R session aborts when a generics fun overwrites a supplied argument

[KaiAragaki]

Apologies if this should be directed to the RStudio repo.

Reprex:

library(R7)

my_generic <- new_generic("my_generic", "x", function(x) {
  x <- x
  R7_dispatch()
})

my_method <- method(my_generic, class_character) <- function(x) {
  x
}

my_generic("x")

This is fine though:

my_generic <- new_generic("my_generic", "x", function(x) {
  ex <- x
  R7_dispatch()
})

my_generic("x")

RStudio version: 2022.07.2+576 (2022.07.2+576)
OS: macOS 12.6

[hadley]

What do you mean by crashes?

[KaiAragaki]

Sorry - not RStudio, but rather the R Session. I'll change the title. See image for details.

Reproduced on Linux (Mint 20.3 Cinnamon), which screams before it dies (see console in background)

[hadley]

Updated reprex:

library(S7)

my_generic <- new_generic("my_generic", "x", function(x) {
  x <- x
  S7_dispatch()
})

method(my_generic, class_character) <- function(x) {
  x
}

my_generic("x")

I also see the crash

[hadley]

Error is coming from https://github.com/RConsortium/OOP-WG/blob/abstract-parent-readonly-property/src/method-dispatch.c#L133, presumably because this isn't an unevaluated promise.