Sudden lib.es6.d.ts errors in a solution that doesn't use TypeScript

[stijnherreman]

TypeScript Version: 2.1.5.0 (as reported by VS 2017 for the TypeScript for Microsoft Visual Studio extension)

Code
None whatsoever. The project does not use TypeScript.

Expected behavior:
No TypeScript errors listed in Visual Studio.

Actual behavior:
The following errors are listed in Visual Studio, since today. I've been using VS 2017 since its official release and haven't seen this problem before.

Error	TS2451	Cannot redeclare block-scoped variable 'JSON'.	Web	C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TypeScript\lib.es6.d.ts	991	Active
Error	TS2451	Cannot redeclare block-scoped variable 'JSON'.	Web	C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TypeScript\lib.es6.d.ts	1018	Active
Error	TS2451	Cannot redeclare block-scoped variable 'JSON'.	Web	C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\Common7\IDE\CommonExtensions\Microsoft\TypeScript\lib.es6.d.ts	5714	Active

[mhegazy]

Seems like a duplicate of #14565. Should be fixed in the next update of VS 2017.