[gcc r17-5137] gccrs: handle lifetimes properly on trait items

[Marc Poulhies via Gcc-cvs]

https://gcc.gnu.org/g:d9e02c1a7dcc4817f9ca76a579ce4a1c821c766f

commit r17-5137-gd9e02c1a7dcc4817f9ca76a579ce4a1c821c766f
Author: Philip Herron <herron.phi...@googlemail.com>
Date:   Tue Sep 15 12:02:11 2026 +0100

    gccrs: handle lifetimes properly on trait items
    
    The patch here means we keep a fresh lifetime scope when resolving each
    trait item when generics are used.
    
    Fixes Rust-GCC/gccrs#4885
    
    gcc/rust/ChangeLog:
    
            * typecheck/rust-hir-trait-resolve.cc 
(TraitItemReference::resolve_item): track lifetimes
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/issues/issue-4885.rs: New test.
    
    Signed-off-by: Philip Herron <herron.phi...@googlemail.com>

Diff:
---
 gcc/rust/typecheck/rust-hir-trait-resolve.cc    | 14 +++++++-
 gcc/testsuite/rust/compile/issues/issue-4885.rs | 43 +++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/gcc/rust/typecheck/rust-hir-trait-resolve.cc 
b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
index 502d0e8f7d8d..c80899979c23 100644
--- a/gcc/rust/typecheck/rust-hir-trait-resolve.cc
+++ b/gcc/rust/typecheck/rust-hir-trait-resolve.cc
@@ -472,10 +472,22 @@ void
 TraitItemReference::resolve_item (const TraitReference *tref,
                                  HIR::TraitItemType &type)
 {
+  auto lifetime_pin = context->push_clean_lifetime_resolver ();
+  for (auto &param : tref->get_hir_trait_ref ()->get_generic_params ())
+    {
+      if (param->get_kind () == HIR::GenericParam::GenericKind::LIFETIME)
+       {
+         auto &lifetime_param = static_cast<HIR::LifetimeParam &> (*param);
+         context->intern_and_insert_lifetime (lifetime_param.get_lifetime ());
+       }
+    }
+
   auto substitutions = inherited_substitutions;
+  tl::optional<TypeCheckContext::LifetimeResolverGuard> binder_pin;
   if (type.has_generics ())
     {
-      auto binder_pin = context->push_lifetime_binder ();
+      binder_pin.emplace (*context,
+                         TypeCheckContext::LifetimeResolverGuard::BINDER);
       TypeCheckBase::ResolveGenericParams (HIR::Item::ItemKind::TypeAlias,
                                           type.get_locus (),
                                           type.get_generic_params (),
diff --git a/gcc/testsuite/rust/compile/issues/issue-4885.rs 
b/gcc/testsuite/rust/compile/issues/issue-4885.rs
new file mode 100644
index 000000000000..b02bc60a9544
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issues/issue-4885.rs
@@ -0,0 +1,43 @@
+// { dg-do compile }
+// { dg-options "-w" }
+
+#![feature(no_core, lang_items)]
+#![no_core]
+
+#[lang = "sized"]
+pub trait Sized {}
+
+pub unsafe trait Searcher<'a> {
+    fn haystack(&self) -> &'a ();
+}
+
+pub trait Pattern<'a>: Sized {
+    type Searcher: Searcher<'a>;
+}
+
+pub trait MultiCharEq {}
+
+struct MultiCharEqPattern<C: MultiCharEq>(C);
+
+struct MultiCharEqSearcher<'a, C: MultiCharEq> {
+    marker: &'a (),
+    c: C,
+}
+
+impl<'a, C: MultiCharEq> Pattern<'a> for MultiCharEqPattern<C> {
+    type Searcher = MultiCharEqSearcher<'a, C>;
+}
+
+unsafe impl<'a, C: MultiCharEq> Searcher<'a> for MultiCharEqSearcher<'a, C> {
+    fn haystack(&self) -> &'a () {
+        self.marker
+    }
+}
+
+impl<'x> MultiCharEq for &'x [i32] {}
+
+pub struct CharSliceSearcher<'a, 'b>(<MultiCharEqPattern<&'b [i32]> as 
Pattern<'a>>::Searcher);
+
+fn main() -> i32 {
+    0
+}