From 518943adf13bea78bfa91011b9b3b27eb8b9b9f4 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Fri, 14 Feb 2025 11:42:31 -0800
Subject: [PATCH] [promises] Bring back non-copyable seqs/joins (#38744)

I made seqs/joins copyable a while ago in anticipation of a nice optimization -- that didn't pan out.

Having them copyable makes it more likely that `Loop` will accept them and try to turn them from promises into the promise factory that it expects, copying the insides... *which is usually wrong* and incredibly frustrating to debug.

Closes #38744

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/38744 from ctiller:promising e7a0e8d0bbf084a764378a855c3e0ef8e5b66c6b
PiperOrigin-RevId: 727006243
---
 src/core/lib/promise/detail/join_state.h    |  84 ++----
 src/core/lib/promise/detail/seq_state.h     | 280 +++-----------------
 src/core/lib/promise/loop.h                 |   4 +-
 tools/codegen/core/gen_join.py              |   7 +-
 tools/codegen/core/templates/seq_state.mako |  10 +-
 5 files changed, 63 insertions(+), 322 deletions(-)

diff --git a/src/core/lib/promise/detail/join_state.h b/src/core/lib/promise/detail/join_state.h
index 767ca8d787dfe..c9dc27bc3e1df 100644
--- a/src/core/lib/promise/detail/join_state.h
+++ b/src/core/lib/promise/detail/join_state.h
@@ -57,11 +57,8 @@ struct JoinState<Traits, P0, P1> {
     Construct(&promise0, std::forward<P0>(p0));
     Construct(&promise1, std::forward<P1>(p1));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -163,12 +160,8 @@ struct JoinState<Traits, P0, P1, P2> {
     Construct(&promise1, std::forward<P1>(p1));
     Construct(&promise2, std::forward<P2>(p2));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -307,13 +300,8 @@ struct JoinState<Traits, P0, P1, P2, P3> {
     Construct(&promise2, std::forward<P2>(p2));
     Construct(&promise3, std::forward<P3>(p3));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -488,14 +476,8 @@ struct JoinState<Traits, P0, P1, P2, P3, P4> {
     Construct(&promise3, std::forward<P3>(p3));
     Construct(&promise4, std::forward<P4>(p4));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-    Construct(&promise4, other.promise4);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -706,15 +688,8 @@ struct JoinState<Traits, P0, P1, P2, P3, P4, P5> {
     Construct(&promise4, std::forward<P4>(p4));
     Construct(&promise5, std::forward<P5>(p5));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-    Construct(&promise4, other.promise4);
-    Construct(&promise5, other.promise5);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -961,16 +936,8 @@ struct JoinState<Traits, P0, P1, P2, P3, P4, P5, P6> {
     Construct(&promise5, std::forward<P5>(p5));
     Construct(&promise6, std::forward<P6>(p6));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-    Construct(&promise4, other.promise4);
-    Construct(&promise5, other.promise5);
-    Construct(&promise6, other.promise6);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -1253,17 +1220,8 @@ struct JoinState<Traits, P0, P1, P2, P3, P4, P5, P6, P7> {
     Construct(&promise6, std::forward<P6>(p6));
     Construct(&promise7, std::forward<P7>(p7));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-    Construct(&promise4, other.promise4);
-    Construct(&promise5, other.promise5);
-    Construct(&promise6, other.promise6);
-    Construct(&promise7, other.promise7);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
@@ -1581,18 +1539,8 @@ struct JoinState<Traits, P0, P1, P2, P3, P4, P5, P6, P7, P8> {
     Construct(&promise7, std::forward<P7>(p7));
     Construct(&promise8, std::forward<P8>(p8));
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-    Construct(&promise0, other.promise0);
-    Construct(&promise1, other.promise1);
-    Construct(&promise2, other.promise2);
-    Construct(&promise3, other.promise3);
-    Construct(&promise4, other.promise4);
-    Construct(&promise5, other.promise5);
-    Construct(&promise6, other.promise6);
-    Construct(&promise7, other.promise7);
-    Construct(&promise8, other.promise8);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) =
+      delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
diff --git a/src/core/lib/promise/detail/seq_state.h b/src/core/lib/promise/detail/seq_state.h
index a83f346983ae3..184cf5f4954c9 100644
--- a/src/core/lib/promise/detail/seq_state.h
+++ b/src/core/lib/promise/detail/seq_state.h
@@ -73,6 +73,37 @@
 // here. The very first state does not have a prior state, and so that state has
 // a partial specialization below. The final state does not have a next state;
 // that state is inlined in BasicSeq since that was simpler to type.
+//
+// The final state machine is built only after a simplification pass over the
+// sequence. This pass examines the sequence and leverages subsequences that
+// are known to be instantaneous to avoid the overhead of the state machine.
+// How do we know something is instantaneous? If the promise factory returns
+// something other than a promise that returns Poll<> then we know we can
+// evaluate it immediately.
+//
+// Simplification proceeds in four phases:
+//
+// Phase 1: Labelling, inside Simplify()
+//   Here we construct a bitfield that tells us which steps are instantaneous
+//   and which ones are not. This allows us to leverage constexpr if over the
+//   bitfield to speed up compilation and simplify the logic herein.
+//   The bitfield is constructed such that the 0 bit corresponds to the last
+//   factory in the sequence, and the n-1 bit corresponds to the first factory.
+//   This is a bit confusing when doing the shifts and masks, but ensures that
+//   the bit pattern that shows up in the generated text is in the same order
+//   as the promise factories in the argument lists to Simplify() and friends,
+//   which greatly aids in debugging.
+// Phase 2: Right Simplification, inside SimplifyRight():
+//   Here we take advantage of the identity Seq(A, I) == Map(A, I) for a
+//   promise A and an instantanious promise factory I. We examine the last
+//   bits of the bitfield and merge together all trailing instantaneous steps
+//   into a single map.
+// Phase 3: Left Simplification, inside SimplifyLeft():
+//   Leveraging the same identity, we now look to the first bits of the
+//   bitfield, and merge any instantaneous steps into the first promise.
+// Phase 4: Middle Simplification, inside SimplifyMiddle():
+//   Here we look at the remaining steps in the bitfield and merge sequences
+//   of instantaneous steps into a single map.
 
