From 56001280fb0fa4591492dc3766b8509dd51826e6 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Tue, 13 Apr 2021 19:27:22 -0400
Subject: [PATCH] Handle concrete Deref<Target=X> bounds in generic args

---
 c-bindings-gen/src/types.rs | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/c-bindings-gen/src/types.rs b/c-bindings-gen/src/types.rs
index 26a0885..bd0c9c5 100644
--- a/c-bindings-gen/src/types.rs
+++ b/c-bindings-gen/src/types.rs
@@ -176,7 +176,7 @@ pub struct GenericTypes<'a, 'b> {
 	self_ty: Option<(String, &'a syn::Path)>,
 	parent: Option<&'b GenericTypes<'b, 'b>>,
 	typed_generics: HashMap<&'a syn::Ident, (String, Option<&'a syn::Path>)>,
-	default_generics: HashMap<&'a syn::Ident, (&'a syn::Type, syn::Type)>,
+	default_generics: HashMap<&'a syn::Ident, (syn::Type, syn::Type)>,
 }
 impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 	pub fn new(self_ty: Option<(String, &'a syn::Path)>) -> Self {
@@ -197,7 +197,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 			match generic {
 				syn::GenericParam::Type(type_param) => {
 					let mut non_lifetimes_processed = false;
-					for bound in type_param.bounds.iter() {
+					'bound_loop: for bound in type_param.bounds.iter() {
 						if let syn::TypeParamBound::Trait(trait_bound) = bound {
 							if let Some(ident) = single_ident_generic_path_to_ident(&trait_bound.path) {
 								match &format!("{}", ident) as &str { "Send" => continue, "Sync" => continue, _ => {} }
@@ -213,6 +213,26 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 								let new_ident = if path != "std::ops::Deref" && path != "core::ops::Deref" {
 									path = "crate::".to_string() + &path;
 									Some(&trait_bound.path)
+								} else if trait_bound.path.segments.len() == 1 {
+									// If we're templated on Deref<Target = ConcreteThing>, store
+									// the reference type in `default_generics` which handles full
+									// types and not just paths.
+									if let syn::PathArguments::AngleBracketed(ref args) =
+											trait_bound.path.segments[0].arguments {
+										for subargument in args.args.iter() {
+											match subargument {
+												syn::GenericArgument::Lifetime(_) => {},
+												syn::GenericArgument::Binding(ref b) => {
+													if &format!("{}", b.ident) != "Target" { return false; }
+													let default = &b.ty;
+													self.default_generics.insert(&type_param.ident, (parse_quote!(&#default), parse_quote!(&#default)));
+													break 'bound_loop;
+												},
+												_ => unimplemented!(),
+											}
+										}
+										None
+									} else { None }
 								} else { None };
 								self.typed_generics.insert(&type_param.ident, (path, new_ident));
 							} else { return false; }
@@ -220,7 +240,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 					}
 					if let Some(default) = type_param.default.as_ref() {
 						assert!(type_param.bounds.is_empty());
-						self.default_generics.insert(&type_param.ident, (default, parse_quote!(&#default)));
+						self.default_generics.insert(&type_param.ident, (default.clone(), parse_quote!(&#default)));
 					}
 				},
 				_ => {},
-- 
2.39.5