R devel - Jan 2025 - binomial()$linkinv no longer accepts integer values

As of r87537, binomial()$linkinv no longer accepts integer arguments.

binomial()$linkinv(1.0)  ## 0.7310586
binomial()$linkinv(1L)

Error in binomial()$linkinv(1L) :
   REAL() can only be applied to a 'numeric', not a 'integer'

   Since R is usually so permissive/sloppy with the distinction between 
integers and numeric/doubles, I'd argue that this is a bug ...

   (This came up because it happens to break lme4's tests.)

    I haven't done the archaeology to figure out when this broke/exactly 
what change in the R code base broke it: it happened within the last 
month or so and it's certainly something upstream of the linkinv 
function itself, as (according to 'git blame') nothing in that function 
has changed in the last 4 years ... (if it were of interest I could 'git 
bisect' to figure it out but maybe someone will save me the trouble ...)

   Thoughts, insights?  Should I post this to r-bugzilla?  Or suck it up 
and accept it as the new reality?

   cheers
    Ben Bolker

===binomial()$linkinv is:

function (eta)
.Call(C_logit_linkinv, eta)
<environment: namespace:stats>

Here is the body of the function in C code:

https://github.com/r-devel/r-svn/blob/195ab0870a8131d01492f8f1d3a2ad514bc7e040/src/library/stats/src/family.c#L72C1-L89C2

SEXP logit_linkinv(SEXP eta)
{
     SEXP ans = PROTECT(shallow_duplicate(eta));
     int i, n = LENGTH(eta);
     double *rans = REAL(ans), *reta = REAL(eta);

     if (!n || !isReal(eta))
	error(_("Argument %s must be a nonempty numeric vector"),
"eta");
     for (i = 0; i < n; i++) {
	double etai = reta[i], tmp;
	tmp = (etai < MTHRESH) ? DBL_EPSILON :
	    ((etai > THRESH) ? INVEPS : exp(etai));
	rans[i] = x_d_opx(tmp);
     }
     UNPROTECT(1);
     return ans;
}

On Wed, 8 Jan 2025 10:57:47 -0500
Ben Bolker <bbolker at gmail.com> wrote:
> I haven't done the archaeology to figure out when this broke/exactly 
> what change in the R code base broke it: it happened within the last 
> month or so
binomial() itself exhibits this property even in R-4.2.2 from more than
two years ago:

R -q -s -e 'getRversion(); binomial()$linkinv(1L)'
# [1] ?4.2.2?
# Error in binomial()$linkinv(1L) : 
#   REAL() can only be applied to a 'numeric', not a 'integer'

It's the `etas` [1] that suddenly became integer due to a change in
seq.int():

R -q -s -e 'str(seq.int(-8, 8, by=1))'
# num [1:17] -8 -7 -6 -5 -4 -3 -2 -1 0 1 ...
R-devel -q -s -e 'str(seq.int(-8, 8, by=1))'
# int [1:17] -8 -7 -6 -5 -4 -3 -2 -1 0 1 ...

-- 
Best regards,
Ivan

[1]
https://github.com/lme4/lme4/blob/54c54a320c23b34fea2f7e613928d1ebe7a3fd37/tests/testthat/test-glmFamily.R#L10C5-L10C25