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Properly remove generic types that are constrained to 'null | undefined' in getNonNullableType (#44219)
* Improve getNonNullableType function * Add tests * More closely match previous behavior * Add non-strict mode test
1 parent 52cefdf commit 3938958

9 files changed

+332
-6
lines changed

‎src/compiler/checker.ts

Lines changed: 9 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -20325,14 +20325,17 @@ namespace ts {
2032520325
}
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2032720327
function getGlobalNonNullableTypeInstantiation(type: Type) {
20328+
// First reduce away any constituents that are assignable to 'undefined' or 'null'. This not only eliminates
20329+
// 'undefined' and 'null', but also higher-order types such as a type parameter 'U extends undefined | null'
20330+
// that isn't eliminated by a NonNullable<T> instantiation.
20331+
const reducedType = getTypeWithFacts(type, TypeFacts.NEUndefinedOrNull);
2032820332
if (!deferredGlobalNonNullableTypeAlias) {
2032920333
deferredGlobalNonNullableTypeAlias = getGlobalSymbol("NonNullable" as __String, SymbolFlags.TypeAlias, /*diagnostic*/ undefined) || unknownSymbol;
2033020334
}
20331-
// Use NonNullable global type alias if available to improve quick info/declaration emit
20332-
if (deferredGlobalNonNullableTypeAlias !== unknownSymbol) {
20333-
return getTypeAliasInstantiation(deferredGlobalNonNullableTypeAlias, [type]);
20334-
}
20335-
return getTypeWithFacts(type, TypeFacts.NEUndefinedOrNull); // Type alias unavailable, fall back to non-higher-order behavior
20335+
// If the NonNullable<T> type is available, return an instantiation. Otherwise just return the reduced type.
20336+
return deferredGlobalNonNullableTypeAlias !== unknownSymbol ?
20337+
getTypeAliasInstantiation(deferredGlobalNonNullableTypeAlias, [reducedType]) :
20338+
reducedType;
2033620339
}
2033720340

2033820341
function getNonNullableType(type: Type): Type {
@@ -24124,7 +24127,7 @@ namespace ts {
2412424127
}
2412524128

2412624129
function isGenericTypeWithUnionConstraint(type: Type) {
24127-
return !!(type.flags & TypeFlags.Instantiable && getBaseConstraintOrType(type).flags & TypeFlags.Union);
24130+
return !!(type.flags & TypeFlags.Instantiable && getBaseConstraintOrType(type).flags & (TypeFlags.Nullable | TypeFlags.Union));
2412824131
}
2412924132

2413024133
function containsGenericType(type: Type): boolean {

‎tests/baselines/reference/nonNullableReduction.js

Lines changed: 33 additions & 0 deletions
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@@ -0,0 +1,33 @@
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//// [nonNullableReduction.ts]
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// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
6+
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function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
8+
f1?.("hello");
9+
f2?.("hello");
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}
11+
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
13+
let z = x!; // NonNullable<T>
14+
}
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function f2<T, U extends null | undefined>(x: T | U) {
17+
let z = x!; // NonNullable<T>
18+
}
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//// [nonNullableReduction.js]
22+
"use strict";
23+
// Repros from #43425
24+
function test(f1, f2) {
25+
f1 === null || f1 === void 0 ? void 0 : f1("hello");
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f2 === null || f2 === void 0 ? void 0 : f2("hello");
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}
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function f1(x) {
29+
var z = x; // NonNullable<T>
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}
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function f2(x) {
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var z = x; // NonNullable<T>
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}

