method-dispatch.md
In S7: An Object Oriented System Meant to Become a Successor to S3 and S4

generics pass ... to methods

unused argument (z = 2)

single dispatch fails with informative messages

Code
  fail(TRUE)
Condition
  Error:
  ! Can't find method for `fail(<logical>)`.
Code
  fail(tibble::tibble())
Condition
  Error:
  ! Can't find method for `fail(S3<tbl_df/tbl/data.frame>)`.
Code
  fail(foo())
Condition
  Error:
  ! Can't find method for `fail(<foo>)`.
Code
  fail(Foo(x = 1))
Condition
  Error:
  ! Can't find method for `fail(S4<Foo>)`.

multiple dispatch fails with informative messages

Code
  fail(TRUE)
Condition
  Error:
  ! Can't find method for generic `fail(x, y)`:
  - x: <logical>
  - y: MISSING
Code
  fail(, TRUE)
Condition
  Error:
  ! Can't find method for generic `fail(x, y)`:
  - x: MISSING
  - y: <logical>
Code
  fail(TRUE, TRUE)
Condition
  Error:
  ! Can't find method for generic `fail(x, y)`:
  - x: <logical>
  - y: <logical>

method dispatch works for class_missing

Code
  foo_wrapper()
Condition
  Error in `foo_wrapper()`:
  ! argument "xx" is missing, with no default

errors from dispatched methods have reasonable tracebacks

Code
  my_generic(10)
Output
  [[1]]
  my_generic(10)

  [[2]]
  S7::S7_dispatch()

  [[3]]
  `method(my_generic, class_double)`(x = 10, ...)

Code
  my_generic(3, 4)
Output
  [[1]]
  my_generic(3, 4)

  [[2]]
  S7::S7_dispatch()

  [[3]]
  `method(my_generic, list(class_double, class_double))`(x = 3, 
      y = 4, ...)