AccessorFindingExpressionVisitor doesn't handle soft casts (i.e. TypeAs expression) but works for hard cast (Convert expression)

AccessorFindingExpressionVisitor fails if the searched expression is hidden behind soft cast. 

E.g. 

searched expression: [c]

fullExpression: [c] as MyBaseClass

doesn't find [c], but ConvertExpression is handled properly:

if fullExpression is:

(MyBaseClass)[c] 

c is found without issue.