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AndaristAndarist
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Fix an issue with types possibly being related to discriminated type despite of incompatible variance
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‎src/compiler/checker.ts

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@@ -20367,6 +20367,28 @@ namespace ts {
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// Compare the remaining non-discriminant properties of each match.
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let result = Ternary.True;
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for (const type of matchingTypes) {
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if (getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(type) & ObjectFlags.Reference && (source as TypeReference).target === (type as TypeReference).target &&
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!isTupleType(source) && !(isMarkerType(source) || isMarkerType(type))) {
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// When strictNullChecks is disabled, the element type of the empty array literal is undefinedWideningType,
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// and an empty array literal wouldn't be assignable to a `never[]` without this check.
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if (isEmptyArrayLiteralType(source)) {
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return Ternary.True;
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}
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// We have type references to the same generic type, and the type references are not marker
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// type references (which are intended by be compared structurally). Obtain the variance
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// information for the type parameters and relate the type arguments accordingly.
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const variances = getVariances((source as TypeReference).target);
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// We return Ternary.Maybe for a recursive invocation of getVariances (signalled by emptyArray). This
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// effectively means we measure variance only from type parameter occurrences that aren't nested in
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// recursive instantiations of the generic type.
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if (variances === emptyArray) {
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return Ternary.Unknown;
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}
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if (!typeArgumentsRelatedTo(getTypeArguments(source as TypeReference), getTypeArguments(type as TypeReference), variances, /* reportErrors */ false, IntersectionState.None)) {
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return Ternary.False;
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}
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}
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result &= propertiesRelatedTo(source, type, /*reportErrors*/ false, excludedProperties, IntersectionState.None);
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if (result) {
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result &= signaturesRelatedTo(source, type, SignatureKind.Call, /*reportStructuralErrors*/ false);

‎tests/baselines/reference/discriminatedUnionWithFailedVarianceCheck.errors.txt

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tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts(20,3): error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G> | ResultTwo<G>'.
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Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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Type 'StringType' is not assignable to type 'G'.
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'StringType' is assignable to the constraint of type 'G', but 'G' could be instantiated with a different subtype of constraint 'UnknownType'.
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tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts(26,11): error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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Type 'StringType' is not assignable to type 'G'.
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'StringType' is assignable to the constraint of type 'G', but 'G' could be instantiated with a different subtype of constraint 'UnknownType'.
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tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts(27,11): error TS2741: Property 'other' is missing in type 'ResultOne<StringType>' but required in type 'ResultTwo<G>'.
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tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts(28,11): error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G> | ResultTwo<G>'.
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Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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==== tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts (4 errors) ====
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interface StringType { prop: string }
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interface UnknownType { prop: unknown }
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interface ResultOne<G extends UnknownType> {
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type: "one";
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value: G["prop"];
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}
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interface ResultTwo<G extends UnknownType> {
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type: "two";
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other: G["prop"];
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}
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// repro #51180
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function callback<G extends UnknownType>(): ResultOne<G> | ResultTwo<G> {
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const dt: ResultOne<StringType> = {
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type: "one",
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value: "abc",
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};
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return dt; // error
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~~~~~~~~~~
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!!! error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G> | ResultTwo<G>'.
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!!! error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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!!! error TS2322: Type 'StringType' is not assignable to type 'G'.
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!!! error TS2322: 'StringType' is assignable to the constraint of type 'G', but 'G' could be instantiated with a different subtype of constraint 'UnknownType'.
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}
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// repro #51180#issuecomment-1279445430
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function callback2<G extends UnknownType>(s: ResultOne<StringType>) {
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const a1: ResultOne<G> = s; // error
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~~
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!!! error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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!!! error TS2322: Type 'StringType' is not assignable to type 'G'.
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!!! error TS2322: 'StringType' is assignable to the constraint of type 'G', but 'G' could be instantiated with a different subtype of constraint 'UnknownType'.
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const a2: ResultTwo<G> = s; // error
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~~
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!!! error TS2741: Property 'other' is missing in type 'ResultOne<StringType>' but required in type 'ResultTwo<G>'.
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!!! related TS2728 tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts:9:3: 'other' is declared here.
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const m: ResultOne<G> | ResultTwo<G> = s; // error
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~
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!!! error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G> | ResultTwo<G>'.
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!!! error TS2322: Type 'ResultOne<StringType>' is not assignable to type 'ResultOne<G>'.
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}

