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GokhanKabarGokhanKabar
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Fix exactOptionalPropertyTypes not enforced through spread-with-ternary (#63240)
When spreading a conditional expression like `{ ...(cond ? { x: obj.optProp } : {}) }` where `optProp` is an optional property, the exactOptionalPropertyTypes check was silently bypassed. The value of an optional property read (e.g. `obj.optProp`) has the internal type `T | missingType`. In `getAnonymousPartialType`, calling `addOptionality` on that type is a no-op because `missingType` is already the first union member, producing a spread type identical to the target's exact optional property type and suppressing the diagnostic. Fix: when a *required* property's type contains `missingType`, normalize it to `undefinedType` before calling `addOptionality`, so the resulting type is `T | undefined | missingType` — distinguishable from the target — and the check fires.
1 parent 9059e5b commit d71cc12

6 files changed

Lines changed: 521 additions & 1 deletion

‎src/compiler/checker.ts‎

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Original file line numberDiff line numberDiff line change
@@ -20135,7 +20135,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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const isSetonlyAccessor = prop.flags & SymbolFlags.SetAccessor && !(prop.flags & SymbolFlags.GetAccessor);
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const flags = SymbolFlags.Property | SymbolFlags.Optional;
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const result = createSymbol(flags, prop.escapedName, getIsLateCheckFlag(prop) | (readonly ? CheckFlags.Readonly : 0));
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result.links.type = isSetonlyAccessor ? undefinedType : addOptionality(getTypeOfSymbol(prop), /*isProperty*/ true);
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let propType = isSetonlyAccessor ? undefinedType : getTypeOfSymbol(prop);
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if (exactOptionalPropertyTypes && !isSetonlyAccessor && !(prop.flags & SymbolFlags.Optional) && containsMissingType(propType)) {
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propType = getUnionType([removeMissingOrUndefinedType(propType), undefinedType]);
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}
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result.links.type = isSetonlyAccessor ? undefinedType : addOptionality(propType, /*isProperty*/ true);
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result.declarations = prop.declarations;
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result.links.nameType = getSymbolLinks(prop).nameType;
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result.links.syntheticOrigin = prop;

‎tests/baselines/reference/exactOptionalPropertyTypes_spreadTernary.errors.txt‎

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exactOptionalPropertyTypes_spreadTernary.ts(13,1): error TS2375: Type '{ parentId: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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Types of property 'parentId' are incompatible.
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Type 'string | undefined' is not assignable to type 'string'.
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Type 'undefined' is not assignable to type 'string'.
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exactOptionalPropertyTypes_spreadTernary.ts(16,1): error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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Types of property 'parentId' are incompatible.
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Type 'string | undefined' is not assignable to type 'string'.
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Type 'undefined' is not assignable to type 'string'.
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exactOptionalPropertyTypes_spreadTernary.ts(20,1): error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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Types of property 'parentId' are incompatible.
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Type 'string | undefined' is not assignable to type 'string'.
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Type 'undefined' is not assignable to type 'string'.
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exactOptionalPropertyTypes_spreadTernary.ts(24,1): error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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Types of property 'parentId' are incompatible.
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Type 'string | undefined' is not assignable to type 'string'.
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Type 'undefined' is not assignable to type 'string'.
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==== exactOptionalPropertyTypes_spreadTernary.ts (4 errors) ====
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// Repro from https://github.com/microsoft/TypeScript/issues/63240
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// exactOptionalPropertyTypes should flag optional-property values spread via ternary
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type Foo = {
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parentId?: string;
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};
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declare const requestBody: Foo;
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declare const cond: boolean;
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let target: Foo;
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// Direct assignment — correctly flagged
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target = { parentId: requestBody.parentId }; // Error
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~~~~~~
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!!! error TS2375: Type '{ parentId: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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!!! error TS2375: Types of property 'parentId' are incompatible.
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!!! error TS2375: Type 'string | undefined' is not assignable to type 'string'.
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!!! error TS2375: Type 'undefined' is not assignable to type 'string'.
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// Spread + ternary with optional property access — must also be flagged
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // Error
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~~~~~~
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!!! error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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!!! error TS2375: Types of property 'parentId' are incompatible.
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!!! error TS2375: Type 'string | undefined' is not assignable to type 'string'.
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!!! error TS2375: Type 'undefined' is not assignable to type 'string'.
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// Destructured optional property — must also be flagged
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const { parentId } = requestBody;
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target = { ...(cond ? { parentId } : {}) }; // Error
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~~~~~~
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!!! error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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!!! error TS2375: Types of property 'parentId' are incompatible.
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!!! error TS2375: Type 'string | undefined' is not assignable to type 'string'.
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!!! error TS2375: Type 'undefined' is not assignable to type 'string'.
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// Explicit `string | undefined` value — must be flagged (was already working)
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const parentId2 = '' as string | undefined;
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target = { ...(cond ? { parentId: parentId2 } : {}) }; // Error
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~~~~~~
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!!! error TS2375: Type '{ parentId?: string | undefined; }' is not assignable to type 'Foo' with 'exactOptionalPropertyTypes: true'. Consider adding 'undefined' to the types of the target's properties.
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!!! error TS2375: Types of property 'parentId' are incompatible.
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!!! error TS2375: Type 'string | undefined' is not assignable to type 'string'.
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!!! error TS2375: Type 'undefined' is not assignable to type 'string'.
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// ------------------------------------------------------------------
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// Valid cases — must NOT produce errors
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// ------------------------------------------------------------------
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// Spreading the whole Foo object is fine (its optional properties are already correctly typed)
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target = { ...(cond ? requestBody : {}) }; // OK
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// A required string value is fine
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const parentId3 = 'hello';
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target = { ...(cond ? { parentId: parentId3 } : {}) }; // OK
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// Spreading an object where the property is narrowed to string
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if (cond && requestBody.parentId !== undefined) {
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // OK — narrowed to string
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}
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‎tests/baselines/reference/exactOptionalPropertyTypes_spreadTernary.js‎

