Nominal types: an edge case not accepted by dialyzer

[ilya-klyuchnikov]

Describe the bug
Code is OK according to the rules (compatibility, type-checking) of nominal types, but is rejected by dialyzer.

To Reproduce

(This code has little sense, it's a minimal repro)

-module(n3).

-export([swap_r/1]).
-nominal t1() :: t2().
-nominal t2() :: integer().
-record(r, {t :: t1()}).

-spec swap_r(#r{}) -> #r{t :: t2()}.
swap_r(#r{t = T}) ->
  #r{t = T}.

dialyzer n3.erl
dialyzer: Analysis failed with error:
n3.erl:10:2: Illegal declaration of #r{t}

Expected behavior
According to the documentation and EEP, t1() and t2() are compatible nominal types, so using a refined record type #r{t :: t2()} should be fine.

Affected versions
Master

Additional context

Swapping definitions of t1() and t2() makes the error disappear:

-module(n4).

-export([swap_r/1]).

-nominal t1() :: integer().
-nominal t2() :: t1().

-record(r, {t :: t1()}).

-spec swap_r(#r{}) -> #r{t :: t2()}.
swap_r(#r{t = T}) ->
  #r{t = T}.

dialyzer n4.erl
(NO ERRORS)

[jhogberg]

Thanks for your report! We'll have it fixed in the same branch as for #9199