[gcc r17-4344] gccrs: walk the binding generic arguments for unconstrained checks

[Arthur Cohen via Gcc-cvs]

https://gcc.gnu.org/g:35f841b5a84fafb934550d964a258f626d19d013

commit r17-4344-g35f841b5a84fafb934550d964a258f626d19d013
Author: Philip Herron <herron.phi...@googlemail.com>
Date:   Tue Sep 8 11:22:27 2026 +0100

    gccrs: walk the binding generic arguments for unconstrained checks
    
    Fixes Rust-GCC/gccrs#4862
    Fixes Rust-GCC/gccrs#4863
    
    gcc/rust/ChangeLog:
    
            * typecheck/rust-hir-type-check-base.cc: walk type bindings
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/issue-4862.rs: New test.
            * rust/compile/issue-4863.rs: New test.
    
    Signed-off-by: Philip Herron <herron.phi...@googlemail.com>

Diff:
---
 gcc/rust/typecheck/rust-hir-type-check-base.cc | 11 +++++++++++
 gcc/testsuite/rust/compile/issue-4862.rs       | 11 +++++++++++
 gcc/testsuite/rust/compile/issue-4863.rs       | 19 +++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/gcc/rust/typecheck/rust-hir-type-check-base.cc 
b/gcc/rust/typecheck/rust-hir-type-check-base.cc
index b53232a57e52..faa6d5ea98ee 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-base.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-base.cc
@@ -197,6 +197,17 @@ TypeCheckBase::check_for_unconstrained (
   walk_types_to_constrain (constrained_symbols, constraint_b);
   walk_type_to_constrain (constrained_symbols, *reference);
 
+  for (const auto &param : params_to_constrain)
+    {
+      auto *ty = param.get_param_ty ();
+      for (const auto &bound : ty->get_specified_bounds ())
+       {
+         const auto &args = bound.get_substitution_arguments ();
+         for (const auto &binding : args.get_binding_args ())
+           walk_type_to_constrain (constrained_symbols, *binding.second);
+       }
+    }
+
   // check for unconstrained
   bool unconstrained = false;
   for (auto &sym : symbols_to_constrain)
diff --git a/gcc/testsuite/rust/compile/issue-4862.rs 
b/gcc/testsuite/rust/compile/issue-4862.rs
new file mode 100644
index 000000000000..17d9c3ca9775
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4862.rs
@@ -0,0 +1,11 @@
+#![feature(no_core, lang_items)]
+#![no_core]
+#[lang = "sized"]
+pub trait Sized {}
+trait Iterator {
+    type Item;
+}
+pub struct Wrapper<I>(I);
+impl<T, I: Iterator<Item = T>> Iterator for Wrapper<I> {
+    type Item = T;
+}
diff --git a/gcc/testsuite/rust/compile/issue-4863.rs 
b/gcc/testsuite/rust/compile/issue-4863.rs
new file mode 100644
index 000000000000..2c7592790c43
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4863.rs
@@ -0,0 +1,19 @@
+#![feature(no_core, lang_items)]
+#![no_core]
+#[lang = "sized"]
+pub trait Sized {}
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    #[lang = "fn_once_output"]
+    type Output;
+    extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
+}
+trait Iterator {
+    type Item;
+}
+pub struct OnceWith<F> {
+    pub f: F,
+}
+impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
+    type Item = A;
+}