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Do we need to use "declare" for type aliased in d.ts files? #1940
Description
I read that declare is required for all top level non-interface elements (i.e. module, class, var) in a declaration .d.ts file.
But do we need it for type aliases too?
Right now this code in tests.d.ts file gives error:
interface ITest {
foo: string;
bar: string;
}
type IMyAlias = ITest;
A 'declare' modifier is required for a top level declaration in a .d.ts file.
For me type aliases are similar to interfaces in this case and should not require declare keyword.
Activity
RyanCavanaugh commentedon May 4, 2015
declareshould be optional on type aliases and interfaces.declare typeanddeclare interfaceare identical totypeandinterfaceDanielRosenwasser commentedon May 4, 2015
How does this affect #2994?
yuit commentedon May 4, 2015
My understanding is that
declare typeis allowed as well asdeclare interface. So we need to stop giving an error for this casedeclare interfaceRyanCavanaugh commentedon May 5, 2015
Yui's interpretation is correct.
Since we already shipped type aliases this way, people have had to write
declare typea bunch of times. We could break them and say "Writetype, notdeclare type", but that would be a massive break for no real reason.Having made that decision, it's only logical to allow
declare interfaceas a synonym forinterfacefor consistency's sake. There are still some places where we're slightly inconsistent, buttypeandinterfaceat least should be fully aligned.