FIX: presence checks for tuples with NULL values works now.

integration_tests/comparisons_test.ucg

@@ -179,3 +179,8 @@ assert {
     ok = NULL != "string",
     desc = "Strings are comparable to null",
 };
+
+assert {
+    ok = (foo in {foo = NULL}),
+    desc = "Null valued fields are still present in tuple",
+};

src/build/mod.rs

@@ -780,6 +780,7 @@ impl<'a> FileBuilder<'a> {
             Expression::Copy(_) => return self.eval_expr(right, scope),
             Expression::Call(_) => return self.eval_expr(right, scope),
             Expression::Simple(Value::Symbol(ref s)) => {
+                let scope = scope.clone().use_curr_val();
                 scope
                     .lookup_sym(s, true)
                     .ok_or(Box::new(error::BuildError::new(
@@ -789,6 +790,7 @@ impl<'a> FileBuilder<'a> {
                     )))
             }
             Expression::Simple(Value::Str(ref s)) => {
+                let scope = scope.clone().use_curr_val();
                 scope
                     .lookup_sym(s, false)
                     .ok_or(Box::new(error::BuildError::new(
@@ -904,6 +906,7 @@ impl<'a> FileBuilder<'a> {
     fn eval_binary(&self, def: &BinaryOpDef, scope: &Scope) -> Result<Rc<Val>, Box<dyn Error>> {
         let kind = &def.kind;
         if let &BinaryExprType::IN = kind {
+            // TODO Should we support this operation on strings too?
             return self.do_element_check(&def.left, &def.right, scope);
         };
         let left = self.eval_expr(&def.left, scope)?;

src/build/scope.rs

@@ -56,6 +56,11 @@ impl Scope {
         }
     }
 
+    pub fn use_curr_val(mut self) -> Self {
+        self.search_curr_val = true;
+        self
+    }
+
     /// Spawn a child scope based on the current scope but without the current
     /// val set.
     pub fn spawn_child(&self) -> Self {