Implement invert()

Author: J-Fields

src/vimscript/expression/evaluate.ts

@@ -1011,7 +1011,13 @@ export class EvaluationContext {
       // TODO: indexof()
       // TODO: input()/inputlist()
       // TODO: insert()
-      // TODO: invert()
+      case 'invert': {
+        const [x] = getArgs(1);
+        // eslint-disable-next-line no-bitwise
+        return int(~toInt(x!));
+      }
+      // TODO: isabsolutepath()
+      // TODO: isdirectory()
       case 'isinf': {
         const [x] = getArgs(1);
         const _x = toFloat(x!);

test/vimscript/expression.test.ts

@@ -673,6 +673,10 @@ suite('Vimscript expressions', () => {
       exprTest('index(["A","C","D","C"], "C", 5)', { value: int(-1) });
     });
 
+    suite('invert', () => {
+      exprTest('invert(123)', { value: int(-124) });
+    });
+
     suite('isnan/isinf', () => {
       exprTest('isnan(2.0 / 3.0)', { value: bool(false) });
       exprTest('isnan(0.0 / 0.0)', { value: bool(true) });