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use string as type of variable in ForInStatement #6302

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use string as type of variable in ForInStatement #6302

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c1dbd7b
use string as type of variable in ForInStatement
vladima Dec 31, 2015
9a2e42c
check destructuring in variable declaration of ForInStatement
vladima Dec 31, 2015
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17 changes: 12 additions & 5 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2510,9 +2510,9 @@ namespace ts {

// Return the inferred type for a variable, parameter, or property declaration
function getTypeForVariableLikeDeclaration(declaration: VariableLikeDeclaration): Type {
// A variable declared in a for..in statement is always of type any
// A variable declared in a for..in statement is always of type string
if (declaration.parent.parent.kind === SyntaxKind.ForInStatement) {
return anyType;
return stringType;
}

if (declaration.parent.parent.kind === SyntaxKind.ForOfStatement) {
Expand Down Expand Up @@ -12691,8 +12691,11 @@ namespace ts {
}
}

const isVariableInForInStatement = node.parent.parent.kind === SyntaxKind.ForInStatement;
// For a binding pattern, check contained binding elements
if (isBindingPattern(node.name)) {
// NOTE: do not check them if this is a binding pattern in variable declaration of ForIn statement
// this situation is already illegal so no need to report misleading errors.
if (isBindingPattern(node.name) && !isVariableInForInStatement) {
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Why is this not allowed?

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because we have not implemented this yet: #3715. I think I'll remove this check so it won't be missed once #3715 is addresssed

forEach((<BindingPattern>node.name).elements, checkSourceElement);
}
// For a parameter declaration with an initializer, error and exit if the containing function doesn't have a body
Expand All @@ -12702,7 +12705,9 @@ namespace ts {
}
// For a binding pattern, validate the initializer and exit
if (isBindingPattern(node.name)) {
if (node.initializer) {
// do not check initializer if this is variable in ForIn statement.
// this situation is already illegal so no need to report misleading errors.
if (node.initializer && !isVariableInForInStatement) {
checkTypeAssignableTo(checkExpressionCached(node.initializer), getWidenedTypeForVariableLikeDeclaration(node), node, /*headMessage*/ undefined);
checkParameterInitializer(node);
}
Expand All @@ -12712,7 +12717,9 @@ namespace ts {
const type = getTypeOfVariableOrParameterOrProperty(symbol);
if (node === symbol.valueDeclaration) {
// Node is the primary declaration of the symbol, just validate the initializer
if (node.initializer) {
// NOTE: do not check initializer if this is variable in ForIn statement.
// this situation is already illegal so no need to report misleading errors.
if (node.initializer && !isVariableInForInStatement) {
checkTypeAssignableTo(checkExpressionCached(node.initializer), type, node, /*headMessage*/ undefined);
checkParameterInitializer(node);
}
Expand Down
28 changes: 14 additions & 14 deletions tests/baselines/reference/capturedLetConstInLoop1.types
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@@ -1,18 +1,18 @@
=== tests/cases/compiler/capturedLetConstInLoop1.ts ===
//==== let
for (let x in {}) {
>x : any
>x : string
>{} : {}

(function() { return x});
>(function() { return x}) : () => any
>function() { return x} : () => any
>x : any
>(function() { return x}) : () => string
>function() { return x} : () => string
>x : string

(() => x);
>(() => x) : () => any
>() => x : () => any
>x : any
>(() => x) : () => string
>() => x : () => string
>x : string
}

for (let x of []) {
Expand Down Expand Up @@ -216,18 +216,18 @@ for (let y = 0; y < 1; ++y) {

//=========const
for (const x in {}) {
>x : any
>x : string
>{} : {}

(function() { return x});
>(function() { return x}) : () => any
>function() { return x} : () => any
>x : any
>(function() { return x}) : () => string
>function() { return x} : () => string
>x : string

(() => x);
>(() => x) : () => any
>() => x : () => any
>x : any
>(() => x) : () => string
>() => x : () => string
>x : string
}

for (const x of []) {
Expand Down
28 changes: 14 additions & 14 deletions tests/baselines/reference/capturedLetConstInLoop1_ES6.types
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Original file line number Diff line number Diff line change
@@ -1,18 +1,18 @@
=== tests/cases/compiler/capturedLetConstInLoop1_ES6.ts ===
//==== let
for (let x in {}) {
>x : any
>x : string
>{} : {}

(function() { return x});
>(function() { return x}) : () => any
>function() { return x} : () => any
>x : any
>(function() { return x}) : () => string
>function() { return x} : () => string
>x : string

(() => x);
>(() => x) : () => any
>() => x : () => any
>x : any
>(() => x) : () => string
>() => x : () => string
>x : string
}

for (let x of []) {
Expand Down Expand Up @@ -216,18 +216,18 @@ for (let y = 0; y < 1; ++y) {

//=========const
for (const x in {}) {
>x : any
>x : string
>{} : {}

(function() { return x});
>(function() { return x}) : () => any
>function() { return x} : () => any
>x : any
>(function() { return x}) : () => string
>function() { return x} : () => string
>x : string

