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weswighamweswigham
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Dont create a union type to infer conditional type branches (#30010)
1 parent 2533d82 commit 2888510

5 files changed

+202
-1
lines changed

‎src/compiler/checker.ts

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14519,7 +14519,8 @@ namespace ts {
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inferFromTypes(getFalseTypeFromConditionalType(<ConditionalType>source), getFalseTypeFromConditionalType(<ConditionalType>target));
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}
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else if (target.flags & TypeFlags.Conditional) {
14522-
inferFromTypes(source, getUnionType([getTrueTypeFromConditionalType(<ConditionalType>target), getFalseTypeFromConditionalType(<ConditionalType>target)]));
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inferFromTypes(source, getTrueTypeFromConditionalType(<ConditionalType>target));
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inferFromTypes(source, getFalseTypeFromConditionalType(<ConditionalType>target));
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}
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else if (target.flags & TypeFlags.UnionOrIntersection) {
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for (const t of (<UnionOrIntersectionType>target).types) {

‎tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.js

Lines changed: 39 additions & 0 deletions
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@@ -0,0 +1,39 @@
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//// [conditionalTypeRelaxingConstraintAssignability.ts]
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export type ElChildren =
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| ElChildren.Void
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| ElChildren.Text;
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export namespace ElChildren {
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export type Void = undefined;
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export type Text = string;
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}
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type Relax<C extends ElChildren> = C extends ElChildren.Text ? ElChildren.Text : C;
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export class Elem<
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C extends ElChildren,
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> {
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constructor(
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private children_: Relax<C>,
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) {
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}
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}
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new Elem(undefined as ElChildren.Void);
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new Elem('' as ElChildren.Text);
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new Elem('' as ElChildren.Void | ElChildren.Text); // error
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new Elem('' as ElChildren); // error
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//// [conditionalTypeRelaxingConstraintAssignability.js]
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"use strict";
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exports.__esModule = true;
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var Elem = /** @class */ (function () {
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function Elem(children_) {
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this.children_ = children_;
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}
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return Elem;
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}());
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exports.Elem = Elem;
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new Elem(undefined);
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new Elem('');
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new Elem(''); // error
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new Elem(''); // error

‎tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.symbols

Lines changed: 73 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,73 @@
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=== tests/cases/compiler/conditionalTypeRelaxingConstraintAssignability.ts ===
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export type ElChildren =
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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| ElChildren.Void
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Void : Symbol(ElChildren.Void, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 3, 29))
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| ElChildren.Text;
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Text : Symbol(ElChildren.Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
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export namespace ElChildren {
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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export type Void = undefined;
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>Void : Symbol(Void, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 3, 29))
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export type Text = string;
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>Text : Symbol(Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
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}
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type Relax<C extends ElChildren> = C extends ElChildren.Text ? ElChildren.Text : C;
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>Relax : Symbol(Relax, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 6, 1))
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>C : Symbol(C, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 11))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>C : Symbol(C, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 11))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Text : Symbol(ElChildren.Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Text : Symbol(ElChildren.Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
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>C : Symbol(C, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 11))
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export class Elem<
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>Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
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C extends ElChildren,
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>C : Symbol(C, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 10, 18))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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> {
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constructor(
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private children_: Relax<C>,
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>children_ : Symbol(Elem.children_, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 13, 14))
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>Relax : Symbol(Relax, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 6, 1))
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>C : Symbol(C, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 10, 18))
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48+
) {
49+
}
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}
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new Elem(undefined as ElChildren.Void);
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>Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
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>undefined : Symbol(undefined)
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Void : Symbol(ElChildren.Void, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 3, 29))
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new Elem('' as ElChildren.Text);
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>Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Text : Symbol(ElChildren.Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
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new Elem('' as ElChildren.Void | ElChildren.Text); // error
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>Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Void : Symbol(ElChildren.Void, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 3, 29))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
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>Text : Symbol(ElChildren.Text, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 4, 31))
69+
70+
new Elem('' as ElChildren); // error
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>Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
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>ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
73+

‎tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.types

Lines changed: 64 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,64 @@
1+
=== tests/cases/compiler/conditionalTypeRelaxingConstraintAssignability.ts ===
2+
export type ElChildren =
3+
>ElChildren : ElChildren
4+
5+
| ElChildren.Void
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>ElChildren : any
7+
8+
| ElChildren.Text;
9+
>ElChildren : any
10+
11+
export namespace ElChildren {
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export type Void = undefined;
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>Void : undefined
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export type Text = string;
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>Text : string
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}
18+
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type Relax<C extends ElChildren> = C extends ElChildren.Text ? ElChildren.Text : C;
20+
>Relax : Relax<C>
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>ElChildren : any
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>ElChildren : any
23+
24+
export class Elem<
25+
>Elem : Elem<C>
26+
27+
C extends ElChildren,
28+
> {
29+
constructor(
30+
private children_: Relax<C>,
31+
>children_ : Relax<C>
32+
33+
) {
34+
}
35+
}
36+
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new Elem(undefined as ElChildren.Void);
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>new Elem(undefined as ElChildren.Void) : Elem<undefined>
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>Elem : typeof Elem
40+
>undefined as ElChildren.Void : undefined
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>undefined : undefined
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>ElChildren : any
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new Elem('' as ElChildren.Text);
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>new Elem('' as ElChildren.Text) : Elem<string>
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>Elem : typeof Elem
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>'' as ElChildren.Text : string
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>'' : ""
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>ElChildren : any
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new Elem('' as ElChildren.Void | ElChildren.Text); // error
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>new Elem('' as ElChildren.Void | ElChildren.Text) : Elem<ElChildren>
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>Elem : typeof Elem
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>'' as ElChildren.Void | ElChildren.Text : ElChildren
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>'' : ""
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>ElChildren : any
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>ElChildren : any
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new Elem('' as ElChildren); // error
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>new Elem('' as ElChildren) : Elem<ElChildren>
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>Elem : typeof Elem
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>'' as ElChildren : ElChildren
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>'' : ""
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‎tests/cases/compiler/conditionalTypeRelaxingConstraintAssignability.ts

Lines changed: 24 additions & 0 deletions
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@@ -0,0 +1,24 @@
1+
// @strict: true
2+
export type ElChildren =
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| ElChildren.Void
4+
| ElChildren.Text;
5+
export namespace ElChildren {
6+
export type Void = undefined;
7+
export type Text = string;
8+
}
9+
10+
type Relax<C extends ElChildren> = C extends ElChildren.Text ? ElChildren.Text : C;
11+
12+
export class Elem<
13+
C extends ElChildren,
14+
> {
15+
constructor(
16+
private children_: Relax<C>,
17+
) {
18+
}
19+
}
20+
21+
new Elem(undefined as ElChildren.Void);
22+
new Elem('' as ElChildren.Text);
23+
new Elem('' as ElChildren.Void | ElChildren.Text); // error
24+
new Elem('' as ElChildren); // error

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