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weswighamweswigham
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Constrain infer type parameters made to preserver distributivity for inlined homomorphic mapped types (#49793)
1 parent e2e3c12 commit 0f86803

5 files changed

Lines changed: 170 additions & 3 deletions

‎src/compiler/checker.ts‎

Lines changed: 9 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -5217,6 +5217,11 @@ m2: ${(this.mapper2 as unknown as DebugTypeMapper).__debugToString().split("\n")
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return typeToTypeNodeHelper(type, context);
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}
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function isHomomorphicMappedTypeWithNonHomomorphicInstantiation(type: MappedType) {
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return isMappedTypeWithKeyofConstraintDeclaration(type)
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&& !(getModifiersTypeFromMappedType(type).flags & TypeFlags.TypeParameter);
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}
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function createMappedTypeNodeFromType(type: MappedType) {
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Debug.assert(!!(type.flags & TypeFlags.Object));
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const readonlyToken = type.declaration.readonlyToken ? factory.createToken(type.declaration.readonlyToken.kind) as ReadonlyKeyword | PlusToken | MinusToken : undefined;
@@ -5226,7 +5231,7 @@ m2: ${(this.mapper2 as unknown as DebugTypeMapper).__debugToString().split("\n")
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if (isMappedTypeWithKeyofConstraintDeclaration(type)) {
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// We have a { [P in keyof T]: X }
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// We do this to ensure we retain the toplevel keyof-ness of the type which may be lost due to keyof distribution during `getConstraintTypeFromMappedType`
5229-
if (!(getModifiersTypeFromMappedType(type).flags & TypeFlags.TypeParameter) && context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams) {
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if (isHomomorphicMappedTypeWithNonHomomorphicInstantiation(type) && context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams) {
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const newParam = createTypeParameter(createSymbol(SymbolFlags.TypeParameter, "T" as __String));
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const name = typeParameterToName(newParam, context);
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newTypeVariable = factory.createTypeReferenceNode(name);
@@ -5242,13 +5247,14 @@ m2: ${(this.mapper2 as unknown as DebugTypeMapper).__debugToString().split("\n")
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const mappedTypeNode = factory.createMappedTypeNode(readonlyToken, typeParameterNode, nameTypeNode, questionToken, templateTypeNode, /*members*/ undefined);
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context.approximateLength += 10;
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const result = setEmitFlags(mappedTypeNode, EmitFlags.SingleLine);
5245-
if (isMappedTypeWithKeyofConstraintDeclaration(type) && !(getModifiersTypeFromMappedType(type).flags & TypeFlags.TypeParameter) && context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams) {
5250+
if (isHomomorphicMappedTypeWithNonHomomorphicInstantiation(type) && context.flags & NodeBuilderFlags.GenerateNamesForShadowedTypeParams) {
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// homomorphic mapped type with a non-homomorphic naive inlining
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// wrap it with a conditional like `SomeModifiersType extends infer U ? {..the mapped type...} : never` to ensure the resulting
52485253
// type stays homomorphic
5254+
const originalConstraint = instantiateType(getConstraintOfTypeParameter(getTypeFromTypeNode((type.declaration.typeParameter.constraint! as TypeOperatorNode).type) as TypeParameter) || unknownType, type.mapper);
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return factory.createConditionalTypeNode(
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typeToTypeNodeHelper(getModifiersTypeFromMappedType(type), context),
5251-
factory.createInferTypeNode(factory.createTypeParameterDeclaration(/*modifiers*/ undefined, factory.cloneNode(newTypeVariable!.typeName) as Identifier)),
5257+
factory.createInferTypeNode(factory.createTypeParameterDeclaration(/*modifiers*/ undefined, factory.cloneNode(newTypeVariable!.typeName) as Identifier, originalConstraint.flags & TypeFlags.Unknown ? undefined : typeToTypeNodeHelper(originalConstraint, context))),
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result,
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factory.createKeywordTypeNode(SyntaxKind.NeverKeyword)
52545260
);

