diff -r 2b13f8a0c8ba -r d65377920b00 src/direct_product.rs
--- a/src/direct_product.rs	Mon May 12 20:40:14 2025 -0500
+++ b/src/direct_product.rs	Mon May 12 21:26:04 2025 -0500
@@ -397,13 +397,9 @@
             .eval_decompose(|a| self.1.eval_decompose(|b| f(Pair(a, b))))
     }
 
-    fn eval_ref_decompose<'b, R>(
-        &'b self,
-        f: impl FnOnce(Pair<D::Reference<'b>, Q::Reference<'b>>) -> R,
-    ) -> R
+    fn eval_ref_decompose<R, F>(&self, f: F) -> R
     where
-        Pair<A, B>: 'b,
-        Self: 'b,
+        F: for<'c> FnOnce(Pair<D::Reference<'c>, Q::Reference<'c>>) -> R,
     {
         self.0
             .eval_ref_decompose(|a| self.1.eval_ref_decompose(|b| f(Pair(a, b))))
@@ -439,6 +435,7 @@
         f: impl FnOnce(Pair<D::Decomposition<'b>, Q::Decomposition<'b>>) -> R,
     ) -> R
     where
+        R: 'b,
         Pair<A, B>: 'b,
         Self: 'b,
     {
@@ -448,13 +445,11 @@
         })
     }
 
-    fn eval_ref_decompose<'b, R>(
-        &'b self,
-        f: impl FnOnce(Pair<D::Reference<'b>, Q::Reference<'b>>) -> R,
-    ) -> R
+    fn eval_ref_decompose<'b, 'c, R, F>(&'b self, f: F) -> R
     where
-        Pair<A, B>: 'b,
+        Pair<A, B>: 'c,
         Self: 'b,
+        F: FnOnce(Pair<D::Reference<'c>, Q::Reference<'c>>) -> R,
     {
         self.0
             .eval_ref_decompose(|a| self.1.eval_ref_decompose(|b| f(Pair(a, b))))