic identifying implicit conformations if a nominal type implicitly satisfies a protocol's requirement. Then I can use that type as the protocol directly.
> 
> The way I'm doing is in the second AST visiting pass of the TypeChecker. When visiting a nominal type node, 
> - Finding all visible protocols in this context
> - For each protocol, add a synthesized conformance, and use the conformance checker to check
> - If fail, remove the synthesized conformance
> 
> Just wondering the proper way to get all visible protocols in a decl context? Right now, I record all the protocols during the type checker's first AST visit pass. Seems not good. Any suggestions to this and to the above conformance checking? 

There’s no data structure that specifically encodes this. The easiest thing to do is use getTopLevelDecls() on the module and dyn_cast each returned result to ProtocolDecl to get the protocols.

	- Doug