From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Wed, 17 Aug 2022 13:19:11 +0000 (+0100)
Subject: Revert "bounded senders"
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=51aba46076a2a56a1e481d24db80bbbcabddca0c;p=rust-experiments.git

Revert "bounded senders"

This reverts commit b87db4d6cbcee96ad05114e699173f48d9a91c86.
---

diff --git a/Cargo.lock b/Cargo.lock
index 41ce6c3..e816493 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -20,18 +20,6 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
-[[package]]
-name = "bytes"
-version = "1.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c4872d67bab6358e59559027aa3b9157c53d9358c51423c17554809a8858e0f8"
-
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-checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
-
 [[package]]
 name = "darling"
 version = "0.14.1"
@@ -106,110 +94,10 @@ name = "foo"
 version = "0.1.0"
 dependencies = [
  "derive_builder",
- "futures",
  "ron",
  "serde",
  "serde-value",
  "serde_json",
- "tokio",
-]
-
-[[package]]
-name = "futures"
-version = "0.3.21"
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-dependencies = [
- "futures-channel",
- "futures-core",
- "futures-executor",
- "futures-io",
- "futures-sink",
- "futures-task",
- "futures-util",
-]
-
-[[package]]
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-version = "0.3.21"
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-dependencies = [
- "futures-core",
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-]
-
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-dependencies = [
- "futures-core",
- "futures-task",
- "futures-util",
-]
-
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- "quote",
- "syn",
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-
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-dependencies = [
- "futures-channel",
- "futures-core",
- "futures-io",
- "futures-macro",
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- "memchr",
- "pin-project-lite",
- "pin-utils",
- "slab",
-]
-
-[[package]]
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-version = "0.1.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
-dependencies = [
- "libc",
 ]
 
 [[package]]
@@ -224,49 +112,6 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1aab8fc367588b89dcee83ab0fd66b72b50b72fa1904d7095045ace2b0c81c35"
 
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-checksum = "327fa5b6a6940e4699ec49a9beae1ea4845c6bab9314e4f84ac68742139d8c53"
-dependencies = [
- "autocfg",
- "scopeguard",
-]
-
-[[package]]
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-checksum = "abb12e687cfb44aa40f41fc3978ef76448f9b6038cad6aef4259d3c095a2382e"
-dependencies = [
- "cfg-if",
-]
-
-[[package]]
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-version = "2.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
-
-[[package]]
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-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "713d550d9b44d89174e066b7a6217ae06234c10cb47819a88290d2b353c31799"
-dependencies = [
- "libc",
- "log",
- "wasi",
- "windows-sys",
-]
-
 [[package]]
 name = "num-traits"
 version = "0.2.14"
@@ -276,22 +121,6 @@ dependencies = [
  "autocfg",
 ]
 
-[[package]]
-name = "num_cpus"
-version = "1.13.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
-dependencies = [
- "hermit-abi",
- "libc",
-]
-
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-
 [[package]]
 name = "ordered-float"
 version = "2.10.0"
@@ -301,41 +130,6 @@ dependencies = [
  "num-traits",
 ]
 
-[[package]]
-name = "parking_lot"
-version = "0.12.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
-dependencies = [
- "lock_api",
- "parking_lot_core",
-]
-
-[[package]]
-name = "parking_lot_core"
-version = "0.9.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
-dependencies = [
- "cfg-if",
- "libc",
- "redox_syscall",
- "smallvec",
- "windows-sys",
-]
-
-[[package]]
-name = "pin-project-lite"
-version = "0.2.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e0a7ae3ac2f1173085d398531c705756c94a4c56843785df85a60c1a0afac116"
-
-[[package]]
-name = "pin-utils"
-version = "0.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.37"
@@ -354,15 +148,6 @@ dependencies = [
  "proc-macro2",
 ]
 
-[[package]]
-name = "redox_syscall"
-version = "0.2.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62f25bc4c7e55e0b0b7a1d43fb893f4fa1361d0abe38b9ce4f323c2adfe6ef42"
-dependencies = [
- "bitflags",
-]
-
 [[package]]
 name = "ron"
 version = "0.7.0"
@@ -380,12 +165,6 @@ version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "73b4b750c782965c211b42f022f59af1fbceabdd026623714f104152f1ec149f"
 
