Flow analysis was failing on our encoding of duplicate late variables.
We add an invalid expression as the initializer on duplicate variables
and flow analysis was seeing this as if the late variable had (declared)
initializer. Changed to use the `hasDeclaredInitializer` flag on
VariableDeclarationImpl to bypass flow analysis in the synthesized
initializer.
Closes#43689
Change-Id: I483caa3bbc3347eb547826e9615a40fe62b586d7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167741
Reviewed-by: Jens Johansen <jensj@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Johnni Winther