1 files changed, 63 insertions, 0 deletions
diff --git a/macro/src/generics.rs b/macro/src/generics.rs
new file mode 100644
index 00000000..3de0330b
--- /dev/null
+++ b/macro/src/generics.rs
@@ -0,0 +1,63 @@
+use crate::syntax::instantiate::NamedImplKey;
+use crate::syntax::resolve::Resolution;
+use crate::syntax::Impl;
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use syn::Token;
+
+pub struct ImplGenerics<'a> {
+    explicit_impl: Option<&'a Impl>,
+    resolve: Resolution<'a>,
+}
+
+pub struct TyGenerics<'a> {
+    key: NamedImplKey<'a>,
+    explicit_impl: Option<&'a Impl>,
+    resolve: Resolution<'a>,
+}
+
+pub fn split_for_impl<'a>(
+    key: NamedImplKey<'a>,
+    explicit_impl: Option<&'a Impl>,
+    resolve: Resolution<'a>,
+) -> (ImplGenerics<'a>, TyGenerics<'a>) {
+    let impl_generics = ImplGenerics {
+        explicit_impl,
+        resolve,
+    };
+    let ty_generics = TyGenerics {
+        key,
+        explicit_impl,
+        resolve,
+    };
+    (impl_generics, ty_generics)
+}
+
+impl<'a> ToTokens for ImplGenerics<'a> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        if let Some(imp) = self.explicit_impl {
+            imp.impl_generics.to_tokens(tokens);
+        } else {
+            self.resolve.generics.to_tokens(tokens);
+        }
+    }
+}
+
+impl<'a> ToTokens for TyGenerics<'a> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        if let Some(imp) = self.explicit_impl {
+            imp.ty_generics.to_tokens(tokens);
+        } else if !self.resolve.generics.lifetimes.is_empty() {
+            let span = self.key.rust.span();
+            self.key
+                .lt_token
+                .unwrap_or_else(|| Token![<](span))
+                .to_tokens(tokens);
+            self.resolve.generics.lifetimes.to_tokens(tokens);
+            self.key
+                .gt_token
+                .unwrap_or_else(|| Token![>](span))
+                .to_tokens(tokens);
+        }
+    }
+}