From b2c45b8eb9f5e9db0448cf19d333cebab41b35aa Mon Sep 17 00:00:00 2001
From: Jake VanderPlas <jakevdp@google.com>
Date: Fri, 28 Feb 2025 15:04:07 -0800
Subject: [PATCH] Improved errors when indexing with floats

---
 jax/_src/numpy/indexing.py       | 27 ++++++++++++++++++++++-----
 tests/lax_numpy_indexing_test.py |  4 ++++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/jax/_src/numpy/indexing.py b/jax/_src/numpy/indexing.py
index a402fb8dc..5d59bb53b 100644
--- a/jax/_src/numpy/indexing.py
+++ b/jax/_src/numpy/indexing.py
@@ -751,13 +751,33 @@ def merge_static_and_dynamic_indices(treedef, static_idx, dynamic_idx):
 def _int(aval):
   return not aval.shape and dtypes.issubdtype(aval.dtype, np.integer)
 
+def _aval_or_none(x):
+  try:
+    return core.get_aval(x)
+  except:
+    return None
+
 def index_to_gather(x_shape: Sequence[int], idx: Sequence[Any],
                     normalize_indices: bool = True) -> _Indexer:
+  # Convert sequences to arrays
+  idx = tuple(lax_numpy.asarray(i, dtype=None if i else int)
+              if isinstance(i, Sequence) else i for i in idx)
+  abstract_idx = [_aval_or_none(i) for i in idx]
+  float_indices = [(i, val, aval) for i, (val, aval) in enumerate(zip(idx, abstract_idx))
+                   if aval is not None and dtypes.issubdtype(aval, np.inexact)]
+
+  # Check for float or complex indices:
+  if float_indices:
+    i, val, aval = float_indices[0]
+    msg = ("Indexer must have integer or boolean type, got indexer "
+           "with type {} at position {}, indexer value {}")
+    raise TypeError(msg.format(aval.dtype.name, i, val))
+
   # Check whether advanced indices are contiguous. We must do this before
   # removing ellipses (https://github.com/jax-ml/jax/issues/25109)
   # If advanced idexing axes do not appear contiguously, NumPy semantics
   # move the advanced axes to the front.
-  is_advanced, = np.nonzero([isinstance(e, (int, Sequence, Array, np.ndarray))
+  is_advanced, = np.nonzero([isinstance(e, (int, np.integer, Array, np.ndarray))
                              or lax_numpy.isscalar(e) for e in idx])
   advanced_axes_are_contiguous = np.all(np.diff(is_advanced) == 1)
 
@@ -862,11 +882,8 @@ def index_to_gather(x_shape: Sequence[int], idx: Sequence[Any],
       gather_slice_shape.append(1)
       continue
 
-    try:
-      abstract_i = core.get_aval(i)
-    except TypeError:
-      abstract_i = None
     # Handle basic int indexes.
+    abstract_i = _aval_or_none(i)
     if isinstance(abstract_i, core.ShapedArray) and _int(abstract_i):
       if core.definitely_equal(x_shape[x_axis], 0):
         # XLA gives error when indexing into an axis of size 0
diff --git a/tests/lax_numpy_indexing_test.py b/tests/lax_numpy_indexing_test.py
index 04225d6c5..63a725ad3 100644
--- a/tests/lax_numpy_indexing_test.py
+++ b/tests/lax_numpy_indexing_test.py
@@ -1120,6 +1120,10 @@ class IndexingTest(jtu.JaxTestCase):
       jnp.zeros(2).at[0.].add(1.)
     with self.assertRaisesRegex(TypeError, BAD_INDEX_TYPE_ERROR):
       jnp.zeros(2).at[0.].set(1.)
+    with self.assertRaisesRegex(TypeError, BAD_INDEX_TYPE_ERROR):
+      jnp.zeros((2, 2))[jnp.arange(2), 1.0]
+    with self.assertRaisesRegex(TypeError, BAD_INDEX_TYPE_ERROR):
+      jnp.zeros((2, 2))[jnp.arange(2), 1 + 1j]
 
   def testStrIndexingError(self):
     msg = "JAX does not support string indexing"