From c866d65966e2fff89f0c6de6c3d2cc6bf9cceed6 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Fri, 5 Aug 2022 08:28:33 -0700
Subject: [PATCH] [promises] Eliminate switch.h (#30317)

* [promises] Eliminate switch.h

Instead build a jump table that we can index into and call the appropriate function. Means that the dispatch mechanism can be done in C++ without a code generator, and so eliminates a bunch of fiddly code.

* fix

* ensure static initialization

* Automated change: Fix sanity tests

Co-authored-by: ctiller <ctiller@users.noreply.github.com>
---
 BUILD                                   |   10 -
 build_autogenerated.yaml                |   16 -
 gRPC-C++.podspec                        |    2 -
 gRPC-Core.podspec                       |    2 -
 grpc.gemspec                            |    1 -
 package.xml                             |    1 -
 src/core/lib/promise/detail/basic_seq.h |   35 +-
 src/core/lib/promise/detail/switch.h    | 1455 -----------------------
 tools/codegen/core/gen_switch.py        |   75 --
 tools/doxygen/Doxyfile.c++.internal     |    1 -
 tools/doxygen/Doxyfile.core.internal    |    1 -
 11 files changed, 27 insertions(+), 1572 deletions(-)
 delete mode 100644 src/core/lib/promise/detail/switch.h
 delete mode 100755 tools/codegen/core/gen_switch.py

diff --git a/BUILD b/BUILD
index ac2f0917d3e..5d82de6b525 100644
--- a/BUILD
+++ b/BUILD
@@ -1395,15 +1395,6 @@ grpc_cc_library(
     ],
 )
 
-grpc_cc_library(
-    name = "switch",
-    language = "c++",
-    public_hdrs = [
-        "src/core/lib/promise/detail/switch.h",
-    ],
-    deps = ["gpr_platform"],
-)
-
 grpc_cc_library(
     name = "basic_join",
     external_deps = [
@@ -1472,7 +1463,6 @@ grpc_cc_library(
         "poll",
         "promise_factory",
         "promise_like",
-        "switch",
     ],
 )
 
