From 37d103f3cfb7be39a1a7d4d1b6d289601d59bfdb Mon Sep 17 00:00:00 2001
From: b-naber <bn@client-141-23-143-226.wlan.tu-berlin.de>
Date: Thu, 19 Nov 2020 18:32:52 +0100
Subject: [PATCH] insert span_fatal call in ast lowering to indicate that
 generic arguments in AssocTyConstraints haven't been fully implemented

---
 compiler/rustc_ast_lowering/src/lib.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index d93655e59050..0fe4259424d0 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1038,6 +1038,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ) -> hir::TypeBinding<'hir> {
         debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
 
+        if let Some(ref gen_args) = constraint.gen_args {
+            self.sess.span_fatal(
+                gen_args.span(),
+                "generic associated types in trait paths are currently not implemented",
+            );
+        }
+
         let kind = match constraint.kind {
             AssocTyConstraintKind::Equality { ref ty } => {
                 hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }