`*_gaps()` functions are not safely scoped for `int` variable names

[mitchelloharawild]

Identified in tidyverts/fable#396

library(tsibble)
#> Registered S3 method overwritten by 'tsibble':
#>   method               from 
#>   as_tibble.grouped_df dplyr
#> 
#> Attaching package: 'tsibble'
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, union

# Works: integer index, but no column named `int`
x_ok <- tsibble(
  time  = 1:5,
  value = c(10, 20, NA, 40, 50),
  index = time
)

scan_gaps(x_ok)
#> # A tsibble: 0 x 1 [?]
#> # ℹ 1 variable: time <int>
has_gaps(x_ok)
#> # A tibble: 1 × 1
#>   .gaps
#>   <lgl>
#> 1 FALSE


# Fails / misbehaves: same data, but with a column named `int`
x_bug <- tsibble(
  time  = 1:5,
  value = c(10, 20, NA, 40, 50),
  int   = 1L,    # problematic name
  index = time
)

x_bug
#> # A tsibble: 5 x 3 [1]
#>    time value   int
#>   <int> <dbl> <int>
#> 1     1    10     1
#> 2     2    20     1
#> 3     3    NA     1
#> 4     4    40     1
#> 5     5    50     1
scan_gaps(x_bug)  # error / unexpected result
#> Error in `summarise()`:
#> ℹ In argument: `time = list2(`:=`("time", seq_generator(time, int)))`.
#> ℹ In group 1: .
#> Caused by error in `if (time_units == 0) ...`:
#> ! the condition has length > 1
has_gaps(x_bug)   # error / unexpected result
#> Error in `summarise()`:
#> ℹ In argument: `.gaps = (length(seq_generator(time, int)) -
#>   length(time)) > 0`.
#> ℹ In group 1: .
#> Caused by error in `if (time_units == 0) ...`:
#> ! the condition has length > 1

^{Created on 2026-01-15 with reprex v2.1.1}