-[[package]]
-name = "scopeguard"
-version = "1.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
-
 [[package]]
 name = "serde"
 version = "1.0.136"
@@ -427,37 +206,6 @@ dependencies = [
  "serde",
 ]
 
-[[package]]
-name = "signal-hook-registry"
-version = "1.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e51e73328dc4ac0c7ccbda3a494dfa03df1de2f46018127f60c693f2648455b0"
-dependencies = [
- "libc",
-]
-
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-version = "0.4.6"
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-checksum = "eb703cfe953bccee95685111adeedb76fabe4e97549a58d16f03ea7b9367bb32"
-
-[[package]]
-name = "smallvec"
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-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2dd574626839106c320a323308629dcb1acfc96e32a8cba364ddc61ac23ee83"
-
-[[package]]
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-version = "0.4.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "66d72b759436ae32898a2af0a14218dbf55efde3feeb170eb623637db85ee1e0"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "strsim"
 version = "0.10.0"
@@ -475,110 +223,8 @@ dependencies = [
  "unicode-xid",
 ]
 
-[[package]]
-name = "tokio"
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- "libc",
- "memchr",
- "mio",
- "num_cpus",
- "once_cell",
- "parking_lot",
- "pin-project-lite",
- "signal-hook-registry",
- "socket2",
- "tokio-macros",
- "winapi",
-]
-
-[[package]]
-name = "tokio-macros"
-version = "1.8.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9724f9a975fb987ef7a3cd9be0350edcbe130698af5b8f7a631e23d42d052484"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "unicode-xid"
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 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
-
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-source = "registry+https://github.com/rust-lang/crates.io-index"
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-
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-dependencies = [
- "winapi-i686-pc-windows-gnu",
- "winapi-x86_64-pc-windows-gnu",
-]
-
-[[package]]
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-source = "registry+https://github.com/rust-lang/crates.io-index"
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- "windows_i686_gnu",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_msvc",
-]
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-
-[[package]]
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diff --git a/Cargo.toml b/Cargo.toml
index 0a62d73..3b562af 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,5 +12,3 @@ serde = { version="1", features=["derive"] }
 ron = "*"
 serde_json = "*"
 derive_builder = { version = "0.11.2", git = "https://github.com/ijackson/rust-derive-builder", rev = "ba0c1a5311bd9f93ddf5f5b8ec2a5f6f03b22fbe" }
-tokio = { version="1", features=["full"] }
-futures = "0.3"
diff --git a/src/main.rs b/src/main.rs
index d9fd485..d5e0cbd 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,70 +5,80 @@
 use std::mem;
 use std::mem::MaybeUninit;
 
-#[tokio::main]
-async fn main(){
-    let (mut tx, mut rx) = futures::channel::mpsc::channel(0);
-    let () = tx.try_send(0).unwrap();
+type S = &'static str;
 
-    for i in 1..=3 {
-        let mut tx2 = tx.clone();
-        let () = tx2.try_send(i).unwrap();
-        assert!{ tx2.try_send(i+10).unwrap_err().is_full() }
-        assert!{ tx.try_send(i+20).unwrap_err().is_full() }
-        eprintln!("S {:?}", i);
-    }
 
-    let m = loop {
-        let m = rx.try_next();
-        let m = if let Ok(Some(m)) = m { m } else { break m };
-        eprintln!("Y {:?}", m);
+#[repr(C)]
+struct Concat<const A: usize, const B: usize>(
+    [S; A], 
+    [S; B],
+);
+
+trait Ish {
+    const N: usize;
+}
+
+trait Has<const N: usize> {
+    const F: [S; N];
+}
+
+struct Inner { i: usize, }
+
+impl Ish for Inner {
+    const N: usize = 1;
+}
+impl Has<1> for Inner {
+    const F: [S; 1] = ["i"];
+}
+
+struct Outer { o: usize, p: usize }
+
+impl Ish for Outer {
+    const N: usize = Inner::N + 2;
+}
+impl Has<{ Inner::N + 2 }> for Outer {
+    const F: [S; Inner::N + 2] = {
+        const TUPLE: Concat<
+                2,
+                { Inner::N },
+            > = Concat(
+                ["o", "p"],
+                Inner::F,
+            );
+        unsafe { mem::transmute(TUPLE) }
     };
-    eprintln!("N {:?}", m);
 }
 
