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Discard types that reduce to never before discriminating by discriminable items (#62275)
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4 files changed

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‎src/compiler/checker.ts‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -24881,7 +24881,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
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function discriminateTypeByDiscriminableItems(target: UnionType, discriminators: (readonly [() => Type, __String])[], related: (source: Type, target: Type) => boolean | Ternary) {
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const types = target.types;
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const include: Ternary[] = types.map(t => t.flags & TypeFlags.Primitive ? Ternary.False : Ternary.True);
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const include: Ternary[] = types.map(t => t.flags & TypeFlags.Primitive || getReducedType(t).flags & TypeFlags.Never ? Ternary.False : Ternary.True);
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for (const [getDiscriminatingType, propertyName] of discriminators) {
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// If the remaining target types include at least one with a matching discriminant, eliminate those that
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// have non-matching discriminants. This ensures that we ignore erroneous discriminators and gradually

‎tests/baselines/reference/contextuallyTypedByDiscriminableUnion2.symbols‎

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//// [tests/cases/compiler/contextuallyTypedByDiscriminableUnion2.ts] ////
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=== contextuallyTypedByDiscriminableUnion2.ts ===
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// https://github.com/microsoft/TypeScript/issues/62256
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type Identifiable = { id: string };
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>Identifiable : Symbol(Identifiable, Decl(contextuallyTypedByDiscriminableUnion2.ts, 0, 0))
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>id : Symbol(id, Decl(contextuallyTypedByDiscriminableUnion2.ts, 2, 21))
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interface EnableA {
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>EnableA : Symbol(EnableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 2, 35))
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readonly enableA: true;
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>enableA : Symbol(EnableA.enableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 4, 19))
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// this introduces a conflicting property with some of the other members of MyComponentProps
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// making relevant final union members reduced nevers
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readonly enableB: true;
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>enableB : Symbol(EnableA.enableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 5, 25))
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}
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interface DisableA {
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>DisableA : Symbol(DisableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 9, 1))
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readonly enableA?: false;
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>enableA : Symbol(DisableA.enableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 11, 20))
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}
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interface EnableB {
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>EnableB : Symbol(EnableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 13, 1))
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readonly enableB?: true;
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>enableB : Symbol(EnableB.enableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 15, 19))
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}
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interface DisableB {
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>DisableB : Symbol(DisableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 17, 1))
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readonly enableB: false;
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>enableB : Symbol(DisableB.enableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 19, 20))
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}
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export interface EnableD<I extends Identifiable> {
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>EnableD : Symbol(EnableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 21, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 23, 25))
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>Identifiable : Symbol(Identifiable, Decl(contextuallyTypedByDiscriminableUnion2.ts, 0, 0))
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readonly enableD: true;
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>enableD : Symbol(EnableD.enableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 23, 50))
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readonly value: I["id"] | null;
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>value : Symbol(EnableD.value, Decl(contextuallyTypedByDiscriminableUnion2.ts, 24, 25))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 23, 25))
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readonly setItem: (item: I | null) => void;
