Is occurrence typing (flow-sensitive typing) a form of dependent typing?
No, I would not consider this a dependent type.  The type of x does not depend on the value of x.
I suppose you could say that the type of the expression x depends on the type of the variable x, but that doesn't make this dependent typing.
You link to Wikipedia, but the Wikipedia article on dependent types say &quot;a dependent type is a type whose definition depends on a value&quot; and says &quot; The return type of a dependent function may depend on the value (not just type) of one of its arguments&quot; and &quot;A dependent pair may have a second value of which the type depends on the first value&quot;.  Here the type of x does not depend on values; only on the types of the variables.  Beware that these English sentences describing terms like &quot;dependent types&quot; or &quot;occurrence types&quot; are not to be taken too seriously and you need to look at the precise mathematical formalism if you want to be precise.
I would not consider the feature you describe as dependent typing.  Rather, I would consider it an instance of flow-sensitive typing.