NullValueAnalysis: Check if cancellation has been requested
NullValueAnalysis: Implement VisitorResult.ThrowsException.
Expressions such as x.Foo where Foo is not an extension method are known to throw exceptions when x == null.
As such, if the expression successfully reaches the end, the analysis can assume that x != null.
If x was known to be null, then the code that follows it (up to the next catch statement) is unreachable.
Same applies to x[...] expressions.
Note: This is not yet implemented for linq expressions, which just ignore ThrowsException and this valuable property.