$ ponyc -l
Building builtin -> /opt/pony/lib/pony/0.13.2-220d430/packages/builtin
Building . -> /Users/iology/test/foo
Generating
 Library reachability
 Selector painting
 Data prototypes
 Data types
 Function prototypes
 Functions
 Descriptors
src/libponyc/ast/ast.c:1614: ast_get_children: Assertion `parent != NULL` failed.

Backtrace:
  0   ponyc                               0x000000010efd95a1 ponyint_assert_fail + 161
  1   ponyc                               0x000000010eeff205 ast_get_children + 69
  2   ponyc                               0x000000010ef4343e emit_fun + 126
  3   ponyc                               0x000000010ef431c9 print_method + 57
  4   ponyc                               0x000000010ef4317d print_methods + 125
  5   ponyc                               0x000000010ef430e8 print_types + 328
  6   ponyc                               0x000000010ef42f32 genheader + 290
  7   ponyc                               0x000000010ef457c9 genlib + 73
  8   ponyc                               0x000000010ef2f045 codegen + 245
  9   ponyc                               0x000000010ef947e3 generate_passes + 51
  10  ponyc                               0x000000010eefaa41 compile_package + 161
  11  ponyc                               0x000000010eefa7ff main + 1103
  12  libdyld.dylib                       0x00007fff90f9d5ad start + 1
  13  ???                                 0x0000000000000002 0x0 + 2
Abort trap: 6

$ ponyc --version
0.13.2-220d430 [debug]
compiled with: llvm 3.9.0 -- Apple LLVM version 8.0.0 (clang-800.0.42.1)