test: Add RVM compiler testing to ACI tests (#509)

code fixes:
  - compiler: add `is_var_bound_in_current_scope` and use it in destructuring so
    only the innermost scope blocks rebinding while still catching duplicates
    within that block.
  - rvm: treat `not` over undefined operands as a successful negation to match
    interpreter semantics.

tests/aci:
   migrate YAML cases to `data.policy.rule` queries with `{x: …}`
  bindings, expand the harness to run interpreter plus RVM (with optional
  skipping), align results to the binding format, add readable timing output,
  and support a `--filter` flag for targeting cases.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/languages/rego/compiler/core.rs

@@ -140,6 +140,14 @@ impl<'a> Compiler<'a> {
         }
     }
 
+    /// Returns true when a variable is already bound in the innermost scope
+    pub fn is_var_bound_in_current_scope(&self, var_name: &str) -> bool {
+        self.scopes
+            .last()
+            .map(|scope| scope.bound_vars.contains_key(var_name))
+            .unwrap_or(false)
+    }
+
     /// Look up a variable in all scopes starting from innermost (like interpreter's lookup_local_var)
     pub fn lookup_local_var(&self, var_name: &str) -> Option<Register> {
         self.scopes

src/languages/rego/compiler/destructuring.rs

@@ -289,7 +289,7 @@ impl<'a> Compiler<'a> {
             return Ok(());
         }
 
-        if self.lookup_local_var(var_name).is_some() {
+        if self.is_var_bound_in_current_scope(var_name) {
             bail!("Variable '{var_name}' already defined in current scope");
         }
 

src/rvm/vm/dispatch.rs

@@ -299,7 +299,10 @@ impl RegoVM {
                 let operand_value = &self.registers[operand as usize];
 
                 if operand_value == &Value::Undefined {
-                    self.registers[dest as usize] = Value::Undefined;
+                    // In Rego, `not expr` succeeds when `expr` has no results.
+                    // When the operand evaluates to undefined we should treat it as
+                    // a successful negation instead of propagating undefined.
+                    self.registers[dest as usize] = Value::Bool(true);
                     return Ok(InstructionOutcome::Continue);
                 }