chore: create a regression test for #6420 (#6421)

compiler/noirc_frontend/src/tests/traits.rs

@@ -340,3 +340,53 @@ fn removes_assumed_parent_traits_after_function_ends() {
     "#;
     assert_no_errors(src);
 }
+
+#[test]
+fn trait_bounds_which_are_dependent_on_generic_types_are_resolved_correctly() {
+    // Regression test for https://github.com/noir-lang/noir/issues/6420
+    let src = r#"
+        trait Foo {
+            fn foo() -> Field;
+        }
+
+        trait Bar<T>: Foo {
+            fn bar(self) -> Field {
+                self.foo()
+            }
+        }
+
+        struct MyStruct<T> {
+            inner: Field,
+        }
+
+        trait MarkerTrait {}
+        impl MarkerTrait for Field {}
+
+        // `MyStruct<T>` implements `Foo` only when its generic type `T` implements `MarkerTrait`.
+        impl<T> Foo for MyStruct<T>
+        where
+            T: MarkerTrait,
+        {
+            fn foo() -> Field {
+                42
+            }
+        }
+
+        // We expect this to succeed as `MyStruct<T>` satisfies `Bar`'s trait bounds
+        // of implementing `Foo` when `T` implements `MarkerTrait`.
+        impl<T> Bar<T> for MyStruct<T>
+        where
+            T: MarkerTrait,
+        {
+            fn bar(self) -> Field {
+                31415
+            }
+        }
+
+        fn main() {
+            let foo: MyStruct<Field> = MyStruct { inner: 42 };
+            let _ = foo.bar();
+        }
+    "#;
+    assert_no_errors(src);
+}