chained_conversion.swift:
#    1| [NamedFunction] foo(x:)
#    1|     InterfaceType = (inout Int) -> Int?
#    1|   getParam(0): [ParamDecl] x
#    1|       Type = Int
#    1|   getBody(): [BraceStmt] { ... }
#    2|     getElement(0): [ReturnStmt] return ...
#    2|       getResult(): [DeclRefExpr] x
#    2|       getResult().getFullyConverted(): [InjectIntoOptionalExpr] (Int?) ...
#    2|         getSubExpr(): [LoadExpr] (Int) ...
#    2|           getSubExpr(): [DotSelfExpr] .self