Crash on typedef enum with negative hexadecimal

[mratsim]

The following makes c2nim crash

/**
 * @brief Machine code object symbol type.
 */
typedef enum amd_comgr_symbol_type_s {
  /**
   * The symbol's type is unknown.
   *
   * The user should not infer any specific type for symbols which return
   * `AMD_COMGR_SYMBOL_TYPE_UNKNOWN`, and these symbols may return different
   * types in future releases.
  */
  AMD_COMGR_SYMBOL_TYPE_UNKNOWN = -0x1,

  /**
   * The symbol's type is not specified.
  */
  AMD_COMGR_SYMBOL_TYPE_NOTYPE = 0x0,

  /**
   * The symbol is associated with a data object, such as a variable, an array,
   * and so on.
  */
  AMD_COMGR_SYMBOL_TYPE_OBJECT = 0x1,

  /**
   * The symbol is associated with a function or other executable code.
  */
  AMD_COMGR_SYMBOL_TYPE_FUNC = 0x2,

  /**
   * The symbol is associated with a section. Symbol table entries of this type
   * exist primarily for relocation.
  */
  AMD_COMGR_SYMBOL_TYPE_SECTION = 0x3,

  /**
   * Conventionally, the symbol's name gives the name of the source file
   * associated with the object file.
  */
  AMD_COMGR_SYMBOL_TYPE_FILE = 0x4,

  /**
   * The symbol labels an uninitialized common block.
  */
  AMD_COMGR_SYMBOL_TYPE_COMMON = 0x5,

  /**
   * The symbol is associated with an AMDGPU Code Object V2 kernel function.
  */
  AMD_COMGR_SYMBOL_TYPE_AMDGPU_HSA_KERNEL = 0xa
} amd_comgr_symbol_type_t;

with

fatal.nim(53)            sysFatal
Error: unhandled exception: ast.nim(1233, 3) `son != nil`  [AssertionDefect]