<!-- 🚨 STOP 🚨 𝗦𝗧𝗢𝗣 🚨 𝑺𝑻𝑶𝑷 🚨 Half of all issues filed here are duplicates, answered in the FAQ, or not appropriate for the bug tracker. Even if you think you've found a *bug*, please read the FAQ first, especially the Common "Bugs" That Aren't Bugs section! Please help us by doing the following steps before logging an issue: * Search: https://github.com/Microsoft/TypeScript/search?type=Issues * Read the FAQ: https://github.com/Microsoft/TypeScript/wiki/FAQ Please fill in the *entire* template below. --> **TypeScript Version:** 4.2.0-dev.20201209 <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** **Expected behavior:** type ``${number}`` can be used to index numeric index signature **Actual behavior:** Error: `Element implicitly has an 'any' type because index expression is not of type 'number'.` <!-- Did you find other bugs that looked similar? --> **Related Issues:** **Code** ```ts declare let t: `${number}`; declare let obj: { [key: number]: number; } const v = obj[t]; ``` **Playground Link:** [Provided](https://www.typescriptlang.org/play?ts=4.2.0-dev.20201209#code/CYUwxgNghgTiAEEQBd7IFzwAYBIDeAdgK4C2ARiDAL5YDcAUPaJLAkqgPZkBWme98QfADaAaxABPTMXKUAutNIUYDKozAcCAZ1QA3eAF54XbsORzaQA)