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Discriminate partial inferences if not complete enough to satisfy constraint
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5 files changed

+149
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5 files changed

+149
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lines changed

‎src/compiler/checker.ts

Lines changed: 32 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11552,7 +11552,38 @@ namespace ts {
1155211552
if (!inferredType) {
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if (inference.indexes) {
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// Build a candidate from all indexes
11555-
(inference.candidates || (inference.candidates = [])).push(getIntersectionType(inference.indexes));
11555+
let aggregateInference = getIntersectionType(inference.indexes);
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const constraint = getConstraintOfTypeParameter(context.signature.typeParameters[index]);
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if (constraint) {
11558+
const instantiatedConstraint = instantiateType(constraint, context);
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if (!context.compareTypes(aggregateInference, getTypeWithThisArgument(instantiatedConstraint, aggregateInference))) {
11560+
if (instantiatedConstraint.flags & TypeFlags.Union) {
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const discriminantProps = findDiscriminantProperties(getPropertiesOfType(aggregateInference), instantiatedConstraint);
11562+
if (discriminantProps) {
11563+
let match: Type;
11564+
findDiscriminant: for (const p of discriminantProps) {
11565+
const candidatePropType = getTypeOfPropertyOfType(aggregateInference, p.escapedName);
11566+
for (const type of (instantiatedConstraint as UnionType).types) {
11567+
const propType = getTypeOfPropertyOfType(type, p.escapedName);
11568+
if (propType && checkTypeAssignableTo(candidatePropType, propType, /*errorNode*/ undefined)) {
11569+
if (match && match !== type) {
11570+
match = undefined;
11571+
break findDiscriminant;
11572+
}
11573+
else {
11574+
match = type;
11575+
}
11576+
}
11577+
}
11578+
}
11579+
if (match) {
11580+
aggregateInference = getSpreadType(match, aggregateInference, /*symbol*/ undefined, /*propegatedFlags*/ 0);
11581+
}
11582+
}
11583+
}
11584+
}
11585+
}
11586+
(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
Original file line numberDiff line numberDiff line change
@@ -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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10+
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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
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,45 @@
1+
=== 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 }`
18+
>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))
29+
30+
declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
31+
>f2 : Symbol(f2, Decl(typeInferenceOnIndexUnion.ts, 4, 76))
32+
>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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40+
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))
45+

‎tests/baselines/reference/typeInferenceOnIndexUnion.types

Lines changed: 52 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,52 @@
1+
=== 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
4+
>k : "a"
5+
>a : number
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>k : "b"
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>b : string
8+
9+
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
13+
>p : T["k"]
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>T : T
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>T : T
16+
17+
const x = f("a"); // expect it to be `{ k: "a", a: number }`
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>x : { k: "a"; a: number; }
19+
>f("a") : { k: "a"; a: number; }
20+
>f : <T extends Options>(p: T["k"]) => T
21+
>"a" : "a"
22+
23+
type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
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>Options2 : Options2
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>k : "a"
26+
>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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32+
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
40+
>T : T
41+
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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; }
44+
>f2("a", { x: 1, y: 2 }) : { k: "a"; c: { x: number; y: number; }; a: number; }
45+
>f2 : <T extends Options2>(p: T["k"], c: T["c"]) => T
46+
>"a" : "a"
47+
>{ x: 1, y: 2 } : { x: number; y: number; }
48+
>x : number
49+
>1 : 1
50+
>y : number
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>2 : 2
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‎tests/cases/compiler/typeInferenceOnIndexUnion.ts

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
1+
type Options = { k: "a", a: number } | { k: "b", b: string };
2+
declare function f<T extends Options>(p: T["k"]): T;
3+
const x = f("a"); // expect it to be `{ k: "a", a: number }`
4+
5+
type Options2 = { k: "a", a: number, c: {} } | { k: "b", b: string, c: {} };
6+
declare function f2<T extends Options2>(p: T["k"], c: T["c"]): T;
7+
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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