From 826dbd9a709de2f883992bdcefa8f2d566d74ecb Mon Sep 17 00:00:00 2001
From: Mingwei Samuel <mingwei.samuel@gmail.com>
Date: Mon, 20 May 2024 10:10:21 -0700
Subject: [PATCH] refactor: simplify `demux_enum()`, somewhat improves error
 messages #1201 (#1204)

---
 hydroflow/src/util/demux_enum.rs              | 49 +++--------
 .../surface_demuxenum_notenum.stderr          | 69 ++-------------
 .../surface_demuxenum_port_extra.stderr       | 27 ++++--
 .../surface_demuxenum_port_missing.stderr     | 23 +++--
 .../surface_demuxenum_wrongenum.rs            |  3 +-
 .../surface_demuxenum_wrongenum.stderr        | 87 +++++++++++++++++--
 .../surface_demuxenum_wrongfields_1.rs        | 23 +++++
 .../surface_demuxenum_wrongfields_1.stderr    | 29 +++++++
 .../surface_demuxenum_wrongfields_2.rs        | 23 +++++
 .../surface_demuxenum_wrongfields_2.stderr    | 29 +++++++
 .../surface_demuxenum_wrongitems.stderr       | 11 ---
 ...tems.rs => surface_demuxenum_wrongtype.rs} |  1 -
 .../surface_demuxenum_wrongtype.stderr        | 14 +++
 hydroflow/tests/surface_demux_enum.rs         | 18 ++--
 hydroflow_lang/src/graph/ops/demux_enum.rs    | 30 +++----
 hydroflow_macro/src/lib.rs                    | 26 +++---
 pusherator/src/demux.rs                       |  7 --
 pusherator/src/lib.rs                         |  1 -
 18 files changed, 289 insertions(+), 181 deletions(-)
 create mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.rs
 create mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.stderr
 create mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.rs
 create mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.stderr
 delete mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.stderr
 rename hydroflow/tests/compile-fail/{surface_demuxenum_wrongitems.rs => surface_demuxenum_wrongtype.rs} (90%)
 create mode 100644 hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.stderr

diff --git a/hydroflow/src/util/demux_enum.rs b/hydroflow/src/util/demux_enum.rs
index 256e03d2907e..a08577d821ea 100644
--- a/hydroflow/src/util/demux_enum.rs
+++ b/hydroflow/src/util/demux_enum.rs
@@ -1,43 +1,22 @@
-//! Traits for the `demux_enum` derive and operator.
+//! Trait for the `demux_enum` derive and operator.
 
 pub use hydroflow_macro::DemuxEnum;
-use pusherator::demux::PusheratorList;
-use pusherator::Pusherator;
-use variadics::Variadic;
 
 /// Trait for use with the `demux_enum` operator.
 ///
-/// This trait is meant to be derived: `#[derive(DemuEnum)]`.
-pub trait DemuxEnum<Nexts>: DemuxEnumItems
-where
-    Nexts: PusheratorListForItems<Self::Items>,
-{
-    /// Pushes self into the corresponding output pusherator.
-    fn demux_enum(self, outputs: &mut Nexts);
-}
-
-/// Fixed output item list for [`DemuxEnum`].
+/// This trait is meant to be derived: `#[derive(DemuxEnum)]`.
 ///
-/// This trait is meant to be derived: `#[derive(DemuEnum)]`.
-pub trait DemuxEnumItems {
-    /// A `var_type!(...)` list of items corresponding to each variant's output type.
-    type Items: Variadic;
+/// The derive will implement this such that `Outputs` can be any tuple where each item is a
+/// `Pusherator` that corresponds to each of the variants of the tuple, in alphabetic order.
+#[diagnostic::on_unimplemented(
+    note = "Ensure there is exactly one output for each enum variant.",
+    note = "Ensure that the type for each output is a tuple of the field for the variant: `()`, `(a,)`, or `(a, b, ...)`."
+)]
+pub trait DemuxEnum<Outputs>: DemuxEnumBase {
+    /// Pushes self into the corresponding output pusherator in `outputs`.
+    fn demux_enum(self, outputs: &mut Outputs);
 }
 
