[gcc r15-8206] gccrs: Fix optional trait parsing

[Arthur Cohen via Gcc-cvs]

https://gcc.gnu.org/g:a3e002aa61e5d2effe7de143604431299114a0ae

commit r15-8206-ga3e002aa61e5d2effe7de143604431299114a0ae
Author: dave <d...@dmetwo.org>
Date:   Wed Nov 15 12:28:27 2023 -0600

    gccrs: 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 <d...@dmetwo.org>

Diff:
---
 gcc/rust/typecheck/rust-hir-type-check-item.cc | 18 ++++++++++++++++++
 gcc/testsuite/rust/compile/issue-2725.rs       |  3 +++
 2 files changed, 21 insertions(+)

diff --git a/gcc/rust/typecheck/rust-hir-type-check-item.cc 
b/gcc/rust/typecheck/rust-hir-type-check-item.cc
index 317d16700aae..68e206924bbd 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-item.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-item.cc
@@ -609,6 +609,24 @@ 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" }