LibJS: Force the lexer to parse a regex when expecting a statement

Author: https://github.com/davidot
Commit: 106f9e30d7
Pull-request: https://github.com/SerenityOS/serenity/pull/9085
Reviewed-by: https://github.com/IdanHo
Reviewed-by: https://github.com/linusg ✅
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibJS/Tests/syntax/slash-after-block.js

@@ -3,4 +3,22 @@ test("slash token resolution in lexer", () => {
     expect("``/foo/").not.toEval();
     expect("1/foo/").not.toEval();
     expect("1/foo").toEval();
+
+    expect("{} /foo/").toEval();
+    expect("{} /=/").toEval();
+    expect("{} /=a/").toEval();
+    expect("{} /* */ /=a/").toEval();
+    expect("{} /* /a/ */ /=a/").toEval();
+
+    expect("(function () {} / 1)").toEval();
+    expect("(function () {} / 1)").toEval();
+
+    expect("+a++ / 1").toEval();
+    expect("+a-- / 1").toEval();
+    expect("a.in / b").toEval();
+    expect("a.instanceof / b").toEval();
+
+    // FIXME: Even more 'reserved' words are valid however the cases below do still need to pass.
+    //expect("a.void / b").toEval();
+    expect("void / b/").toEval();
 });