Segfault when testing call

[brodieG]

This could well be an alike issue:

> x <- quote(a + b)
> validate(x, 2 + 3)
Error: object 'a' not found
Error in validate(x, 2 + 3) : 
  Validation expression for argument `current` produced an error (see previous error).
> x <- quote(quote(a + b))
> validate(x, 2 + 3)
Error in validate(x, 2 + 3) : 
  Argument `current` should be type "language" (is "double")
> validate(x, quote(2 + 3))
Error in validate(x, quote(2 + 3)) : 
  Argument `current` should be "symbol" (is "double") for token `2` in: `{2}` + 3
> validate(x, quote(x2 + x3))
Warning: stack imbalance in '.Call', 6 then 4

 *** caught bus error ***
address 0x106c29ff8, cause 'non-existent physical address'

Possible actions:
1: abort (with core dump, if enabled)
2: normal R exit
3: exit R without saving workspace
4: exit R saving workspace