Strange `FrozenError` on `Psych.load`

[shyouhei]

Is it intentional for the following Ruby code to raise FrozenError ?

Psych.safe_load(<<~'end', aliases: true, freeze: true)
  ---
  foo: &foo
    <<: *foo
end

Possibilities:

• Psych should accept this YAML and properly return a frozen, recursive hash.
• Psych should raise Psych::AnchorNotDefined instead of FrozenError.
• FrozenError is the legit exception here.

I have no idea if the YAML in question is valid or not at the first place.

[tenderlove]

• Psych should accept this YAML and properly return a frozen, recursive hash.

IMO this is the correct behavior. I'm not sure how hard it is to implement though.