Add regression test.

Author: jseyfried

src/test/run-pass/type-macros-simple.rs

@@ -15,3 +15,22 @@ macro_rules! Tuple {
 fn main() {
     let x: Tuple!(i32, i32) = (1, 2);
 }
+
+fn issue_36540() {
+    let i32 = 0;
+    macro_rules! m { () => { i32 } }
+    struct S<T = m!()>(m!(), T) where T: Trait<m!()>;
+
+    let x: m!() = m!();
+    std::cell::Cell::<m!()>::new(m!());
+    impl<T = m!()> std::ops::Index<m!()> for Trait<(m!(), T)>
+        where T: Trait<m!()>
+    {
+        type Output = m!();
+        fn index(&self, i: m!()) -> &m!() {
+            unimplemented!()
+        }
+    }
+}
+
+trait Trait<T> {}