$success
[1] FALSE

$message
$message$message
[1] "be"              "a call to `fun`" "is"              "\"NULL\""       

$message$wrap
$message$wrap[[1]]
NULL

$message$wrap[[2]]
NULL



$call.match
fun(abc = a, bcd = b, efg = NULL)

$call.ind
NULL[[4]]

$call.ind.sub.par
$call.ind.sub.par[[1]]
NULL

$call.ind.sub.par[[2]]
[1] 4


$call.orig
fun(a, b, NULL)

$success
[1] FALSE

$message
$message$message
[1] "have"                            "argument `b` after argument `a`"
[3] "has"                             "`d`"                            

$message$wrap
$message$wrap[[1]]
NULL

$message$wrap[[2]]
NULL



$call.match
ff(a = 1, d = 2, c = 3)

$call.ind
NULL

$call.ind.sub.par
NULL

$call.orig
ff(a = 1, d = 2, c = 3)

Arguments must be LANGSXP, SYMSXP, or R_NilValue

Error in vetr:::lang_alike(cc, 1:10) : 
  Arguments must be LANGSXP, SYMSXP, or R_NilValue

vetr:::lang_alike(ce, cc, match.call.env = 1:10)

Argument `match.call.env` must be an environment or NULL

Error in vetr:::lang_alike(ce, cc, match.call.env = 1:10) : 
  Argument `match.call.env` must be an environment or NULL

[1] "be"              "a call to `fun`" "is"              "a call to `FUN`"

[1] "be"            "a call to `+`" "is"            "a call to `-`"

[1] "have"                          "argument `e` after argument 1"
[3] "has"                           "unnamed argument"

[1] "have"                             "argument `bcd` as first argument"
[3] "has"                              "`c`"

[1] "be"              "a call to `fun`" "is"              "\"NULL\""

$success
[1] FALSE

$message
$message$message
[1] "have"                      "identical constant values"
[3] ""                          ""                         

$message$wrap
$message$wrap[[1]]
NULL

$message$wrap[[2]]
NULL



$call.match
a ~ b + 2
<environment: 0x7f8de2864120>

$call.ind
NULL[[3]][[3]]

$call.ind.sub.par
$call.ind.sub.par[[1]]
NULL

$call.ind.sub.par[[2]]
[1] 3


$call.orig
a ~ b + 2
<environment: 0x7f8de2864120>

$success
[1] FALSE

$message
$message$message
[1] "be"  "`b`" "is"  "`c`"

$message$wrap
$message$wrap[[1]]
NULL

$message$wrap[[2]]
NULL



$call.match
a ~ b + log(c) + b - 1
<environment: 0x7f8de2864120>

$call.ind
NULL[[3]][[2]][[2]][[3]][[2]]

$call.ind.sub.par
$call.ind.sub.par[[1]]
NULL

$call.ind.sub.par[[2]]
[1] 3


$call.orig
a ~ b + log(c) + b - 1
<environment: 0x7f8de2864120>