From eb8e71330a9894233c6559104756176b9a77188c Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Thu, 30 Nov 2023 18:25:01 +0400
Subject: [PATCH] fix: forward type parameters

---
 ambassador/src/register.rs                  |  5 ++-
 ambassador/tests/run-pass/generic_method.rs | 46 +++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 ambassador/tests/run-pass/generic_method.rs

diff --git a/ambassador/src/register.rs b/ambassador/src/register.rs
index 37fe0e4..b8dd281 100644
--- a/ambassador/src/register.rs
+++ b/ambassador/src/register.rs
@@ -312,6 +312,9 @@ fn build_method_invocation(
         })
         .collect();
 
-    let method_invocation = quote! { #field_ident.#method_ident(#argument_list) };
+    let generics = method_sig.generics.split_for_impl().1;
+    let turbofish = generics.as_turbofish();
+
+    let method_invocation = quote! { #field_ident.#method_ident #turbofish(#argument_list) };
     method_invocation
 }
diff --git a/ambassador/tests/run-pass/generic_method.rs b/ambassador/tests/run-pass/generic_method.rs
new file mode 100644
index 0000000..4acea3e
--- /dev/null
+++ b/ambassador/tests/run-pass/generic_method.rs
@@ -0,0 +1,46 @@
+extern crate ambassador;
+
+use ambassador::{delegatable_trait, Delegate};
+
+trait StaticFn {
+    fn call() -> bool;
+}
+
+struct StaticTrue;
+struct StaticFalse;
+
+impl StaticFn for StaticTrue {
+    fn call() -> bool {
+        true
+    }
+}
+
+impl StaticFn for StaticFalse {
+    fn call() -> bool {
+        false
+    }
+}
+
+#[delegatable_trait]
+pub trait StaticCall {
+    fn call<C: StaticFn>(&self) -> bool;
+}
+
+pub struct BaseCaller;
+
+impl StaticCall for BaseCaller {
+    fn call<C: StaticFn>(&self) -> bool {
+        C::call()
+    }
+}
+
+#[derive(Delegate)]
+#[delegate(StaticCall)]
+pub struct WrappedCaller(BaseCaller);
+
+fn main() {
+    let c = WrappedCaller(BaseCaller);
+    // Verify that the generic type is correctly passed through without relying on type inference.
+    assert!(c.call::<StaticTrue>());
+    assert!(!c.call::<StaticFalse>());
+}