-/// Helper trait to bound a [`PusheratorList`] variadic to some coresponding item list variadic.
-///
-/// A pusherator list `var_type!(PushA, PushB, PushC)` implements `PusheratorListForItems<var_type!(ItemA, ItemB, ItemC)>`,
-/// where `PushA: Pusherator<Item = ItemA>`, etc.
-pub trait PusheratorListForItems<Items>: PusheratorList
-where
-    Items: Variadic,
-{
-}
-impl<HeadPush, RestPush, Head, Rest> PusheratorListForItems<(Head, Rest)> for (HeadPush, RestPush)
-where
-    HeadPush: Pusherator<Item = Head>,
-    RestPush: PusheratorListForItems<Rest>,
-    Rest: Variadic,
-{
-}
-impl PusheratorListForItems<()> for () {}
+/// Base implementation to constrain that `DemuxEnum<SOMETHING>` is implemented.
+#[diagnostic::on_unimplemented(note = "Use `#[derive(hydroflow::DemuxEnum)]`")]
+pub trait DemuxEnumBase {}
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_notenum.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_notenum.stderr
index 330a78540e5b..57d301082118 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_notenum.stderr
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_notenum.stderr
@@ -1,9 +1,10 @@
-error[E0277]: the trait bound `Shape: DemuxEnumItems` is not satisfied
+error[E0277]: the trait bound `Shape: DemuxEnumBase` is not satisfied
   --> tests/compile-fail/surface_demuxenum_notenum.rs:12:28
    |
 12 |         ]) -> demux_enum::<Shape>();
-   |                            ^^^^^ the trait `DemuxEnumItems` is not implemented for `Shape`
+   |                            ^^^^^ the trait `DemuxEnumBase` is not implemented for `Shape`
    |
+   = note: Use `#[derive(hydroflow::DemuxEnum)]`
 note: required by a bound in `check_impl_demux_enum`
   --> tests/compile-fail/surface_demuxenum_notenum.rs:8:18
    |
@@ -62,72 +63,20 @@ help: if there were a trait named `Example` with associated type `Square` implem
 15 |         my_demux[<Shape as Example>::Square] -> for_each(std::mem::drop);
    |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error[E0277]: the trait bound `Shape: DemuxEnumItems` is not satisfied
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:12:15
-   |
-12 |         ]) -> demux_enum::<Shape>();
-   |               ^^^^^^^^^^^^^^^^^^^^^ the trait `DemuxEnumItems` is not implemented for `Shape`
-
 error[E0277]: the trait bound `Shape: DemuxEnum<_>` is not satisfied
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:12:28
-   |
-12 |         ]) -> demux_enum::<Shape>();
-   |                            ^^^^^ the trait `DemuxEnum<_>` is not implemented for `Shape`
-   |
-note: required by a bound in `__typeguard_demux_enum_fn`
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:8:18
-   |
-8  |       let mut df = hydroflow_syntax! {
-   |  __________________^
-9  | |         my_demux = source_iter([
-10 | |             Shape { area: 10.0 },
-11 | |             Shape { area: 9.0 },
-...  |
-16 | |         my_demux[Ellipse] -> for_each(std::mem::drop);
-17 | |     };
-   | |_____^ required by this bound in `__typeguard_demux_enum_fn`
-   = note: this error originates in the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0277]: the trait bound `Shape: DemuxEnum<(impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, ()))))>` is not satisfied
   --> tests/compile-fail/surface_demuxenum_notenum.rs:12:15
    |
-12 |         ]) -> demux_enum::<Shape>();
-   |               ^^^^^^^^^^^^^^^^^^^^^ the trait `DemuxEnum<(impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, ()))))>` is not implemented for `Shape`
-   |
-note: required by a bound in `__typeguard_demux_enum_fn`
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:8:18
-   |
 8  |       let mut df = hydroflow_syntax! {
-   |  __________________^
+   |  __________________-
 9  | |         my_demux = source_iter([
 10 | |             Shape { area: 10.0 },
 11 | |             Shape { area: 9.0 },
-...  |
-16 | |         my_demux[Ellipse] -> for_each(std::mem::drop);
-17 | |     };
-   | |_____^ required by this bound in `__typeguard_demux_enum_fn`
-   = note: this error originates in the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error[E0277]: the trait bound `Shape: DemuxEnum<(impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, ()))))>` is not satisfied
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:9:20
-   |
-9  |           my_demux = source_iter([
-   |  ____________________^
-10 | |             Shape { area: 10.0 },
-11 | |             Shape { area: 9.0 },
 12 | |         ]) -> demux_enum::<Shape>();
-   | |___________________________________^ the trait `DemuxEnum<(impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, (impl Pusherator<Item = _>, ()))))>` is not implemented for `Shape`
-   |
-note: required by a bound in `__typeguard_demux_enum_fn`
-  --> tests/compile-fail/surface_demuxenum_notenum.rs:8:18
-   |
-8  |       let mut df = hydroflow_syntax! {
-   |  __________________^
-9  | |         my_demux = source_iter([
-10 | |             Shape { area: 10.0 },
-11 | |             Shape { area: 9.0 },
+   | |               ^^^^^^^^^^^^^^^^^^^^^ the trait `DemuxEnum<_>` is not implemented for `Shape`
 ...  |
 16 | |         my_demux[Ellipse] -> for_each(std::mem::drop);
 17 | |     };
-   | |_____^ required by this bound in `__typeguard_demux_enum_fn`
-   = note: this error originates in the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
+   | |_____- required by a bound introduced by this call
+   |
+   = note: Ensure there is exactly one output for each enum variant.
+   = note: Ensure that the type for each output is a tuple of the field for the variant: `()`, `(a,)`, or `(a, b, ...)`.
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_port_extra.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_port_extra.stderr
index 5732d5cf44ea..e998c9f500da 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_port_extra.stderr
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_port_extra.stderr
@@ -8,20 +8,31 @@ error[E0599]: no variant named `Ellipse` found for enum `Shape`
    |                  ^^^^^^^ variant not found in `Shape`
 
