proposal: add ' min-tsc-version' config on d.ts file and tsconfig.json

[WanderWang]

consider this code :

//some-lib.d.ts
declare function foo():number | undefined

//a.ts
foo();

when somebody use some-lib.d.ts with tsc1.8 , they will got a exception some-lib.d.ts(1,33): error TS2304: Cannot find name 'undefined'. . And they will be confused because they may not know about strict-null features in TypeScript 2.0

So I think we should add a 'min-tsc-version' on d.ts file , for example :

//some-lib.d.ts


/// min-tsc-version : 2.0.0
declare function foo():number | undefined

//tsconfig.json
{
    “compileOption": {
        "min-tsc-version":2.0.0
    }
}

[yahiko00]

Although I dislike the option name "min-tsc-version", why not. A kind of compatibility system could be helpful to manage our codebase.

[WanderWang]

Another user story :

We write some typescript code with ts2.0 features , and VSCode .

becauseof vscode use TypeScript 1.8.10 now , so my code will got some error message from tss 1.8 ( including in vscode ) .

If here is a " min-tsc-version " in tsconfig.json , VSCode could report a friendly error message to let developers set custom typescript-sdk path in VSCode

[mhegazy]

the problem is it is not guaranteed to fail. so in most cases you will get the warning and will find it annoying.

you can see similar discussion in #10412, #6702 (comment) and in #7573.