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//// [tests/cases/compiler/exactOptionalPropertyTypes_spreadTernary.ts] ////
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//// [exactOptionalPropertyTypes_spreadTernary.ts]
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type Foo = {
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parentId?: string;
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};
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declare const requestBody: Foo;
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declare const cond: boolean;
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let target: Foo;
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// Direct assignment — correctly flagged
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target = { parentId: requestBody.parentId }; // Error
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// Spread + ternary with optional property access — must also be flagged
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // Error
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// Destructured optional property — must also be flagged
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const { parentId } = requestBody;
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target = { ...(cond ? { parentId } : {}) }; // Error
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// Explicit `string | undefined` value — must be flagged (was already working)
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const parentId2 = '' as string | undefined;
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target = { ...(cond ? { parentId: parentId2 } : {}) }; // Error
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// ------------------------------------------------------------------
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// Valid cases — must NOT produce errors
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// ------------------------------------------------------------------
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// Spreading the whole Foo object is fine (its optional properties are already correctly typed)
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target = { ...(cond ? requestBody : {}) }; // OK
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// A required string value is fine
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const parentId3 = 'hello';
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target = { ...(cond ? { parentId: parentId3 } : {}) }; // OK
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// Spreading an object where the property is narrowed to string
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if (cond && requestBody.parentId !== undefined) {
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // OK — narrowed to string
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}
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//// [exactOptionalPropertyTypes_spreadTernary.js]
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"use strict";
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// Repro from https://github.com/microsoft/TypeScript/issues/63240
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// exactOptionalPropertyTypes should flag optional-property values spread via ternary
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let target;
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// Direct assignment — correctly flagged
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target = { parentId: requestBody.parentId }; // Error
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// Spread + ternary with optional property access — must also be flagged
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target = Object.assign({}, (cond ? { parentId: requestBody.parentId } : {})); // Error
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// Destructured optional property — must also be flagged
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const { parentId } = requestBody;
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target = Object.assign({}, (cond ? { parentId } : {})); // Error
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// Explicit `string | undefined` value — must be flagged (was already working)
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const parentId2 = '';
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target = Object.assign({}, (cond ? { parentId: parentId2 } : {})); // Error
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// ------------------------------------------------------------------
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// Valid cases — must NOT produce errors
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// ------------------------------------------------------------------
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// Spreading the whole Foo object is fine (its optional properties are already correctly typed)
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target = Object.assign({}, (cond ? requestBody : {})); // OK
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// A required string value is fine
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const parentId3 = 'hello';
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target = Object.assign({}, (cond ? { parentId: parentId3 } : {})); // OK
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// Spreading an object where the property is narrowed to string
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if (cond && requestBody.parentId !== undefined) {
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target = Object.assign({}, (cond ? { parentId: requestBody.parentId } : {})); // OK — narrowed to string
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}

‎tests/baselines/reference/exactOptionalPropertyTypes_spreadTernary.symbols‎

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//// [tests/cases/compiler/exactOptionalPropertyTypes_spreadTernary.ts] ////
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=== exactOptionalPropertyTypes_spreadTernary.ts ===
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// Repro from https://github.com/microsoft/TypeScript/issues/63240
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// exactOptionalPropertyTypes should flag optional-property values spread via ternary
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type Foo = {
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>Foo : Symbol(Foo, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 0, 0))
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parentId?: string;
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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};
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declare const requestBody: Foo;
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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>Foo : Symbol(Foo, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 0, 0))
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declare const cond: boolean;
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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let target: Foo;
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>Foo : Symbol(Foo, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 0, 0))
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// Direct assignment — correctly flagged
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target = { parentId: requestBody.parentId }; // Error
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 12, 10))
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>requestBody.parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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// Spread + ternary with optional property access — must also be flagged
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // Error
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 15, 23))
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>requestBody.parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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// Destructured optional property — must also be flagged
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const { parentId } = requestBody;
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 18, 7))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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target = { ...(cond ? { parentId } : {}) }; // Error
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 19, 23))
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// Explicit `string | undefined` value — must be flagged (was already working)
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const parentId2 = '' as string | undefined;
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>parentId2 : Symbol(parentId2, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 22, 5))
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target = { ...(cond ? { parentId: parentId2 } : {}) }; // Error
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 23, 23))
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>parentId2 : Symbol(parentId2, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 22, 5))
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// ------------------------------------------------------------------
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// Valid cases — must NOT produce errors
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// ------------------------------------------------------------------
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// Spreading the whole Foo object is fine (its optional properties are already correctly typed)
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target = { ...(cond ? requestBody : {}) }; // OK
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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// A required string value is fine
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const parentId3 = 'hello';
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>parentId3 : Symbol(parentId3, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 33, 5))
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target = { ...(cond ? { parentId: parentId3 } : {}) }; // OK
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 34, 23))
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>parentId3 : Symbol(parentId3, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 33, 5))
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// Spreading an object where the property is narrowed to string
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if (cond && requestBody.parentId !== undefined) {
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>requestBody.parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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>undefined : Symbol(undefined)
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target = { ...(cond ? { parentId: requestBody.parentId } : {}) }; // OK — narrowed to string
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>target : Symbol(target, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 9, 3))
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>cond : Symbol(cond, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 8, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 38, 27))
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>requestBody.parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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>requestBody : Symbol(requestBody, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 7, 13))
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>parentId : Symbol(parentId, Decl(exactOptionalPropertyTypes_spreadTernary.ts, 3, 12))
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}
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