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>setItem : Symbol(EnableD.setItem, Decl(contextuallyTypedByDiscriminableUnion2.ts, 25, 33))
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>item : Symbol(item, Decl(contextuallyTypedByDiscriminableUnion2.ts, 26, 21))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 23, 25))
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}
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export interface DisableD<I extends Identifiable> {
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>DisableD : Symbol(DisableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 27, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 29, 26))
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>Identifiable : Symbol(Identifiable, Decl(contextuallyTypedByDiscriminableUnion2.ts, 0, 0))
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readonly enableD: false;
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>enableD : Symbol(DisableD.enableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 29, 51))
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readonly value: I["id"];
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>value : Symbol(DisableD.value, Decl(contextuallyTypedByDiscriminableUnion2.ts, 30, 26))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 29, 26))
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readonly setItem: (item: I) => void;
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>setItem : Symbol(DisableD.setItem, Decl(contextuallyTypedByDiscriminableUnion2.ts, 31, 26))
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>item : Symbol(item, Decl(contextuallyTypedByDiscriminableUnion2.ts, 32, 21))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 29, 26))
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}
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type MyComponentProps<I extends Identifiable> = (EnableA | DisableA) &
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>MyComponentProps : Symbol(MyComponentProps, Decl(contextuallyTypedByDiscriminableUnion2.ts, 33, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 35, 22))
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>Identifiable : Symbol(Identifiable, Decl(contextuallyTypedByDiscriminableUnion2.ts, 0, 0))
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>EnableA : Symbol(EnableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 2, 35))
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>DisableA : Symbol(DisableA, Decl(contextuallyTypedByDiscriminableUnion2.ts, 9, 1))
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(EnableB | DisableB) &
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>EnableB : Symbol(EnableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 13, 1))
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>DisableB : Symbol(DisableB, Decl(contextuallyTypedByDiscriminableUnion2.ts, 17, 1))
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(DisableD<I> | EnableD<I>);
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>DisableD : Symbol(DisableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 27, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 35, 22))
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>EnableD : Symbol(EnableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 21, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 35, 22))
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const MyComponent = <I extends Identifiable>(props: MyComponentProps<I>) => {};
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>MyComponent : Symbol(MyComponent, Decl(contextuallyTypedByDiscriminableUnion2.ts, 39, 5))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 39, 21))
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>Identifiable : Symbol(Identifiable, Decl(contextuallyTypedByDiscriminableUnion2.ts, 0, 0))
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>props : Symbol(props, Decl(contextuallyTypedByDiscriminableUnion2.ts, 39, 45))
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>MyComponentProps : Symbol(MyComponentProps, Decl(contextuallyTypedByDiscriminableUnion2.ts, 33, 1))
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>I : Symbol(I, Decl(contextuallyTypedByDiscriminableUnion2.ts, 39, 21))
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declare const item: string | null;
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>item : Symbol(item, Decl(contextuallyTypedByDiscriminableUnion2.ts, 41, 13))
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MyComponent({
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>MyComponent : Symbol(MyComponent, Decl(contextuallyTypedByDiscriminableUnion2.ts, 39, 5))
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enableD: true,
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>enableD : Symbol(enableD, Decl(contextuallyTypedByDiscriminableUnion2.ts, 43, 13))
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value: item,
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>value : Symbol(value, Decl(contextuallyTypedByDiscriminableUnion2.ts, 44, 16))
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>item : Symbol(item, Decl(contextuallyTypedByDiscriminableUnion2.ts, 41, 13))
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setItem: (item) => {},
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>setItem : Symbol(setItem, Decl(contextuallyTypedByDiscriminableUnion2.ts, 45, 14))
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>item : Symbol(item, Decl(contextuallyTypedByDiscriminableUnion2.ts, 46, 12))
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});
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‎tests/baselines/reference/contextuallyTypedByDiscriminableUnion2.types‎

