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Instantiate generic conditional infer source types in the context of the target conditional (microsoft#31545)
* Instantiate generic conditional infer source types in the context of the target conditional * Add test case from microsoft#26627
1 parent d75de60 commit fd1e22b

5 files changed

+253
-2
lines changed

‎src/compiler/checker.ts

+12-2
Original file line numberDiff line numberDiff line change
@@ -13527,9 +13527,19 @@ namespace ts {
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// Two conditional types 'T1 extends U1 ? X1 : Y1' and 'T2 extends U2 ? X2 : Y2' are related if
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// one of T1 and T2 is related to the other, U1 and U2 are identical types, X1 is related to X2,
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// and Y1 is related to Y2.
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if (isTypeIdenticalTo((<ConditionalType>source).extendsType, (<ConditionalType>target).extendsType) &&
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const sourceParams = (source as ConditionalType).root.inferTypeParameters;
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let sourceExtends = (<ConditionalType>source).extendsType;
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let mapper: TypeMapper | undefined;
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if (sourceParams) {
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// If the source has infer type parameters, we instantiate them in the context of the target
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const ctx = createInferenceContext(sourceParams, /*signature*/ undefined, InferenceFlags.None, isRelatedTo);
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inferTypes(ctx.inferences, (<ConditionalType>target).extendsType, sourceExtends, InferencePriority.NoConstraints | InferencePriority.AlwaysStrict);
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sourceExtends = instantiateType(sourceExtends, ctx.mapper);
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mapper = ctx.mapper;
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}
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if (isTypeIdenticalTo(sourceExtends, (<ConditionalType>target).extendsType) &&
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(isRelatedTo((<ConditionalType>source).checkType, (<ConditionalType>target).checkType) || isRelatedTo((<ConditionalType>target).checkType, (<ConditionalType>source).checkType))) {
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if (result = isRelatedTo(getTrueTypeFromConditionalType(<ConditionalType>source), getTrueTypeFromConditionalType(<ConditionalType>target), reportErrors)) {
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if (result = isRelatedTo(instantiateType(getTrueTypeFromConditionalType(<ConditionalType>source), mapper), getTrueTypeFromConditionalType(<ConditionalType>target), reportErrors)) {
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result &= isRelatedTo(getFalseTypeFromConditionalType(<ConditionalType>source), getFalseTypeFromConditionalType(<ConditionalType>target), reportErrors);
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}
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if (result) {

‎tests/baselines/reference/identicalGenericConditionalsWithInferRelated.js

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@@ -0,0 +1,48 @@
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//// [identicalGenericConditionalsWithInferRelated.ts]
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function f<X>(arg: X) {
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type Cond1 = X extends [infer A] ? A : never;
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type Cond2 = X extends [infer A] ? A : never;
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let x: Cond1 = null as any;
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let y: Cond2 = null as any;
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x = y; // is err, should be ok
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y = x; // is err, should be ok
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}
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// repro from https://github.com/microsoft/TypeScript/issues/26627
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export type Constructor<T> = new (...args: any[]) => T
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export type MappedResult<T> =
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T extends Boolean ? boolean :
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T extends Number ? number :
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T extends String ? string :
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T
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interface X {
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never>
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}
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class Y implements X {
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never> {
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throw new Error()
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}
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}
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//// [identicalGenericConditionalsWithInferRelated.js]
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"use strict";
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exports.__esModule = true;
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function f(arg) {
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var x = null;
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var y = null;
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x = y; // is err, should be ok
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y = x; // is err, should be ok
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}
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var Y = /** @class */ (function () {
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function Y() {
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}
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Y.prototype.decode = function (ctor) {
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throw new Error();
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};
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return Y;
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}());

