From b5b15392096d4b8f2aebfa89615f56aa7fe15283 Mon Sep 17 00:00:00 2001
From: Sebastian Fischer <sebf.fischer@gmail.com>
Date: Wed, 20 May 2026 08:12:23 +0200
Subject: [PATCH] fix(pad): padding value must be 0-dimensional

---
 R/op-pad.R                      |  8 ++++++++
 tests/testthat/_snaps/op-pad.md | 11 +++++++++++
 tests/testthat/test-op-pad.R    |  8 ++++++++
 3 files changed, 27 insertions(+)

diff --git a/R/op-pad.R b/R/op-pad.R
index b6182098..06df4e9f 100644
--- a/R/op-pad.R
+++ b/R/op-pad.R
@@ -14,6 +14,14 @@ infer_types_pad <- function(
 ) {
   assert_vts_are_tensors(operand, padding_value)
 
+  # (I2): padding_value must be a 0-dimensional tensor.
+  if (length(shape(padding_value)) != 0L) {
+    cli_abort(c(
+      "{.arg padding_value} must be a 0-dimensional tensor.",
+      x = "Got shape {shapevec_repr(shape(padding_value))}."
+    ))
+  }
+
   # (C1)
   assert_vts_have_same_dtype(operand, padding_value)
 
diff --git a/tests/testthat/_snaps/op-pad.md b/tests/testthat/_snaps/op-pad.md
index 92a7d37d..4f5787b5 100644
--- a/tests/testthat/_snaps/op-pad.md
+++ b/tests/testthat/_snaps/op-pad.md
@@ -34,3 +34,14 @@
       ! edge_padding_low must have length equal to operand rank
       x length(edge_padding_low): 1, operand_rank: 2
 
+---
+
+    Code
+      infer_types_pad(operand, padding_value, edge_padding_low = cnst(low, "i64",
+        length(low)), edge_padding_high = cnst(high, "i64", length(high)),
+      interior_padding = cnst(interior, "i64", length(interior)))
+    Condition
+      Error in `infer_types_pad()`:
+      ! `padding_value` must be a 0-dimensional tensor.
+      x Got shape (2).
+
diff --git a/tests/testthat/test-op-pad.R b/tests/testthat/test-op-pad.R
index 55a06078..fe6947ef 100644
--- a/tests/testthat/test-op-pad.R
+++ b/tests/testthat/test-op-pad.R
@@ -85,4 +85,12 @@ test_that("errors", {
   )
   # (C2) wrong length
   check(vt("f32", c(2L, 3L)), vt("f32", integer()), c(0L), c(0L, 0L), c(0L, 0L))
+  # (I2) padding_value must be a 0-dimensional tensor
+  check(
+    vt("f32", c(2L, 3L)),
+    vt("f32", 2L),
+    c(0L, 0L),
+    c(0L, 0L),
+    c(0L, 0L)
+  )
 })