Crystal: Block arguments and local variables not visible in flat rescue/ensure/else

[straight-shoota]

5114 introduced new possibilities to use rescue, ensure and else with blocks. However the following examples shows, that variables are unexpectedly handled:

%w(foo bar).each do |x|
ensure
  p x   # => ERROR: undefined local variable or method 'x'
end

This should be equivalent to:

%w(foo bar).each do |x|
  begin
  ensure
    p x
  end
end

Which compiles without errors. Block arguments are initialized in every block run, they are before the implicit begin and should be visible in rescue, ensure and else branches.

Second example:

%w(foo bar).each do |x|
  foo = x
ensure
  p foo.upcase   # => ERROR: undefined method 'foo'
end

Which should be equivalent to:

%w(foo bar).each do |x|
  begin
    foo = x
  ensure
    p foo.upcase   # => ERROR: undefined method 'upcase' for Nil (compile-time type is (String | Nil))
  end
end

The variable foo should be visible in rescue, ensure and else branches but be nilable there, just like in the expressive variant.

/cc @MakeNowJust

[MakeNowJust]

Good catch!