‎tests/baselines/reference/discriminatedUnionWithFailedVarianceCheck.symbols

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=== tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts ===
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interface StringType { prop: string }
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>StringType : Symbol(StringType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 0))
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>prop : Symbol(StringType.prop, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 22))
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interface UnknownType { prop: unknown }
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>UnknownType : Symbol(UnknownType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 37))
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>prop : Symbol(UnknownType.prop, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 23))
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interface ResultOne<G extends UnknownType> {
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 2, 20))
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>UnknownType : Symbol(UnknownType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 37))
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type: "one";
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>type : Symbol(ResultOne.type, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 2, 44))
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value: G["prop"];
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>value : Symbol(ResultOne.value, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 3, 14))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 2, 20))
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}
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interface ResultTwo<G extends UnknownType> {
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>ResultTwo : Symbol(ResultTwo, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 5, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 6, 20))
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>UnknownType : Symbol(UnknownType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 37))
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type: "two";
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>type : Symbol(ResultTwo.type, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 6, 44))
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other: G["prop"];
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>other : Symbol(ResultTwo.other, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 7, 14))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 6, 20))
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}
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// repro #51180
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function callback<G extends UnknownType>(): ResultOne<G> | ResultTwo<G> {
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>callback : Symbol(callback, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 9, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 13, 18))
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>UnknownType : Symbol(UnknownType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 37))
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 13, 18))
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>ResultTwo : Symbol(ResultTwo, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 5, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 13, 18))
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const dt: ResultOne<StringType> = {
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>dt : Symbol(dt, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 14, 7))
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>StringType : Symbol(StringType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 0))
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type: "one",
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>type : Symbol(type, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 14, 37))
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value: "abc",
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>value : Symbol(value, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 15, 16))
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};
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return dt; // error
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>dt : Symbol(dt, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 14, 7))
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}
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// repro #51180#issuecomment-1279445430
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function callback2<G extends UnknownType>(s: ResultOne<StringType>) {
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>callback2 : Symbol(callback2, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 20, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 19))
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>UnknownType : Symbol(UnknownType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 37))
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>s : Symbol(s, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 42))
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>StringType : Symbol(StringType, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 0, 0))
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const a1: ResultOne<G> = s; // error
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>a1 : Symbol(a1, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 25, 9))
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 19))
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>s : Symbol(s, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 42))
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const a2: ResultTwo<G> = s; // error
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>a2 : Symbol(a2, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 26, 9))
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>ResultTwo : Symbol(ResultTwo, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 5, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 19))
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>s : Symbol(s, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 42))
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const m: ResultOne<G> | ResultTwo<G> = s; // error
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>m : Symbol(m, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 27, 9))
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>ResultOne : Symbol(ResultOne, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 1, 39))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 19))
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>ResultTwo : Symbol(ResultTwo, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 5, 1))
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>G : Symbol(G, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 19))
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>s : Symbol(s, Decl(discriminatedUnionWithFailedVarianceCheck.ts, 24, 42))
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}

‎tests/baselines/reference/discriminatedUnionWithFailedVarianceCheck.types

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=== tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts ===
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interface StringType { prop: string }
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>prop : string
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interface UnknownType { prop: unknown }
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>prop : unknown
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interface ResultOne<G extends UnknownType> {
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type: "one";
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>type : "one"
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value: G["prop"];
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>value : G["prop"]
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}
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interface ResultTwo<G extends UnknownType> {
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type: "two";
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>type : "two"
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other: G["prop"];
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>other : G["prop"]
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}
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// repro #51180
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function callback<G extends UnknownType>(): ResultOne<G> | ResultTwo<G> {
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>callback : <G extends UnknownType>() => ResultOne<G> | ResultTwo<G>
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const dt: ResultOne<StringType> = {
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>dt : ResultOne<StringType>
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>{ type: "one", value: "abc", } : { type: "one"; value: string; }
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type: "one",
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>type : "one"
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>"one" : "one"
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value: "abc",
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>value : string
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>"abc" : "abc"
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};
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return dt; // error
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>dt : ResultOne<StringType>
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}
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// repro #51180#issuecomment-1279445430
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function callback2<G extends UnknownType>(s: ResultOne<StringType>) {
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>callback2 : <G extends UnknownType>(s: ResultOne<StringType>) => void
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>s : ResultOne<StringType>
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const a1: ResultOne<G> = s; // error
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>a1 : ResultOne<G>
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>s : ResultOne<StringType>
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const a2: ResultTwo<G> = s; // error
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>a2 : ResultTwo<G>
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>s : ResultOne<StringType>
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const m: ResultOne<G> | ResultTwo<G> = s; // error
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>m : ResultOne<G> | ResultTwo<G>
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>s : ResultOne<StringType>
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}

‎tests/cases/compiler/discriminatedUnionWithFailedVarianceCheck.ts

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// @strict: true
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// @noEmit: true
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interface StringType { prop: string }
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interface UnknownType { prop: unknown }
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interface ResultOne<G extends UnknownType> {
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type: "one";
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value: G["prop"];
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}
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interface ResultTwo<G extends UnknownType> {
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type: "two";
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other: G["prop"];
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}
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// repro #51180
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function callback<G extends UnknownType>(): ResultOne<G> | ResultTwo<G> {
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const dt: ResultOne<StringType> = {
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type: "one",
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value: "abc",
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};
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return dt; // error
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}
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// repro #51180#issuecomment-1279445430
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function callback2<G extends UnknownType>(s: ResultOne<StringType>) {
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const a1: ResultOne<G> = s; // error
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const a2: ResultTwo<G> = s; // error
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const m: ResultOne<G> | ResultTwo<G> = s; // error
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}

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