diff --git a/src/test/ui/issues/issue-66768.rs b/src/test/ui/issues/issue-66768.rs
new file mode 100644
index 0000000000000..ce42c8b01cc32
--- /dev/null
+++ b/src/test/ui/issues/issue-66768.rs
@@ -0,0 +1,205 @@
+// Regression test for #66768.
+// check-pass
+#![allow(dead_code)]
+//-^ "dead code" is needed to reproduce the issue.
+
+use std::marker::PhantomData;
+use std::ops::{Add, Mul};
+
+fn problematic_function<Space>(material_surface_element: Edge2dElement)
+where
+    DefaultAllocator: FiniteElementAllocator<DimU1, Space>,
+{
+    let _: Point2<f64> = material_surface_element.map_reference_coords().into();
+}
+
+impl<T> ArrayLength<T> for UTerm {
+    type ArrayType = ();
+}
+impl<T, N: ArrayLength<T>> ArrayLength<T> for UInt<N, B0> {
+    type ArrayType = GenericArrayImplEven<T, N>;
+}
+impl<T, N: ArrayLength<T>> ArrayLength<T> for UInt<N, B1> {
+    type ArrayType = GenericArrayImplOdd<T, N>;
+}
+impl<U> Add<U> for UTerm {
+    type Output = U;
+    fn add(self, _: U) -> Self::Output {
+        unimplemented!()
+    }
+}
+impl<Ul, Ur> Add<UInt<Ur, B1>> for UInt<Ul, B0>
+where
+    Ul: Add<Ur>,
+{
+    type Output = UInt<Sum<Ul, Ur>, B1>;
+    fn add(self, _: UInt<Ur, B1>) -> Self::Output {
+        unimplemented!()
+    }
+}
+impl<U> Mul<U> for UTerm {
+    type Output = UTerm;
+    fn mul(self, _: U) -> Self {
+        unimplemented!()
+    }
+}
+impl<Ul, B, Ur> Mul<UInt<Ur, B>> for UInt<Ul, B0>
+where
+    Ul: Mul<UInt<Ur, B>>,
+{
+    type Output = UInt<Prod<Ul, UInt<Ur, B>>, B0>;
+    fn mul(self, _: UInt<Ur, B>) -> Self::Output {
+        unimplemented!()
+    }
+}
+impl<Ul, B, Ur> Mul<UInt<Ur, B>> for UInt<Ul, B1>
+where
+    Ul: Mul<UInt<Ur, B>>,
+    UInt<Prod<Ul, UInt<Ur, B>>, B0>: Add<UInt<Ur, B>>,
+{
+    type Output = Sum<UInt<Prod<Ul, UInt<Ur, B>>, B0>, UInt<Ur, B>>;
+    fn mul(self, _: UInt<Ur, B>) -> Self::Output {
+        unimplemented!()
+    }
+}
+impl<N, R, C> Allocator<N, R, C> for DefaultAllocator
+where
+    R: DimName,
+    C: DimName,
+    R::Value: Mul<C::Value>,
+    Prod<R::Value, C::Value>: ArrayLength<N>,
+{
+    type Buffer = ArrayStorage<N, R, C>;
+    fn allocate_uninitialized(_: R, _: C) -> Self::Buffer {
+        unimplemented!()
+    }
+    fn allocate_from_iterator<I>(_: R, _: C, _: I) -> Self::Buffer {
+        unimplemented!()
+    }
+}
+impl<N, C> Allocator<N, Dynamic, C> for DefaultAllocator {
+    type Buffer = VecStorage<N, Dynamic, C>;
+    fn allocate_uninitialized(_: Dynamic, _: C) -> Self::Buffer {
+        unimplemented!()
+    }
+    fn allocate_from_iterator<I>(_: Dynamic, _: C, _: I) -> Self::Buffer {
+        unimplemented!()
+    }
+}
+impl DimName for DimU1 {
+    type Value = U1;
+    fn name() -> Self {
+        unimplemented!()
