error TS2339: Property 'x' does not exist on type 'Y'

Question

I don\'t understand why this code generates TypeScript error. (It\'s not the original code and is a bit derived, so please ignore the non-sense in the example):

Answer 1

Starting with TypeScript 2.2 using dot notation to access indexed properties is allowed. You won't get error TS2339 on your example.

See Dotted property for types with string index signatures in TypeScript 2.2 release note.