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ahejlsbergahejlsberg
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Merge pull request microsoft#27357 from Microsoft/fixBivariantInferences
Make contravariant inferences only from pure contravariant positions
2 parents 98ec1e8 + f59229b commit d7219b2

5 files changed

Lines changed: 97 additions & 3 deletions

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‎src/compiler/checker.ts‎

Lines changed: 11 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -13462,6 +13462,7 @@ namespace ts {
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let symbolStack: Symbol[];
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let visited: Map<boolean>;
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let contravariant = false;
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let bivariant = false;
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let propagationType: Type;
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let allowComplexConstraintInference = true;
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inferFromTypes(originalSource, originalTarget);
@@ -13548,11 +13549,13 @@ namespace ts {
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}
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if (priority === inference.priority) {
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const candidate = propagationType || source;
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if (contravariant) {
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inference.contraCandidates = append(inference.contraCandidates, candidate);
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// We make contravariant inferences only if we are in a pure contravariant position,
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// i.e. only if we have not descended into a bivariant position.
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if (contravariant && !bivariant) {
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inference.contraCandidates = appendIfUnique(inference.contraCandidates, candidate);
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}
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else {
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inference.candidates = append(inference.candidates, candidate);
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inference.candidates = appendIfUnique(inference.candidates, candidate);
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}
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}
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if (!(priority & InferencePriority.ReturnType) && target.flags & TypeFlags.TypeParameter && !isTypeParameterAtTopLevel(originalTarget, <TypeParameter>target)) {
@@ -13800,7 +13803,12 @@ namespace ts {
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function inferFromSignature(source: Signature, target: Signature, skipParameters: boolean) {
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if (!skipParameters) {
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const saveBivariant = bivariant;
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const kind = target.declaration ? target.declaration.kind : SyntaxKind.Unknown;
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// Once we descend into a bivariant signature we remain bivariant for all nested inferences
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bivariant = bivariant || kind === SyntaxKind.MethodDeclaration || kind === SyntaxKind.MethodSignature || kind === SyntaxKind.Constructor;
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forEachMatchingParameterType(source, target, inferFromContravariantTypes);
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bivariant = saveBivariant;
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}
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const sourceTypePredicate = getTypePredicateOfSignature(source);
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const targetTypePredicate = getTypePredicateOfSignature(target);

‎tests/baselines/reference/bivariantInferences.js‎

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,17 @@
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//// [bivariantInferences.ts]
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// Repro from #27337
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interface Array<T> {
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equalsShallow<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>): boolean;
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}
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declare const a: (string | number)[] | null[] | undefined[] | {}[];
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declare const b: (string | number)[] | null[] | undefined[] | {}[];
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let x = a.equalsShallow(b);
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//// [bivariantInferences.js]
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"use strict";
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// Repro from #27337
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var x = a.equalsShallow(b);

‎tests/baselines/reference/bivariantInferences.symbols‎

Lines changed: 31 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,31 @@
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=== tests/cases/conformance/types/typeRelationships/typeInference/bivariantInferences.ts ===
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// Repro from #27337
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interface Array<T> {
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>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(bivariantInferences.ts, 0, 0))
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>T : Symbol(T, Decl(lib.es5.d.ts, --, --), Decl(bivariantInferences.ts, 2, 16))
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equalsShallow<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>): boolean;
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>equalsShallow : Symbol(Array.equalsShallow, Decl(bivariantInferences.ts, 2, 20))
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>T : Symbol(T, Decl(bivariantInferences.ts, 3, 18))
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>this : Symbol(this, Decl(bivariantInferences.ts, 3, 21))
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>ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(bivariantInferences.ts, 3, 18))
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>other : Symbol(other, Decl(bivariantInferences.ts, 3, 44))
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>ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(bivariantInferences.ts, 3, 18))
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}
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declare const a: (string | number)[] | null[] | undefined[] | {}[];
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>a : Symbol(a, Decl(bivariantInferences.ts, 6, 13))
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declare const b: (string | number)[] | null[] | undefined[] | {}[];
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>b : Symbol(b, Decl(bivariantInferences.ts, 7, 13))
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let x = a.equalsShallow(b);
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>x : Symbol(x, Decl(bivariantInferences.ts, 9, 3))
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>a.equalsShallow : Symbol(equalsShallow, Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20))
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>a : Symbol(a, Decl(bivariantInferences.ts, 6, 13))
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>equalsShallow : Symbol(equalsShallow, Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20), Decl(bivariantInferences.ts, 2, 20))
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>b : Symbol(b, Decl(bivariantInferences.ts, 7, 13))
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‎tests/baselines/reference/bivariantInferences.types‎

Lines changed: 26 additions & 0 deletions
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@@ -0,0 +1,26 @@
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=== tests/cases/conformance/types/typeRelationships/typeInference/bivariantInferences.ts ===
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// Repro from #27337
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interface Array<T> {
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equalsShallow<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>): boolean;
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>equalsShallow : <T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean
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>this : ReadonlyArray<T>
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>other : ReadonlyArray<T>
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}
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declare const a: (string | number)[] | null[] | undefined[] | {}[];
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>a : (string | number)[] | null[] | undefined[] | {}[]
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>null : null
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declare const b: (string | number)[] | null[] | undefined[] | {}[];
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>b : (string | number)[] | null[] | undefined[] | {}[]
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>null : null
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let x = a.equalsShallow(b);
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>x : boolean
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>a.equalsShallow(b) : boolean
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>a.equalsShallow : (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean)
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>a : (string | number)[] | null[] | undefined[] | {}[]
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>equalsShallow : (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean) | (<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>) => boolean)
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>b : (string | number)[] | null[] | undefined[] | {}[]
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‎tests/cases/conformance/types/typeRelationships/typeInference/bivariantInferences.ts‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
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// @strict: true
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// Repro from #27337
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interface Array<T> {
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equalsShallow<T>(this: ReadonlyArray<T>, other: ReadonlyArray<T>): boolean;
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}
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declare const a: (string | number)[] | null[] | undefined[] | {}[];
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declare const b: (string | number)[] | null[] | undefined[] | {}[];
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let x = a.equalsShallow(b);

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