[gcc r16-2981] gccrs: Fix ICE during const eval of const capacity

[Arthur Cohen via Gcc-cvs]

https://gcc.gnu.org/g:948e4a63455c090afd491c7b669896d47ae08559

commit r16-2981-g948e4a63455c090afd491c7b669896d47ae08559
Author: Philip Herron <herron.phi...@googlemail.com>
Date:   Thu Jul 31 21:46:42 2025 +0100

    gccrs: Fix ICE during const eval of const capacity
    
    We assert that struct expressions during code-gen must be of TyTy::ADTType
    but we can simply just check for this and return error_mark_node to make
    this safe.
    
    Fixes Rust-GCC#3960
    
    gcc/rust/ChangeLog:
    
            * backend/rust-compile-expr.cc (CompileExpr::visit): check for 
ADTType instead of assert
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/issue-3960.rs: New test.
    
    Signed-off-by: Philip Herron <herron.phi...@googlemail.com>

Diff:
---
 gcc/rust/backend/rust-compile-expr.cc    | 2 ++
 gcc/testsuite/rust/compile/issue-3960.rs | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/gcc/rust/backend/rust-compile-expr.cc 
b/gcc/rust/backend/rust-compile-expr.cc
index 547bb7c27a8e..8deb55ab77d6 100644
--- a/gcc/rust/backend/rust-compile-expr.cc
+++ b/gcc/rust/backend/rust-compile-expr.cc
@@ -490,6 +490,8 @@ CompileExpr::visit (HIR::StructExprStructFields 
&struct_expr)
       rust_error_at (struct_expr.get_locus (), "unknown type");
       return;
     }
+  if (!tyty->is<TyTy::ADTType> ())
+    return;
 
   // it must be an ADT
   rust_assert (tyty->get_kind () == TyTy::TypeKind::ADT);
diff --git a/gcc/testsuite/rust/compile/issue-3960.rs 
b/gcc/testsuite/rust/compile/issue-3960.rs
new file mode 100644
index 000000000000..57329f0d48aa
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-3960.rs
@@ -0,0 +1,7 @@
+fn main() {
+    struct G {
+        g: (),
+    }
+    let g = [0; G { g: () }];
+    // { dg-error "mismatched types, expected .usize. but got .G. .E0308." "" 
{ target *-*-* } .-1 }
+}