Add `typeArguments` to Invocation.
Add constructors to Invocation, making it less necessary for users to create their own implementations.
Add tests.
Add Symbol.unaryMinus and Symbol.empty constants.
Change-Id: I70cb3265f9413617cf57fce1297e393a29eeb26a
Reviewed-on: https://dart-review.googlesource.com/40741
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>
Lasse Reichstein Holst Nielsen