Poor error recovery when `enum` is used as a parameter name

<!-- 🚨 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. --> <!-- Please try to reproduce the issue with `typescript@next`. It may have already been fixed. --> **TypeScript Version:** 3.6.2 <!-- Search terms you tried before logging this (so others can find this issue more easily) --> **Search Terms:** expression expected reserved word **Code** ```ts function converter<Enum>(values: string[], enums: Enum[]): Map<Enum, string> { return new Map<Enum, string>( enums.map((enum: Enum, index: number) => [ enum, values[index] ]) ); } ``` **Expected behavior:** After some confusion why this displays so many red curlies, the error should make it clear to me that the reserved word `enum` is accidentaly being used as an argument name. An error is given on `enum` saying something along the lines of *You cannot use enum as a variable/argument because it is a reserved word*. **Actual behavior:** After a LOT of confusion, one realizes that the reserved word `enum` is accidentally being used as an argument name. An error is given on several parts in the above code, where the most helpful one is *Expression expected (ts1109)*, which is just unnecesarily confusing. **[Playground Link](https://www.typescriptlang.org/play/?ssl=1&ssc=1&pln=2&pc=22#code/GYVwdgxgLglg9mABBBA3ApgJylgPAUTBAFsA+AClQEMAbEdAZwC5EGpMYwBzAbQF0ANInRFizRIRL8AlCwCyVAA4FRQth26lEAbwBQASEzooITEjDoA7ogXLJxNe05cKB-SJIMAdMSXlyHsQs9kKcACboAB4sogBGWNKIALxaPMKqiNR0jDzhUXyIfNIG0gDcugC+QA)** <!-- A link to a TypeScript Playground "Share" link which demonstrates this b…