Is the tooltip display for Typescript types in VSCode reliable? No need for unnecessary type assertions

Exploring the concept of const assertions in TypeScript

Looking at the array allDeviceTypes depicted below, VSCode indicates it has a return type of string[] when hovering over the variable name.

https://i.sstatic.net/gIYch.png

However, upon using a const assertion to narrow down the type, I observe the desired narrowed type, but encounter an error from TSLint:

This assertion is unnecessary since it does not change the type of the expression. (no-unnecessary-type-assertion)tslint(1)

So, what's the verdict? Is the type of the expression truly unaltered or could there be a display issue with VSCode 1.40.0 and TSlint 5.11.0?

https://i.sstatic.net/u5q7c.png

typescriptvisual-studio-codetslint

Answer №1

Visual Studio Code (VS code) communicates with a TypeScript language server to provide accurate type information when hovering over code, ensuring it displays the same data as the TypeScript compiler.

In some cases, TS lint has shown signs of being unreliable, and a simple search reveals that others have encountered issues with this particular rule as well.

Another factor to take into account is that TS lint is nearing deprecation, as highlighted in this post by the maintainers: .

It may be worthwhile to transition to ES lint instead, or alternatively, consider disabling the rule on the problematic line.

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