From 4c6ca5b4244e01bdad5496d6e1186ee87b21eb03 Mon Sep 17 00:00:00 2001
From: xunilrj <xunilrj@hotmail.com>
Date: Thu, 3 Oct 2024 16:15:09 +0100
Subject: [PATCH 1/2] return type checked trait constraints

---
 sway-core/src/type_system/ast_elements/type_parameter.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sway-core/src/type_system/ast_elements/type_parameter.rs b/sway-core/src/type_system/ast_elements/type_parameter.rs
index e79a4bfce64..f5a3da2b56e 100644
--- a/sway-core/src/type_system/ast_elements/type_parameter.rs
+++ b/sway-core/src/type_system/ast_elements/type_parameter.rs
@@ -213,7 +213,7 @@ impl TypeParameter {
             // Type check trait constraints only after type checking all type parameters.
             // This is required because a trait constraint may use other type parameters.
             // Ex: `struct Struct2<A, B> where A : MyAdd<B>`
-            for type_param in &new_type_params {
+            for type_param in new_type_params.iter_mut() {
                 TypeParameter::type_check_trait_constraints(handler, ctx.by_ref(), type_param)?;
             }
 
@@ -327,7 +327,7 @@ impl TypeParameter {
     fn type_check_trait_constraints(
         handler: &Handler,
         mut ctx: TypeCheckContext,
-        type_parameter: &TypeParameter,
+        type_parameter: &mut TypeParameter,
     ) -> Result<(), ErrorEmitted> {
         let type_engine = ctx.engines.te();
 
@@ -372,6 +372,8 @@ impl TypeParameter {
             },
         );
 
+        type_parameter.trait_constraints = trait_constraints_with_supertraits;
+
         // Insert the trait constraints into the namespace.
         type_parameter.insert_into_namespace_constraints(handler, ctx.by_ref())?;
 

From 0407765e5f07c8e01d34f479559df22386f00bd0 Mon Sep 17 00:00:00 2001
From: xunilrj <xunilrj@hotmail.com>
Date: Thu, 24 Oct 2024 07:50:43 +0100
Subject: [PATCH 2/2] more tests

---
 .../generic_where_in_impl_self/src/main.sw     | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_where_in_impl_self/src/main.sw b/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_where_in_impl_self/src/main.sw
index 4c3e852777f..474043af251 100644
--- a/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_where_in_impl_self/src/main.sw
+++ b/test/src/e2e_vm_tests/test_programs/should_pass/language/generic_where_in_impl_self/src/main.sw
@@ -27,9 +27,27 @@ impl<K> CallTrait<K> where K: Trait {
     }
 }
 
+// https://github.com/FuelLabs/sway/issues/6382
+trait Devour<T> { fn eat(t: T); }
+struct Brain { }
+struct Zombie { }
+
+impl Devour<Brain> for Zombie {
+    fn eat(_b: Brain) { }
+}
+
+fn feed<T, U>(t: T) where U: Devour<T> {
+    U::eat(t);
+}
+
 fn main() -> bool {
     let _  = call_trait(1);
     let ct = CallTrait::<u64> {};
     assert(ct.call_trait(1) == 42);
+
+    // https://github.com/FuelLabs/sway/issues/6382
+    let b = Brain{};
+    feed::<Brain, Zombie>(b);
+
     true
 }