From 8b185c03daf002c2243b1966d495ba39acc15587 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Thu, 25 Apr 2024 20:08:27 +0000
Subject: [PATCH] Write out real generics when calling trait methods

This avoids issues where a trait has a generic which can't be
resolved.
---
 c-bindings-gen/src/blocks.rs | 12 ++++++++----
 c-bindings-gen/src/main.rs   | 20 +++++---------------
 2 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/c-bindings-gen/src/blocks.rs b/c-bindings-gen/src/blocks.rs
index d01da1c..dc160d2 100644
--- a/c-bindings-gen/src/blocks.rs
+++ b/c-bindings-gen/src/blocks.rs
@@ -780,14 +780,18 @@ pub fn write_method_call_params<W: std::io::Write>(w: &mut W, sig: &syn::Signatu
 /// Prints concrete generic parameters for a struct/trait/function, including the less-than and
 /// greater-than symbols, if any generic parameters are defined.
 pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, generics_impld: &syn::PathArguments, types: &TypeResolver, concrete_lifetimes: bool) {
-	maybe_write_generics_intern(w, generics, generics_impld, types, concrete_lifetimes, false);
+	maybe_write_generics_intern(w, generics, Some(generics_impld), types, concrete_lifetimes, false);
 }
 
 pub fn maybe_write_non_lifetime_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, generics_impld: &syn::PathArguments, types: &TypeResolver) {
-	maybe_write_generics_intern(w, generics, generics_impld, types, false, true);
+	maybe_write_generics_intern(w, generics, Some(generics_impld), types, false, true);
 }
 
-fn maybe_write_generics_intern<W: std::io::Write>(w: &mut W, generics: &syn::Generics, generics_impld: &syn::PathArguments, types: &TypeResolver, concrete_lifetimes: bool, dummy_lifetimes: bool) {
+pub fn maybe_write_type_non_lifetime_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver) {
+	maybe_write_generics_intern(w, generics, None, types, false, true);
+}
+
+fn maybe_write_generics_intern<W: std::io::Write>(w: &mut W, generics: &syn::Generics, generics_impld: Option<&syn::PathArguments>, types: &TypeResolver, concrete_lifetimes: bool, dummy_lifetimes: bool) {
 	let mut gen_types = GenericTypes::new(None);
 	assert!(gen_types.learn_generics(generics, types));
 	if generics.params.is_empty() { return; }
@@ -821,7 +825,7 @@ fn maybe_write_generics_intern<W: std::io::Write>(w: &mut W, generics: &syn::Gen
 				if types.understood_c_type(&syn::parse_quote!(#type_ident), Some(&gen_types)) {
 					types.write_c_type_in_generic_param(&mut out, &syn::parse_quote!(#type_ident), Some(&gen_types), false);
 				} else {
-					if let syn::PathArguments::AngleBracketed(args) = generics_impld {
+					if let Some(syn::PathArguments::AngleBracketed(args)) = generics_impld {
 						if let syn::GenericArgument::Type(ty) = &args.args[idx] {
 							types.write_c_type_in_generic_param(&mut out, &ty, Some(&gen_types), false);
 						}
diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
index 358e30b..fd4ea8f 100644
--- a/c-bindings-gen/src/main.rs
+++ b/c-bindings-gen/src/main.rs
@@ -1201,23 +1201,13 @@ fn writeln_impl<W: std::io::Write>(w: &mut W, w_uses: &mut HashSet<String, NonRa
 										}
 									}
 
-									let mut t_gen_args = String::new();
-									for (idx, _) in $trait.generics.params.iter().enumerate() {
-										if idx != 0 { t_gen_args += ", " };
-										t_gen_args += "_"
-									}
-									// rustc doesn't like <_> if the _ is actually a lifetime, so
-									// if all the parameters are lifetimes just skip it.
-									let mut nonlifetime_param = false;
-									for param in $trait.generics.params.iter() {
-										if let syn::GenericParam::Lifetime(_) = param {}
-										else { nonlifetime_param = true; }
-									}
-									if !nonlifetime_param { t_gen_args = String::new(); }
+									let mut t_gen_args_vec = Vec::new();
+									maybe_write_type_non_lifetime_generics(&mut t_gen_args_vec, &$trait.generics, &trait_resolver);
+									let t_gen_args = String::from_utf8(t_gen_args_vec).unwrap();
 									if takes_self {
-										write!(w, "<native{} as {}<{}>>::{}(unsafe {{ &mut *(this_arg as *mut native{}) }}, ", ident, $trait_path, t_gen_args, $m.sig.ident, ident).unwrap();
+										write!(w, "<native{} as {}{}>::{}(unsafe {{ &mut *(this_arg as *mut native{}) }}, ", ident, $trait_path, t_gen_args, $m.sig.ident, ident).unwrap();
 									} else {
-										write!(w, "<native{} as {}<{}>>::{}(", ident, $trait_path, t_gen_args, $m.sig.ident).unwrap();
+										write!(w, "<native{} as {}{}>::{}(", ident, $trait_path, t_gen_args, $m.sig.ident).unwrap();
 									}
 
 									let mut real_type = "".to_string();
-- 
2.39.5