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Discriminate partial inferences if not complete enough to satisfy constraint
1 parent aa9a886 commit 031a370

5 files changed

Lines changed: 149 additions & 1 deletion

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‎src/compiler/checker.ts‎

Lines changed: 32 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11552,7 +11552,38 @@ namespace ts {
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if (!inferredType) {
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if (inference.indexes) {
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// Build a candidate from all indexes
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(inference.candidates || (inference.candidates = [])).push(getIntersectionType(inference.indexes));
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let aggregateInference = getIntersectionType(inference.indexes);
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const constraint = getConstraintOfTypeParameter(context.signature.typeParameters[index]);
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if (constraint) {
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const instantiatedConstraint = instantiateType(constraint, context);
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if (!context.compareTypes(aggregateInference, getTypeWithThisArgument(instantiatedConstraint, aggregateInference))) {
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if (instantiatedConstraint.flags & TypeFlags.Union) {
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const discriminantProps = findDiscriminantProperties(getPropertiesOfType(aggregateInference), instantiatedConstraint);
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if (discriminantProps) {
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let match: Type;
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findDiscriminant: for (const p of discriminantProps) {
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const candidatePropType = getTypeOfPropertyOfType(aggregateInference, p.escapedName);
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for (const type of (instantiatedConstraint as UnionType).types) {
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const propType = getTypeOfPropertyOfType(type, p.escapedName);
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if (propType && checkTypeAssignableTo(candidatePropType, propType, /*errorNode*/ undefined)) {
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if (match && match !== type) {
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match = undefined;
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break findDiscriminant;
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}
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else {
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match = type;
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}
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}
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}
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}
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if (match) {
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aggregateInference = getSpreadType(match, aggregateInference, /*symbol*/ undefined, /*propegatedFlags*/ 0);
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}
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}
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}
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}
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}
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(inference.candidates || (inference.candidates = [])).push(aggregateInference);
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}
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if (inference.candidates) {
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// Extract all object literal types and replace them with a single widened and normalized type.

‎tests/baselines/reference/typeInferenceOnIndexUnion.js‎

Lines changed: 13 additions & 0 deletions
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@@ -0,0 +1,13 @@
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//// [typeInferenceOnIndexUnion.ts]
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type Options = { k: "a", a: number } | { k: "b", b: string };
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declare function f<T extends Options>(p: T["k"]): T;
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const x = f("a"); // expect it to be `{ k: "a", a: number }`
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type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
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declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
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const x2 = f2("a", { x: 1, y: 2 }); // expect it to be `{ k: "a", a: number, c: {x: number, y: number} }`
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//// [typeInferenceOnIndexUnion.js]
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var x = f("a"); // expect it to be `{ k: "a", a: number }`
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var x2 = f2("a", { x: 1, y: 2 }); // expect it to be `{ k: "a", a: number, c: {x: number, y: number} }`

