From 890083d64fc0ee2ccf298be549827e9c0a975628 Mon Sep 17 00:00:00 2001
From: Bryan Henry <bryanhenry@google.com>
Date: Sun, 13 Sep 2020 10:34:31 -0700
Subject: [PATCH] Preserve docs on aliases

---
 macro/src/expand.rs | 2 ++
 syntax/mod.rs       | 1 +
 syntax/parse.rs     | 3 ++-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/macro/src/expand.rs b/macro/src/expand.rs
index 955ad5f5..c35044b3 100644
--- a/macro/src/expand.rs
+++ b/macro/src/expand.rs
@@ -657,9 +657,11 @@ fn expand_rust_function_shim_impl(
 }
 
 fn expand_type_alias(alias: &TypeAlias) -> TokenStream {
+    let doc = &alias.doc;
     let ident = &alias.ident;
     let ty = &alias.ty;
     quote! {
+        #doc
         pub type #ident = #ty;
     }
 }
diff --git a/syntax/mod.rs b/syntax/mod.rs
index f52a582c..8ef3c8b9 100644
--- a/syntax/mod.rs
+++ b/syntax/mod.rs
@@ -79,6 +79,7 @@ pub struct ExternFn {
 }
 
 pub struct TypeAlias {
+    pub doc: Doc,
     pub type_token: Token![type],
     pub ident: Ident,
     pub eq_token: Token![=],
diff --git a/syntax/parse.rs b/syntax/parse.rs
index 3ac53047..c1c565fd 100644
--- a/syntax/parse.rs
+++ b/syntax/parse.rs
@@ -396,9 +396,10 @@ fn parse_extern_verbatim(cx: &mut Errors, tokens: &TokenStream, lang: Lang) -> R
         let eq_token: Token![=] = input.parse()?;
         let ty: RustType = input.parse()?;
         let semi_token: Token![;] = input.parse()?;
-        attrs::parse_doc(cx, &attrs);
+        let doc = attrs::parse_doc(cx, &attrs);
 
         Ok(TypeAlias {
+            doc,
             type_token,
             ident,
             eq_token,