FIX: TRUE and FALSE can also be functions

Previously the engine was internally transforming TRUE() to TRUE

Note that the friendly giant implements this only for
compatibility reasons

base/src/test/test_true_false.rs

@@ -0,0 +1,25 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+
+#[test]
+fn true_false_arguments() {
+    let mut model = new_empty_model();
+    model._set("A1", "=TRUE( )");
+    model._set("A2", "=FALSE( )");
+    model._set("A3", "=TRUE( 4 )");
+    model._set("A4", "=FALSE( 4 )");
+
+    model.evaluate();
+
+    assert_eq!(model._get_text("A1"), *"TRUE");
+    assert_eq!(model._get_text("A2"), *"FALSE");
+
+    assert_eq!(model._get_formula("A1"), *"=TRUE()");
+    assert_eq!(model._get_formula("A2"), *"=FALSE()");
+
+    assert_eq!(model._get_text("A3"), *"#ERROR!");
+    assert_eq!(model._get_text("A4"), *"#ERROR!");
+    assert_eq!(model._get_formula("A3"), *"=TRUE(4)");
+    assert_eq!(model._get_formula("A4"), *"=FALSE(4)");
+}