From f84d081a7e705da1f3e920801319424b53cfd8b0 Mon Sep 17 00:00:00 2001
From: Jeffrey Seyfried <jeffrey.seyfried@gmail.com>
Date: Tue, 6 Sep 2016 09:47:35 +0000
Subject: [PATCH] Avoid instaiblity errors in code generated by
 `syntax_ext::deriving::call_intrinsic()`.

---
 src/libsyntax_ext/deriving/mod.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 5582166c12e9..fcbce3638908 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -338,10 +338,19 @@ fn hygienic_type_parameter(item: &Annotatable, base: &str) -> String {
 
 /// Constructs an expression that calls an intrinsic
 fn call_intrinsic(cx: &ExtCtxt,
-                  span: Span,
+                  mut span: Span,
                   intrinsic: &str,
                   args: Vec<P<ast::Expr>>)
                   -> P<ast::Expr> {
+    span.expn_id = cx.codemap().record_expansion(codemap::ExpnInfo {
+        call_site: span,
+        callee: codemap::NameAndSpan {
+            format: codemap::MacroAttribute(intern("derive")),
+            span: Some(span),
+            allow_internal_unstable: true,
+        },
+    });
+
     let path = cx.std_path(&["intrinsics", intrinsic]);
     let call = cx.expr_call_global(span, path, args);