 error[E0308]: mismatched types
-  --> tests/compile-fail/surface_demuxenum_port_extra.rs:12:18
+  --> tests/compile-fail/surface_demuxenum_port_extra.rs:17:15
    |
 12 |       let mut df = hydroflow_syntax! {
-   |  __________________^
+   |  __________________-
 13 | |         my_demux = source_iter([
 14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
 15 | |             Shape::Square(9.0),
-...  |
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Shape>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 4 elements
+18 | |         my_demux[Rectangle] -> for_each(std::mem::drop);
+   | |                                ------------------------ one of the found opaque types
+19 | |         my_demux[Circle] -> for_each(std::mem::drop);
+   | |                             ------------------------ one of the found opaque types
 20 | |         my_demux[Square] -> for_each(std::mem::drop);
-   | |                             ------------------------ the found opaque type
+   | |                             ------------------------ one of the found opaque types
 21 | |         my_demux[Ellipse] -> for_each(std::mem::drop);
+   | |                              ------------------------ one of the found opaque types
 22 | |     };
-   | |_____^ expected `()`, found `(impl Pusherator<Item = _>, ())`
+   | |_____- arguments to this function are incorrect
    |
-   = note: expected unit type `()`
-                  found tuple `(impl Pusherator<Item = _>, ())`
-   = note: this error originates in the macro `$crate::var_expr` which comes from the expansion of the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: expected mutable reference `&mut (_, _, _)`
+              found mutable reference `&mut (impl Pusherator<Item = _>, impl Pusherator<Item = _>, impl Pusherator<Item = _>, impl Pusherator<Item = _>)`
+note: method defined here
+  --> src/util/demux_enum.rs
+   |
+   |     fn demux_enum(self, outputs: &mut Outputs);
+   |        ^^^^^^^^^^
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_port_missing.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_port_missing.stderr
index 70e3f9585ec2..e51294ec63fc 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_port_missing.stderr
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_port_missing.stderr
@@ -1,16 +1,25 @@
 error[E0308]: mismatched types
-  --> tests/compile-fail/surface_demuxenum_port_missing.rs:12:18
+  --> tests/compile-fail/surface_demuxenum_port_missing.rs:17:15
    |
 12 |       let mut df = hydroflow_syntax! {
-   |  __________________^
+   |  __________________-
 13 | |         my_demux = source_iter([
 14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
 15 | |             Shape::Square(9.0),
-...  |
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Shape>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 2 elements
+18 | |         my_demux[Rectangle] -> for_each(std::mem::drop);
+   | |                                ------------------------ one of the found opaque types
 19 | |         my_demux[Circle] -> for_each(std::mem::drop);
+   | |                             ------------------------ one of the found opaque types
 20 | |     };
-   | |_____^ expected `(_, ())`, found `()`
+   | |_____- arguments to this function are incorrect
    |
-   = note:  expected tuple `(_, ())`
-           found unit type `()`
-   = note: this error originates in the macro `$crate::var_expr` which comes from the expansion of the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: expected mutable reference `&mut (_, _, _)`
+              found mutable reference `&mut (impl Pusherator<Item = _>, impl Pusherator<Item = _>)`
+note: method defined here
+  --> src/util/demux_enum.rs
+   |
+   |     fn demux_enum(self, outputs: &mut Outputs);
+   |        ^^^^^^^^^^
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.rs b/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.rs
index b5e6acffc827..71ef0b72edc5 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.rs
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.rs
@@ -14,11 +14,10 @@ fn main() {
             Shape::Rectangle { w: 10.0, h: 8.0 },
             Shape::Square(9.0),
             Shape::Circle { r: 5.0 },
-        ]) -> demux_enum::<Option>();
+        ]) -> demux_enum::<Option<()>>();
         my_demux[Rectangle] -> for_each(std::mem::drop);
         my_demux[Circle] -> for_each(std::mem::drop);
         my_demux[Square] -> for_each(std::mem::drop);
-        my_demux[Square] -> for_each(std::mem::drop);
     };
     df.run_available();
 }
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.stderr
index 04bfaf8bb2d1..5442d45103f8 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.stderr
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongenum.stderr
@@ -1,11 +1,86 @@
-error: Output connection conflicts with below ($DIR/tests/compile-fail/surface_demuxenum_wrongenum.rs:21:18) (1/2)
+error[E0277]: the trait bound `std::option::Option<()>: DemuxEnumBase` is not satisfied
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:17:28
+   |
+17 |         ]) -> demux_enum::<Option<()>>();
+   |                            ^^^^^^^^^^ the trait `DemuxEnumBase` is not implemented for `std::option::Option<()>`
+   |
+   = note: Use `#[derive(hydroflow::DemuxEnum)]`
+   = help: the trait `DemuxEnumBase` is implemented for `Shape`
+note: required by a bound in `check_impl_demux_enum`
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:12:18
+   |
+12 |       let mut df = hydroflow_syntax! {
+   |  __________________^
+13 | |         my_demux = source_iter([
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+...  |
+20 | |         my_demux[Square] -> for_each(std::mem::drop);
+21 | |     };
+   | |_____^ required by this bound in `check_impl_demux_enum`
+   = note: this error originates in the macro `hydroflow_syntax` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0599]: no variant named `Circle` found for enum `std::option::Option<()>`
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:19:18
+   |
+19 |         my_demux[Circle] -> for_each(std::mem::drop);
+   |                  ^^^^^^ variant not found in `std::option::Option<()>`
+
+error[E0599]: no variant named `Rectangle` found for enum `std::option::Option<()>`
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:18:18
+   |
+18 |         my_demux[Rectangle] -> for_each(std::mem::drop);
+   |                  ^^^^^^^^^ variant not found in `std::option::Option<()>`
+
+error[E0599]: no variant named `Square` found for enum `std::option::Option<()>`
   --> tests/compile-fail/surface_demuxenum_wrongenum.rs:20:18
    |
 20 |         my_demux[Square] -> for_each(std::mem::drop);
-   |                  ^^^^^^
+   |                  ^^^^^^ variant not found in `std::option::Option<()>`
+
+error[E0277]: the trait bound `std::option::Option<()>: DemuxEnum<_>` is not satisfied
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:17:15
+   |
+12 |       let mut df = hydroflow_syntax! {
+   |  __________________-
+13 | |         my_demux = source_iter([
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Option<()>>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `DemuxEnum<_>` is not implemented for `std::option::Option<()>`
+...  |
+20 | |         my_demux[Square] -> for_each(std::mem::drop);
+21 | |     };
+   | |_____- required by a bound introduced by this call
+   |
+   = note: Ensure there is exactly one output for each enum variant.
+   = note: Ensure that the type for each output is a tuple of the field for the variant: `()`, `(a,)`, or `(a, b, ...)`.
+   = help: the trait `DemuxEnum<(__PusheratorCircle, __PusheratorRectangle, __PusheratorSquare)>` is implemented for `Shape`
 
