Fix clippy unused_unit warnings in host_bindgen macro for void return functions

Co-authored-by: jsturtevant <648372+jsturtevant@users.noreply.github.com>

Author: Copilot

src/hyperlight_component_util/src/guest.rs

@@ -68,6 +68,15 @@ fn emit_import_extern_decl<'a, 'b, 'c>(
                     ResourceItemName::Static(mn) => quote! { #mn },
                 },
             };
+            // Only emit the allow attribute if unmarshal is not empty
+            let unmarshal_with_attr = if unmarshal.is_empty() {
+                quote! {}
+            } else {
+                quote! {
+                    #[allow(clippy::unused_unit)]
+                    #unmarshal
+                }
+            };
             let decl = quote! {
                 fn #n(&mut self, #(#param_decls),*) -> #result_decl {
                     let mut args = ::alloc::vec::Vec::new();
@@ -78,8 +87,7 @@ fn emit_import_extern_decl<'a, 'b, 'c>(
                         ::hyperlight_common::flatbuffer_wrappers::function_types::ReturnType::VecBytes,
                     );
                     let ::core::result::Result::Ok(#ret) = #ret else { panic!("bad return from guest {:?}", #ret) };
-                    #[allow(clippy::unused_unit)]
-                    #unmarshal
+                    #unmarshal_with_attr
                 }
             };
             match fnname {

src/hyperlight_component_util/src/hl.rs

@@ -655,7 +655,7 @@ pub fn emit_hl_unmarshal_param(s: &mut State, id: Ident, pt: &Value) -> TokenStr
 /// are no names in it (i.e. a unit type)
 pub fn emit_hl_unmarshal_result(s: &mut State, id: Ident, rt: &etypes::Result) -> TokenStream {
     match rt {
-        etypes::Result::Named(rs) if rs.is_empty() => quote! { () },
+        etypes::Result::Named(rs) if rs.is_empty() => TokenStream::new(),
         etypes::Result::Unnamed(vt) => {
             let toks = emit_hl_unmarshal_value(s, id, vt);
             quote! { { #toks }.0 }

src/hyperlight_host/tests/wit_test.proptest-regressions

@@ -0,0 +1,10 @@
+# Seeds for failure cases proptest has generated in the past. It is
+# automatically read and these particular cases re-run before any
+# novel cases are generated.
+#
+# It is recommended to check this file in to source control so that
+# everyone who runs the test benefits from these saved cases.
+cc 9e697e3320100630afae15901d82d23237f04e3d8090ec2c9ecb211fbf322909 # shrinks to x = 0.0
+cc 033b8487116d6b64d1c321ca2475618b943551b670ed562648c12f3a7586243a # shrinks to x = EnumA
+cc 37f8b1a347c5a2a096a8904b918c0f049b729c80e329ed63dc1b501258a2973b # shrinks to x = false
+cc f401ff3b24d9e0b6a5332fbaecbb5cde12d13d932d33d27a5d15ce2ea73a1125 # shrinks to x = 'A'