From 3b58d1c799f5c2da75a58ba1ca6c9c49fbb5ca7c Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Thu, 22 Apr 2021 17:37:36 -0700
Subject: [PATCH] Move empty enum check to before filling in variants

---
 macro/src/clang.rs | 21 ++++++++++++++++++---
 syntax/check.rs    |  8 --------
 2 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/macro/src/clang.rs b/macro/src/clang.rs
index a2e34255..23ea8ad2 100644
--- a/macro/src/clang.rs
+++ b/macro/src/clang.rs
@@ -2,8 +2,8 @@ use crate::syntax::attrs::OtherAttrs;
 use crate::syntax::namespace::Namespace;
 use crate::syntax::report::Errors;
 use crate::syntax::{Api, Discriminant, Doc, Enum, ForeignName, Pair, Variant};
-use proc_macro2::Ident;
-use quote::format_ident;
+use proc_macro2::{Delimiter, Group, Ident, TokenStream};
+use quote::{format_ident, quote};
 use serde::Deserialize;
 use std::env;
 use std::fs;
@@ -49,7 +49,15 @@ pub fn load(cx: &mut Errors, apis: &mut [Api]) {
     for api in apis {
         if let Api::Enum(enm) = api {
             if enm.variants_from_header {
-                variants_from_header.push(enm);
+                if enm.variants.is_empty() {
+                    variants_from_header.push(enm);
+                } else {
+                    let span = span_for_enum_error(enm);
+                    cx.error(
+                        span,
+                        "enum with #![variants_from_header] must be written with no explicit variants",
+                    );
+                }
             }
         }
     }
@@ -237,3 +245,10 @@ fn discriminant_value(mut clang: &[Node]) -> ParsedDiscriminant {
         }
     }
 }
+
+fn span_for_enum_error(enm: &Enum) -> TokenStream {
+    let enum_token = enm.enum_token;
+    let mut brace_token = Group::new(Delimiter::Brace, TokenStream::new());
+    brace_token.set_span(enm.brace_token.span);
+    quote!(#enum_token #brace_token)
+}
diff --git a/syntax/check.rs b/syntax/check.rs
index 2c383370..38be4b64 100644
--- a/syntax/check.rs
+++ b/syntax/check.rs
@@ -357,14 +357,6 @@ fn check_api_enum(cx: &mut Check, enm: &Enum) {
         );
     }
 
-    if enm.variants_from_header && !enm.variants.is_empty() {
-        let span = span_for_enum_error(enm);
-        cx.error(
-            span,
-            "enum with #![variants_from_header] must be written with no explicit variants",
-        );
-    }
-
     for derive in &enm.derives {
         if derive.what == Trait::Default || derive.what == Trait::ExternType {
             let msg = format!("derive({}) on shared enum is not supported", derive);