TypeScript 1.7.5, but also in master:

Code

let nativeTextarea: HTMLTextAreaElement;
nativeTextarea.minLength;

let nativeInput: HTMLInputElement;
nativeInput.minLength;

Expected behavior:
No compiler error.

Actual behavior:
Compiler error: Property 'minLength' does not exist on type 'HTMLTextAreaElement', Property 'minLength' does not exist on type 'HTMLInputElement'

HTML5 spec: https://www.w3.org/TR/html5/forms.html#the-maxlength-and-minlength-attributes