Empty array's type is inferred as never[] even though array's type is known #20946

TypeScript Version: 2.7.0-dev.20171230
Code

interface MyInterface {
	data?: [{
		x: number;
	}];
}

let myVar: MyInterface = {};
/*
  ts-bug.ts(13,2): error TS2322: Type 'never[]' is not assignable to type '[{ x: number; }] | undefined'.
    Type 'never[]' is not assignable to type '[{ x: number; }]'.
    Property '0' is missing in type 'never[]'.
*/
myVar.data = [];

tsconfig.json:

{
  "compilerOptions": {
    "target": "ESNEXT",
    "module": "commonjs",

    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noImplicitThis": true,
    "alwaysStrict": true
  }
}

Expected behavior:

No compile error shall occur.

Actual behavior:

ts-bug.ts(13,1): error TS2322: Type 'never[]' is not assignable to type '[{ x: number; }] | undefined'.
  Type 'never[]' is not assignable to type '[{ x: number; }]'.
    Property '0' is missing in type 'never[]'.

Side notes:

• The compilation works fine if data?: number[]; is specified.
• I conjecture that the compilation breaks if and only if data's type is an inline object type:
  • data?: [{}] also breaks.
  • data?: MyObject[] with interface MyObject {} at the beginning of the file works!
  • data?: {}[], data?: Array<{x: number}>; and data?: {x: number}[]; work fine.

Related issues:

See also #9322, #13140. However, in these issues contrary to this one, the array's type has not been explicitly specified in the code.