Bug: lib typedefs are indistinguishable

[straight-shoota]

When using a lib type as generic argument, it seems that different types referencing the same base type are considered identical.
This would be expected for alias, but not for type where each definition is a distinct type.

lib LibFoo
  type A = Void
  type B = Void
end

class Bar(T)
  def bar
    T
  end
end

Bar(LibFoo::A).new.bar # => LibFoo::A
Bar(LibFoo::B).new.bar # => LibFoo::A

In the interpreter it works fine (the second call returns LibFoo::A), so this looks like a codegen bug.

Originally discovered in #16686

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[straight-shoota]

Simplified, without generics:

lib LibFoo
  type A = Void
  type B = Void
end
 
LibFoo::A # => LibFoo::A
LibFoo::B # => LibFoo::A

[ysbaddaden]

Notes:

• lib doesn't have to be private;
• it mistakens for the first type (reversing access to LibFoo::B then LibFoo::A resolves to LibFoo::B twice).

Aside: I recall discussions to deprecate type in favor to just alias.