-error: Output connection conflicts with above ($DIR/tests/compile-fail/surface_demuxenum_wrongenum.rs:20:18) (2/2)
-  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:21:18
+error[E0271]: type mismatch resolving `<impl Pusherator<Item = Option<()>> as Pusherator>::Item == Shape`
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:17:15
+   |
+13 |           my_demux = source_iter([
+   |  ____________________-
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Option<()>>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^^^^^-
+   | |_______________|________________________|
+   |                 |                        required by a bound introduced by this call
+   |                 expected `Shape`, found `Option<()>`
+   |
+   = note: expected enum `Shape`
+              found enum `std::option::Option<()>`
+note: required by a bound in `pivot_run_sg_1v1`
+  --> tests/compile-fail/surface_demuxenum_wrongenum.rs:13:20
    |
-21 |         my_demux[Square] -> for_each(std::mem::drop);
-   |                  ^^^^^^
+13 |           my_demux = source_iter([
+   |  ____________________^
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Option<()>>();
+   | |________________________________________^ required by this bound in `pivot_run_sg_1v1`
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.rs b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.rs
new file mode 100644
index 000000000000..7f0025f42ef6
--- /dev/null
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.rs
@@ -0,0 +1,23 @@
+use hydroflow::util::demux_enum::DemuxEnum;
+use hydroflow::hydroflow_syntax;
+
+fn main() {
+    #[derive(DemuxEnum)]
+    enum Shape {
+        Square(f64),
+        Rectangle { w: f64, h: f64 },
+        Circle { r: f64 },
+    }
+
+    let mut df = hydroflow_syntax! {
+        my_demux = source_iter([
+            Shape::Rectangle { w: 10.0, h: 8.0 },
+            Shape::Square(9.0),
+            Shape::Circle { r: 5.0 },
+        ]) -> demux_enum::<Shape>();
+        my_demux[Rectangle] -> for_each(std::mem::drop);
+        my_demux[Circle] -> for_each(std::mem::drop);
+        my_demux[Square] -> for_each(|side: u32| ());
+    };
+    df.run_available();
+}
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.stderr
new file mode 100644
index 000000000000..7999543b4c0b
--- /dev/null
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_1.stderr
@@ -0,0 +1,29 @@
+error[E0271]: type mismatch resolving `<impl Pusherator<Item = u32> as Pusherator>::Item == (f64,)`
+  --> tests/compile-fail/surface_demuxenum_wrongfields_1.rs:17:15
+   |
+12 |       let mut df = hydroflow_syntax! {
+   |  __________________-
+13 | |         my_demux = source_iter([
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Shape>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^ expected `(f64,)`, found `u32`
+...  |
+20 | |         my_demux[Square] -> for_each(|side: u32| ());
+21 | |     };
+   | |_____- required by a bound introduced by this call
+   |
+   = note: expected tuple `(f64,)`
+               found type `u32`
+note: required for `Shape` to implement `DemuxEnum<(impl Pusherator<Item = (f64,)>, impl Pusherator<Item = (f64, f64)>, impl Pusherator<Item = u32>)>`
+  --> tests/compile-fail/surface_demuxenum_wrongfields_1.rs:5:14
+   |
+5  |     #[derive(DemuxEnum)]
+   |              ^^^^^^^^^ unsatisfied trait bound introduced in this `derive` macro
+6  |     enum Shape {
+   |          ^^^^^
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: this error originates in the derive macro `DemuxEnum` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.rs b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.rs
new file mode 100644
index 000000000000..f350c4bf8a07
--- /dev/null
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.rs
@@ -0,0 +1,23 @@
+use hydroflow::util::demux_enum::DemuxEnum;
+use hydroflow::hydroflow_syntax;
+
+fn main() {
+    #[derive(DemuxEnum)]
+    enum Shape {
+        Square(f64),
+        Rectangle { w: f64, h: f64 },
+        Circle { r: f64 },
+    }
+
+    let mut df = hydroflow_syntax! {
+        my_demux = source_iter([
+            Shape::Rectangle { w: 10.0, h: 8.0 },
+            Shape::Square(9.0),
+            Shape::Circle { r: 5.0 },
+        ]) -> demux_enum::<Shape>();
+        my_demux[Rectangle] -> for_each(std::mem::drop);
+        my_demux[Circle] -> for_each(std::mem::drop);
+        my_demux[Square] -> for_each(|side: (u32,)| ());
+    };
+    df.run_available();
+}
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.stderr
new file mode 100644
