Vendor dependencies

Let's see how I like this workflow.

vendor/cxxbridge-macro/src/generics.rs

@@ -0,0 +1,91 @@
+use crate::syntax::instantiate::NamedImplKey;
+use crate::syntax::resolve::Resolution;
+use crate::syntax::{Impl, Lifetimes};
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use syn::{Lifetime, 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);
+        }
+    }
+}
+
+pub struct UnderscoreLifetimes<'a> {
+    generics: &'a Lifetimes,
+}
+
+impl Lifetimes {
+    pub fn to_underscore_lifetimes(&self) -> UnderscoreLifetimes {
+        UnderscoreLifetimes { generics: self }
+    }
+}
+
+impl<'a> ToTokens for UnderscoreLifetimes<'a> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let Lifetimes {
+            lt_token,
+            lifetimes,
+            gt_token,
+        } = self.generics;
+        lt_token.to_tokens(tokens);
+        for pair in lifetimes.pairs() {
+            let (lifetime, punct) = pair.into_tuple();
+            let lifetime = Lifetime::new("'_", lifetime.span());
+            lifetime.to_tokens(tokens);
+            punct.to_tokens(tokens);
+        }
+        gt_token.to_tokens(tokens);
+    }
+}