Handlng zero sized locals. (#4414)

crates/cairo-lang-sierra-generator/src/local_variables.rs

@@ -13,7 +13,7 @@ use cairo_lang_utils::ordered_hash_map::OrderedHashMap;
 use cairo_lang_utils::ordered_hash_set::OrderedHashSet;
 use cairo_lang_utils::unordered_hash_map::UnorderedHashMap;
 use cairo_lang_utils::unordered_hash_set::UnorderedHashSet;
-use itertools::{zip_eq, Itertools};
+use itertools::{chain, zip_eq, Itertools};
 use lowering::borrow_check::analysis::{Analyzer, BackAnalysis, StatementLocation};
 use lowering::borrow_check::demand::DemandReporter;
 use lowering::borrow_check::Demand;
@@ -49,7 +49,15 @@ pub fn analyze_ap_changes(
         lowered_function,
         used_after_revoke: Default::default(),
         block_callers: Default::default(),
-        non_ap_based: UnorderedHashSet::from_iter(lowered_function.parameters.iter().cloned()),
+        non_ap_based: UnorderedHashSet::from_iter(chain!(
+            // Parameters are not ap based.
+            lowered_function.parameters.iter().cloned(),
+            // All empty variables are not ap based.
+            lowered_function.variables.iter().filter_map(|(id, var)| {
+                let info = db.get_type_info(db.get_concrete_type_id(var.ty).ok()?).ok()?;
+                if info.zero_sized { Some(id) } else { None }
+            })
+        )),
         aliases: Default::default(),
         partial_param_parents: Default::default(),
     };

tests/bug_samples/lib.cairo

@@ -40,3 +40,4 @@ mod inconsistent_gas;
 mod partial_param_local;
 mod loop_break_in_match;
 mod generic_cycles;
+mod zero_sized_locals;

tests/bug_samples/zero_sized_locals.cairo

@@ -0,0 +1,22 @@
+#[derive(Drop)]
+struct ZeroSized {}
+
+#[inline(never)]
+fn use_zero_sized(ref value: ZeroSized) -> felt252 {
+    0
+}
+
+fn foo(ref value: ZeroSized, array_with_data: Array<felt252>) {
+    if 1 == 0 {
+        use_zero_sized(ref value);
+    }
+    // Unkown ap change tracking, while not using `value`.
+    let mut data_span = array_with_data.span();
+    let a: Option<Array<Array<felt252>>> = Serde::deserialize(ref data_span);
+}
+
+#[test]
+fn call_foo() {
+    let mut value = ZeroSized {};
+    foo(ref value, array![0]);
+}