Cherry pick const folding fix. (#8454)

Author: gilbens-starkware

crates/cairo-lang-lowering/src/optimizations/const_folding.rs

@@ -965,54 +965,62 @@ impl<'a> ConstFoldingContext<'a> {
             let index = self.as_int(info.inputs[1].var_id)?.to_usize()?;
             if let Some(VarInfo::Snapshot(arr_info)) = self.var_info.get(&info.inputs[0].var_id) {
                 if let VarInfo::Array(infos) = arr_info.as_ref() {
-                    if let Some(Some(output_var_info)) = infos.get(index) {
-                        let arm = &info.arms[0];
-                        let output_var_info = output_var_info.clone();
-                        let box_info =
-                            VarInfo::Box(VarInfo::Snapshot(output_var_info.clone().into()).into());
-                        self.var_info.insert(arm.var_ids[0], box_info);
-                        if let VarInfo::Const(value) = output_var_info {
-                            let value_ty = value.ty(db).ok()?;
-                            let value_box_ty = corelib::core_box_ty(db, value_ty);
-                            let location = info.location;
-                            let boxed_var =
-                                Variable::with_default_context(db, value_box_ty, location);
-                            let boxed = self.variables.alloc(boxed_var.clone());
-                            let unused_boxed = self.variables.alloc(boxed_var);
-                            let snapped = self.variables.alloc(Variable::with_default_context(
-                                db,
-                                TypeLongId::Snapshot(value_box_ty).intern(db),
-                                location,
-                            ));
+                    match infos.get(index) {
+                        Some(Some(output_var_info)) => {
+                            let arm = &info.arms[0];
+                            let output_var_info = output_var_info.clone();
+                            let box_info = VarInfo::Box(
+                                VarInfo::Snapshot(output_var_info.clone().into()).into(),
+                            );
+                            self.var_info.insert(arm.var_ids[0], box_info);
+                            if let VarInfo::Const(value) = output_var_info {
+                                let value_ty = value.ty(db).ok()?;
+                                let value_box_ty = corelib::core_box_ty(db, value_ty);
+                                let location = info.location;
+                                let boxed_var =
+                                    Variable::with_default_context(db, value_box_ty, location);
+                                let boxed = self.variables.alloc(boxed_var.clone());
+                                let unused_boxed = self.variables.alloc(boxed_var);
+                                let snapped = self.variables.alloc(Variable::with_default_context(
+                                    db,
+                                    TypeLongId::Snapshot(value_box_ty).intern(db),
+                                    location,
+                                ));
+                                return Some((
+                                    vec![
+                                        Statement::Const(StatementConst {
+                                            value: ConstValue::Boxed(value.into()),
+                                            output: boxed,
+                                        }),
+                                        Statement::Snapshot(StatementSnapshot {
+                                            input: VarUsage { var_id: boxed, location },
+                                            outputs: [unused_boxed, snapped],
+                                        }),
+                                        Statement::Call(StatementCall {
+                                            function: self
+                                                .box_forward_snapshot
+                                                .concretize(
+                                                    db,
+                                                    vec![GenericArgumentId::Type(value_ty)],
+                                                )
+                                                .lowered(db),
+                                            inputs: vec![VarUsage { var_id: snapped, location }],
+                                            with_coupon: false,
+                                            outputs: vec![arm.var_ids[0]],
+                                            location: info.location,
+                                        }),
+                                    ],
+                                    BlockEnd::Goto(arm.block_id, Default::default()),
+                                ));
+                            }
+                        }
+                        None => {
                             return Some((
-                                vec![
-                                    Statement::Const(StatementConst {
-                                        value: ConstValue::Boxed(value.into()),
-                                        output: boxed,
-                                    }),
-                                    Statement::Snapshot(StatementSnapshot {
-                                        input: VarUsage { var_id: boxed, location },
-                                        outputs: [unused_boxed, snapped],
-                                    }),
-                                    Statement::Call(StatementCall {
-                                        function: self
-                                            .box_forward_snapshot
-                                            .concretize(db, vec![GenericArgumentId::Type(value_ty)])
-                                            .lowered(db),
-                                        inputs: vec![VarUsage { var_id: snapped, location }],
-                                        with_coupon: false,
-                                        outputs: vec![arm.var_ids[0]],
-                                        location: info.location,
-                                    }),
-                                ],
-                                BlockEnd::Goto(arm.block_id, Default::default()),
+                                vec![],
+                                BlockEnd::Goto(info.arms[1].block_id, Default::default()),
                             ));
                         }
-                    } else {
-                        return Some((
-                            vec![],
-                            BlockEnd::Goto(info.arms[1].block_id, Default::default()),
-                        ));
+                        Some(None) => {}
                     }
                 }
             }