foo(bar(x -> expr))
However, it did not consider poly method invocations nested inside _other_ lambda expressions:
foo(y -> bar(x -> expr))
Assuming 'bar' is a poly method invocation, the lambda expression x->expr can impact the type arguments of 'foo', and thus should be considered as part of the set of constraints 'C', as described in 18.5.2.
In general, we need to consider all lambda result expressions that are i) poly method invocations, ii) poly class instance creations, or iii) conditionals/parenthesizeds that wrap on of these.