EmptyPredictionContext done

Signed-off-by: Mike Lischke <[email protected]>

src/atn/EmptyPredictionContext.ts

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+import { PredictionContext } from "./PredictionContext.js";
+import { SingletonPredictionContext } from "./SingletonPredictionContext.js";
+
+export class EmptyPredictionContext extends SingletonPredictionContext {
+    /**
+     * Represents {@code $} in local context prediction, which means wildcard.
+     * {@code *+x = *}.
+     */
+    // eslint-disable-next-line @typescript-eslint/naming-convention
+    public static readonly Instance = new EmptyPredictionContext();
+
+    public constructor() {
+        super(null, PredictionContext.EMPTY_RETURN_STATE);
+    }
+
+    public override isEmpty(): boolean {
+        return true;
+    }
+
+    public override getParent(_index: number): PredictionContext | null {
+        return null;
+    }
+
+    public override getReturnState(_index: number): number {
+        return this.returnState;
+    }
+
+    public override equals(other: unknown): boolean {
+
+        return this === other;
+    }
+
+    public override toString(): string {
+        return "$";
+    }
+
+    static {
+        PredictionContext.EMPTY = new EmptyPredictionContext();
+    }
+}