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fix(50340): typeof ... === "undefined" check on discriminated union of undefined and object type doesn't narrow correctly #50344

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merged 3 commits into from
Aug 31, 2022
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fix(50340): typeof ... === "undefined" check on discriminated union of undefined and object type doesn't narrow correctly #50344

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b4e02ab
fix(50340): narrow type by discriminant in typeof
a-tarasyuk Aug 17, 2022
5ffac1f
add additional test cases
a-tarasyuk Aug 27, 2022
c75043e
Merge branch 'main' of https://github.com/microsoft/TypeScript into f…
a-tarasyuk Aug 27, 2022
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8 changes: 8 additions & 0 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -25328,11 +25328,19 @@ namespace ts {
}
const target = getReferenceCandidate(typeOfExpr.expression);
if (!isMatchingReference(reference, target)) {
const propertyAccess = getDiscriminantPropertyAccess(typeOfExpr.expression, type);
if (propertyAccess) {
return narrowTypeByDiscriminant(type, propertyAccess, t => narrowTypeByLiteralExpression(t, literal, assumeTrue));
}
if (strictNullChecks && optionalChainContainsReference(target, reference) && assumeTrue === (literal.text !== "undefined")) {
return getAdjustedTypeWithFacts(type, TypeFacts.NEUndefinedOrNull);
}
return type;
}
return narrowTypeByLiteralExpression(type, literal, assumeTrue);
}

function narrowTypeByLiteralExpression(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
return assumeTrue ?
narrowTypeByTypeName(type, literal.text) :
getTypeWithFacts(type, typeofNEFacts.get(literal.text) || TypeFacts.TypeofNEHostObject);
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31 changes: 31 additions & 0 deletions tests/baselines/reference/narrowingTypeofUndefined.js
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@@ -0,0 +1,31 @@
//// [narrowingTypeofUndefined.ts]
declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }

if (typeof a.error === 'undefined') {
a.result.prop; // number
}
else {
a.error.prop; // string
}

if (typeof a.error !== 'undefined') {
a.error.prop; // string
}
else {
a.result.prop; // number
}


//// [narrowingTypeofUndefined.js]
if (typeof a.error === 'undefined') {
a.result.prop; // number
}
else {
a.error.prop; // string
}
if (typeof a.error !== 'undefined') {
a.error.prop; // string
}
else {
a.result.prop; // number
}
52 changes: 52 additions & 0 deletions tests/baselines/reference/narrowingTypeofUndefined.symbols
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Original file line number Diff line number Diff line change
@@ -0,0 +1,52 @@
=== tests/cases/compiler/narrowingTypeofUndefined.ts ===
declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 67))
>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 85))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))

if (typeof a.error === 'undefined') {
>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))

a.result.prop; // number
>a.result.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
>a.result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
}
else {
a.error.prop; // string
>a.error.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
}

if (typeof a.error !== 'undefined') {
>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))

a.error.prop; // string
>a.error.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
>a.error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>error : Symbol(error, Decl(narrowingTypeofUndefined.ts, 0, 18), Decl(narrowingTypeofUndefined.ts, 0, 67))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 27))
}
else {
a.result.prop; // number
>a.result.prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
>a.result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
>a : Symbol(a, Decl(narrowingTypeofUndefined.ts, 0, 13))
>result : Symbol(result, Decl(narrowingTypeofUndefined.ts, 0, 43), Decl(narrowingTypeofUndefined.ts, 0, 85))
>prop : Symbol(prop, Decl(narrowingTypeofUndefined.ts, 0, 95))
}

58 changes: 58 additions & 0 deletions tests/baselines/reference/narrowingTypeofUndefined.types
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Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
=== tests/cases/compiler/narrowingTypeofUndefined.ts ===
declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }
>a : { error: { prop: string;}; result: undefined; } | { error: undefined; result: { prop: number;}; }
>error : { prop: string; }
>prop : string
>result : undefined
>error : undefined
>result : { prop: number; }
>prop : number

if (typeof a.error === 'undefined') {
>typeof a.error === 'undefined' : boolean
>typeof a.error : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
>a.error : { prop: string; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>error : { prop: string; }
>'undefined' : "undefined"

a.result.prop; // number
>a.result.prop : number
>a.result : { prop: number; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>result : { prop: number; }
>prop : number
}
else {
a.error.prop; // string
>a.error.prop : string
>a.error : { prop: string; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>error : { prop: string; }
>prop : string
}

if (typeof a.error !== 'undefined') {
>typeof a.error !== 'undefined' : boolean
>typeof a.error : "string" | "number" | "bigint" | "boolean" | "symbol" | "undefined" | "object" | "function"
>a.error : { prop: string; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>error : { prop: string; }
>'undefined' : "undefined"

a.error.prop; // string
>a.error.prop : string
>a.error : { prop: string; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>error : { prop: string; }
>prop : string
}
else {
a.result.prop; // number
>a.result.prop : number
>a.result : { prop: number; }
>a : { error: { prop: string; }; result: undefined; } | { error: undefined; result: { prop: number; }; }
>result : { prop: number; }
>prop : number
}

15 changes: 15 additions & 0 deletions tests/cases/compiler/narrowingTypeofUndefined.ts
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@@ -0,0 +1,15 @@
declare const a: { error: { prop: string }, result: undefined } | { error: undefined, result: { prop: number } }

if (typeof a.error === 'undefined') {
a.result.prop; // number
}
else {
a.error.prop; // string
}

if (typeof a.error !== 'undefined') {
a.error.prop; // string
}
else {
a.result.prop; // number
}
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