index 000000000000..5a276edc5467
--- /dev/null
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongfields_2.stderr
@@ -0,0 +1,29 @@
+error[E0271]: type mismatch resolving `<impl Pusherator<Item = (u32,)> as Pusherator>::Item == (f64,)`
+  --> tests/compile-fail/surface_demuxenum_wrongfields_2.rs:17:15
+   |
+12 |       let mut df = hydroflow_syntax! {
+   |  __________________-
+13 | |         my_demux = source_iter([
+14 | |             Shape::Rectangle { w: 10.0, h: 8.0 },
+15 | |             Shape::Square(9.0),
+16 | |             Shape::Circle { r: 5.0 },
+17 | |         ]) -> demux_enum::<Shape>();
+   | |               ^^^^^^^^^^^^^^^^^^^^^ expected `(f64,)`, found `(u32,)`
+...  |
+20 | |         my_demux[Square] -> for_each(|side: (u32,)| ());
+21 | |     };
+   | |_____- required by a bound introduced by this call
+   |
+   = note: expected tuple `(f64,)`
+              found tuple `(u32,)`
+note: required for `Shape` to implement `DemuxEnum<(impl Pusherator<Item = (f64,)>, impl Pusherator<Item = (f64, f64)>, impl Pusherator<Item = (u32,)>)>`
+  --> tests/compile-fail/surface_demuxenum_wrongfields_2.rs:5:14
+   |
+5  |     #[derive(DemuxEnum)]
+   |              ^^^^^^^^^ unsatisfied trait bound introduced in this `derive` macro
+6  |     enum Shape {
+   |          ^^^^^
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: associated types for the current `impl` cannot be restricted in `where` clauses
+   = note: this error originates in the derive macro `DemuxEnum` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.stderr
deleted file mode 100644
index 6abb71d56aef..000000000000
--- a/hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error: Output connection conflicts with below ($DIR/tests/compile-fail/surface_demuxenum_wrongitems.rs:17:18) (1/2)
-  --> tests/compile-fail/surface_demuxenum_wrongitems.rs:16:18
-   |
-16 |         my_demux[Square] -> for_each(std::mem::drop);
-   |                  ^^^^^^
-
-error: Output connection conflicts with above ($DIR/tests/compile-fail/surface_demuxenum_wrongitems.rs:16:18) (2/2)
-  --> tests/compile-fail/surface_demuxenum_wrongitems.rs:17:18
-   |
-17 |         my_demux[Square] -> for_each(std::mem::drop);
-   |                  ^^^^^^
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.rs b/hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.rs
similarity index 90%
rename from hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.rs
rename to hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.rs
index 4c08cab45624..12431cf527dc 100644
--- a/hydroflow/tests/compile-fail/surface_demuxenum_wrongitems.rs
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.rs
@@ -14,7 +14,6 @@ fn main() {
         my_demux[Rectangle] -> for_each(std::mem::drop);
         my_demux[Circle] -> for_each(std::mem::drop);
         my_demux[Square] -> for_each(std::mem::drop);
-        my_demux[Square] -> for_each(std::mem::drop);
     };
     df.run_available();
 }
diff --git a/hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.stderr b/hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.stderr
new file mode 100644
index 000000000000..4c9892b48e79
--- /dev/null
+++ b/hydroflow/tests/compile-fail/surface_demuxenum_wrongtype.stderr
@@ -0,0 +1,14 @@
+error[E0271]: type mismatch resolving `<impl Pusherator<Item = Shape> as Pusherator>::Item == {integer}`
+  --> tests/compile-fail/surface_demuxenum_wrongtype.rs:13:41
+   |
+13 |         my_demux = source_iter(0..5) -> demux_enum::<Shape>();
+   |                    ---------------------^^^^^^^^^^^^^^^^^^^^^
+   |                    |                    |
+   |                    |                    expected integer, found `Shape`
+   |                    required by a bound introduced by this call
+   |
+note: required by a bound in `pivot_run_sg_1v1`
+  --> tests/compile-fail/surface_demuxenum_wrongtype.rs:13:20
+   |
+13 |         my_demux = source_iter(0..5) -> demux_enum::<Shape>();
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `pivot_run_sg_1v1`
diff --git a/hydroflow/tests/surface_demux_enum.rs b/hydroflow/tests/surface_demux_enum.rs
index 9cd0680f431e..0ac214aca6da 100644
--- a/hydroflow/tests/surface_demux_enum.rs
+++ b/hydroflow/tests/surface_demux_enum.rs
@@ -1,5 +1,5 @@
-use hydroflow::util::demux_enum::{DemuxEnum, DemuxEnumItems};
-use hydroflow::{hydroflow_syntax, var_args, var_expr, var_type};
+use hydroflow::hydroflow_syntax;
+use hydroflow::util::demux_enum::{DemuxEnum, DemuxEnumBase};
 use multiplatform_test::multiplatform_test;
 use pusherator::for_each::ForEach;
 