 namespace grpc_core {
 namespace promise_detail {
@@ -719,12 +750,7 @@ struct SeqState<Traits, P, F0> {
   tail0:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.current_promise, other.prior.current_promise);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -841,13 +867,7 @@ struct SeqState<Traits, P, F0, F1> {
   tail1:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.current_promise, other.prior.prior.current_promise);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -1014,16 +1034,7 @@ struct SeqState<Traits, P, F0, F1, F2> {
   tail2:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.current_promise,
-              other.prior.prior.prior.current_promise);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -1238,18 +1249,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3> {
   tail3:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.current_promise,
-              other.prior.prior.prior.prior.current_promise);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -1521,20 +1521,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4> {
   tail4:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.current_promise,
-              other.prior.prior.prior.prior.prior.current_promise);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -1858,22 +1845,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5> {
   tail5:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.prior.current_promise,
-              other.prior.prior.prior.prior.prior.prior.current_promise);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -2251,24 +2223,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6> {
   tail6:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.current_promise,
-              other.prior.prior.prior.prior.prior.prior.prior.current_promise);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -2703,28 +2658,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6, F7> {
   tail7:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.current_promise,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.current_promise);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -3218,33 +3152,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6, F7, F8> {
   tail8:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.prior.current_promise,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.prior
-            .current_promise);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.prior
-            .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -3801,37 +3709,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6, F7, F8, F9> {
   tail9:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .current_promise,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .current_promise);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.prior
-            .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -4450,41 +4328,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10> {
   tail10:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .current_promise,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .prior.current_promise);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.prior
-            .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
@@ -5168,45 +5012,7 @@ struct SeqState<Traits, P, F0, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11> {
   tail11:
     Destruct(&prior.next_factory);
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept
-      : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .prior.current_promise,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .prior.prior.current_promise);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                   .next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.prior.prior.prior
-                  .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.prior
-            .next_factory);
-    Construct(
-        &prior.prior.prior.prior.prior.prior.prior.prior.next_factory,
-        other.prior.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.prior.next_factory,
-              other.prior.prior.prior.prior.next_factory);
-    Construct(&prior.prior.prior.next_factory,
-              other.prior.prior.prior.next_factory);
-    Construct(&prior.prior.next_factory, other.prior.prior.next_factory);
-    Construct(&prior.next_factory, other.prior.next_factory);
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept
       : state(other.state), whence(other.whence) {
diff --git a/src/core/lib/promise/loop.h b/src/core/lib/promise/loop.h
index 7cb6e0f0a8ab8..27df03bcfcae7 100644
--- a/src/core/lib/promise/loop.h
+++ b/src/core/lib/promise/loop.h
@@ -33,8 +33,8 @@ namespace grpc_core {
 //
 // Input:
 //
-// 1. A Loop combinator takes as input only one promise or promise factory.
-// 2. This input promise or promise factory should have a return type of either
+// 1. A Loop combinator takes as input only one promise factory.
+// 2. This input promise factory should have a return type of either
 //    a.  LoopCtl<T> which is an alias for std::variant<Continue, T>
 //    b.  Or Poll<LoopCtl<T>>
 //
diff --git a/tools/codegen/core/gen_join.py b/tools/codegen/core/gen_join.py
index 4f53a982d4174..3ab47ccd28f0b 100755
--- a/tools/codegen/core/gen_join.py
+++ b/tools/codegen/core/gen_join.py
@@ -38,12 +38,7 @@
     Construct(&promise${i}, std::forward<P${i}>(p${i}));
 % endfor
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) {
-    DCHECK(other.ready.none());
-% for i in range(0,n):
-    Construct(&promise${i}, other.promise${i});
-% endfor
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(const JoinState& other) = delete;
   JoinState& operator=(const JoinState& other) = delete;
   JoinState& operator=(JoinState&& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION JoinState(JoinState&& other) noexcept {
diff --git a/tools/codegen/core/templates/seq_state.mako b/tools/codegen/core/templates/seq_state.mako
index e3b3b0711c830..02e7cb9b32099 100644
--- a/tools/codegen/core/templates/seq_state.mako
+++ b/tools/codegen/core/templates/seq_state.mako
@@ -237,15 +237,7 @@ tail${i}:
     Destruct(&${"prior."*(n-1-i)}next_factory);
 % endfor
   }
-  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) noexcept : state(other.state), whence(other.whence) {
-    DCHECK(state == State::kState0);
-    Construct(&${"prior."*(n-1)}current_promise,
-            other.${"prior."*(n-1)}current_promise);
-% for i in range(0,n-1):
-    Construct(&${"prior."*(n-1-i)}next_factory,
-              other.${"prior."*(n-1-i)}next_factory);
-% endfor
-  }
+  GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(const SeqState& other) = delete;
   SeqState& operator=(const SeqState& other) = delete;
   GPR_ATTRIBUTE_ALWAYS_INLINE_FUNCTION SeqState(SeqState&& other) noexcept : state(other.state), whence(other.whence) {
     DCHECK(state == State::kState0);