‎tests/baselines/reference/declarationEmitMappedTypeDistributivityPreservesConstraints.js‎

Lines changed: 61 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,61 @@
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//// [tests/cases/compiler/declarationEmitMappedTypeDistributivityPreservesConstraints.ts] ////
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//// [types.ts]
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type Fns = Record<string, (...params: unknown[]) => unknown>
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type Map<T extends Fns> = { [K in keyof T]: T[K]; };
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type AllArg<T extends Fns> = { [K in keyof T]: Parameters<T[K]> };
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function fn<T extends { x: Map<T['x']> }>(sliceIndex: T): AllArg<T['x']> {
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return null!;
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}
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export default { fn };
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//// [reexport.ts]
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import test from "./types";
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export default { test };
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//// [types.js]
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"use strict";
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exports.__esModule = true;
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function fn(sliceIndex) {
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return null;
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}
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exports["default"] = { fn: fn };
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//// [reexport.js]
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"use strict";
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exports.__esModule = true;
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var types_1 = require("./types");
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exports["default"] = { test: types_1["default"] };
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//// [types.d.ts]
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declare type Fns = Record<string, (...params: unknown[]) => unknown>;
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declare type Map<T extends Fns> = {
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[K in keyof T]: T[K];
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};
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declare type AllArg<T extends Fns> = {
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[K in keyof T]: Parameters<T[K]>;
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};
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declare function fn<T extends {
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x: Map<T['x']>;
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}>(sliceIndex: T): AllArg<T['x']>;
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declare const _default: {
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fn: typeof fn;
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};
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export default _default;
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//// [reexport.d.ts]
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declare const _default: {
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test: {
52+
fn: <T_1 extends {
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x: T_1["x"] extends infer T extends {
54+
[x: string]: (...params: unknown[]) => unknown;
55+
} ? { [K in keyof T]: T_1["x"][K]; } : never;
56+
}>(sliceIndex: T_1) => T_1["x"] extends infer T_2 extends {
57+
[x: string]: (...params: unknown[]) => unknown;
58+
} ? { [K_1 in keyof T_2]: Parameters<T_1["x"][K_1]>; } : never;
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};
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};
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export default _default;

‎tests/baselines/reference/declarationEmitMappedTypeDistributivityPreservesConstraints.symbols‎

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@@ -0,0 +1,49 @@
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=== tests/cases/compiler/types.ts ===
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type Fns = Record<string, (...params: unknown[]) => unknown>
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>Fns : Symbol(Fns, Decl(types.ts, 0, 0))
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>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
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>params : Symbol(params, Decl(types.ts, 0, 27))
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type Map<T extends Fns> = { [K in keyof T]: T[K]; };
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>Map : Symbol(Map, Decl(types.ts, 0, 60))
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>T : Symbol(T, Decl(types.ts, 2, 9))
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>Fns : Symbol(Fns, Decl(types.ts, 0, 0))
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>K : Symbol(K, Decl(types.ts, 2, 29))
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>T : Symbol(T, Decl(types.ts, 2, 9))
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>T : Symbol(T, Decl(types.ts, 2, 9))
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>K : Symbol(K, Decl(types.ts, 2, 29))
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type AllArg<T extends Fns> = { [K in keyof T]: Parameters<T[K]> };
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>AllArg : Symbol(AllArg, Decl(types.ts, 2, 52))
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>T : Symbol(T, Decl(types.ts, 4, 12))
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>Fns : Symbol(Fns, Decl(types.ts, 0, 0))
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>K : Symbol(K, Decl(types.ts, 4, 32))
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>T : Symbol(T, Decl(types.ts, 4, 12))
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>Parameters : Symbol(Parameters, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(types.ts, 4, 12))
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>K : Symbol(K, Decl(types.ts, 4, 32))
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function fn<T extends { x: Map<T['x']> }>(sliceIndex: T): AllArg<T['x']> {
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>fn : Symbol(fn, Decl(types.ts, 4, 66))
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>T : Symbol(T, Decl(types.ts, 6, 12))
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>x : Symbol(x, Decl(types.ts, 6, 23))
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>Map : Symbol(Map, Decl(types.ts, 0, 60))
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>T : Symbol(T, Decl(types.ts, 6, 12))
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>sliceIndex : Symbol(sliceIndex, Decl(types.ts, 6, 42))
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>T : Symbol(T, Decl(types.ts, 6, 12))
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>AllArg : Symbol(AllArg, Decl(types.ts, 2, 52))
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>T : Symbol(T, Decl(types.ts, 6, 12))
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return null!;
38+
}
39+
40+
export default { fn };
41+
>fn : Symbol(fn, Decl(types.ts, 10, 16))
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=== tests/cases/compiler/reexport.ts ===
44+
import test from "./types";
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>test : Symbol(test, Decl(reexport.ts, 0, 6))
46+
47+
export default { test };
48+
>test : Symbol(test, Decl(reexport.ts, 1, 16))
49+

