fix(evaluator): update lazy scope cache when variable is reassigned (#2075)

fix(evaluator): update lazy scope cache when variable is reassigned (fixes #2074)

When a variable is reassigned with a new ValueRef (for example, via |=
which creates a new value via deep_copy), force update the lazy scope
cache to avoid stale references in subsequent subscript assignments.

Signed-off-by: John Gardiner Myers <jgmyers@proofpoint.com>

Author: johngmyers

crates/evaluator/src/lazy.rs

@@ -389,4 +389,18 @@ impl<'ctx> Evaluator<'ctx> {
             scope.cache.insert(key.to_string(), value.clone());
         }
     }
+
+    /// Force update the lazy scope cache with a new value.
+    /// This is used when a variable is reassigned with a new ValueRef
+    /// (for example, via |= which creates a new value via deep_copy)
+    /// to avoid stale references in subsequent subscript assignments.
+    #[inline]
+    pub(crate) fn update_lazy_scope_cache(&self, pkgpath: &str, key: &str, value: &ValueRef) {
+        let mut lazy_scopes = self.lazy_scopes.borrow_mut();
+        if let Some(scope) = lazy_scopes.get_mut(pkgpath) {
+            if scope.cache.contains_key(key) {
+                scope.cache.insert(key.to_string(), value.clone());
+            }
+        }
+    }
 }

crates/evaluator/src/scope.rs

@@ -330,7 +330,10 @@ impl<'ctx> Evaluator<'ctx> {
             if variables.get(&name.to_string()).is_some() {
                 variables.insert(name.to_string(), value.clone());
                 if save_lazy_scope {
-                    self.set_value_to_lazy_scope(&current_pkgpath, name, &value)
+                    self.set_value_to_lazy_scope(&current_pkgpath, name, &value);
+                    // Also force update the cache to avoid stale references when
+                    // the variable is reassigned with a new value (for example, via |=)
+                    self.update_lazy_scope_cache(&current_pkgpath, name, &value);
                 }
                 existed = true;
             }

tests/grammar/assign/aug_assign_subscript_0/main.k

@@ -0,0 +1,8 @@
+# Test for issue #2074: augmented assignment followed by subscript assignment
+# in if block caused the subscript assignment to be silently ignored.
+
+_map = {}
+if True:
+    _map |= {a: 1}
+    _map["b"] = 2
+result = _map

tests/grammar/assign/aug_assign_subscript_0/stdout.golden

@@ -0,0 +1,3 @@
+result:
+  a: 1
+  b: 2

tests/grammar/assign/aug_assign_subscript_1/main.k

@@ -0,0 +1,6 @@
+# Test for issue #2074: binary | reassignment followed by subscript assignment in if block
+_map = {}
+if True:
+    _map = _map | {a: 1}
+    _map["b"] = 2
+result = _map

tests/grammar/assign/aug_assign_subscript_1/stdout.golden

@@ -0,0 +1,3 @@
+result:
+  a: 1
+  b: 2

tests/grammar/assign/aug_assign_subscript_2/main.k

@@ -0,0 +1,7 @@
+# Test for issue #2074: multiple subscript assignments after |= in if block
+_map = {}
+if True:
+    _map |= {a: 1}
+    _map["b"] = 2
+    _map["c"] = 3
+result = _map

tests/grammar/assign/aug_assign_subscript_2/stdout.golden

@@ -0,0 +1,4 @@
+result:
+  a: 1
+  b: 2
+  c: 3

tests/grammar/assign/aug_assign_subscript_3/main.k

@@ -0,0 +1,6 @@
+# Test for issue #2074: |= on list followed by subscript assignment in if block
+_list = []
+if True:
+    _list |= [1]
+    _list[0] = 99
+result = _list

tests/grammar/assign/aug_assign_subscript_3/stdout.golden

@@ -0,0 +1,2 @@
+result:
+- 99