‎tests/baselines/reference/nonNullableReduction.symbols

Lines changed: 61 additions & 0 deletions
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@@ -0,0 +1,61 @@
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=== tests/cases/compiler/nonNullableReduction.ts ===
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// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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>Transform1 : Symbol(Transform1, Decl(nonNullableReduction.ts, 0, 0))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 2, 16))
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>value : Symbol(value, Decl(nonNullableReduction.ts, 2, 23))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 2, 16))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 2, 16))
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type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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>Transform2 : Symbol(Transform2, Decl(nonNullableReduction.ts, 2, 85))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 3, 16))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 3, 16))
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>value : Symbol(value, Decl(nonNullableReduction.ts, 3, 42))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 3, 16))
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>value : Symbol(value, Decl(nonNullableReduction.ts, 3, 78))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 3, 16))
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function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
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>test : Symbol(test, Decl(nonNullableReduction.ts, 3, 98))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 5, 14))
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>f1 : Symbol(f1, Decl(nonNullableReduction.ts, 5, 17))
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>Transform1 : Symbol(Transform1, Decl(nonNullableReduction.ts, 0, 0))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 5, 14))
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>f2 : Symbol(f2, Decl(nonNullableReduction.ts, 5, 35))
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>Transform2 : Symbol(Transform2, Decl(nonNullableReduction.ts, 2, 85))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 5, 14))
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f1?.("hello");
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>f1 : Symbol(f1, Decl(nonNullableReduction.ts, 5, 17))
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f2?.("hello");
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>f2 : Symbol(f2, Decl(nonNullableReduction.ts, 5, 35))
35+
}
36+
37+
function f1<T>(x: T | (string extends T ? null | undefined : never)) {
38+
>f1 : Symbol(f1, Decl(nonNullableReduction.ts, 8, 1))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 10, 12))
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>x : Symbol(x, Decl(nonNullableReduction.ts, 10, 15))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 10, 12))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 10, 12))
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let z = x!; // NonNullable<T>
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>z : Symbol(z, Decl(nonNullableReduction.ts, 11, 7))
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>x : Symbol(x, Decl(nonNullableReduction.ts, 10, 15))
47+
}
48+
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function f2<T, U extends null | undefined>(x: T | U) {
50+
>f2 : Symbol(f2, Decl(nonNullableReduction.ts, 12, 1))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 14, 12))
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>U : Symbol(U, Decl(nonNullableReduction.ts, 14, 14))
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>x : Symbol(x, Decl(nonNullableReduction.ts, 14, 43))
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>T : Symbol(T, Decl(nonNullableReduction.ts, 14, 12))
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>U : Symbol(U, Decl(nonNullableReduction.ts, 14, 14))
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let z = x!; // NonNullable<T>
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>z : Symbol(z, Decl(nonNullableReduction.ts, 15, 7))
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>x : Symbol(x, Decl(nonNullableReduction.ts, 14, 43))
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}
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‎tests/baselines/reference/nonNullableReduction.types

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@@ -0,0 +1,50 @@
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=== tests/cases/compiler/nonNullableReduction.ts ===
2+
// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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>Transform1 : Transform1<T>
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>value : string
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8+
type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
9+
>Transform2 : Transform2<T>
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>value : string
11+
>value : string
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13+
function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
14+
>test : <T>(f1: Transform1<T>, f2: Transform2<T>) => void
15+
>f1 : Transform1<T>
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>f2 : Transform2<T>
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18+
f1?.("hello");
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>f1?.("hello") : T | undefined
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>f1 : ((value: string) => T) | undefined
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>"hello" : "hello"
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23+
f2?.("hello");
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>f2?.("hello") : T | undefined
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>f2 : ((value: string) => T) | ((value: string) => T) | undefined
26+
>"hello" : "hello"
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}
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
30+
>f1 : <T>(x: T | (string extends T ? null | undefined : never)) => void
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>x : T | (string extends T ? null | undefined : never)
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>null : null
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let z = x!; // NonNullable<T>
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>z : NonNullable<T>
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>x! : NonNullable<T>
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>x : T | (string extends T ? null | undefined : never)
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}
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function f2<T, U extends null | undefined>(x: T | U) {
41+
>f2 : <T, U extends null | undefined>(x: T | U) => void
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>null : null
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>x : T | U
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let z = x!; // NonNullable<T>
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>z : NonNullable<T>
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>x! : NonNullable<T>
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>x : T | U
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}
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‎tests/baselines/reference/nonNullableReductionNonStrict.js

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@@ -0,0 +1,32 @@
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//// [nonNullableReductionNonStrict.ts]
2+
// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
5+
type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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7+
function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
8+
f1?.("hello");
9+
f2?.("hello");
10+
}
11+
12+
function f1<T>(x: T | (string extends T ? null | undefined : never)) {
13+
let z = x!; // NonNullable<T>
14+
}
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function f2<T, U extends null | undefined>(x: T | U) {
17+
let z = x!; // NonNullable<T>
18+
}
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20+
21+
//// [nonNullableReductionNonStrict.js]
22+
// Repros from #43425
23+
function test(f1, f2) {
24+
f1 === null || f1 === void 0 ? void 0 : f1("hello");
25+
f2 === null || f2 === void 0 ? void 0 : f2("hello");
26+
}
27+
function f1(x) {
28+
var z = x; // NonNullable<T>
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}
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function f2(x) {
31+
var z = x; // NonNullable<T>
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}

