From 1429964a9cb2f9c3be3ca1fc903fcda4ff9f74f3 Mon Sep 17 00:00:00 2001
From: dave <dave@dmetwo.org>
Date: Wed, 15 Nov 2023 12:28:27 -0600
Subject: [PATCH] Fix optional trait parsing

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check-item.cc (TypeCheckItem::visit): Check for ?Trait in visitor

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2725.rs: New test.

Signed-off-by: Dave Evans <dave@dmetwo.org>
---
 gcc/rust/typecheck/rust-hir-type-check-item.cc | 18 ++++++++++++++++++
 gcc/testsuite/rust/compile/issue-2725.rs       |  3 +++
 2 files changed, 21 insertions(+)
 create mode 100644 gcc/testsuite/rust/compile/issue-2725.rs

diff --git a/gcc/rust/typecheck/rust-hir-type-check-item.cc b/gcc/rust/typecheck/rust-hir-type-check-item.cc
index 87313af9a587..802d5845e171 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-item.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-item.cc
@@ -518,6 +518,24 @@ TypeCheckItem::visit (HIR::Module &module)
 void
 TypeCheckItem::visit (HIR::Trait &trait)
 {
+  if (trait.has_type_param_bounds ())
+    {
+      for (auto &tp_bound : trait.get_type_param_bounds ())
+        {
+          if (tp_bound.get ()->get_bound_type ()
+              == HIR::TypeParamBound::BoundType::TRAITBOUND)
+            {
+              HIR::TraitBound &tb
+                  = static_cast<HIR::TraitBound &> (*tp_bound.get ());
+              if (tb.get_polarity () == BoundPolarity::AntiBound)
+                {
+                  rust_error_at (tb.get_locus (),
+                                 "%<?Trait%> is not permitted in supertraits");
+                }
+            }
+        }
+    }
+
   TraitReference *trait_ref = TraitResolver::Resolve (trait);
   if (trait_ref->is_error ())
     {
diff --git a/gcc/testsuite/rust/compile/issue-2725.rs b/gcc/testsuite/rust/compile/issue-2725.rs
new file mode 100644
index 000000000000..a344bc8d4641
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-2725.rs
@@ -0,0 +1,3 @@
+#[lang = "sized"]
+pub trait Sized {}
+trait Trait: ?Sized {} // { dg-error ".?Trait. is not permitted in supertraits" }