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Treat 'yield;' as 'yield undefined;' #22297

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Mar 8, 2018
Merged

Treat 'yield;' as 'yield undefined;' #22297

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2fbcd36
Treat 'yield;' as 'yield undefined;'
Mar 2, 2018
f910468
Use undefinedWideningType
Mar 2, 2018
0fca702
Merge branch 'master' into yieldNothing
Mar 8, 2018
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112 changes: 43 additions & 69 deletions src/compiler/checker.ts
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Expand Up @@ -18380,27 +18380,23 @@ 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);
}
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) : undefinedType;
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I appreciate the refactoring that is part of this PR -- it make the code much easier to read. But I want to point out that this is the only line needed to fix the bug. The bug would get fixed a lot faster if we could just review a one-line fix and look at the refactor separately.

// 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 @@ -19353,62 +19349,40 @@ 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);
}
}

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
10 changes: 5 additions & 5 deletions tests/baselines/reference/FunctionDeclaration9_es6.types
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@@ -1,11 +1,11 @@
=== tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration9_es6.ts ===
function * foo() {
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>

var v = { [yield]: foo }
>v : { [x: number]: () => IterableIterator<any>; }
>{ [yield]: foo } : { [x: number]: () => IterableIterator<any>; }
>[yield] : () => IterableIterator<any>
>v : { [x: number]: () => IterableIterator<undefined>; }
>{ [yield]: foo } : { [x: number]: () => IterableIterator<undefined>; }
>[yield] : () => IterableIterator<undefined>
>yield : any
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>
}
2 changes: 1 addition & 1 deletion tests/baselines/reference/YieldExpression13_es6.types
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@@ -1,5 +1,5 @@
=== tests/cases/conformance/es6/yieldExpressions/YieldExpression13_es6.ts ===
function* foo() { yield }
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>
>yield : any

2 changes: 1 addition & 1 deletion tests/baselines/reference/YieldExpression3_es6.types
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@@ -1,6 +1,6 @@
=== tests/cases/conformance/es6/yieldExpressions/YieldExpression3_es6.ts ===
function* foo() {
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>

yield
>yield : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/YieldExpression4_es6.types
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@@ -1,6 +1,6 @@
=== tests/cases/conformance/es6/yieldExpressions/YieldExpression4_es6.ts ===
function* foo() {
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>

yield;
>yield : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types
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Expand Up @@ -11,7 +11,7 @@ class C2 {
>C2 : C2

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types
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Expand Up @@ -11,7 +11,7 @@ class C2 {
>C2 : C2

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.classMethods.esnext.types
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Expand Up @@ -11,7 +11,7 @@ class C2 {
>C2 : C2

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types
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Expand Up @@ -4,7 +4,7 @@ async function * f1() {
}
=== tests/cases/conformance/emitter/es2015/asyncGenerators/F2.ts ===
async function * f2() {
>f2 : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types
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Expand Up @@ -4,7 +4,7 @@ async function * f1() {
}
=== tests/cases/conformance/emitter/es5/asyncGenerators/F2.ts ===
async function * f2() {
>f2 : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.esnext.types
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Expand Up @@ -4,7 +4,7 @@ async function * f1() {
}
=== tests/cases/conformance/emitter/esnext/asyncGenerators/F2.ts ===
async function * f2() {
>f2 : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types
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Expand Up @@ -5,8 +5,8 @@ const f1 = async function * () {
}
=== tests/cases/conformance/emitter/es2015/asyncGenerators/F2.ts ===
const f2 = async function * () {
>f2 : () => AsyncIterableIterator<any>
>async function * () { const x = yield;} : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>
>async function * () { const x = yield;} : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types
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Expand Up @@ -5,8 +5,8 @@ const f1 = async function * () {
}
=== tests/cases/conformance/emitter/es5/asyncGenerators/F2.ts ===
const f2 = async function * () {
>f2 : () => AsyncIterableIterator<any>
>async function * () { const x = yield;} : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>
>async function * () { const x = yield;} : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/emitter.asyncGenerators.functionExpressions.esnext.types
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Expand Up @@ -5,8 +5,8 @@ const f1 = async function * () {
}
=== tests/cases/conformance/emitter/esnext/asyncGenerators/F2.ts ===
const f2 = async function * () {
>f2 : () => AsyncIterableIterator<any>
>async function * () { const x = yield;} : () => AsyncIterableIterator<any>
>f2 : () => AsyncIterableIterator<undefined>
>async function * () { const x = yield;} : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
6 changes: 3 additions & 3 deletions tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types
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Expand Up @@ -9,11 +9,11 @@ const o1 = {
}
=== tests/cases/conformance/emitter/es2015/asyncGenerators/O2.ts ===
const o2 = {
>o2 : { f(): AsyncIterableIterator<any>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<any>; }
>o2 : { f(): AsyncIterableIterator<undefined>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<undefined>; }