diff --git a/build_autogenerated.yaml b/build_autogenerated.yaml
index fef1c076d5c..a982dfd0757 100644
--- a/build_autogenerated.yaml
+++ b/build_autogenerated.yaml
@@ -866,7 +866,6 @@ libs:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/intra_activity_waiter.h
   - src/core/lib/promise/latch.h
@@ -2051,7 +2050,6 @@ libs:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/intra_activity_waiter.h
   - src/core/lib/promise/latch.h
@@ -3667,7 +3665,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/join.h
   - src/core/lib/promise/poll.h
   - src/core/lib/promise/promise.h
@@ -4081,7 +4078,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -4929,7 +4925,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -6138,7 +6133,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -6222,7 +6216,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/for_each.h
   - src/core/lib/promise/intra_activity_waiter.h
@@ -7558,7 +7551,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/intra_activity_waiter.h
   - src/core/lib/promise/join.h
   - src/core/lib/promise/latch.h
@@ -7723,7 +7715,6 @@ targets:
   - src/core/lib/promise/detail/basic_seq.h
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/poll.h
   - src/core/lib/promise/seq.h
@@ -7809,7 +7800,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -7887,7 +7877,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -8238,7 +8227,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/observable.h
   - src/core/lib/promise/poll.h
   - src/core/lib/promise/promise.h
@@ -8567,7 +8555,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/intra_activity_waiter.h
   - src/core/lib/promise/join.h
@@ -9122,7 +9109,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/exec_ctx_wakeup_scheduler.h
   - src/core/lib/promise/loop.h
   - src/core/lib/promise/map.h
@@ -9313,7 +9299,6 @@ targets:
   - src/core/lib/promise/detail/basic_seq.h
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/poll.h
   - src/core/lib/promise/seq.h
   src:
@@ -11175,7 +11160,6 @@ targets:
   - src/core/lib/promise/detail/promise_factory.h
   - src/core/lib/promise/detail/promise_like.h
   - src/core/lib/promise/detail/status.h
-  - src/core/lib/promise/detail/switch.h
   - src/core/lib/promise/poll.h
   - src/core/lib/promise/try_seq.h
   src:
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index 16bfd11741d..2597838fd64 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -825,7 +825,6 @@ Pod::Spec.new do |s|
                       'src/core/lib/promise/detail/promise_factory.h',
                       'src/core/lib/promise/detail/promise_like.h',
                       'src/core/lib/promise/detail/status.h',
-                      'src/core/lib/promise/detail/switch.h',
                       'src/core/lib/promise/exec_ctx_wakeup_scheduler.h',
                       'src/core/lib/promise/intra_activity_waiter.h',
                       'src/core/lib/promise/latch.h',
@@ -1680,7 +1679,6 @@ Pod::Spec.new do |s|
                               'src/core/lib/promise/detail/promise_factory.h',
                               'src/core/lib/promise/detail/promise_like.h',
                               'src/core/lib/promise/detail/status.h',
-                              'src/core/lib/promise/detail/switch.h',
                               'src/core/lib/promise/exec_ctx_wakeup_scheduler.h',
                               'src/core/lib/promise/intra_activity_waiter.h',
                               'src/core/lib/promise/latch.h',
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index fcd4ca59e6b..0bf5b88aba9 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -1340,7 +1340,6 @@ Pod::Spec.new do |s|
                       'src/core/lib/promise/detail/promise_factory.h',
                       'src/core/lib/promise/detail/promise_like.h',
                       'src/core/lib/promise/detail/status.h',
-                      'src/core/lib/promise/detail/switch.h',
                       'src/core/lib/promise/exec_ctx_wakeup_scheduler.h',
                       'src/core/lib/promise/intra_activity_waiter.h',
                       'src/core/lib/promise/latch.h',
@@ -2302,7 +2301,6 @@ Pod::Spec.new do |s|
                               'src/core/lib/promise/detail/promise_factory.h',
                               'src/core/lib/promise/detail/promise_like.h',
                               'src/core/lib/promise/detail/status.h',
-                              'src/core/lib/promise/detail/switch.h',
                               'src/core/lib/promise/exec_ctx_wakeup_scheduler.h',
                               'src/core/lib/promise/intra_activity_waiter.h',
                               'src/core/lib/promise/latch.h',
diff --git a/grpc.gemspec b/grpc.gemspec
index 543dc485c53..b45550cd2ec 100644
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -1253,7 +1253,6 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/lib/promise/detail/promise_factory.h )
   s.files += %w( src/core/lib/promise/detail/promise_like.h )
   s.files += %w( src/core/lib/promise/detail/status.h )
-  s.files += %w( src/core/lib/promise/detail/switch.h )
   s.files += %w( src/core/lib/promise/exec_ctx_wakeup_scheduler.h )
   s.files += %w( src/core/lib/promise/intra_activity_waiter.h )
   s.files += %w( src/core/lib/promise/latch.h )
diff --git a/package.xml b/package.xml
index 6d1bd92223c..471e31dd4cd 100644
--- a/package.xml
+++ b/package.xml
@@ -1235,7 +1235,6 @@
     <file baseinstalldir="/" name="src/core/lib/promise/detail/promise_factory.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/promise/detail/promise_like.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/promise/detail/status.h" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/promise/detail/switch.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/promise/exec_ctx_wakeup_scheduler.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/promise/intra_activity_waiter.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/promise/latch.h" role="src" />
diff --git a/src/core/lib/promise/detail/basic_seq.h b/src/core/lib/promise/detail/basic_seq.h
index 2687d1f2568..1e4756d8a37 100644
--- a/src/core/lib/promise/detail/basic_seq.h
+++ b/src/core/lib/promise/detail/basic_seq.h
@@ -17,6 +17,8 @@
 
 #include <grpc/support/port_platform.h>
 
+#include <stddef.h>
+
 #include <array>
 #include <cassert>
 #include <new>
@@ -30,12 +32,29 @@
 #include "src/core/lib/gprpp/construct_destruct.h"
 #include "src/core/lib/promise/detail/promise_factory.h"
 #include "src/core/lib/promise/detail/promise_like.h"
-#include "src/core/lib/promise/detail/switch.h"
 #include "src/core/lib/promise/poll.h"
 
 namespace grpc_core {
 namespace promise_detail {
 
+// Given f0, ..., fn, call function idx and return the result.
+template <typename R, typename A, R (*... f)(A* arg)>
+class JumpTable {
+ public:
+  JumpTable() = delete;
+  JumpTable(const JumpTable&) = delete;
+
+  static R Run(size_t idx, A* arg) { return fs_[idx](arg); }
+
+ private:
+  using Fn = R (*)(A* arg);
+  static const Fn fs_[sizeof...(f)];
+};
+
+template <typename R, typename A, R (*... f)(A* arg)>
+const typename JumpTable<R, A, f...>::Fn
+    JumpTable<R, A, f...>::fs_[sizeof...(f)] = {f...};
+
 // Helper for SeqState to evaluate some common types to all partial
 // specializations.
 template <template <typename> class Traits, typename FPromise, typename FNext>
@@ -334,16 +353,14 @@ class BasicSeq {
   // parameter unpacking can work.
   template <char I>
   struct RunStateStruct {
-    BasicSeq* s;
-    Poll<Result> operator()() { return s->RunState<I>(); }
+    static Poll<Result> Run(BasicSeq* s) { return s->RunState<I>(); }
   };
 
