fix(moo): Add missing Lexer methods (#43477)

types/moo/index.d.ts

@@ -96,6 +96,19 @@ export interface Lexer {
      * to reset() to explicitly control the internal state of the lexer.
      */
     save(): LexerState;
+    /**
+     * Transitions to the provided state and pushes the state onto the state
+     * stack.
+     */
+    pushState(state: string): void;
+    /**
+     * Returns back to the previous state in the stack.
+     */
+    popState(): void;
+    /**
+     * Transitiosn to the provided state. Does not push onto the state stack.
+     */
+    setState(state: string): void;
 
     [Symbol.iterator](): Iterator<Token>;
 }

types/moo/moo-tests.ts

@@ -55,6 +55,11 @@ lexer = moo.states({
     },
 });
 
+lexer.pushState('lit');
+lexer.popState();
+lexer.setState('lit');
+lexer.popState();
+
 moo.compile({
     myError: moo.error
 });