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Support promise-like types in contextual return type of async function

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Ron Buckton
2018-09-20 17:33:45 -07:00
parent 219bb44b4d
commit 80dba4d63b
4 changed files with 99 additions and 3 deletions
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27
src/compiler/checker.ts
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@@ -495,6 +495,7 @@ namespace ts {
let deferredGlobalESSymbolType: ObjectType;
let deferredGlobalTypedPropertyDescriptorType: GenericType;
let deferredGlobalPromiseType: GenericType;
let deferredGlobalPromiseLikeType: GenericType;
let deferredGlobalPromiseConstructorSymbol: Symbol | undefined;
let deferredGlobalPromiseConstructorLikeType: ObjectType;
let deferredGlobalIterableType: GenericType;
@@ -8538,6 +8539,10 @@ namespace ts {
return deferredGlobalPromiseType || (deferredGlobalPromiseType = getGlobalType("Promise" as __String, /*arity*/ 1, reportErrors)) || emptyGenericType;
}
function getGlobalPromiseLikeType(reportErrors: boolean) {
return deferredGlobalPromiseLikeType || (deferredGlobalPromiseLikeType = getGlobalType("PromiseLike" as __String, /*arity*/ 1, reportErrors)) || emptyGenericType;
}
function getGlobalPromiseConstructorSymbol(reportErrors: boolean): Symbol | undefined {
return deferredGlobalPromiseConstructorSymbol || (deferredGlobalPromiseConstructorSymbol = getGlobalValueSymbol("Promise" as __String, reportErrors));
}
@@ -16393,9 +16398,13 @@ namespace ts {
}
const contextualReturnType = getContextualReturnType(func);
return functionFlags & FunctionFlags.Async
? contextualReturnType && getAwaitedTypeOfPromise(contextualReturnType) // Async function
: contextualReturnType; // Regular function
if (contextualReturnType) {
if (functionFlags & FunctionFlags.Async) { // Async function
const contextualAwaitedType = getAwaitedTypeOfPromise(contextualReturnType);
return contextualAwaitedType && getUnionType([contextualAwaitedType, createPromiseLikeType(contextualAwaitedType)]);
}
return contextualReturnType; // Regular function
}
}
return undefined;
}
@@ -20796,6 +20805,18 @@ namespace ts {
return emptyObjectType;
}
function createPromiseLikeType(promisedType: Type): Type {
// creates a `PromiseLike<T>` type where `T` is the promisedType argument
const globalPromiseLikeType = getGlobalPromiseLikeType(/*reportErrors*/ true);
if (globalPromiseLikeType !== emptyGenericType) {
// if the promised type is itself a promise, get the underlying type; otherwise, fallback to the promised type
promisedType = getAwaitedType(promisedType) || emptyObjectType;
return createTypeReference(globalPromiseLikeType, [promisedType]);
}
return emptyObjectType;
}
function createPromiseReturnType(func: FunctionLikeDeclaration | ImportCall, promisedType: Type) {
const promiseType = createPromiseType(promisedType);
if (promiseType === emptyObjectType) {