   // Similarly placate those compilers for
   // DestructCurrentPromiseAndSubsequentFactories
   template <char I>
   struct DestructCurrentPromiseAndSubsequentFactoriesStruct {
-    BasicSeq* s;
-    void operator()() {
+    static void Run(BasicSeq* s) {
       return s->DestructCurrentPromiseAndSubsequentFactories<I>();
     }
   };
@@ -356,7 +373,8 @@ class BasicSeq {
   // Duff's device like mechanic for evaluating sequences.
   template <char... I>
   Poll<Result> Run(absl::integer_sequence<char, I...>) {
-    return Switch<Poll<Result>>(state_, RunStateStruct<I>{this}...);
+    return JumpTable<Poll<Result>, BasicSeq, RunStateStruct<I>::Run...>::Run(
+        state_, this);
   }
 
   // Run the appropriate destructors for a given state.
@@ -366,8 +384,9 @@ class BasicSeq {
   // which can choose the correct instance at runtime to destroy everything.
   template <char... I>
   void RunDestruct(absl::integer_sequence<char, I...>) {
-    Switch<void>(
-        state_, DestructCurrentPromiseAndSubsequentFactoriesStruct<I>{this}...);
+    JumpTable<void, BasicSeq,
+              DestructCurrentPromiseAndSubsequentFactoriesStruct<I>::Run...>::
+        Run(state_, this);
   }
 
