ts.NodeArray<T> no longer mixes well with Array.isArray()

[SlurpTheo]

TypeScript Version: 2.6.1

Code

const arr: ts.NodeArray<ts.VariableDeclaration> = node as ts.NodeArray<ts.VariableDeclaration>;
if (Array.isArray(arr)) {
	const x = arr;
	const y = x[0].getText;	// getText() no longer in IntelliSense
}

Expected behavior:
Control-flow analysis used to know that x was an array of ts.VariableDeclaration.

Actual behavior:
Now it's all mixed-up (intersectioned with any[]).

[ghost]

Looks like a duplicate of #17002. (NodeArray inherits from ReadonlyArray)

[SlurpTheo]

@andy-ms It does look very similar only my code was not an issue in 2.4.2 (#17002 says it was happening in 2.4.1).

[ghost]

Oh, that's because ts.NodeArray was mutable back then.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.