(() => x);
>(() => x) : () => any
>() => x : () => any
>x : any
>(() => x) : () => string
>() => x : () => string
>x : string
}

for (const x of []) {
Expand Down
36 changes: 18 additions & 18 deletions tests/baselines/reference/capturedLetConstInLoop2.types
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Expand Up @@ -37,7 +37,7 @@ function foo0_1(x) {
>x : any

for (let x in []) {
>x : any
>x : string
>[] : undefined[]

let a = arguments.length;
Expand All @@ -47,17 +47,17 @@ function foo0_1(x) {
>length : number

(function() { return x + a });
>(function() { return x + a }) : () => any
>function() { return x + a } : () => any
>x + a : any
>x : any
>(function() { return x + a }) : () => string
>function() { return x + a } : () => string
>x + a : string
>x : string
>a : number

(() => x + a);
>(() => x + a) : () => any
>() => x + a : () => any
>x + a : any
>x : any
>(() => x + a) : () => string
>() => x + a : () => string
>x + a : string
>x : string
>a : number
}
}
Expand Down Expand Up @@ -400,7 +400,7 @@ function foo0_1_c(x) {
>x : any

for (const x in []) {
>x : any
>x : string
>[] : undefined[]

const a = arguments.length;
Expand All @@ -410,17 +410,17 @@ function foo0_1_c(x) {
>length : number

(function() { return x + a });
>(function() { return x + a }) : () => any
>function() { return x + a } : () => any
>x + a : any
>x : any
>(function() { return x + a }) : () => string
>function() { return x + a } : () => string
>x + a : string
>x : string
>a : number

(() => x + a);
>(() => x + a) : () => any
>() => x + a : () => any
>x + a : any
>x : any
>(() => x + a) : () => string
>() => x + a : () => string
>x + a : string
>x : string
>a : number
}
}
Expand Down
36 changes: 18 additions & 18 deletions tests/baselines/reference/capturedLetConstInLoop2_ES6.types
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Expand Up @@ -36,7 +36,7 @@ function foo0_1(x) {
>x : any

for (let x in []) {
>x : any
>x : string
>[] : undefined[]

let a = arguments.length;
Expand All @@ -46,17 +46,17 @@ function foo0_1(x) {
>length : number

(function() { return x + a });
>(function() { return x + a }) : () => any
>function() { return x + a } : () => any
>x + a : any
>x : any
>(function() { return x + a }) : () => string
>function() { return x + a } : () => string
>x + a : string
>x : string
>a : number

(() => x + a);
>(() => x + a) : () => any
>() => x + a : () => any
>x + a : any
>x : any
>(() => x + a) : () => string
>() => x + a : () => string
>x + a : string
>x : string
>a : number
}
}
Expand Down Expand Up @@ -399,7 +399,7 @@ function foo0_1_c(x) {
>x : any

for (const x in []) {
>x : any
>x : string
>[] : undefined[]

const a = arguments.length;
Expand All @@ -409,17 +409,17 @@ function foo0_1_c(x) {
>length : number

(function() { return x + a });
>(function() { return x + a }) : () => any
>function() { return x + a } : () => any
>x + a : any
>x : any
>(function() { return x + a }) : () => string
>function() { return x + a } : () => string
>x + a : string
>x : string
>a : number

(() => x + a);
>(() => x + a) : () => any
>() => x + a : () => any
>x + a : any
>x : any
>(() => x + a) : () => string
>() => x + a : () => string
>x + a : string
>x : string
>a : number
}
}
Expand Down
56 changes: 28 additions & 28 deletions tests/baselines/reference/capturedLetConstInLoop3.types
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Expand Up @@ -42,32 +42,32 @@ function foo0_1(x) {
>x : any

for (let x in []) {
>x : any
>x : string
>[] : undefined[]

var v = x;
>v : any
>x : any
>v : string
>x : string

(function() { return x + v });
>(function() { return x + v }) : () => any
>function() { return x + v } : () => any
>x + v : any
>x : any
>v : any
>(function() { return x + v }) : () => string
>function() { return x + v } : () => string
>x + v : string
>x : string
>v : string

(() => x + v);
>(() => x + v) : () => any
>() => x + v : () => any
>x + v : any
>x : any
>v : any
>(() => x + v) : () => string
>() => x + v : () => string
>x + v : string
>x : string
>v : string
}

use(v);
>use(v) : any
>use : (a: any) => any
>v : any
>v : string
}

function foo1(x) {
Expand Down Expand Up @@ -438,32 +438,32 @@ function foo0_1_c(x) {
>x : any

for (const x in []) {
>x : any
>x : string
>[] : undefined[]

var v = x;
>v : any
>x : any
>v : string
>x : string

(function() { return x + v });
>(function() { return x + v }) : () => any
>function() { return x + v } : () => any
>x + v : any
>x : any
>v : any
>(function() { return x + v }) : () => string
>function() { return x + v } : () => string
>x + v : string
>x : string
>v : string

(() => x + v);
>(() => x + v) : () => any
>() => x + v : () => any
>x + v : any
>x : any
>v : any
>(() => x + v) : () => string
>() => x + v : () => string
>x + v : string
>x : string
>v : string
}

use(v);
>use(v) : any
>use : (a: any) => any
>v : any
>v : string
}

function foo1_c(x) {
Expand Down
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