  public:
diff --git a/src/core/lib/promise/detail/switch.h b/src/core/lib/promise/detail/switch.h
deleted file mode 100644
index 84b119119b0..00000000000
--- a/src/core/lib/promise/detail/switch.h
+++ /dev/null
@@ -1,1455 +0,0 @@
-/*
- * Copyright 2021 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/*
- * Automatically generated by tools/codegen/core/gen_switch.py
- */
-
-#ifndef GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H
-#define GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H
-
-#include <grpc/support/port_platform.h>
-
-#include <stdlib.h>
-
-namespace grpc_core {
-
-template <typename R, typename F0>
-R Switch(char idx, F0 f0) {
-  switch (idx) {
-    case 0:
-      return f0();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1>
-R Switch(char idx, F0 f0, F1 f1) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2>
-R Switch(char idx, F0 f0, F1 f1, F2 f2) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22,
-         F23 f23) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26, typename F27>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26, F27 f27) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-    case 27:
-      return f27();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26, typename F27, typename F28>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26, F27 f27, F28 f28) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-    case 27:
-      return f27();
-    case 28:
-      return f28();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26, typename F27, typename F28,
-          typename F29>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26, F27 f27, F28 f28, F29 f29) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-    case 27:
-      return f27();
-    case 28:
-      return f28();
-    case 29:
-      return f29();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26, typename F27, typename F28,
-          typename F29, typename F30>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26, F27 f27, F28 f28, F29 f29, F30 f30) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-    case 27:
-      return f27();
-    case 28:
-      return f28();
-    case 29:
-      return f29();
-    case 30:
-      return f30();
-  }
-  abort();
-}
-
-template <typename R, typename F0, typename F1, typename F2, typename F3,
-          typename F4, typename F5, typename F6, typename F7, typename F8,
-          typename F9, typename F10, typename F11, typename F12, typename F13,
-          typename F14, typename F15, typename F16, typename F17, typename F18,
-          typename F19, typename F20, typename F21, typename F22, typename F23,
-          typename F24, typename F25, typename F26, typename F27, typename F28,
-          typename F29, typename F30, typename F31>
-R Switch(char idx, F0 f0, F1 f1, F2 f2, F3 f3, F4 f4, F5 f5, F6 f6, F7 f7,
-         F8 f8, F9 f9, F10 f10, F11 f11, F12 f12, F13 f13, F14 f14, F15 f15,
-         F16 f16, F17 f17, F18 f18, F19 f19, F20 f20, F21 f21, F22 f22, F23 f23,
-         F24 f24, F25 f25, F26 f26, F27 f27, F28 f28, F29 f29, F30 f30,
-         F31 f31) {
-  switch (idx) {
-    case 0:
-      return f0();
-    case 1:
-      return f1();
-    case 2:
-      return f2();
-    case 3:
-      return f3();
-    case 4:
-      return f4();
-    case 5:
-      return f5();
-    case 6:
-      return f6();
-    case 7:
-      return f7();
-    case 8:
-      return f8();
-    case 9:
-      return f9();
-    case 10:
-      return f10();
-    case 11:
-      return f11();
-    case 12:
-      return f12();
-    case 13:
-      return f13();
-    case 14:
-      return f14();
-    case 15:
-      return f15();
-    case 16:
-      return f16();
-    case 17:
-      return f17();
-    case 18:
-      return f18();
-    case 19:
-      return f19();
-    case 20:
-      return f20();
-    case 21:
-      return f21();
-    case 22:
-      return f22();
-    case 23:
-      return f23();
-    case 24:
-      return f24();
-    case 25:
-      return f25();
-    case 26:
-      return f26();
-    case 27:
-      return f27();
-    case 28:
-      return f28();
-    case 29:
-      return f29();
-    case 30:
-      return f30();
-    case 31:
-      return f31();
-  }
-  abort();
-}
-
-}  // namespace grpc_core
-
-#endif  // GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H
diff --git a/tools/codegen/core/gen_switch.py b/tools/codegen/core/gen_switch.py
deleted file mode 100755
index 6667959aec3..00000000000
--- a/tools/codegen/core/gen_switch.py
+++ /dev/null
@@ -1,75 +0,0 @@
-#!/usr/bin/env python3
-
-# Copyright 2021 gRPC authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-import sys
-
-
-# utility: print a big comment block into a set of files
-def put_banner(files, banner):
-    for f in files:
-        print('/*', file=f)
-        for line in banner:
-            print(' * %s' % line, file=f)
-        print(' */', file=f)
-        print('', file=f)
-
-
-with open('src/core/lib/promise/detail/switch.h', 'w') as H:
-    # copy-paste copyright notice from this file
-    with open(sys.argv[0]) as my_source:
-        copyright = []
-        for line in my_source:
-            if line[0] != '#':
-                break
-        for line in my_source:
-            if line[0] == '#':
-                copyright.append(line)
-                break
-        for line in my_source:
-            if line[0] != '#':
-                break
-            copyright.append(line)
-        put_banner([H], [line[2:].rstrip() for line in copyright])
-
-    put_banner([H], ["Automatically generated by %s" % sys.argv[0]])
-
-    print("#ifndef GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H)
-    print("#define GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H)
-    print('', file=H)
-    print('#include <grpc/impl/codegen/port_platform.h>', file=H)
-    print('', file=H)
-    print("#include <stdlib.h>", file=H)
-    print('', file=H)
-    print("namespace grpc_core {", file=H)
-
-    for n in range(1, 33):
-        print('', file=H)
-        print("template <typename R, %s> R Switch(char idx, %s) {" % (
-            ", ".join("typename F%d" % i for i in range(0, n)),
-            ", ".join("F%d f%d" % (i, i) for i in range(0, n)),
-        ),
-              file=H)
-        print("  switch (idx) {", file=H)
-        for i in range(0, n):
-            print("   case %d: return f%d();" % (i, i), file=H)
-        print("  }", file=H)
-        print("  abort();", file=H)
-        print("}", file=H)
-
-    print('', file=H)
-    print("}", file=H)
-    print('', file=H)
-    print("#endif // GRPC_CORE_LIB_PROMISE_DETAIL_SWITCH_H", file=H)
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index f727f0e233b..6bdffa36b8f 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -2236,7 +2236,6 @@ src/core/lib/promise/detail/basic_seq.h \
 src/core/lib/promise/detail/promise_factory.h \
 src/core/lib/promise/detail/promise_like.h \
 src/core/lib/promise/detail/status.h \
-src/core/lib/promise/detail/switch.h \
 src/core/lib/promise/exec_ctx_wakeup_scheduler.h \
 src/core/lib/promise/intra_activity_waiter.h \
 src/core/lib/promise/latch.h \
diff --git a/tools/doxygen/Doxyfile.core.internal b/tools/doxygen/Doxyfile.core.internal
index 27d6a58314d..cfe051cd0fc 100644
--- a/tools/doxygen/Doxyfile.core.internal
+++ b/tools/doxygen/Doxyfile.core.internal
@@ -2029,7 +2029,6 @@ src/core/lib/promise/detail/basic_seq.h \
 src/core/lib/promise/detail/promise_factory.h \
 src/core/lib/promise/detail/promise_like.h \
 src/core/lib/promise/detail/status.h \
-src/core/lib/promise/detail/switch.h \
 src/core/lib/promise/exec_ctx_wakeup_scheduler.h \
 src/core/lib/promise/intra_activity_waiter.h \
 src/core/lib/promise/latch.h \