Lines changed: 136 additions & 0 deletions
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//// [tests/cases/compiler/contextuallyTypedByDiscriminableUnion2.ts] ////
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=== contextuallyTypedByDiscriminableUnion2.ts ===
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// https://github.com/microsoft/TypeScript/issues/62256
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type Identifiable = { id: string };
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>Identifiable : Identifiable
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> : ^^^^^^^^^^^^
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>id : string
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> : ^^^^^^
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interface EnableA {
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readonly enableA: true;
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>enableA : true
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> : ^^^^
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>true : true
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> : ^^^^
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// this introduces a conflicting property with some of the other members of MyComponentProps
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// making relevant final union members reduced nevers
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readonly enableB: true;
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>enableB : true
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> : ^^^^
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>true : true
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> : ^^^^
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}
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interface DisableA {
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readonly enableA?: false;
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>enableA : false | undefined
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> : ^^^^^^^^^^^^^^^^^
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>false : false
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> : ^^^^^
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}
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interface EnableB {
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readonly enableB?: true;
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>enableB : true | undefined
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> : ^^^^^^^^^^^^^^^^
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>true : true
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> : ^^^^
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}
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interface DisableB {
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readonly enableB: false;
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>enableB : false
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> : ^^^^^
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>false : false
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> : ^^^^^
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}
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export interface EnableD<I extends Identifiable> {
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readonly enableD: true;
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>enableD : true
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> : ^^^^
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>true : true
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> : ^^^^
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readonly value: I["id"] | null;
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>value : I["id"] | null
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> : ^^^^^^^^^^^^^^
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readonly setItem: (item: I | null) => void;
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>setItem : (item: I | null) => void
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> : ^ ^^ ^^^^^
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>item : I | null
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> : ^^^^^^^^
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}
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export interface DisableD<I extends Identifiable> {
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readonly enableD: false;
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>enableD : false
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> : ^^^^^
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>false : false
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> : ^^^^^
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readonly value: I["id"];
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>value : I["id"]
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> : ^^^^^^^
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readonly setItem: (item: I) => void;
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>setItem : (item: I) => void
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> : ^ ^^ ^^^^^
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>item : I
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> : ^
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}
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type MyComponentProps<I extends Identifiable> = (EnableA | DisableA) &
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>MyComponentProps : (EnableA & EnableB & DisableD<I>) | (EnableA & EnableB & EnableD<I>) | (DisableA & EnableB & DisableD<I>) | (DisableA & EnableB & EnableD<I>) | (DisableA & DisableB & DisableD<I>) | (DisableA & DisableB & EnableD<I>)
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> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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(EnableB | DisableB) &
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(DisableD<I> | EnableD<I>);
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const MyComponent = <I extends Identifiable>(props: MyComponentProps<I>) => {};
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>MyComponent : <I extends Identifiable>(props: MyComponentProps<I>) => void
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> : ^ ^^^^^^^^^ ^^ ^^ ^^^^^^^^^
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><I extends Identifiable>(props: MyComponentProps<I>) => {} : <I extends Identifiable>(props: MyComponentProps<I>) => void
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> : ^ ^^^^^^^^^ ^^ ^^ ^^^^^^^^^
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>props : (EnableA & EnableB & DisableD<I>) | (EnableA & EnableB & EnableD<I>) | (DisableA & EnableB & DisableD<I>) | (DisableA & EnableB & EnableD<I>) | (DisableA & DisableB & DisableD<I>) | (DisableA & DisableB & EnableD<I>)
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> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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declare const item: string | null;
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>item : string | null
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> : ^^^^^^^^^^^^^
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MyComponent({
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>MyComponent({ enableD: true, value: item, setItem: (item) => {},}) : void
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> : ^^^^
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>MyComponent : <I extends Identifiable>(props: MyComponentProps<I>) => void
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> : ^ ^^^^^^^^^ ^^ ^^ ^^^^^^^^^
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>{ enableD: true, value: item, setItem: (item) => {},} : { enableD: true; value: string | null; setItem: (item: Identifiable | null) => void; }
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> : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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enableD: true,
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>enableD : true
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> : ^^^^
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>true : true
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> : ^^^^
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value: item,
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>value : string | null
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> : ^^^^^^^^^^^^^
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>item : string | null
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> : ^^^^^^^^^^^^^
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setItem: (item) => {},
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>setItem : (item: Identifiable | null) => void
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> : ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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>(item) => {} : (item: Identifiable | null) => void
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> : ^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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>item : Identifiable | null
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> : ^^^^^^^^^^^^^^^^^^^
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});
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‎tests/cases/compiler/contextuallyTypedByDiscriminableUnion2.ts‎

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// @strict: true
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// @noEmit: true
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// https://github.com/microsoft/TypeScript/issues/62256
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type Identifiable = { id: string };
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interface EnableA {
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readonly enableA: true;
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// this introduces a conflicting property with some of the other members of MyComponentProps
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// making relevant final union members reduced nevers
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readonly enableB: true;
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}
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interface DisableA {
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readonly enableA?: false;
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}
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interface EnableB {
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readonly enableB?: true;
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}
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interface DisableB {
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readonly enableB: false;
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}
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export interface EnableD<I extends Identifiable> {
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readonly enableD: true;
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readonly value: I["id"] | null;
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readonly setItem: (item: I | null) => void;
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}
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export interface DisableD<I extends Identifiable> {
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readonly enableD: false;
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readonly value: I["id"];
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readonly setItem: (item: I) => void;
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}
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type MyComponentProps<I extends Identifiable> = (EnableA | DisableA) &
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(EnableB | DisableB) &
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(DisableD<I> | EnableD<I>);
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const MyComponent = <I extends Identifiable>(props: MyComponentProps<I>) => {};
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declare const item: string | null;
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MyComponent({
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enableD: true,
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value: item,
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setItem: (item) => {},
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});

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