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
6 changes: 3 additions & 3 deletions tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types
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Expand Up @@ -9,11 +9,11 @@ const o1 = {
}
=== tests/cases/conformance/emitter/es5/asyncGenerators/O2.ts ===
const o2 = {
>o2 : { f(): AsyncIterableIterator<any>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<any>; }
>o2 : { f(): AsyncIterableIterator<undefined>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<undefined>; }

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
6 changes: 3 additions & 3 deletions tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.esnext.types
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Expand Up @@ -9,11 +9,11 @@ const o1 = {
}
=== tests/cases/conformance/emitter/esnext/asyncGenerators/O2.ts ===
const o2 = {
>o2 : { f(): AsyncIterableIterator<any>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<any>; }
>o2 : { f(): AsyncIterableIterator<undefined>; }
>{ async * f() { const x = yield; }} : { f(): AsyncIterableIterator<undefined>; }

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = yield;
>x : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/generatorES6InAMDModule.types
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@@ -1,6 +1,6 @@
=== tests/cases/compiler/generatorES6InAMDModule.ts ===
export function* foo() {
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>

yield
>yield : any
Expand Down
2 changes: 1 addition & 1 deletion tests/baselines/reference/generatorES6_1.types
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@@ -1,6 +1,6 @@
=== tests/cases/compiler/generatorES6_1.ts ===
function* foo() {
>foo : () => IterableIterator<any>
>foo : () => IterableIterator<undefined>

yield
>yield : any
Expand Down
9 changes: 0 additions & 9 deletions tests/baselines/reference/generatorTypeCheck48.errors.txt
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This file was deleted.

2 changes: 1 addition & 1 deletion tests/baselines/reference/generatorTypeCheck48.types
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@@ -1,6 +1,6 @@
=== tests/cases/conformance/es6/yieldExpressions/generatorTypeCheck48.ts ===
function* g() {
>g : () => IterableIterator<any>
>g : () => IterableIterator<undefined>

yield;
>yield : any
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/parser.asyncGenerators.classMethods.esnext.types
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Expand Up @@ -140,7 +140,7 @@ class C13 {
>C13 : C13

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

yield;
>yield : any
Expand Down Expand Up @@ -250,7 +250,7 @@ class C22 {
>C22 : C22

async * f() {
>f : () => AsyncIterableIterator<any>
>f : () => AsyncIterableIterator<undefined>

const x = { [yield]: 1 };
>x : { [x: number]: number; }
Expand Down
4 changes: 2 additions & 2 deletions tests/baselines/reference/parser.asyncGenerators.functionDeclarations.esnext.types
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Expand Up @@ -88,7 +88,7 @@ async function * f12() {
}
=== tests/cases/conformance/parser/ecmascriptnext/asyncGenerators/yieldIsOk.ts ===
async function * f13() {
>f13 : () => AsyncIterableIterator<any>
>f13 : () => AsyncIterableIterator<undefined>

yield;
>yield : any
Expand Down Expand Up @@ -157,7 +157,7 @@ async function * f20() {
}
=== tests/cases/conformance/parser/ecmascriptnext/asyncGenerators/yieldInNestedComputedPropertyIsOk.ts ===
async function * f21() {
>f21 : () => AsyncIterableIterator<any>
>f21 : () => AsyncIterableIterator<undefined>

const x = { [yield]: 1 };
>x : { [x: number]: number; }
Expand Down
8 changes: 4 additions & 4 deletions tests/baselines/reference/parser.asyncGenerators.functionExpressions.esnext.types
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Expand Up @@ -113,8 +113,8 @@ const f12 = async function * () {
};
=== tests/cases/conformance/parser/ecmascriptnext/asyncGenerators/yieldIsOk.ts ===
const f13 = async function * () {
>f13 : () => AsyncIterableIterator<any>
>async function * () { yield;} : () => AsyncIterableIterator<any>
>f13 : () => AsyncIterableIterator<undefined>
>async function * () { yield;} : () => AsyncIterableIterator<undefined>

yield;
>yield : any
Expand Down Expand Up @@ -198,8 +198,8 @@ const f20 = async function * () {
};
=== tests/cases/conformance/parser/ecmascriptnext/asyncGenerators/yieldInNestedComputedPropertyIsOk.ts ===
const f21 = async function *() {
>f21 : () => AsyncIterableIterator<any>
>async function *() { const x = { [yield]: 1 };} : () => AsyncIterableIterator<any>
>f21 : () => AsyncIterableIterator<undefined>
>async function *() { const x = { [yield]: 1 };} : () => AsyncIterableIterator<undefined>

const x = { [yield]: 1 };
>x : { [x: number]: number; }
Expand Down
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