[clang] NRVO: Improvements and handling of more cases.
This expands NRVO propagation for more cases:
Parse analysis improvement:
* Lambdas and Blocks with dependent return type can have their variables
marked as NRVO Candidates.
Variable instantiation improvements:
* Fixes crash when instantiating NRVO variables in Blocks.
* Functions, Lambdas, and Blocks which have auto return type have their
variables' NRVO status propagated. For Blocks with non-auto return type,
as a limitation, this propagation does not consider the actual return
type.
This also implements exclusion of VarDecls which are references to
dependent types.
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Reviewed By: Quuxplusone
Differential Revision: https://reviews.llvm.org/D99696