class Crystal::NoReturnFilter
inherits Crystal::TypeFilter
¶
In code like:
x = 1 if ... x = "hi" unreachable! end
x type must be Int32 after the if, because the String type
doesn't matter afterwards as unreachable code comes. However, if
unreachable! is only temporarily unreachable (because of type propagation
that condition can change) we also want to bind x to String. But we
want to do that conditionally on the if's then block being NoReturn or
not.
This filter does that. It receives the var's type (String in this case)
and applies a filter to the then (or else) part of the if: if it's
no return, we return just that. If not, we return the var's type.