From 8f2285a714e01da6885101977c4b6f1bba56a154 Mon Sep 17 00:00:00 2001
From: Angus Hollands <goosey15@gmail.com>
Date: Fri, 27 Oct 2023 10:31:37 +0100
Subject: [PATCH] fix: drop lengths recursively (#2775)

* fix: drop lengths recursively

* test: ensure slicing from-typetracer works
---
 src/awkward/contents/bitmaskedarray.py     |  2 +-
 src/awkward/contents/bytemaskedarray.py    |  2 +-
 src/awkward/contents/indexedarray.py       |  2 +-
 src/awkward/contents/indexedoptionarray.py |  2 +-
 src/awkward/contents/listarray.py          |  2 +-
 src/awkward/contents/listoffsetarray.py    |  2 +-
 src/awkward/contents/unionarray.py         |  2 +-
 tests/test_2765_slice_from_typetracer.py   | 15 +++++++++++++++
 8 files changed, 22 insertions(+), 7 deletions(-)
 create mode 100644 tests/test_2765_slice_from_typetracer.py

diff --git a/src/awkward/contents/bitmaskedarray.py b/src/awkward/contents/bitmaskedarray.py
index ae5e8e2fe5..b5c1370efd 100644
--- a/src/awkward/contents/bitmaskedarray.py
+++ b/src/awkward/contents/bitmaskedarray.py
@@ -311,7 +311,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         tt = TypeTracer.instance()
         return BitMaskedArray(
             self._mask.to_nplike(tt),
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             self._valid_when,
             unknown_length if forget_length else self.length,
             self._lsb_order,
diff --git a/src/awkward/contents/bytemaskedarray.py b/src/awkward/contents/bytemaskedarray.py
index ab82e40764..1ba6f8966d 100644
--- a/src/awkward/contents/bytemaskedarray.py
+++ b/src/awkward/contents/bytemaskedarray.py
@@ -234,7 +234,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         mask = self._mask.to_nplike(tt)
         return ByteMaskedArray(
             mask.forget_length() if forget_length else mask,
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             self._valid_when,
             parameters=self._parameters,
         )
diff --git a/src/awkward/contents/indexedarray.py b/src/awkward/contents/indexedarray.py
index d990dea323..eb5f595337 100644
--- a/src/awkward/contents/indexedarray.py
+++ b/src/awkward/contents/indexedarray.py
@@ -224,7 +224,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         index = self._index.to_nplike(TypeTracer.instance())
         return IndexedArray(
             index.forget_length() if forget_length else index,
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             parameters=self._parameters,
         )
 
diff --git a/src/awkward/contents/indexedoptionarray.py b/src/awkward/contents/indexedoptionarray.py
index f1d9568a55..cee5e77326 100644
--- a/src/awkward/contents/indexedoptionarray.py
+++ b/src/awkward/contents/indexedoptionarray.py
@@ -213,7 +213,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         index = self._index.to_nplike(TypeTracer.instance())
         return IndexedOptionArray(
             index.forget_length() if forget_length else index,
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             parameters=self._parameters,
         )
 
diff --git a/src/awkward/contents/listarray.py b/src/awkward/contents/listarray.py
index 98f153925b..26f872f421 100644
--- a/src/awkward/contents/listarray.py
+++ b/src/awkward/contents/listarray.py
@@ -228,7 +228,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         return ListArray(
             starts.forget_length() if forget_length else starts,
             self._stops.to_nplike(tt),
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             parameters=self._parameters,
         )
 
diff --git a/src/awkward/contents/listoffsetarray.py b/src/awkward/contents/listoffsetarray.py
index c6aa5f1d8f..d3efb08698 100644
--- a/src/awkward/contents/listoffsetarray.py
+++ b/src/awkward/contents/listoffsetarray.py
@@ -211,7 +211,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         offsets = self._offsets.to_nplike(TypeTracer.instance())
         return ListOffsetArray(
             offsets.forget_length() if forget_length else offsets,
-            self._content._to_typetracer(False),
+            self._content._to_typetracer(forget_length),
             parameters=self._parameters,
         )
 
diff --git a/src/awkward/contents/unionarray.py b/src/awkward/contents/unionarray.py
index 2d0647ce77..95ddfca6e4 100644
--- a/src/awkward/contents/unionarray.py
+++ b/src/awkward/contents/unionarray.py
@@ -486,7 +486,7 @@ def _to_typetracer(self, forget_length: bool) -> Self:
         return UnionArray(
             tags.forget_length() if forget_length else tags,
             self._index.to_nplike(tt),
-            [x._to_typetracer(False) for x in self._contents],
+            [x._to_typetracer(forget_length) for x in self._contents],
             parameters=self._parameters,
         )
 
diff --git a/tests/test_2765_slice_from_typetracer.py b/tests/test_2765_slice_from_typetracer.py
new file mode 100644
index 0000000000..b144e7f9be
--- /dev/null
+++ b/tests/test_2765_slice_from_typetracer.py
@@ -0,0 +1,15 @@
+import awkward as ak
+
+
+def test():
+    array = ak.typetracer.typetracer_from_form(
+        ak.forms.from_type(
+            ak.types.from_datashape("{x: var * {y:int64}}", highlevel=False)
+        )
+    )
+    sliced = array[0, "x", 0]
+    assert sliced.type.is_equal_to(
+        ak.types.ScalarType(
+            ak.types.RecordType([ak.types.NumpyType("int64")], ["y"]), None
+        )
+    )