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Inline isThenableType

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This commit is contained in:
Ron Buckton
2017-02-02 21:43:51 -08:00
parent 56a360c7ff
commit 94b37b1f20
1 changed files with 2 additions and 21 deletions
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23
src/compiler/checker.ts
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@@ -16661,26 +16661,6 @@ namespace ts {
return promisedType && getAwaitedType(promisedType, errorNode);
}
/**
* Determines whether a type has a callable 'then' method.
*/
function isThenableType(type: Type) {
//
// {
// then( // thenFunction
// ): any;
// }
//
const thenFunction = getTypeOfPropertyOfType(type, "then");
const thenSignatures = thenFunction ? getSignaturesOfType(thenFunction, SignatureKind.Call) : emptyArray;
if (thenSignatures.length > 0) {
return true;
}
return false;
}
/**
* Gets the "promised type" of a promise.
* @param type The type of the promise.
@@ -16842,7 +16822,8 @@ namespace ts {
// of a runtime problem. If the user wants to return this value from an async
// function, they would need to wrap it in some other value. If they want it to
// be treated as a promise, they can cast to <any>.
if (isThenableType(type)) {
const thenFunction = getTypeOfPropertyOfType(type, "then");
if (thenFunction && getSignaturesOfType(thenFunction, SignatureKind.Call).length > 0) {
if (errorNode) {
error(errorNode, Diagnostics.Type_used_as_operand_to_await_or_the_return_type_of_an_async_function_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member);
}