Stop relying on `impl Deref { type Target = Self; ...`

... this has a tendency to cause `reached the recursion limit while
auto-dereferencing` errors, and even a dumb struct copy suffices to
avoid it.

diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
index 12d0772fbb496fab0c8522f04119a8c7a19bd408..dce1f876ceb1020025f42a7a30a127ca5decf656 100644 (file)
--- a/c-bindings-gen/src/main.rs
+++ b/c-bindings-gen/src/main.rs
@@ -646,12 +646,22 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty
                writeln!(w, " for {} {{", trait_name).unwrap();
                impl_trait_for_c!(t, "", types, &syn::PathArguments::None);
                writeln!(w, "}}\n").unwrap();
+
+               writeln!(w, "struct {}Ref({});", trait_name, trait_name).unwrap();
+               write!(w, "impl").unwrap();
+               maybe_write_lifetime_generics(w, &t.generics, types);
+               write!(w, " rust{}", t.ident).unwrap();
+               maybe_write_generics(w, &t.generics, &syn::PathArguments::None, types, false);
+               writeln!(w, " for {}Ref {{", trait_name).unwrap();
+               impl_trait_for_c!(t, ".0", types, &syn::PathArguments::None);
+               writeln!(w, "}}\n").unwrap();
+
                writeln!(w, "// We're essentially a pointer already, or at least a set of pointers, so allow us to be used").unwrap();
                writeln!(w, "// directly as a Deref trait in higher-level structs:").unwrap();
-               writeln!(w, "impl core::ops::Deref for {} {{\n\ttype Target = Self;", trait_name).unwrap();
-               writeln!(w, "\tfn deref(&self) -> &Self {{\n\t\tself\n\t}}\n}}").unwrap();
+               writeln!(w, "impl core::ops::Deref for {} {{\n\ttype Target = {}Ref;", trait_name, trait_name).unwrap();
+               writeln!(w, "\tfn deref(&self) -> &Self::Target {{\n\t\tunsafe {{ &*(self as *const _ as *const {}Ref) }}\n\t}}\n}}", trait_name).unwrap();
                writeln!(w, "impl core::ops::DerefMut for {} {{", trait_name).unwrap();
-               writeln!(w, "\tfn deref_mut(&mut self) -> &mut Self {{\n\t\tself\n\t}}\n}}").unwrap();
+               writeln!(w, "\tfn deref_mut(&mut self) -> &mut {}Ref {{\n\t\tunsafe {{ &mut *(self as *mut _ as *mut {}Ref) }}\n\t}}\n}}", trait_name, trait_name).unwrap();
        }
 
        writeln!(w, "/// Calls the free function if one is set").unwrap();