diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index b7363a7..36bdf21 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -129,7 +129,7 @@ jobs:
         },
         {
           "name": "Run Clippy",
-          "run": "nix develop --command cargo -- clippy -- -D warnings"
+          "run": "nix develop --command cargo -- clippy -- -D warnings -W clippy::must_use_candidate"
         }
       ]
     }
diff --git a/little_learner/src/auto_diff.rs b/little_learner/src/auto_diff.rs
index 8debc49..eede557 100644
--- a/little_learner/src/auto_diff.rs
+++ b/little_learner/src/auto_diff.rs
@@ -250,12 +250,12 @@ impl<A, Tag> DifferentiableContents<A, Tag> {
             }
             (
                 DifferentiableContents::Vector(v1, rank1),
-                DifferentiableContents::Vector(v2, _rank2),
+                DifferentiableContents::Vector(v2, rank2),
             ) => {
                 assert_eq!(
                     v1.len(),
                     v2.len(),
-                    "Must map two vectors of the same length, got {rank1} and {_rank2}"
+                    "Must map two vectors of the same length, got {rank1} and {rank2}"
                 );
                 assert_ne!(
                     v1.len(),
diff --git a/little_learner/src/block.rs b/little_learner/src/block.rs
index 576fccd..f0bea64 100644
--- a/little_learner/src/block.rs
+++ b/little_learner/src/block.rs
@@ -1,4 +1,4 @@
-use crate::auto_diff::{Differentiable, RankedDifferentiableTagged};
+use crate::auto_diff::{Differentiable, RankedDifferentiable, RankedDifferentiableTagged};
 use crate::ext::relu;
 use crate::traits::NumLike;
 
@@ -7,30 +7,39 @@ pub struct Block<F, const N: usize> {
     ranks: [usize; N],
 }
 
-pub fn compose<'a, A, T, B, C, F, G, const N: usize, const M: usize>(
+/// Does the second argument first, so compose(b1, b2) performs b2 on its input, and then b1.
+pub fn compose<'a, 'c, 'd, A, T, B, C, F, G, const N: usize, const M: usize>(
     b1: Block<F, N>,
     b2: Block<G, M>,
     j: usize,
-) -> Block<impl FnOnce(A, &'a [T]) -> C, { N + M }>
+) -> Block<impl FnOnce(&'a A, &'d [T]) -> C, { N + M }>
 where
-    F: FnOnce(A, &'a [T]) -> B,
-    G: FnOnce(B, &'a [T]) -> C,
-    T: 'a,
+    F: FnOnce(&'a A, &'d [T]) -> B,
+    G: for<'b> FnOnce(&'b B, &'d [T]) -> C,
+    A: 'a,
+    T: 'd,
 {
     let mut ranks = [0usize; N + M];
-    ranks.copy_from_slice(&b1.ranks[..N]);
-    ranks[N..(M + N)].copy_from_slice(&b2.ranks[..M]);
+    ranks[..N].copy_from_slice(&b1.ranks);
+    ranks[N..(M + N)].copy_from_slice(&b2.ranks);
     Block {
-        f: move |t, theta| (b2.f)((b1.f)(t, theta), &theta[j..]),
+        f: move |t, theta| {
+            let intermediate = (b1.f)(t, theta);
+            (b2.f)(&intermediate, &theta[j..])
+        },
         ranks,
     }
 }
 
-pub fn dense<'a, 'b, A, Tag>(
+#[must_use]
+pub fn dense<'b, A, Tag>(
     input_len: usize,
     neuron_count: usize,
 ) -> Block<
-    impl FnOnce(&'a RankedDifferentiableTagged<A, Tag, 1>, &'b [Differentiable<A>]) -> Differentiable<A>,
+    impl for<'a> FnOnce(
+        &'a RankedDifferentiableTagged<A, Tag, 1>,
+        &'b [Differentiable<A>],
+    ) -> RankedDifferentiable<A, 1>,
     2,
 >
 where
@@ -38,12 +47,16 @@ where
     A: NumLike + PartialOrd + Default,
 {
     Block {
-        f: |t, theta: &'b [Differentiable<A>]| -> Differentiable<A> {
+        f: for<'a> |t: &'a RankedDifferentiableTagged<A, Tag, 1>,
+                    theta: &'b [Differentiable<A>]|
+                 -> RankedDifferentiable<A, 1> {
             relu(
                 t,
                 &(theta[0].clone().attach_rank().unwrap()),
                 &(theta[1].clone().attach_rank().unwrap()),
             )
+            .attach_rank()
+            .unwrap()
         },
         ranks: [input_len, neuron_count],
     }
diff --git a/little_learner/src/lib.rs b/little_learner/src/lib.rs
index 615732e..3cb333e 100644
--- a/little_learner/src/lib.rs
+++ b/little_learner/src/lib.rs
@@ -1,6 +1,7 @@
 #![allow(incomplete_features)]
 #![feature(generic_const_exprs)]
 #![feature(array_methods)]
+#![feature(closure_lifetime_binder)]
 
 pub mod auto_diff;
 pub mod block;
diff --git a/little_learner_app/src/main.rs b/little_learner_app/src/main.rs
index b917512..2578c76 100644
--- a/little_learner_app/src/main.rs
+++ b/little_learner_app/src/main.rs
@@ -3,6 +3,8 @@
 
 use crate::rms_example::rms_example;
 use little_learner::auto_diff::RankedDifferentiable;
+use little_learner::block;
+use ordered_float::NotNan;
 
 mod iris;
 mod rms_example;
@@ -20,4 +22,6 @@ fn main() {
     }
     let _xs = RankedDifferentiable::of_vector(xs);
     let _ys = RankedDifferentiable::of_vector(ys);
+
+    let _network = block::compose(block::dense::<NotNan<f64>, ()>(6, 3), block::dense(4, 6), 2);
 }