From b31b6cb6c2ed683778f32b4708d8e6abe5e84f5d Mon Sep 17 00:00:00 2001
From: Boxy <rust@boxyuwu.dev>
Date: Thu, 19 Dec 2024 04:28:59 +0000
Subject: [PATCH] update trait_solver_5

---
 code/examples/stderr/trait_solver_5.stderr | 12 ------------
 code/examples/trait_solver_5.rs            |  8 +++-----
 src/trait_solver/5.md                      |  6 ++++--
 3 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/code/examples/stderr/trait_solver_5.stderr b/code/examples/stderr/trait_solver_5.stderr
index 230656c..e69de29 100644
--- a/code/examples/stderr/trait_solver_5.stderr
+++ b/code/examples/stderr/trait_solver_5.stderr
@@ -1,12 +0,0 @@
-error[E0119]: conflicting implementations of trait `Overlap<_>` for type `()`
- --> examples/trait_solver_5.rs:6:1
-  |
-5 | impl<T, U: Sub<T>> Overlap<T> for U {}
-  | ----------------------------------- first implementation here
-6 | impl<T> Overlap<T> for () {}
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `()`
-  |
-  = note: downstream crates may implement trait `Sub<_>` for type `()`
-
-For more information about this error, try `rustc --explain E0119`.
-error: could not compile `code` (example "trait_solver_5") due to 1 previous error
diff --git a/code/examples/trait_solver_5.rs b/code/examples/trait_solver_5.rs
index 7b91770..2d0ff86 100644
--- a/code/examples/trait_solver_5.rs
+++ b/code/examples/trait_solver_5.rs
@@ -1,8 +1,6 @@
-trait Super {}
-trait Sub<T>: Super {}
+pub trait Super {}
+pub trait Sub<T>: Super {}
 
-trait Overlap<T> {}
+pub trait Overlap<T> {}
 impl<T, U: Sub<T>> Overlap<T> for U {}
 impl<T> Overlap<T> for () {}
-
-fn main() {}
diff --git a/src/trait_solver/5.md b/src/trait_solver/5.md
index fbfab7f..bdfaa71 100644
--- a/src/trait_solver/5.md
+++ b/src/trait_solver/5.md
@@ -1,4 +1,4 @@
-# Trait Solver 5 @BoxyUwU @WaffleLapkin
+# Trait Solver 5 @BoxyUwU @WaffleLapkin @lcnr
 
 {{#include ../include/quiz-is-wip.md}}
 
@@ -13,6 +13,8 @@
 {{#include ../../code/examples/stderr/trait_solver_5.stderr}}
 ```
 
-<!-- FIXME: explanation (also: doesn't error on newer versions)-->
+In order for these impls to overlap the type `()` must implement `Sub<T>` for some type `T`, the `Sub` trait is public so in theory some downstream crate could implement `(): Sub<Local>`. However, the supertrait `Super` cannot be implement for the type `()` by any downstream crates as `impl Super for () {` would not pass the orphan check in downstream crates 
+
+If we were to introduce an `impl Super for () {` to this example then coherence would forbid this code.
 
 </details>