Compiler internals question: TIdTable tables

[cdome]

I need advice from the Nim compiler ninja.

I am inside semResolvedCall(semcall.nim) function and I have instance of 
TCandidate object which has **bindings** field. It is a table from generic 
param types to concrete param types. How do I extract a **concreate return 
type**? I don't need anything else. I just can't figure out how to construct a 
valid key for TIdTable table.

So far I am doing it in a silly way:
    
    
    for pair in x.bindings.pairs:
        result.typ = PType(pair.value)
        break