@@ -12,16 +12,13 @@ fn test_manual_impl() {
         Rectangle { w: usize, h: usize },
         Circle { r: usize },
     }
-    impl DemuxEnumItems for Shape {
-        type Items = var_type!(usize, (usize, usize), (usize,));
-    }
-    impl<Square, Rectangle, Circle> DemuxEnum<var_type!(Square, Rectangle, Circle)> for Shape
+    impl<Square, Rectangle, Circle> DemuxEnum<(Square, Rectangle, Circle)> for Shape
     where
         Square: Pusherator<Item = usize>,
         Rectangle: Pusherator<Item = (usize, usize)>,
         Circle: Pusherator<Item = (usize,)>,
     {
-        fn demux_enum(self, var_args!(sq, re, ci): &mut var_type!(Square, Rectangle, Circle)) {
+        fn demux_enum(self, (sq, re, ci): &mut (Square, Rectangle, Circle)) {
             match self {
                 Self::Square(s) => sq.give(s),
                 Self::Rectangle { w, h } => re.give((w, h)),
@@ -29,13 +26,14 @@ fn test_manual_impl() {
             }
         }
     }
+    impl DemuxEnumBase for Shape {}
 
     let vals = [
         Shape::Square(5),
         Shape::Rectangle { w: 5, h: 6 },
         Shape::Circle { r: 6 },
     ];
-    let mut nexts = var_expr!(
+    let mut nexts = (
         ForEach::new(|x| println!("1 {:?}", x)),
         ForEach::new(|x| println!("2 {:?}", x)),
         ForEach::new(|x| println!("3 {:?}", x)),
@@ -59,7 +57,7 @@ fn test_derive() {
         Shape::Rectangle { w: 5, h: 6 },
         Shape::Circle { r: 6 },
     ];
-    let mut nexts = var_expr!(
+    let mut nexts = (
         ForEach::new(|x| println!("1 {:?}", x)),
         ForEach::new(|x| println!("2 {:?}", x)),
         ForEach::new(|x| println!("3 {:?}", x)),
@@ -85,7 +83,7 @@ pub fn test_demux_enum() {
             Shape::Circle { r: 5.0 },
         ]) -> demux_enum::<Shape>();
 
