From e5c151c31844b0ee3a4546baae9ee9519953cf61 Mon Sep 17 00:00:00 2001
From: romintomasetti <romin.tomasetti@gmail.com>
Date: Fri, 23 Oct 2026 13:35:50 +0000
Subject: [PATCH] bulk: check index type contract

The index type is deduced from the Shape type.

https://eel.is/c++draft/exec#bulk-4
Signed-off-by: romintomasetti <romin.tomasetti@gmail.com>
---
 test/stdexec/algos/adaptors/test_bulk.cpp | 39 +++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/test/stdexec/algos/adaptors/test_bulk.cpp b/test/stdexec/algos/adaptors/test_bulk.cpp
index 7a33a458f..1214d38dc 100644
--- a/test/stdexec/algos/adaptors/test_bulk.cpp
+++ b/test/stdexec/algos/adaptors/test_bulk.cpp
@@ -618,6 +618,45 @@ namespace
     ex::start(op);
   }
 
+  template <std::integral Expected>
+  struct CheckIndexType
+  {
+    template <std::integral Deduced>
+    void operator()(Deduced const, bool& as_expected) const noexcept
+    {
+      as_expected = std::same_as<Expected, Deduced>;
+    }
+  };
+
+  TEST_CASE("bulk index type is deduced from shape type", "[adaptors][bulk]")
+  {
+    {
+      // The index type matches.
+      auto const [value] =
+        ex::sync_wait(ex::just(false) | ex::bulk(ex::par, int(1), CheckIndexType<int>{})).value();
+      CHECK(value == true);
+    }
+    {
+      // The index type does not match.
+      auto const [value] =
+        ex::sync_wait(ex::just(true) | ex::bulk(ex::par, int(1), CheckIndexType<size_t>{})).value();
+      CHECK(value == false);
+    }
+    {
+      // The index type matches.
+      auto const [value] = ex::sync_wait(ex::just(false)
+                                         | ex::bulk(ex::par, size_t(1), CheckIndexType<size_t>{}))
+                             .value();
+      CHECK(value == true);
+    }
+    {
+      // The index type does not match.
+      auto const [value] =
+        ex::sync_wait(ex::just(true) | ex::bulk(ex::par, size_t(1), CheckIndexType<int>{})).value();
+      CHECK(value == false);
+    }
+  }
+
 #if !STDEXEC_NO_STDCPP_EXCEPTIONS()
   TEST_CASE("bulk can throw, and set_error will be called", "[adaptors][bulk]")
   {