Passing wrong keyword args causes hang

[cgay]

Using Open Dylan 2020.1 or master branch from a few days ago, the following program hangs indefinitely. Remove , help: "help" from the call to print-synopsis and it doesn't hang.

(I feel like I must be missing some obvious mistake because we would have noticed this before.)

#1141 seems at least tangentially relevant, in that open generics are obviously handled quite differently from sealed generics.

==> hang/hang.dylan <==
Module: hang

define open generic print-synopsis
    (parser :: <string>, subcmd :: false-or(<integer>), #key stream);

define method print-synopsis
    (parser :: <string>, subcmd == #f,
     #key stream :: <stream> = *standard-output*)
  format-out("print-synopsis(p, #f)\n");
  force-out();
end method;

define method print-synopsis
    (parser :: <string>, subcmd :: <integer>,
     #key stream :: <stream> = *standard-output*)
  format-out("print-synopsis(p, s)\n");
  force-out();
end method;

// Remove the help arg and no hang.
print-synopsis("string", #f, stream: *standard-output*, help: "help");


==> hang/library.dylan <==
Module: dylan-user

define library hang
  use common-dylan;
  use io;
end library hang;

define module hang
  use common-dylan;
  use format-out;
  use standard-io;
end module hang;

[cgay]

$ lldb _build/bin/hang
(lldb) target create "_build/bin/hang"
Current executable set to '/home/cgay/dylan/play/hang/_build/bin/hang' (x86_64).
(lldb) run
Process 13242 launched: '/home/cgay/dylan/play/hang/_build/bin/hang' (x86_64)
Process 13242 stopped
* thread #1, name = 'Main thread', stop reason = signal SIGSEGV: invalid address (fault address: 0xb)
    frame #0: 0x00007ffff7e2c8cc libdylan.so`rest_key_mep_4 + 412
libdylan.so`rest_key_mep_4:
->  0x7ffff7e2c8cc <+412>: movq   0x8(%r9), %rdi
    0x7ffff7e2c8d0 <+416>: movq   0x8(%rcx), %r14
    0x7ffff7e2c8d4 <+420>: leaq   0x1(%rbx), %r8
    0x7ffff7e2c8d8 <+424>: cmpq   $0x2, %rbx
(lldb) bt
* thread #1, name = 'Main thread', stop reason = signal SIGSEGV: invalid address (fault address: 0xb)
  * frame #0: 0x00007ffff7e2c8cc libdylan.so`rest_key_mep_4 + 412
    frame #1: 0x00007ffff7d3f5fb libdylan.so`invalid-keyword-trap(mepargs=0x00007fffffffe550, disphdr=<unavailable>, engine-node=0x00007ffff6750c40, key=0x00007ffff7fb30a0, keyvec=<un\
available>, implicit?=<unavailable>, .next=<unavailable>, .function=<unavailable>) at boot.dylan:994:5
    frame #2: 0x00007ffff7dc1701 libdylan.so`implicit_keyed_single_method_3 at x86_64-linux-runtime.ll:0
    frame #3: 0x00007ffff7dc0e65 libdylan.so`general_engine_node_n at x86_64-linux-runtime.ll:0
    frame #4: 0x00007ffff7fb02fd libhang.so`_Init_hang__X_hang_for_user + 109
    frame #5: 0x0000000000401149 hang`main + 25
    frame #6: 0x00007ffff722509b libc.so.6`__libc_start_main(main=(hang`main), argc=1, argv=0x00007fffffffe808, init=<unavailable>, fini=<unavailable>, rtld_fini=<unavailable>, stack_\
end=0x00007fffffffe7f8) at libc-start.c:308:16
    frame #7: 0x000000000040106a hang`_start + 42