1 files changed, 96 insertions, 0 deletions
diff --git a/third_party/rust/darling/src/macros_public.rs b/third_party/rust/darling/src/macros_public.rs
new file mode 100644
index 0000000000..c264fcc2a8
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+++ b/third_party/rust/darling/src/macros_public.rs
@@ -0,0 +1,96 @@
+//! Macros that should be exported from both `darling_core` and `darling`.
+//! Note that these are **sym-linked** into the main code, and so cannot declare on items that are exported differently
+//! in `darling_core` vs. `darling`.
+
+/// Generator for `UsesTypeParam` impls that unions the used type parameters of the selected fields.
+///
+/// # Usage
+/// The macro takes the type implementing the trait as the first argument, then a comma-separated list of
+/// fields for the rest of its arguments.
+///
+/// The type of each passed-in field must implement `UsesTypeParams`, or the resulting code won't compile.
+///
+/// ```rust
+/// # extern crate syn;
+/// # use darling_core::uses_type_params;
+/// #
+/// struct MyField {
+///     ty: syn::Type,
+/// }
+///
+/// uses_type_params!(MyField, ty);
+///
+/// fn main() {
+///     // no test run
+/// }
+/// ```
+///
+/// `darling` cannot derive this trait automatically, as it doesn't know which information extracted from
+/// proc-macro input is meant to constitute "using" the type parameter, but crate consumers should
+/// implement it by hand or using the macro.
+#[macro_export]
+macro_rules! uses_type_params {
+    ($impl_type:ty, $accessor:ident) => {
+        impl $crate::usage::UsesTypeParams for $impl_type {
+            fn uses_type_params<'gen>(
+                &self,
+                options: &$crate::usage::Options,
+                type_set: &'gen $crate::usage::IdentSet
+            ) -> $crate::usage::IdentRefSet<'gen> {
+                self.$accessor.uses_type_params(options, type_set)
+            }
+        }
+    };
+    ($impl_type:ty, $first:ident, $($field:ident),+) => {
+        impl $crate::usage::UsesTypeParams for $impl_type {
+            fn uses_type_params<'gen>(
+                &self,
+                options: &$crate::usage::Options,
+                type_set: &'gen $crate::usage::IdentSet
+            ) -> $crate::usage::IdentRefSet<'gen> {
+                let mut hits = self.$first.uses_type_params(options, type_set);
+                $(
+                    hits.extend(self.$field.uses_type_params(options, type_set));
+                )*
+                hits
+            }
+        }
+    };
+}
+
+/// Generator for `UsesLifetimes` impls that unions the used lifetimes of the selected fields.
+///
+/// # Usage
+/// The macro takes the type implementing the trait as the first argument, then a comma-separated list of
+/// fields for the rest of its arguments.
+///
+/// The type of each passed-in field must implement `UsesLifetimes`, or the resulting code won't compile.
+#[macro_export]
+macro_rules! uses_lifetimes {
+    ($impl_type:ty, $accessor:ident) => {
+        impl $crate::usage::UsesLifetimes for $impl_type {
+            fn uses_lifetimes<'gen>(
+                &self,
+                options: &$crate::usage::Options,
+                type_set: &'gen $crate::usage::LifetimeSet
+            ) -> $crate::usage::LifetimeRefSet<'gen> {
+                self.$accessor.uses_lifetimes(options, type_set)
+            }
+        }
+    };
+    ($impl_type:ty, $first:ident, $($field:ident),+) => {
+        impl $crate::usage::UsesLifetimes for $impl_type {
+            fn uses_lifetimes<'gen>(
+                &self,
+                options: &$crate::usage::Options,
+                type_set: &'gen $crate::usage::LifetimeSet
+            ) -> $crate::usage::LifetimeRefSet<'gen> {
+                let mut hits = self.$first.uses_lifetimes(options, type_set);
+                $(
+                    hits.extend(self.$field.uses_lifetimes(options, type_set));
+                )*
+                hits
+            }
+        }
+    };
+}