Try and fail to make nodes object-safe in node graph

node-graph/gcore/src/ops.rs

@@ -0,0 +1,37 @@
+use std::{borrow::Borrow, marker::PhantomData};
+
+use crate::Node;
+
+#[derive(Default)]
+pub struct AddNode<T>(PhantomData<T>);
+impl<T: std::ops::Add + 'static + Copy> Node for AddNode<T> {
+    type Output<'a> = <T as std::ops::Add>::Output;
+    type Input<'a> = (T, T);
+    fn eval<'a, I: Borrow<Self::Input<'a>>>(&'a self, input: I) -> T::Output {
+        input.borrow().0 + input.borrow().1
+    }
+}
+
+#[derive(Default)]
+/// Destructures a Tuple of two values and returns the first one
+pub struct FstNode<T, U>(PhantomData<T>, PhantomData<U>);
+impl<T: Copy, U> Node for FstNode<T, U> {
+    type Output<'a> = &'a T where Self: 'a;
+    type Input<'a> = &'a (T, U) where Self: 'a;
+    fn eval<'a, I: Borrow<Self::Input<'a>>>(&'a self, input: I) -> Self::Output<'a> {
+        let &(ref a, _) = input.borrow();
+        a
+    }
+}
+
+#[derive(Default)]
+/// Destructures a Tuple of two values and returns the first one
+pub struct SndNode<T, U>(PhantomData<T>, PhantomData<U>);
+impl<T, U: Copy> Node for SndNode<T, U> {
+    type Output<'a> = &'a U where Self: 'a;
+    type Input<'a> = &'a (T, U) where Self: 'a;
+    fn eval<'a, I: Borrow<Self::Input<'a>>>(&'a self, input: I) -> Self::Output<'a> {
+        let &(_, ref b) = input.borrow();
+        b
+    }
+}