From 76eed6fb43c1d675195aff896efb325828c76498 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Wed, 2 Mar 2022 03:19:46 +0000
Subject: [PATCH] Add function-call generic parameters when they're resovable

We really shouldn't ever actually need to do this - rustc should be
smart enough to figure out what we're doing given all the
parameters are concrete types, but this appears to be failing
sometimes.
---
 c-bindings-gen/src/blocks.rs | 54 ++++++++++++++++++++++++------------
 c-bindings-gen/src/main.rs   | 12 +++++++-
 c-bindings-gen/src/types.rs  |  2 +-
 3 files changed, 49 insertions(+), 19 deletions(-)

diff --git a/c-bindings-gen/src/blocks.rs b/c-bindings-gen/src/blocks.rs
index 5034b09..e97fb65 100644
--- a/c-bindings-gen/src/blocks.rs
+++ b/c-bindings-gen/src/blocks.rs
@@ -745,27 +745,47 @@ pub fn write_method_call_params<W: std::io::Write>(w: &mut W, sig: &syn::Signatu
 pub fn maybe_write_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver, concrete_lifetimes: bool) {
 	let mut gen_types = GenericTypes::new(None);
 	assert!(gen_types.learn_generics(generics, types));
-	if !generics.params.is_empty() {
-		write!(w, "<").unwrap();
-		for (idx, generic) in generics.params.iter().enumerate() {
-			match generic {
-				syn::GenericParam::Type(type_param) => {
-					write!(w, "{}", if idx != 0 { ", " } else { "" }).unwrap();
-					let type_ident = &type_param.ident;
-					types.write_c_type_in_generic_param(w, &syn::parse_quote!(#type_ident), Some(&gen_types), false);
-				},
-				syn::GenericParam::Lifetime(lt) => {
-					if concrete_lifetimes {
-						write!(w, "'static").unwrap();
-					} else {
-						write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
+	if generics.params.is_empty() { return; }
+	for generic in generics.params.iter() {
+		match generic {
+			syn::GenericParam::Type(type_param) => {
+				for bound in type_param.bounds.iter() {
+					match bound {
+						syn::TypeParamBound::Trait(t) => {
+							if let Some(trait_bound) = types.maybe_resolve_path(&t.path, None) {
+								if types.skip_path(&trait_bound) {
+									// Just hope rust deduces generic params if some bounds are skipable.
+									return;
+								}
+							}
+						}
+						_ => {},
 					}
-				},
-				_ => unimplemented!(),
+				}
 			}
+			_ => {},
+		}
+	}
+
+	write!(w, "<").unwrap();
+	for (idx, generic) in generics.params.iter().enumerate() {
+		match generic {
+			syn::GenericParam::Type(type_param) => {
+				write!(w, "{}", if idx != 0 { ", " } else { "" }).unwrap();
+				let type_ident = &type_param.ident;
+				types.write_c_type_in_generic_param(w, &syn::parse_quote!(#type_ident), Some(&gen_types), false);
+			},
+			syn::GenericParam::Lifetime(lt) => {
+				if concrete_lifetimes {
+					write!(w, "'static").unwrap();
+				} else {
+					write!(w, "{}'{}", if idx != 0 { ", " } else { "" }, lt.lifetime.ident).unwrap();
+				}
+			},
+			_ => unimplemented!(),
 		}
-		write!(w, ">").unwrap();
 	}
+	write!(w, ">").unwrap();
 }
 
 pub fn maybe_write_lifetime_generics<W: std::io::Write>(w: &mut W, generics: &syn::Generics, types: &TypeResolver) {
diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
index c6a74f6..97f44a4 100644
--- a/c-bindings-gen/src/main.rs
+++ b/c-bindings-gen/src/main.rs
@@ -1647,10 +1647,20 @@ fn writeln_fn<'a, 'b, W: std::io::Write>(w: &mut W, f: &'a syn::ItemFn, types: &
 	writeln_fn_docs(w, &f.attrs, "", types, Some(&gen_types), f.sig.inputs.iter(), &f.sig.output);
 
 	write!(w, "#[no_mangle]\npub extern \"C\" fn {}(", f.sig.ident).unwrap();
+
+
 	write_method_params(w, &f.sig, "", types, Some(&gen_types), false, true);
 	write!(w, " {{\n\t").unwrap();
 	write_method_var_decl_body(w, &f.sig, "", types, Some(&gen_types), false);
-	write!(w, "{}::{}(", types.module_path, f.sig.ident).unwrap();
+	write!(w, "{}::{}", types.module_path, f.sig.ident).unwrap();
+
+	let mut function_generic_args = Vec::new();
+	maybe_write_generics(&mut function_generic_args, &f.sig.generics, types, true);
+	if !function_generic_args.is_empty() {
+		write!(w, "::{}", String::from_utf8(function_generic_args).unwrap()).unwrap();
+	}
+	write!(w, "(").unwrap();
+
 	write_method_call_params(w, &f.sig, "", types, Some(&gen_types), "", false);
 	writeln!(w, "\n}}\n").unwrap();
 }
diff --git a/c-bindings-gen/src/types.rs b/c-bindings-gen/src/types.rs
index 21b0458..88d6640 100644
--- a/c-bindings-gen/src/types.rs
+++ b/c-bindings-gen/src/types.rs
@@ -827,7 +827,7 @@ impl<'a, 'c: 'a> TypeResolver<'a, 'c> {
 	// *************************************************
 
 	/// Returns true we if can just skip passing this to C entirely
-	fn skip_path(&self, full_path: &str) -> bool {
+	pub fn skip_path(&self, full_path: &str) -> bool {
 		full_path == "bitcoin::secp256k1::Secp256k1" ||
 		full_path == "bitcoin::secp256k1::Signing" ||
 		full_path == "bitcoin::secp256k1::Verification"
-- 
2.30.2