[gcc r17-2253] gccrs: Fix crash when resolving invalid enum item

https://gcc.gnu.org/g:79e5f790e70a3a090cf0b43d1bac4a42c18dc4f0

commit r17-2253-g79e5f790e70a3a090cf0b43d1bac4a42c18dc4f0
Author: Philip Herron <[email protected]>
Date:   Mon Jun 29 12:01:59 2026 +0100

    gccrs: Fix crash when resolving invalid enum item
    
    Fixes Rust-GCC#1617
    
    gcc/rust/ChangeLog:
    
            * typecheck/rust-hir-type-check-item.cc (TypeCheckItem::visit): check valid
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/issue-4617.rs: New test.
    
    Signed-off-by: Philip Herron <[email protected]>

Diff:
---
 gcc/rust/typecheck/rust-hir-type-check-item.cc | 8 +++++---
 gcc/testsuite/rust/compile/issue-4617.rs       | 8 ++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/gcc/rust/typecheck/rust-hir-type-check-item.cc b/gcc/rust/typecheck/rust-hir-type-check-item.cc
index 055ce2b2832b..065615a23b0a 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-item.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-item.cc
@@ -421,9 +421,11 @@ TypeCheckItem::visit (HIR::Enum &enum_decl)
     {
       TyTy::VariantDef *field_type
 	= TypeCheckEnumItem::Resolve (*variant, discriminant_value);
-
-      discriminant_value++;
-      variants.push_back (field_type);
+      if (field_type)
+	{
+	  discriminant_value++;
+	  variants.push_back (field_type);
+	}
     }
 
   // Check for zero-variant enum compatibility
diff --git a/gcc/testsuite/rust/compile/issue-4617.rs b/gcc/testsuite/rust/compile/issue-4617.rs
new file mode 100644
index 000000000000..202310071d1b
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4617.rs
@@ -0,0 +1,8 @@
+#![feature(no_core)]
+#![no_core]
+
+struct Apple;
+
+enum Delicious {
+    ApplePie = Apple::PIE, // { dg-error "failed to resolve path segment using an impl Probe" }
+}