bug: type parameter shadowing type definition crashes repl

[crusso]

crusso@crusso-Virtual-Machine:~/motoko/src$ rlwrap moc
Motoko compiler (source 0.16.3-92-g7dca1ce41)

type t = T -> T -> T; type t = T -> T_1 -> T_1 type T = (); type T = () type t = T -> T -> T; OOPS! You've triggered a compiler bug. Please report this at https://github.com/dfinity/motoko/issues/new with the following details:

Motoko (source 0.16.3-92-g7dca1ce41)

Fatal error: exception Dom.Make(X).Clash(_)
Raised at Dom.Make.disjoint_add in file "lang_utils/dom.ml", line 17, characters 45-60
Called from Mo_frontend__Typing.add_typs in file "mo_frontend/typing.ml", line 349, characters 11-60
Called from Mo_frontend__Typing.check_typ_binds in file "mo_frontend/typing.ml", line 921, characters 17-53
Called from Mo_frontend__Typing.check_typ' in file "mo_frontend/typing.ml", line 765, characters 26-51
Called from Mo_frontend__Typing.check_typ in file "mo_frontend/typing.ml" (inlined), line 735, characters 10-28
Called from Mo_frontend__Typing.check_typ_def in file "mo_frontend/typing.ml", line 857, characters 10-28
Called from Mo_frontend__Typing.infer_dec_typdecs in file "mo_frontend/typing.ml", line 4427, characters 12-57
Called from Mo_frontend__Typing.infer_block_typdecs.(fun) in file "mo_frontend/typing.ml", line 4365, characters 19-44
Called from Stdlib__List.fold_left in file "list.ml", line 121, characters 24-34
Called from Mo_frontend__Typing.infer_block_typdecs in file "mo_frontend/typing.ml", line 4364, characters 4-172
Called from Mo_frontend__Typing.infer_block_decs in file "mo_frontend/typing.ml", line 4039, characters 17-46
Called from Mo_frontend__Typing.infer_block in file "mo_frontend/typing.ml", line 4017, characters 14-42
Called from Mo_frontend__Typing.infer_prog.(fun) in file "mo_frontend/typing.ml", line 4563, characters 26-62
Called from Mo_frontend__Typing.recover_opt.(fun) in file "mo_frontend/typing.ml", line 136, characters 55-60
Called from Mo_frontend__Typing.recover_with in file "mo_frontend/typing.ml", line 135, characters 56-59
Called from Diag.with_message_store in file "lang_utils/diag.ml", line 103, characters 10-13
Called from Pipeline.infer_prog.(fun) in file "pipeline/pipeline.ml", line 192, characters 12-69
Called from Stdlib__Fun.protect in file "fun.ml", line 33, characters 8-15
Re-raised at Stdlib__Fun.protect in file "fun.ml", line 38, characters 6-52
Called from Pipeline.load_decl in file "pipeline/pipeline.ml", line 534, characters 19-91
Called from Diag.bind in file "lang_utils/diag.ml", line 32, characters 27-30
Called from Diag.bind in file "lang_utils/diag.ml", line 32, characters 27-30
Called from Diag.bind in file "lang_utils/diag.ml", line 32, characters 27-30
Called from Pipeline.run_stdin in file "pipeline/pipeline.ml", line 673, characters 28-64
Called from Pipeline.run_files_and_stdin.loop in file "pipeline/pipeline.ml", line 711, characters 42-63
Called from Pipeline.run_files_and_stdin in file "pipeline/pipeline.ml", line 712, characters 6-14
Called from Dune__exe__Moc.process_files in file "exes/moc.ml", line 280, characters 17-53
Called from Dune__exe__Moc in file "exes/moc.ml", line 394, characters 10-29

[crusso]

Oddly, compilation of similar code succeeds.

crusso@crusso-Virtual-Machine:~/motoko/test/fail$ more type-shadowing-bug.mo
type t = <T> T -> <T> T -> T;
do { type T = ();
     type t = <T> T -> <T> T -> T;
}
crusso@crusso-Virtual-Machine:~/motoko/test/fail$ moc --check type-shadowing-bug.mo
crusso@crusso-Virtual-Machine:~/motoko/test/fail$