+    }
+}
+impl DimName for DimU2 {
+    type Value = U2;
+    fn name() -> Self {
+        unimplemented!()
+    }
+}
+impl<N, D> From<VectorN<N, D>> for Point<N, D>
+where
+    DefaultAllocator: Allocator<N, D>,
+{
+    fn from(_: VectorN<N, D>) -> Self {
+        unimplemented!()
+    }
+}
+impl<GeometryDim, NodalDim> FiniteElementAllocator<GeometryDim, NodalDim> for DefaultAllocator where
+    DefaultAllocator: Allocator<f64, GeometryDim> + Allocator<f64, NodalDim>
+{
+}
+impl ReferenceFiniteElement for Edge2dElement {
+    type NodalDim = DimU1;
+}
+impl FiniteElement<DimU2> for Edge2dElement {
+    fn map_reference_coords(&self) -> Vector2<f64> {
+        unimplemented!()
+    }
+}
+
+type Owned<N, R, C> = <DefaultAllocator as Allocator<N, R, C>>::Buffer;
+type MatrixMN<N, R, C> = Matrix<N, R, C, Owned<N, R, C>>;
+type VectorN<N, D> = MatrixMN<N, D, DimU1>;
+type Vector2<N> = VectorN<N, DimU2>;
+type Point2<N> = Point<N, DimU2>;
+type U1 = UInt<UTerm, B1>;
+type U2 = UInt<UInt<UTerm, B1>, B0>;
+type Sum<A, B> = <A as Add<B>>::Output;
+type Prod<A, B> = <A as Mul<B>>::Output;
+
+struct GenericArray<T, U: ArrayLength<T>> {
+    _data: U::ArrayType,
+}
+struct GenericArrayImplEven<T, U> {
+    _parent2: U,
+    _marker: T,
+}
+struct GenericArrayImplOdd<T, U> {
+    _parent2: U,
+    _data: T,
+}
+struct B0;
+struct B1;
+struct UTerm;
+struct UInt<U, B> {
+    _marker: PhantomData<(U, B)>,
+}
+struct DefaultAllocator;
+struct Dynamic;
+struct DimU1;
+struct DimU2;
+struct Matrix<N, R, C, S> {
+    _data: S,
+    _phantoms: PhantomData<(N, R, C)>,
+}
+struct ArrayStorage<N, R, C>
+where
+    R: DimName,
+    C: DimName,
+    R::Value: Mul<C::Value>,
+    Prod<R::Value, C::Value>: ArrayLength<N>,
+{
+    _data: GenericArray<N, Prod<R::Value, C::Value>>,
+}
+struct VecStorage<N, R, C> {
+    _data: N,
+    _nrows: R,
+    _ncols: C,
+}
+struct Point<N, D>
+where
+    DefaultAllocator: Allocator<N, D>,
+{
+    _coords: VectorN<N, D>,
+}
+struct Edge2dElement;
+
+trait ArrayLength<T> {
+    type ArrayType;
+}
+trait Allocator<Scalar, R, C = DimU1> {
+    type Buffer;
+    fn allocate_uninitialized(nrows: R, ncols: C) -> Self::Buffer;
+    fn allocate_from_iterator<I>(nrows: R, ncols: C, iter: I) -> Self::Buffer;
+}
+trait DimName {
+    type Value;
+    fn name() -> Self;
+}
+trait FiniteElementAllocator<GeometryDim, NodalDim>:
+    Allocator<f64, GeometryDim> + Allocator<f64, NodalDim>
+{
+}
+trait ReferenceFiniteElement {
+    type NodalDim;
+}
+trait FiniteElement<GeometryDim>: ReferenceFiniteElement
+where
+    DefaultAllocator: FiniteElementAllocator<GeometryDim, Self::NodalDim>,
+{
+    fn map_reference_coords(&self) -> VectorN<f64, GeometryDim>;
+}
+
+fn main() {}