-        my_demux[Square] -> map(|s| s * s) -> out;
+        my_demux[Square] -> map(|(s,)| s * s) -> out;
         my_demux[Circle] -> map(|(r,)| std::f64::consts::PI * r * r) -> out;
         my_demux[Rectangle] -> map(|(w, h)| w * h) -> out;
 
diff --git a/hydroflow_lang/src/graph/ops/demux_enum.rs b/hydroflow_lang/src/graph/ops/demux_enum.rs
index 9d976c3848d4..4d2e2cef755f 100644
--- a/hydroflow_lang/src/graph/ops/demux_enum.rs
+++ b/hydroflow_lang/src/graph/ops/demux_enum.rs
@@ -17,20 +17,23 @@ use crate::diagnostic::{Diagnostic, Level};
 /// #[derive(DemuxEnum)]
 /// enum Shape {
 ///     Square(f64),
-///     Rectangle { w: f64, h: f64 },
+///     Rectangle(f64, f64),
 ///     Circle { r: f64 },
+///     Triangle { w: f64, h: f64 }
 /// }
 ///
 /// let mut df = hydroflow_syntax! {
 ///     my_demux = source_iter([
 ///         Shape::Square(9.0),
-///         Shape::Rectangle { w: 10.0, h: 8.0 },
+///         Shape::Rectangle(10.0, 8.0),
 ///         Shape::Circle { r: 5.0 },
+///         Shape::Triangle { w: 12.0, h: 13.0 },
 ///     ]) -> demux_enum::<Shape>();
 ///
 ///     my_demux[Square] -> map(|s| s * s) -> out;
 ///     my_demux[Circle] -> map(|(r,)| std::f64::consts::PI * r * r) -> out;
 ///     my_demux[Rectangle] -> map(|(w, h)| w * h) -> out;
+///     my_demux[Circle] -> map(|(w, h)| 0.5 * w * h) -> out;
 ///
 ///     out = union() -> for_each(|area| println!("Area: {}", area));
 /// };
@@ -114,7 +117,7 @@ pub const DEMUX_ENUM: OperatorConstraints = OperatorConstraints {
         // Note this uses the `enum_type`'s span.
         let write_prologue = quote_spanned! {enum_type.span()=>
             let _ = |__val: #enum_type| {
-                fn check_impl_demux_enum<T: ?Sized + #root::util::demux_enum::DemuxEnumItems>(_: &T) {}
+                fn check_impl_demux_enum<T: ?Sized + #root::util::demux_enum::DemuxEnumBase>(_: &T) {}
                 check_impl_demux_enum(&__val);
                 type Enum = #enum_type;
                 match __val {
@@ -126,20 +129,13 @@ pub const DEMUX_ENUM: OperatorConstraints = OperatorConstraints {
         };
         let write_iterator = quote_spanned! {op_span=>
             let #ident = {
-                fn __typeguard_demux_enum_fn<__EnumType, __Outputs>(__outputs: __Outputs)
-                    -> impl #root::pusherator::Pusherator<Item = __EnumType>
-                where
-                    __Outputs: #root::util::demux_enum::PusheratorListForItems<<__EnumType as #root::util::demux_enum::DemuxEnumItems>::Items>,
-                    __EnumType: #root::util::demux_enum::DemuxEnum::<__Outputs>,
-                {
-                    #root::pusherator::demux::Demux::new(
-                        <__EnumType as #root::util::demux_enum::DemuxEnum::<__Outputs>>::demux_enum,
-                        __outputs,
-                    )
-                }
-                __typeguard_demux_enum_fn::<#enum_type, _>(
-                    #root::var_expr!( #( #sorted_outputs ),* )
-                )
+                let mut __outputs = ( #( #sorted_outputs, )* );
+                #root::pusherator::for_each::ForEach::new(move |__item: #enum_type| {
+                    #root::util::demux_enum::DemuxEnum::demux_enum(
+                        __item,
+                        &mut __outputs,
+                    );
+                })
             };
         };
 
