Preserve integer exponents in size powers

Author: t-kalinowski

R/manifest.R

@@ -518,9 +518,7 @@ dims2f_eval_base_env[["%%"]] <- function(e1, e2) {
   )
 }
 dims2f_eval_base_env[["^"]] <- function(e1, e2) {
-  glue(
-    "(real({e1}, kind=c_double))**(real({e2}, kind=c_double))"
-  )
+  glue("(real({e1}, kind=c_double))**({e2})")
 }
 dims2f_eval_base_env[["abs"]] <- function(x) glue("abs({x})")
 # Fortran INT() truncates toward zero, like as.integer() in R.

tests/testthat/test-sizes-arithmetic.R

@@ -178,6 +178,29 @@ test_that("size powers use the double domain before casting", {
   expect_quick_identical(constant, list())
 })
 
+test_that("size powers retain integer exponent type", {
+  fn <- function(x, exponent, scale) {
+    declare(
+      type(x = integer(1)),
+      type(exponent = integer(1)),
+      type(scale = integer(1))
+    )
+    out <- double(as.integer((x^exponent) * scale) + 10L)
+    for (i in seq_len(length(out))) {
+      out[i] <- as.double(i)
+    }
+    out
+  }
+
+  code <- r2f(fn)
+  expect_match(as.character(code), "**(exponent)", fixed = TRUE)
+  expect_false(
+    grepl("real(exponent, kind=c_double)", as.character(code), fixed = TRUE)
+  )
+
+  expect_quick_identical(fn, list(-2L, -1L, 4L))
+})
+
 test_that("dim/length/nrow/ncol are supported in allocation sizes", {
   vec <- function(x) {
     declare(type(x = double(NA)))