‎tests/baselines/reference/declarationEmitMappedTypeDistributivityPreservesConstraints.types‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,33 @@
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=== tests/cases/compiler/types.ts ===
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type Fns = Record<string, (...params: unknown[]) => unknown>
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>Fns : { [x: string]: (...params: unknown[]) => unknown; }
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>params : unknown[]
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type Map<T extends Fns> = { [K in keyof T]: T[K]; };
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>Map : Map<T>
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type AllArg<T extends Fns> = { [K in keyof T]: Parameters<T[K]> };
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>AllArg : AllArg<T>
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function fn<T extends { x: Map<T['x']> }>(sliceIndex: T): AllArg<T['x']> {
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>fn : <T extends { x: Map<T['x']>; }>(sliceIndex: T) => AllArg<T['x']>
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>x : Map<T["x"]>
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>sliceIndex : T
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17+
return null!;
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>null! : null
19+
>null : null
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}
21+
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export default { fn };
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>{ fn } : { fn: <T extends { x: Map<T["x"]>; }>(sliceIndex: T) => AllArg<T["x"]>; }
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>fn : <T extends { x: Map<T["x"]>; }>(sliceIndex: T) => AllArg<T["x"]>
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=== tests/cases/compiler/reexport.ts ===
27+
import test from "./types";
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>test : { fn: <T extends { x: { [K in keyof T["x"]]: T["x"][K]; }; }>(sliceIndex: T) => { [K in keyof T["x"]]: Parameters<T["x"][K]>; }; }
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export default { test };
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>{ test } : { test: { fn: <T extends { x: { [K in keyof T["x"]]: T["x"][K]; }; }>(sliceIndex: T) => { [K in keyof T["x"]]: Parameters<T["x"][K]>; }; }; }
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>test : { fn: <T extends { x: { [K in keyof T["x"]]: T["x"][K]; }; }>(sliceIndex: T) => { [K in keyof T["x"]]: Parameters<T["x"][K]>; }; }
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‎tests/cases/compiler/declarationEmitMappedTypeDistributivityPreservesConstraints.ts‎

Lines changed: 18 additions & 0 deletions
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@@ -0,0 +1,18 @@
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// @declaration: true
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// @filename: types.ts
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type Fns = Record<string, (...params: unknown[]) => unknown>
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type Map<T extends Fns> = { [K in keyof T]: T[K]; };
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type AllArg<T extends Fns> = { [K in keyof T]: Parameters<T[K]> };
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function fn<T extends { x: Map<T['x']> }>(sliceIndex: T): AllArg<T['x']> {
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return null!;
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}
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export default { fn };
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// @filename: reexport.ts
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import test from "./types";
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export default { test };

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