Cleaned up code for auto-assigning trait implementation arguments to implementation parameters

Author: IsaacShelton

Diff for: src/resolve/expr/call.rs

@@ -85,27 +85,32 @@ pub fn call_callee(
         let arg_concrete_trait = impl_poly_catalog.bake().resolve_trait(&imp.target)?;
         let function = ctx.asg.funcs.get(callee.function).unwrap();
 
-        let poly_impl_name = if let Some(name) = &impl_using.name {
-            name.clone()
-        } else {
-            function
-                .impl_params
-                .params
-                .iter()
-                .filter(|(param_name, param)| {
-                    param.trait_ref == arg_concrete_trait.trait_ref
-                        && !used_names.contains(*param_name)
-                })
-                .map(|(param_name, _)| param_name)
-                .next()
-                .ok_or_else(|| {
-                    ResolveError::other(
-                        "No implementation parameter left for implementation argument",
-                        impl_arg.source,
-                    )
-                })?
-                .clone()
-        };
+        let poly_impl_name = impl_using
+            .name
+            .as_ref()
+            .ok_or(())
+            .or_else(|_| {
+                function
+                    .impl_params
+                    .params
+                    .iter()
+                    .filter(|(param_name, param)| {
+                        param.trait_ref == arg_concrete_trait.trait_ref
+                            && !used_names.contains(*param_name)
+                    })
+                    .map(|(param_name, _)| param_name)
+                    .next()
+                    .ok_or_else(|| {
+                        ResolveError::other(
+                            format!(
+                                "Excess implementation of trait '{}' is not used by callee",
+                                arg_concrete_trait.display(&ctx.asg)
+                            ),
+                            impl_arg.source,
+                        )
+                    })
+            })?
+            .clone();
 
         if !used_names.insert(poly_impl_name.clone()) {
             return Err(ResolveError::other(