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Factor out a getYieldedTypeOfYieldExpression helper #22416

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Mar 8, 2018
Merged

Factor out a getYieldedTypeOfYieldExpression helper #22416

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114 changes: 46 additions & 68 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -18523,27 +18523,25 @@ namespace ts {

function checkAndAggregateYieldOperandTypes(func: FunctionLikeDeclaration, checkMode: CheckMode): Type[] {
const aggregatedTypes: Type[] = [];
const functionFlags = getFunctionFlags(func);
const isAsync = (getFunctionFlags(func) & FunctionFlags.Async) !== 0;
forEachYieldExpression(<Block>func.body, yieldExpression => {
const expr = yieldExpression.expression;
if (expr) {
let type = checkExpressionCached(expr, checkMode);
if (yieldExpression.asteriskToken) {
// A yield* expression effectively yields everything that its operand yields
type = checkIteratedTypeOrElementType(type, yieldExpression.expression, /*allowStringInput*/ false, (functionFlags & FunctionFlags.Async) !== 0);
}
if (functionFlags & FunctionFlags.Async) {
type = checkAwaitedType(type, expr, yieldExpression.asteriskToken
? Diagnostics.Type_of_iterated_elements_of_a_yield_Asterisk_operand_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member
: Diagnostics.Type_of_yield_operand_in_an_async_generator_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member);
}
pushIfUnique(aggregatedTypes, type);
if (yieldExpression.expression) { // TODO: GH#22297
pushIfUnique(aggregatedTypes, getYieldedTypeOfYieldExpression(yieldExpression, isAsync, checkMode));
}
});

return aggregatedTypes;
}

function getYieldedTypeOfYieldExpression(node: YieldExpression, isAsync: boolean, checkMode?: CheckMode): Type {
const errorNode = node.expression || node;
const expressionType = node.expression ? checkExpressionCached(node.expression, checkMode) : undefinedWideningType;
// A `yield*` expression effectively yields everything that its operand yields
const yieldedType = node.asteriskToken ? checkIteratedTypeOrElementType(expressionType, errorNode, /*allowStringInput*/ false, isAsync) : expressionType;
return !isAsync ? yieldedType : getAwaitedType(yieldedType, errorNode, node.asteriskToken
? Diagnostics.Type_of_iterated_elements_of_a_yield_Asterisk_operand_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member
: Diagnostics.Type_of_yield_operand_in_an_async_generator_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member);
}

function isExhaustiveSwitchStatement(node: SwitchStatement): boolean {
if (!node.possiblyExhaustive) {
return false;
Expand Down Expand Up @@ -19499,62 +19497,42 @@ namespace ts {
}
}

if (node.expression) {
const func = getContainingFunction(node);
// If the user's code is syntactically correct, the func should always have a star. After all,
// we are in a yield context.
const functionFlags = func && getFunctionFlags(func);
if (node.asteriskToken) {
// Async generator functions prior to ESNext require the __await, __asyncDelegator,
// and __asyncValues helpers
if ((functionFlags & FunctionFlags.AsyncGenerator) === FunctionFlags.AsyncGenerator &&
languageVersion < ScriptTarget.ESNext) {
checkExternalEmitHelpers(node, ExternalEmitHelpers.AsyncDelegatorIncludes);
}

// Generator functions prior to ES2015 require the __values helper
if ((functionFlags & FunctionFlags.AsyncGenerator) === FunctionFlags.Generator &&
languageVersion < ScriptTarget.ES2015 && compilerOptions.downlevelIteration) {
checkExternalEmitHelpers(node, ExternalEmitHelpers.Values);
}
}

if (functionFlags & FunctionFlags.Generator) {
const expressionType = checkExpressionCached(node.expression);
let expressionElementType: Type;
const nodeIsYieldStar = !!node.asteriskToken;
if (nodeIsYieldStar) {
expressionElementType = checkIteratedTypeOrElementType(expressionType, node.expression, /*allowStringInput*/ false, (functionFlags & FunctionFlags.Async) !== 0);
}

// There is no point in doing an assignability check if the function
// has no explicit return type because the return type is directly computed
// from the yield expressions.
const returnType = getEffectiveReturnTypeNode(func);
if (returnType) {
const signatureElementType = getIteratedTypeOfGenerator(getTypeFromTypeNode(returnType), (functionFlags & FunctionFlags.Async) !== 0) || anyType;
if (nodeIsYieldStar) {
checkTypeAssignableTo(
functionFlags & FunctionFlags.Async
? getAwaitedType(expressionElementType, node.expression, Diagnostics.Type_of_iterated_elements_of_a_yield_Asterisk_operand_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member)
: expressionElementType,
signatureElementType,
node.expression,
/*headMessage*/ undefined);
}
else {
checkTypeAssignableTo(
functionFlags & FunctionFlags.Async
? getAwaitedType(expressionType, node.expression, Diagnostics.Type_of_yield_operand_in_an_async_generator_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member)
: expressionType,
signatureElementType,
node.expression,
/*headMessage*/ undefined);
}
}
const func = getContainingFunction(node);
const functionFlags = func ? getFunctionFlags(func) : FunctionFlags.Normal;

if (!(functionFlags & FunctionFlags.Generator)) {
// If the user's code is syntactically correct, the func should always have a star. After all, we are in a yield context.
return anyType;
}

if (node.asteriskToken) {
// Async generator functions prior to ESNext require the __await, __asyncDelegator,
// and __asyncValues helpers
if ((functionFlags & FunctionFlags.AsyncGenerator) === FunctionFlags.AsyncGenerator &&
languageVersion < ScriptTarget.ESNext) {
checkExternalEmitHelpers(node, ExternalEmitHelpers.AsyncDelegatorIncludes);
}

// Generator functions prior to ES2015 require the __values helper
if ((functionFlags & FunctionFlags.AsyncGenerator) === FunctionFlags.Generator &&
languageVersion < ScriptTarget.ES2015 && compilerOptions.downlevelIteration) {
checkExternalEmitHelpers(node, ExternalEmitHelpers.Values);
}
}

if (!node.expression) return anyType; // TODO: GH#22297

const isAsync = (functionFlags & FunctionFlags.Async) !== 0;
const yieldedType = getYieldedTypeOfYieldExpression(node, isAsync);
// There is no point in doing an assignability check if the function
// has no explicit return type because the return type is directly computed
// from the yield expressions.
const returnType = getEffectiveReturnTypeNode(func);
if (returnType) {
const signatureElementType = getIteratedTypeOfGenerator(getTypeFromTypeNode(returnType), isAsync) || anyType;
checkTypeAssignableTo(yieldedType, signatureElementType, node.expression || node, /*headMessage*/ undefined);
}

// Both yield and yield* expressions have type 'any'
return anyType;
}
Expand Down