diff --git a/hydroflow_macro/src/lib.rs b/hydroflow_macro/src/lib.rs
index bbcdced058c6..0091d5cc1b6f 100644
--- a/hydroflow_macro/src/lib.rs
+++ b/hydroflow_macro/src/lib.rs
@@ -272,21 +272,17 @@ pub fn derive_answer_fn(item: proc_macro::TokenStream) -> proc_macro::TokenStrea
         .map(|variant| match &variant.fields {
             syn::Fields::Named(fields) => {
                 let field_types = fields.named.iter().map(|field| &field.ty);
-                parse_quote! {
+                quote! {
                     ( #( #field_types, )* )
                 }
             }
             syn::Fields::Unnamed(fields) => {
-                if 1 == fields.unnamed.len() {
-                    fields.unnamed.first().unwrap().ty.clone()
-                } else {
-                    let field_types = fields.unnamed.iter().map(|field| &field.ty);
-                    parse_quote! {
-                        ( #( #field_types, )* )
-                    }
+                let field_types = fields.unnamed.iter().map(|field| &field.ty);
+                quote! {
+                    ( #( #field_types, )* )
                 }
             }
-            syn::Fields::Unit => parse_quote!(()),
+            syn::Fields::Unit => quote!(()),
         })
         .collect::<Vec<_>>();
 
@@ -330,7 +326,7 @@ pub fn derive_answer_fn(item: proc_macro::TokenStream) -> proc_macro::TokenStrea
                     (quote!( { #( #idents, )* } ), quote!( ( #( #idents, )* ) ))
                 }
                 syn::Fields::Unnamed(_) => {
-                    (quote!( ( #( #idents ),* ) ), quote!( ( #( #idents ),* ) ))
+                    (quote!( ( #( #idents ),* ) ), quote!( ( #( #idents, )* ) ))
                 }
                 syn::Fields::Unit => (quote!(), quote!(())),
             };
@@ -340,13 +336,13 @@ pub fn derive_answer_fn(item: proc_macro::TokenStream) -> proc_macro::TokenStrea
         });
 
     quote! {
-        impl #impl_generics #root::util::demux_enum::DemuxEnum<#root::variadics::var_type!( #( #variant_pusherator_generics, )* )>
+        impl #impl_generics #root::util::demux_enum::DemuxEnum<( #( #variant_pusherator_generics, )* )>
             for #ident #ty_generics #where_clause
         {
             fn demux_enum(
                 self,
-                #root::variadics::var_args!( #( #variant_pusherator_localvars, )* ):
-                    &mut #root::variadics::var_type!( #( #variant_pusherator_generics, )* )
+                ( #( #variant_pusherator_localvars, )* ):
+                    &mut ( #( #variant_pusherator_generics, )* )
             ) {
                 match self {
                     #( #variant_pats, )*
@@ -354,9 +350,7 @@ pub fn derive_answer_fn(item: proc_macro::TokenStream) -> proc_macro::TokenStrea
             }
         }
 
-        impl #impl_generics_item #root::util::demux_enum::DemuxEnumItems for #ident #ty_generics #where_clause_item {
-            type Items = #root::variadics::var_type!( #( #variant_output_types, )* );
-        }
+        impl #impl_generics_item #root::util::demux_enum::DemuxEnumBase for #ident #ty_generics #where_clause_item {}
     }
     .into()
 }
diff --git a/pusherator/src/demux.rs b/pusherator/src/demux.rs
index db653adc4abd..53890f09cc86 100644
--- a/pusherator/src/demux.rs
+++ b/pusherator/src/demux.rs
@@ -2,11 +2,6 @@ use std::marker::PhantomData;
 
 use super::Pusherator;
 
-variadics::variadic_trait! {
-    /// A variadic list of Pusherators.
-    pub variadic<T> PusheratorList where T: Pusherator {}
-}
-
 pub struct Demux<Func, Nexts, Item> {
     func: Func,
     nexts: Nexts,
@@ -15,7 +10,6 @@ pub struct Demux<Func, Nexts, Item> {
 impl<Func, Nexts, Item> Pusherator for Demux<Func, Nexts, Item>
 where
     Func: FnMut(Item, &mut Nexts),
-    Nexts: PusheratorList,
 {
     type Item = Item;
     fn give(&mut self, item: Self::Item) {
@@ -25,7 +19,6 @@ where
 impl<Func, Nexts, Item> Demux<Func, Nexts, Item>
 where
     Func: FnMut(Item, &mut Nexts),
-    Nexts: PusheratorList,
 {
     pub fn new(func: Func, nexts: Nexts) -> Self {
         Self {
diff --git a/pusherator/src/lib.rs b/pusherator/src/lib.rs
index 7837d7214f1a..687c159fc058 100644
--- a/pusherator/src/lib.rs
+++ b/pusherator/src/lib.rs
@@ -115,7 +115,6 @@ pub trait PusheratorBuild {
     ) -> Self::Output<demux::Demux<Func, Nexts, Self::ItemOut>>
     where
         Self: Sized,
-        Nexts: demux::PusheratorList,
         Func: FnMut(Self::ItemOut, &mut Nexts),
     {
         self.push_to(demux::Demux::new(func, nexts))