gccrs: Fix ICE in array ref constexpr

Since 898d55ad7e2 was fixed to remove the VIEW_CONVERT_EXPR from
array expressions we can now turn on the array element access
const expr.

Fixes Rust-GCC#3563

gcc/rust/ChangeLog:

	* backend/rust-constexpr.cc (eval_store_expression): turn this back on

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3563.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/gcc/testsuite/rust/compile/issue-3563.rs b/gcc/testsuite/rust/compile/issue-3563.rs
new file mode 100644
index 0000000..46e7624
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-3563.rs
@@ -0,0 +1,17 @@
+pub struct AA {
+    pub data: [u8; 10],
+}
+
+impl AA {
+    pub const fn new() -> Self {
+        let mut res: AA = AA { data: [0; 10] };
+        res.data[0] = 5;
+        res
+    }
+}
+
+static mut BB: AA = AA::new();
+
+fn main() {
+    let _ptr = unsafe { &mut BB };
+}