Crystal: "Unwrapping" unrelated nilable values in case branches not working and not rejected by the compiler

[dawkot]

def int? : Int32?
    2
end

case true
when x = int?
    puts x # not reached
else
    puts ":("
end

[asterite]

This:

case exp
when something
  do_something
else
  do_something_else
end

is rewritten to:

if something === exp
  do_something
else
  do_something_else
end

In your case, your code is equivalent to:

if (x = int?) === true
  puts x
else
  puts ":("
end

and 2 === true is false.

Everything is working as expected. This is not a bug.

[asterite]

You probably wanted to write:

# Note that there's no case expression
case
when x = int?
  puts x
else
  puts ":("
end