refactor(variadics): Improvements prepping for release (#974)

- Adds the "spread"/"splat" `...` syntax to the three variadics macros.
- Adds `#[sealed]` traits.
- Adds testing of error messages.
- Improves docs: `README.md` and Rust docs.

Author: MingweiSamuel

Cargo.lock

@@ -2,7 +2,7 @@
 
 use ref_cast::RefCast;
 use sealed::sealed;
-use variadics::Variadic;
+use variadics::{variadic_trait, Variadic};
 
 use super::Handoff;
 use crate::scheduled::graph::HandoffData;
@@ -140,24 +140,17 @@ where
     }
 }
 
-/// A variadic list of Handoff types, represented using a lisp-style tuple structure.
-///
-/// This trait is sealed and not meant to be implemented or used directly. Instead tuple lists (which already implement this trait) should be used, for example:
-/// ```ignore
-/// type MyHandoffList = (VecHandoff<usize>, (VecHandoff<String>, (TeeingHandoff<u32>, ())));
-/// ```
-/// The [`var_expr!`](variadics::var_expr) macro simplifies usage of this kind:
-/// ```ignore
-/// type MyHandoffList = var_expr!(VecHandoff<usize>, VecHandoff<String>, TeeingHandoff<u32>);
-/// ```
-#[sealed]
-pub trait HandoffList: Variadic {}
-#[sealed]
-impl<H, L> HandoffList for (H, L)
-where
-    H: 'static + Handoff,
-    L: HandoffList,
-{
+variadic_trait! {
+    /// A variadic list of Handoff types, represented using a lisp-style tuple structure.
+    ///
+    /// This trait is sealed and not meant to be implemented or used directly. Instead tuple lists (which already implement this trait) should be used, for example:
+    /// ```ignore
+    /// type MyHandoffList = (VecHandoff<usize>, (VecHandoff<String>, (TeeingHandoff<u32>, ())));
+    /// ```
+    /// The [`var_expr!`](crate::var) macro simplifies usage of this kind:
+    /// ```ignore
+    /// type MyHandoffList = var_expr!(VecHandoff<usize>, VecHandoff<String>, TeeingHandoff<u32>);
+    /// ```
+    #[sealed]
+    pub variadic<T> HandoffList where T: 'static + Handoff {}
 }
-#[sealed]
-impl HandoffList for () {}

hydroflow/src/scheduled/handoff/handoff_list.rs

@@ -1,4 +1,4 @@
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     struct Shape {

hydroflow/tests/compile-fail/surface_demuxenum_notenum.rs

@@ -1,5 +1,5 @@
 use hydroflow::util::demux_enum::DemuxEnum;
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     #[derive(DemuxEnum)]

hydroflow/tests/compile-fail/surface_demuxenum_port_duplicate.rs

@@ -9,11 +9,3 @@ error: Output connection conflicts with above ($DIR/tests/compile-fail/surface_d
    |
 21 |         my_demux[Square] -> for_each(std::mem::drop);
    |                  ^^^^^^
-
-warning: unused import: `var_args`
- --> tests/compile-fail/surface_demuxenum_port_duplicate.rs:2:35
-  |
-2 | use hydroflow::{hydroflow_syntax, var_args};
-  |                                   ^^^^^^^^
-  |
-  = note: `#[warn(unused_imports)]` on by default

hydroflow/tests/compile-fail/surface_demuxenum_port_duplicate.stderr

@@ -1,5 +1,5 @@
 use hydroflow::util::demux_enum::DemuxEnum;
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     #[derive(DemuxEnum)]

hydroflow/tests/compile-fail/surface_demuxenum_port_elided.rs

@@ -3,11 +3,3 @@ error: Output port from `demux_enum(..)` must be specified and must be a valid i
    |
 22 |         my_demux -> for_each(std::mem::drop);
    |         ^^^^^^^^
-
-warning: unused import: `var_args`
- --> tests/compile-fail/surface_demuxenum_port_elided.rs:2:35
-  |
-2 | use hydroflow::{hydroflow_syntax, var_args};
-  |                                   ^^^^^^^^
-  |
-  = note: `#[warn(unused_imports)]` on by default

hydroflow/tests/compile-fail/surface_demuxenum_port_elided.stderr

@@ -1,5 +1,5 @@
 use hydroflow::util::demux_enum::DemuxEnum;
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     #[derive(DemuxEnum)]

hydroflow/tests/compile-fail/surface_demuxenum_port_extra.rs

@@ -1,5 +1,5 @@
 use hydroflow::util::demux_enum::DemuxEnum;
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     #[derive(DemuxEnum)]

hydroflow/tests/compile-fail/surface_demuxenum_port_extramissing.rs

@@ -1,5 +1,5 @@
 use hydroflow::util::demux_enum::DemuxEnum;
-use hydroflow::{hydroflow_syntax, var_args};
+use hydroflow::hydroflow_syntax;
 
 fn main() {
     #[derive(DemuxEnum)]