‎tests/baselines/reference/identicalGenericConditionalsWithInferRelated.symbols

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@@ -0,0 +1,100 @@
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=== tests/cases/compiler/identicalGenericConditionalsWithInferRelated.ts ===
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function f<X>(arg: X) {
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>f : Symbol(f, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 0))
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 11))
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>arg : Symbol(arg, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 14))
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 11))
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type Cond1 = X extends [infer A] ? A : never;
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>Cond1 : Symbol(Cond1, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 23))
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 11))
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>A : Symbol(A, Decl(identicalGenericConditionalsWithInferRelated.ts, 1, 33))
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>A : Symbol(A, Decl(identicalGenericConditionalsWithInferRelated.ts, 1, 33))
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type Cond2 = X extends [infer A] ? A : never;
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>Cond2 : Symbol(Cond2, Decl(identicalGenericConditionalsWithInferRelated.ts, 1, 49))
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 11))
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>A : Symbol(A, Decl(identicalGenericConditionalsWithInferRelated.ts, 2, 33))
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>A : Symbol(A, Decl(identicalGenericConditionalsWithInferRelated.ts, 2, 33))
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let x: Cond1 = null as any;
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>x : Symbol(x, Decl(identicalGenericConditionalsWithInferRelated.ts, 4, 7))
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>Cond1 : Symbol(Cond1, Decl(identicalGenericConditionalsWithInferRelated.ts, 0, 23))
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let y: Cond2 = null as any;
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>y : Symbol(y, Decl(identicalGenericConditionalsWithInferRelated.ts, 5, 7))
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>Cond2 : Symbol(Cond2, Decl(identicalGenericConditionalsWithInferRelated.ts, 1, 49))
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x = y; // is err, should be ok
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>x : Symbol(x, Decl(identicalGenericConditionalsWithInferRelated.ts, 4, 7))
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>y : Symbol(y, Decl(identicalGenericConditionalsWithInferRelated.ts, 5, 7))
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y = x; // is err, should be ok
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>y : Symbol(y, Decl(identicalGenericConditionalsWithInferRelated.ts, 5, 7))
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>x : Symbol(x, Decl(identicalGenericConditionalsWithInferRelated.ts, 4, 7))
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}
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// repro from https://github.com/microsoft/TypeScript/issues/26627
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export type Constructor<T> = new (...args: any[]) => T
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>Constructor : Symbol(Constructor, Decl(identicalGenericConditionalsWithInferRelated.ts, 8, 1))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 24))
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>args : Symbol(args, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 34))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 24))
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export type MappedResult<T> =
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>MappedResult : Symbol(MappedResult, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 54))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 12, 25))
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T extends Boolean ? boolean :
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 12, 25))
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>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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T extends Number ? number :
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 12, 25))
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>Number : Symbol(Number, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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T extends String ? string :
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 12, 25))
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>String : Symbol(String, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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T
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 12, 25))
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interface X {
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 16, 5))
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never>
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>decode : Symbol(X.decode, Decl(identicalGenericConditionalsWithInferRelated.ts, 19, 13))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 11))
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>Constructor : Symbol(Constructor, Decl(identicalGenericConditionalsWithInferRelated.ts, 8, 1))
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>ctor : Symbol(ctor, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 39))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 11))
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>MappedResult : Symbol(MappedResult, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 54))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 11))
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>Constructor : Symbol(Constructor, Decl(identicalGenericConditionalsWithInferRelated.ts, 8, 1))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 89))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 20, 89))
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}
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class Y implements X {
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>Y : Symbol(Y, Decl(identicalGenericConditionalsWithInferRelated.ts, 21, 1))
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>X : Symbol(X, Decl(identicalGenericConditionalsWithInferRelated.ts, 16, 5))
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never> {
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>decode : Symbol(Y.decode, Decl(identicalGenericConditionalsWithInferRelated.ts, 23, 22))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 11))
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>Constructor : Symbol(Constructor, Decl(identicalGenericConditionalsWithInferRelated.ts, 8, 1))
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>ctor : Symbol(ctor, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 39))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 11))
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>MappedResult : Symbol(MappedResult, Decl(identicalGenericConditionalsWithInferRelated.ts, 11, 54))
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>C : Symbol(C, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 11))
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>Constructor : Symbol(Constructor, Decl(identicalGenericConditionalsWithInferRelated.ts, 8, 1))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 89))
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>T : Symbol(T, Decl(identicalGenericConditionalsWithInferRelated.ts, 24, 89))
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throw new Error()
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>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
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}
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}
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‎tests/baselines/reference/identicalGenericConditionalsWithInferRelated.types

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=== tests/cases/compiler/identicalGenericConditionalsWithInferRelated.ts ===
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function f<X>(arg: X) {
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>f : <X>(arg: X) => void
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>arg : X
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type Cond1 = X extends [infer A] ? A : never;
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>Cond1 : X extends [infer A] ? A : never
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type Cond2 = X extends [infer A] ? A : never;
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>Cond2 : X extends [infer A] ? A : never
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let x: Cond1 = null as any;
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>x : X extends [infer A] ? A : never
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>null as any : any
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>null : null
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let y: Cond2 = null as any;
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>y : X extends [infer A] ? A : never
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>null as any : any
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>null : null
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x = y; // is err, should be ok
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>x = y : X extends [infer A] ? A : never
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>x : X extends [infer A] ? A : never
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>y : X extends [infer A] ? A : never
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y = x; // is err, should be ok
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>y = x : X extends [infer A] ? A : never
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>y : X extends [infer A] ? A : never
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>x : X extends [infer A] ? A : never
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}
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// repro from https://github.com/microsoft/TypeScript/issues/26627
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export type Constructor<T> = new (...args: any[]) => T
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>Constructor : Constructor<T>
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>args : any[]
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export type MappedResult<T> =
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>MappedResult : MappedResult<T>
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T extends Boolean ? boolean :
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T extends Number ? number :
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T extends String ? string :
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T
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interface X {
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never>
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>decode : <C extends Constructor<any>>(ctor: C) => MappedResult<C extends Constructor<infer T> ? T : never>
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>ctor : C
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}
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class Y implements X {
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>Y : Y
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never> {
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>decode : <C extends Constructor<any>>(ctor: C) => MappedResult<C extends Constructor<infer T> ? T : never>
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>ctor : C
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throw new Error()
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>new Error() : Error
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>Error : ErrorConstructor
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}
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}
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‎tests/cases/compiler/identicalGenericConditionalsWithInferRelated.ts

+28
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@@ -0,0 +1,28 @@
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function f<X>(arg: X) {
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type Cond1 = X extends [infer A] ? A : never;
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type Cond2 = X extends [infer A] ? A : never;
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let x: Cond1 = null as any;
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let y: Cond2 = null as any;
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x = y; // is err, should be ok
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y = x; // is err, should be ok
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}
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// repro from https://github.com/microsoft/TypeScript/issues/26627
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export type Constructor<T> = new (...args: any[]) => T
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export type MappedResult<T> =
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T extends Boolean ? boolean :
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T extends Number ? number :
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T extends String ? string :
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T
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interface X {
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never>
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}
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class Y implements X {
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decode<C extends Constructor<any>>(ctor: C): MappedResult<C extends Constructor<infer T> ? T : never> {
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throw new Error()
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}
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}

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