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Make optional properties assignable to string index signatures #41921

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Jan 7, 2021
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Make optional properties assignable to string index signatures #41921

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6 changes: 5 additions & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -18478,7 +18478,11 @@ namespace ts {
continue;
}
if (kind === IndexKind.String || isNumericLiteralName(prop.escapedName)) {
const related = isRelatedTo(getTypeOfSymbol(prop), target, reportErrors);
const propType = getTypeOfSymbol(prop);
const type = propType.flags & TypeFlags.Undefined || !(kind === IndexKind.String && prop.flags & SymbolFlags.Optional)
? propType
: getTypeWithFacts(propType, TypeFacts.NEUndefined);
const related = isRelatedTo(type, target, reportErrors);
if (!related) {
if (reportErrors) {
reportError(Diagnostics.Property_0_is_incompatible_with_index_signature, symbolToString(prop));
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47 changes: 47 additions & 0 deletions tests/baselines/reference/optionalPropertyAssignableToStringIndexSignature.errors.txt
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tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts(6,1): error TS2322: Type '{ k1: string | undefined; }' is not assignable to type '{ [key: string]: string; }'.
Property 'k1' is incompatible with index signature.
Type 'string | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts(10,1): error TS2322: Type '{ 1?: string | undefined; }' is not assignable to type '{ [key: number]: string; }'.
Property '1' is incompatible with index signature.
Type 'string | undefined' is not assignable to type 'string'.
Type 'undefined' is not assignable to type 'string'.
tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts(13,5): error TS2322: Type '{ k1?: undefined; }' is not assignable to type '{ [key: string]: string; }'.
Property 'k1' is incompatible with index signature.
Type 'undefined' is not assignable to type 'string'.


==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts (3 errors) ====
declare let optionalProperties: { k1?: string };
declare let undefinedProperties: { k1: string | undefined };

declare let stringDictionary: { [key: string]: string };
stringDictionary = optionalProperties; // ok
stringDictionary = undefinedProperties; // error
~~~~~~~~~~~~~~~~
!!! error TS2322: Type '{ k1: string | undefined; }' is not assignable to type '{ [key: string]: string; }'.
!!! error TS2322: Property 'k1' is incompatible with index signature.
!!! error TS2322: Type 'string | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.

declare let probablyArray: { [key: number]: string };
declare let numberLiteralKeys: { 1?: string };
probablyArray = numberLiteralKeys; // error
~~~~~~~~~~~~~
!!! error TS2322: Type '{ 1?: string | undefined; }' is not assignable to type '{ [key: number]: string; }'.
!!! error TS2322: Property '1' is incompatible with index signature.
!!! error TS2322: Type 'string | undefined' is not assignable to type 'string'.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.

