Return tokens to emitted symbols on EmitResult

[tmat]

Return tokens to emitted symbols on EmitResult

[tmat]

@333fred FYI

[333fred]

API Review

• Could we just not use local functions here to make it easier?
  • Would require more wrapping of C# that we don't want to introduce.
• Tokens aren't really understood by the compiler, and it seems odd that we'd return them.
• This seems like it would be a significant chunk of work
• There are other cases that would need to be considered, such as anonymous function symbols.

Conclusion: Needs work. We'll work offline to determine the future of the proposal.

[tmat]

Tokens aren't really understood by the compiler, and it seems odd that we'd return them.

We do have ISymbol.MetadataToken public API that returns token of a PE symbol, or 0 if the symbol isn't a PE symbol with a token.

The proposed API is essentially similar to the existing API, it would instead work on symbols defined in source. I agree we should not try to implement it for symbols that are emitted as implementation details. A rule of thumb could be to support it for definitions that are named in the code and have tokens (named type, method or local function, field, property, event, parameter, generic parameter symbol).

The Semantic Search scenario that uses local function is just one hosting scenario. In general hosting scenario a host application uses Roslyn compilation to emit assembly, then loads the assembly and then interacts with the loaded entities via Reflection. The mapping between ISymbol and the emitted metadata might get complicated. E.g. when the host needs to distinguish 2 method overloads, or needs to find a symbol whose name is mangled (local function, explicit interface implementation, etc.).

Note also that EmitDifferenceResult, which derives from EmitResult and is used for EnC returns handles (tokens) to the methods and types it emitted.