-14:58 <+Diziet> TIL that if you have a sender for a bounded 
-                futures::channel::mpsc::channel, you can always cheat and 
-                squeeze an extra message in: clone your sender (giving you a 
-                free slot); try_send is guaranteed to succeed because you have 
-                a reserved slot; then drop your cloned sender and now your 
-                message lives on the heap somewhere
-14:58 <+nickm> that's evil 
-14:58 <+nickm> let's not do it in arti?
-14:59 <+Diziet> I have a use for it
-14:59 <+nickm> not in arti I hope? 
-14:59 <+Diziet> We want to send channel padding negotiation cells
-15:00 <+Diziet> We only want to wake up to send such a cell when the output is 
-                writeable, so it wants to be in the inner select where we read 
-                the input
-15:00 <+Diziet> This trick lets us put the renegotiation message into the input 
-                without adding *any* code to the hot path in the reactor
-15:01 <+Diziet> The reactor code for handling the control message can do this 
-                even though it doesn't know (and can't know) the output is 
-                unblocked.
-15:02 <+nickm> Hm. I still think this might be a bad idea, but I'm less 
-               certain.  One request: Please define a new wrapper for 
-               mpsc::channel that explicitly has these semantics; maybe some 
-               kind of "semibounded" channel?
-15:02 <+Diziet> Well, the semantics we need don't actually include that the 
-                message gets delivered.
-15:02 <+nickm> Ah.  Then that's okay.
-15:02 <+Diziet> We can keep the cloned sender around until the *next* channel 
-                renegotiation message.
-15:02 <+nickm> try_send is correct if we don't care if it gets delivered 
-15:03 <+Diziet> We care that *this* message will get delivered *eventually*, 
-                *unless* some other superseding message arises.
-15:03 <+Diziet> So we need try_send to succeed but we don't care if dropping 
-                the sender drops the message it was queueing
-15:04 <+nickm> Hrrm.  Then I think a wrapper might be right.  Unless this is 
-               docmented behavior?
-15:04 <+Diziet> That every channel comes with a sending slot *is* documented
-15:04 <+Diziet> That the sending slot is reserved *for that channel* is not 
-                documented but is implied by the semantics of Sink
-15:05 <+Diziet> What happens if you drop the sender after using the slot is 
-                *not* documented but that is the part we don't care about (so 
-                long as it's not some crazy malfunction or panic)
-15:05 <+Diziet> So I think the right answer is to c&p my ad-hoc experiment into 
-                a test case :-)
-15:05 <+nickm> also add careful comments :)
-15:05 <+Diziet> Absolutely!
-15:05 <+nickm> eta: You may have thoughts on the above too
+/*
+const fn plus<const N: usize>
+(x: &'static [S],
+ b: &'static [S],
+ ary: &mut [MaybeUninit<S>],
+)
+ -> &'static [S]
+{
+//    unsafe {
+        
+//    }
+    panic!()
+}
+
+struct Outer { o: usize, }
+impl Ish for Outer {
+    const N: usize = Inner::N + 1;
+    const F: &'static [S] = {
+        static mut ARY: [MaybeUninit<S>; Inner::N + 1] = [MaybeUninit::uninit(); Inner::N + 1];
+
+        plus::<{Inner::N + 1}>(
+            Inner::F,
+            &["o"],
+            &mut ARY[..],
+        )
+    };
+}
+*/
+
+fn main(){
+    eprintln!("IF {:?}", Inner::F);
+    eprintln!("OF {:?}", Outer::F);
+}