1 files changed, 43 insertions, 0 deletions
diff --git a/vendor/derivative/src/utils.rs b/vendor/derivative/src/utils.rs
new file mode 100644
index 000000000..9db21f5be
--- /dev/null
+++ b/vendor/derivative/src/utils.rs
@@ -0,0 +1,43 @@
+use proc_macro2;
+
+use ast;
+use attr;
+use bound;
+use syn;
+
+/// Make generic with all the generics in the input, plus a bound `T: <trait_path>` for each
+/// generic field type that will be shown.
+pub fn build_impl_generics<F, G, H>(
+    item: &ast::Input,
+    trait_path: &syn::Path,
+    needs_debug_bound: F,
+    field_bound: G,
+    input_bound: H,
+) -> syn::Generics
+where
+    F: Fn(&attr::Field) -> bool,
+    G: Fn(&attr::Field) -> Option<&[syn::WherePredicate]>,
+    H: Fn(&attr::Input) -> Option<&[syn::WherePredicate]>,
+{
+    let generics = bound::without_defaults(item.generics);
+    let generics = bound::with_where_predicates_from_fields(item, &generics, field_bound);
+
+    match input_bound(&item.attrs) {
+        Some(predicates) => bound::with_where_predicates(&generics, predicates),
+        None => bound::with_bound(item, &generics, needs_debug_bound, trait_path),
+    }
+}
+
+/// Construct a name for the inner type parameter that can't collide with any
+/// type parameters of the item. This is achieved by starting with a base and
+/// then concatenating the names of all other type parameters.
+pub fn hygienic_type_parameter(item: &ast::Input, base: &str) -> syn::Ident {
+    let mut typaram = String::with_capacity(150);
+    typaram.push_str(base);
+    let typaram = item.generics.type_params().fold(typaram, |mut acc, ty| {
+        acc.push_str(&format!("{}", &ty.ident));
+        acc
+    });
+
+    syn::Ident::new(&typaram, proc_macro2::Span::call_site())
+}