From c98ebb54cc7f57f8c4c31d01ec69c81b172e49b1 Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Thu, 23 Jun 2022 16:13:06 +0000
Subject: [PATCH] Generate mutable references in `default_generics` when
 relevant

As we move towards resolving generics via the new `Type`-based
interface instead of the string-based one, we need to ensure we
retain the mutability flag when resolving references, which we do
here.
---
 c-bindings-gen/src/blocks.rs |  2 +-
 c-bindings-gen/src/types.rs  | 29 +++++++++++++++++++----------
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/c-bindings-gen/src/blocks.rs b/c-bindings-gen/src/blocks.rs
index 5072f8a..84a971b 100644
--- a/c-bindings-gen/src/blocks.rs
+++ b/c-bindings-gen/src/blocks.rs
@@ -576,7 +576,7 @@ pub fn write_method_params<W: std::io::Write>(w: &mut W, sig: &syn::Signature, t
 					},
 					_ => unimplemented!(),
 				}
-				w.write(&c_type).unwrap();
+				w.write_all(&c_type).unwrap();
 			}
 		}
 	}
diff --git a/c-bindings-gen/src/types.rs b/c-bindings-gen/src/types.rs
index 16cc067..8f5e667 100644
--- a/c-bindings-gen/src/types.rs
+++ b/c-bindings-gen/src/types.rs
@@ -190,7 +190,7 @@ pub struct GenericTypes<'a, 'b> {
 	self_ty: Option<String>,
 	parent: Option<&'b GenericTypes<'b, 'b>>,
 	typed_generics: HashMap<&'a syn::Ident, String>,
-	default_generics: HashMap<&'a syn::Ident, (syn::Type, syn::Type)>,
+	default_generics: HashMap<&'a syn::Ident, (syn::Type, syn::Type, syn::Type)>,
 }
 impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 	pub fn new(self_ty: Option<String>) -> Self {
@@ -226,6 +226,10 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 								if non_lifetimes_processed { return false; }
 								non_lifetimes_processed = true;
 								if path != "std::ops::Deref" && path != "core::ops::Deref" {
+									let p = string_path_to_syn_path(&path);
+									let ref_ty = parse_quote!(&#p);
+									let mut_ref_ty = parse_quote!(&mut #p);
+									self.default_generics.insert(&type_param.ident, (syn::Type::Path(syn::TypePath { qself: None, path: p }), ref_ty, mut_ref_ty));
 									new_typed_generics.insert(&type_param.ident, Some(path));
 								} else {
 									// If we're templated on Deref<Target = ConcreteThing>, store
@@ -240,7 +244,7 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 												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)));
+													self.default_generics.insert(&type_param.ident, (parse_quote!(&#default), parse_quote!(&#default), parse_quote!(&mut #default)));
 													break 'bound_loop;
 												},
 												_ => unimplemented!(),
@@ -255,7 +259,7 @@ 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.clone(), parse_quote!(&#default)));
+						self.default_generics.insert(&type_param.ident, (default.clone(), parse_quote!(&#default), parse_quote!(&mut #default)));
 					}
 				},
 				_ => {},
@@ -288,10 +292,11 @@ impl<'a, 'p: 'a> GenericTypes<'a, 'p> {
 										qself: None, path: string_path_to_syn_path(&resolved)
 									});
 									let ref_ty = parse_quote!(&#ty);
+									let mut_ref_ty = parse_quote!(&mut #ty);
 									if types.crate_types.traits.get(&resolved).is_some() {
-										self.default_generics.insert(p_ident, (ty, ref_ty));
+										self.default_generics.insert(p_ident, (ty, ref_ty, mut_ref_ty));
 									} else {
-										self.default_generics.insert(p_ident, (ref_ty.clone(), ref_ty));
+										self.default_generics.insert(p_ident, (ref_ty.clone(), ref_ty, mut_ref_ty));
 									}
 
 									*gen = Some(resolved);
@@ -383,16 +388,20 @@ impl<'a, 'b, 'c: 'a + 'b> ResolveType<'c> for Option<&GenericTypes<'a, 'b>> {
 			match ty {
 				syn::Type::Path(p) => {
 					if let Some(ident) = p.path.get_ident() {
-						if let Some((ty, _)) = us.default_generics.get(ident) {
-							return ty;
+						if let Some((ty, _, _)) = us.default_generics.get(ident) {
+							return self.resolve_type(ty);
 						}
 					}
 				},
-				syn::Type::Reference(syn::TypeReference { elem, .. }) => {
+				syn::Type::Reference(syn::TypeReference { elem, mutability, .. }) => {
 					if let syn::Type::Path(p) = &**elem {
 						if let Some(ident) = p.path.get_ident() {
-							if let Some((_, refty)) = us.default_generics.get(ident) {
-								return refty;
+							if let Some((_, refty, mut_ref_ty)) = us.default_generics.get(ident) {
+								if mutability.is_some() {
+									return self.resolve_type(mut_ref_ty);
+								} else {
+									return self.resolve_type(refty);
+								}
 							}
 						}
 					}
-- 
2.39.5