‎tests/baselines/reference/typeInferenceOnIndexUnion.symbols‎

Lines changed: 45 additions & 0 deletions
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@@ -0,0 +1,45 @@
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=== tests/cases/compiler/typeInferenceOnIndexUnion.ts ===
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type Options = { k: "a", a: number } | { k: "b", b: string };
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>Options : Symbol(Options, Decl(typeInferenceOnIndexUnion.ts, 0, 0))
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>k : Symbol(k, Decl(typeInferenceOnIndexUnion.ts, 0, 16))
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>a : Symbol(a, Decl(typeInferenceOnIndexUnion.ts, 0, 24))
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>k : Symbol(k, Decl(typeInferenceOnIndexUnion.ts, 0, 40))
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>b : Symbol(b, Decl(typeInferenceOnIndexUnion.ts, 0, 48))
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declare function f<T extends Options>(p: T["k"]): T;
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>f : Symbol(f, Decl(typeInferenceOnIndexUnion.ts, 0, 61))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 1, 19))
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>Options : Symbol(Options, Decl(typeInferenceOnIndexUnion.ts, 0, 0))
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>p : Symbol(p, Decl(typeInferenceOnIndexUnion.ts, 1, 38))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 1, 19))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 1, 19))
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const x = f("a"); // expect it to be `{ k: "a", a: number }`
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>x : Symbol(x, Decl(typeInferenceOnIndexUnion.ts, 2, 5))
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>f : Symbol(f, Decl(typeInferenceOnIndexUnion.ts, 0, 61))
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type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
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>Options2 : Symbol(Options2, Decl(typeInferenceOnIndexUnion.ts, 2, 17))
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>k : Symbol(k, Decl(typeInferenceOnIndexUnion.ts, 4, 17))
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>a : Symbol(a, Decl(typeInferenceOnIndexUnion.ts, 4, 25))
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>c : Symbol(c, Decl(typeInferenceOnIndexUnion.ts, 4, 36))
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>k : Symbol(k, Decl(typeInferenceOnIndexUnion.ts, 4, 48))
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>b : Symbol(b, Decl(typeInferenceOnIndexUnion.ts, 4, 56))
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>c : Symbol(c, Decl(typeInferenceOnIndexUnion.ts, 4, 67))
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declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
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>f2 : Symbol(f2, Decl(typeInferenceOnIndexUnion.ts, 4, 76))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 5, 20))
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>Options2 : Symbol(Options2, Decl(typeInferenceOnIndexUnion.ts, 2, 17))
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>p : Symbol(p, Decl(typeInferenceOnIndexUnion.ts, 5, 40))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 5, 20))
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>c : Symbol(c, Decl(typeInferenceOnIndexUnion.ts, 5, 50))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 5, 20))
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>T : Symbol(T, Decl(typeInferenceOnIndexUnion.ts, 5, 20))
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const x2 = f2("a", { x: 1, y: 2 }); // expect it to be `{ k: "a", a: number, c: {x: number, y: number} }`
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>x2 : Symbol(x2, Decl(typeInferenceOnIndexUnion.ts, 6, 5))
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>f2 : Symbol(f2, Decl(typeInferenceOnIndexUnion.ts, 4, 76))
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>x : Symbol(x, Decl(typeInferenceOnIndexUnion.ts, 6, 20))
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>y : Symbol(y, Decl(typeInferenceOnIndexUnion.ts, 6, 26))
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‎tests/baselines/reference/typeInferenceOnIndexUnion.types‎

Lines changed: 52 additions & 0 deletions
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=== tests/cases/compiler/typeInferenceOnIndexUnion.ts ===
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type Options = { k: "a", a: number } | { k: "b", b: string };
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>Options : Options
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>k : "a"
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>a : number
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>k : "b"
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>b : string
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declare function f<T extends Options>(p: T["k"]): T;
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>f : <T extends Options>(p: T["k"]) => T
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>T : T
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>Options : Options
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>p : T["k"]
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>T : T
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>T : T
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const x = f("a"); // expect it to be `{ k: "a", a: number }`
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>x : { k: "a"; a: number; }
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>f("a") : { k: "a"; a: number; }
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>f : <T extends Options>(p: T["k"]) => T
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>"a" : "a"
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type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
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>Options2 : Options2
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>k : "a"
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>a : number
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>c : {}
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>k : "b"
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>b : string
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>c : {}
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declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
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>f2 : <T extends Options2>(p: T["k"], c: T["c"]) => T
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>T : T
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>Options2 : Options2
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>p : T["k"]
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>T : T
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>c : T["c"]
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>T : T
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>T : T
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const x2 = f2("a", { x: 1, y: 2 }); // expect it to be `{ k: "a", a: number, c: {x: number, y: number} }`
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>x2 : { k: "a"; c: { x: number; y: number; }; a: number; }
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>f2("a", { x: 1, y: 2 }) : { k: "a"; c: { x: number; y: number; }; a: number; }
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>f2 : <T extends Options2>(p: T["k"], c: T["c"]) => T
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>"a" : "a"
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>{ x: 1, y: 2 } : { x: number; y: number; }
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>x : number
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>1 : 1
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>y : number
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>2 : 2
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‎tests/cases/compiler/typeInferenceOnIndexUnion.ts‎

Lines changed: 7 additions & 0 deletions
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@@ -0,0 +1,7 @@
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type Options = { k: "a", a: number } | { k: "b", b: string };
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declare function f<T extends Options>(p: T["k"]): T;
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const x = f("a"); // expect it to be `{ k: "a", a: number }`
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type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
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declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
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const x2 = f2("a", { x: 1, y: 2 }); // expect it to be `{ k: "a", a: number, c: {x: number, y: number} }`

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