declare let optionalUndefined: { k1?: undefined };
let dict: { [key: string]: string } = optionalUndefined; // error
~~~~
!!! error TS2322: Type '{ k1?: undefined; }' is not assignable to type '{ [key: string]: string; }'.
!!! error TS2322: Property 'k1' is incompatible with index signature.
!!! error TS2322: Type 'undefined' is not assignable to type 'string'.
Comment on lines +36 to +41
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@andrewbranch andrewbranch Dec 10, 2020 •
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This is the only mildly interesting thing about this PR. We check if the property type is undefined before filtering undefined out of it in order to keep this error. (Otherwise we would end up checking if never is assignable to string.)

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@DanielRosenwasser DanielRosenwasser Jan 4, 2021 •
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I actually think the ?: string | undefined -> [x: string]: string one is actually weirder.


function f<T>() {
let optional: { k1?: T } = undefined!;
let dict: { [key: string]: T | number } = optional; // ok
}

31 changes: 31 additions & 0 deletions tests/baselines/reference/optionalPropertyAssignableToStringIndexSignature.js
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//// [optionalPropertyAssignableToStringIndexSignature.ts]
declare let optionalProperties: { k1?: string };
declare let undefinedProperties: { k1: string | undefined };

declare let stringDictionary: { [key: string]: string };
stringDictionary = optionalProperties; // ok
stringDictionary = undefinedProperties; // error

declare let probablyArray: { [key: number]: string };
declare let numberLiteralKeys: { 1?: string };
probablyArray = numberLiteralKeys; // error

declare let optionalUndefined: { k1?: undefined };
let dict: { [key: string]: string } = optionalUndefined; // error

function f<T>() {
let optional: { k1?: T } = undefined!;
let dict: { [key: string]: T | number } = optional; // ok
}


//// [optionalPropertyAssignableToStringIndexSignature.js]
"use strict";
stringDictionary = optionalProperties; // ok
stringDictionary = undefinedProperties; // error
probablyArray = numberLiteralKeys; // error
var dict = optionalUndefined; // error
function f() {
var optional = undefined;
var dict = optional; // ok
}
59 changes: 59 additions & 0 deletions tests/baselines/reference/optionalPropertyAssignableToStringIndexSignature.symbols
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=== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts ===
declare let optionalProperties: { k1?: string };
>optionalProperties : Symbol(optionalProperties, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 0, 11))
>k1 : Symbol(k1, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 0, 33))

declare let undefinedProperties: { k1: string | undefined };
>undefinedProperties : Symbol(undefinedProperties, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 1, 11))
>k1 : Symbol(k1, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 1, 34))

declare let stringDictionary: { [key: string]: string };
>stringDictionary : Symbol(stringDictionary, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 3, 11))
>key : Symbol(key, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 3, 33))

stringDictionary = optionalProperties; // ok
>stringDictionary : Symbol(stringDictionary, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 3, 11))
>optionalProperties : Symbol(optionalProperties, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 0, 11))

stringDictionary = undefinedProperties; // error
>stringDictionary : Symbol(stringDictionary, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 3, 11))
>undefinedProperties : Symbol(undefinedProperties, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 1, 11))

declare let probablyArray: { [key: number]: string };
>probablyArray : Symbol(probablyArray, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 7, 11))
>key : Symbol(key, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 7, 30))

declare let numberLiteralKeys: { 1?: string };
>numberLiteralKeys : Symbol(numberLiteralKeys, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 8, 11))
>1 : Symbol(1, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 8, 32))

probablyArray = numberLiteralKeys; // error
>probablyArray : Symbol(probablyArray, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 7, 11))
>numberLiteralKeys : Symbol(numberLiteralKeys, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 8, 11))

declare let optionalUndefined: { k1?: undefined };
>optionalUndefined : Symbol(optionalUndefined, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 11, 11))
>k1 : Symbol(k1, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 11, 32))

let dict: { [key: string]: string } = optionalUndefined; // error
>dict : Symbol(dict, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 12, 3))
>key : Symbol(key, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 12, 13))
>optionalUndefined : Symbol(optionalUndefined, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 11, 11))

function f<T>() {
>f : Symbol(f, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 12, 56))
>T : Symbol(T, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 14, 11))

let optional: { k1?: T } = undefined!;
>optional : Symbol(optional, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 15, 4))
>k1 : Symbol(k1, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 15, 16))
>T : Symbol(T, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 14, 11))
>undefined : Symbol(undefined)

let dict: { [key: string]: T | number } = optional; // ok
>dict : Symbol(dict, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 16, 4))
>key : Symbol(key, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 16, 14))
>T : Symbol(T, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 14, 11))
>optional : Symbol(optional, Decl(optionalPropertyAssignableToStringIndexSignature.ts, 15, 4))
}

60 changes: 60 additions & 0 deletions tests/baselines/reference/optionalPropertyAssignableToStringIndexSignature.types
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=== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts ===
declare let optionalProperties: { k1?: string };
>optionalProperties : { k1?: string | undefined; }
>k1 : string | undefined

declare let undefinedProperties: { k1: string | undefined };
>undefinedProperties : { k1: string | undefined; }
>k1 : string | undefined

declare let stringDictionary: { [key: string]: string };
>stringDictionary : { [key: string]: string; }
>key : string

stringDictionary = optionalProperties; // ok
>stringDictionary = optionalProperties : { k1?: string | undefined; }
>stringDictionary : { [key: string]: string; }
>optionalProperties : { k1?: string | undefined; }

stringDictionary = undefinedProperties; // error
>stringDictionary = undefinedProperties : { k1: string | undefined; }
>stringDictionary : { [key: string]: string; }
>undefinedProperties : { k1: string | undefined; }

declare let probablyArray: { [key: number]: string };
>probablyArray : { [key: number]: string; }
>key : number

declare let numberLiteralKeys: { 1?: string };
>numberLiteralKeys : { 1?: string | undefined; }
>1 : string | undefined

probablyArray = numberLiteralKeys; // error
>probablyArray = numberLiteralKeys : { 1?: string | undefined; }
>probablyArray : { [key: number]: string; }
>numberLiteralKeys : { 1?: string | undefined; }

declare let optionalUndefined: { k1?: undefined };
>optionalUndefined : { k1?: undefined; }
>k1 : undefined

let dict: { [key: string]: string } = optionalUndefined; // error
>dict : { [key: string]: string; }
>key : string
>optionalUndefined : { k1?: undefined; }

function f<T>() {
>f : <T>() => void

let optional: { k1?: T } = undefined!;
>optional : { k1?: T | undefined; }
>k1 : T | undefined
>undefined! : never
>undefined : undefined

let dict: { [key: string]: T | number } = optional; // ok
>dict : { [key: string]: number | T; }
>key : string
>optional : { k1?: T | undefined; }
}

20 changes: 20 additions & 0 deletions ...Relationships/assignmentCompatibility/optionalPropertyAssignableToStringIndexSignature.ts
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// @strict: true

declare let optionalProperties: { k1?: string };
declare let undefinedProperties: { k1: string | undefined };

declare let stringDictionary: { [key: string]: string };
stringDictionary = optionalProperties; // ok
stringDictionary = undefinedProperties; // error

declare let probablyArray: { [key: number]: string };
declare let numberLiteralKeys: { 1?: string };
probablyArray = numberLiteralKeys; // error

declare let optionalUndefined: { k1?: undefined };
let dict: { [key: string]: string } = optionalUndefined; // error

function f<T>() {
let optional: { k1?: T } = undefined!;
let dict: { [key: string]: T | number } = optional; // ok
}