‎tests/baselines/reference/nonNullableReductionNonStrict.symbols

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=== tests/cases/compiler/nonNullableReductionNonStrict.ts ===
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// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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>Transform1 : Symbol(Transform1, Decl(nonNullableReductionNonStrict.ts, 0, 0))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 2, 16))
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>value : Symbol(value, Decl(nonNullableReductionNonStrict.ts, 2, 23))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 2, 16))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 2, 16))
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type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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>Transform2 : Symbol(Transform2, Decl(nonNullableReductionNonStrict.ts, 2, 85))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 3, 16))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 3, 16))
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>value : Symbol(value, Decl(nonNullableReductionNonStrict.ts, 3, 42))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 3, 16))
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>value : Symbol(value, Decl(nonNullableReductionNonStrict.ts, 3, 78))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 3, 16))
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function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
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>test : Symbol(test, Decl(nonNullableReductionNonStrict.ts, 3, 98))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 5, 14))
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>f1 : Symbol(f1, Decl(nonNullableReductionNonStrict.ts, 5, 17))
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>Transform1 : Symbol(Transform1, Decl(nonNullableReductionNonStrict.ts, 0, 0))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 5, 14))
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>f2 : Symbol(f2, Decl(nonNullableReductionNonStrict.ts, 5, 35))
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>Transform2 : Symbol(Transform2, Decl(nonNullableReductionNonStrict.ts, 2, 85))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 5, 14))
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f1?.("hello");
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>f1 : Symbol(f1, Decl(nonNullableReductionNonStrict.ts, 5, 17))
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f2?.("hello");
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>f2 : Symbol(f2, Decl(nonNullableReductionNonStrict.ts, 5, 35))
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}
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
38+
>f1 : Symbol(f1, Decl(nonNullableReductionNonStrict.ts, 8, 1))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 10, 12))
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>x : Symbol(x, Decl(nonNullableReductionNonStrict.ts, 10, 15))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 10, 12))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 10, 12))
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let z = x!; // NonNullable<T>
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>z : Symbol(z, Decl(nonNullableReductionNonStrict.ts, 11, 7))
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>x : Symbol(x, Decl(nonNullableReductionNonStrict.ts, 10, 15))
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}
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function f2<T, U extends null | undefined>(x: T | U) {
50+
>f2 : Symbol(f2, Decl(nonNullableReductionNonStrict.ts, 12, 1))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 14, 12))
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>U : Symbol(U, Decl(nonNullableReductionNonStrict.ts, 14, 14))
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>x : Symbol(x, Decl(nonNullableReductionNonStrict.ts, 14, 43))
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>T : Symbol(T, Decl(nonNullableReductionNonStrict.ts, 14, 12))
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>U : Symbol(U, Decl(nonNullableReductionNonStrict.ts, 14, 14))
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let z = x!; // NonNullable<T>
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>z : Symbol(z, Decl(nonNullableReductionNonStrict.ts, 15, 7))
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>x : Symbol(x, Decl(nonNullableReductionNonStrict.ts, 14, 43))
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}
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‎tests/baselines/reference/nonNullableReductionNonStrict.types

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=== tests/cases/compiler/nonNullableReductionNonStrict.ts ===
2+
// Repros from #43425
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4+
type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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>Transform1 : Transform1<T>
6+
>value : string
7+
8+
type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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>Transform2 : Transform2<T>
10+
>value : string
11+
>value : string
12+
13+
function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
14+
>test : <T>(f1: Transform1<T>, f2: Transform2<T>) => void
15+
>f1 : Transform1<T>
16+
>f2 : Transform2<T>
17+
18+
f1?.("hello");
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>f1?.("hello") : T
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>f1 : (value: string) => T
21+
>"hello" : "hello"
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23+
f2?.("hello");
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>f2?.("hello") : T
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>f2 : ((value: string) => T) | ((value: string) => T)
26+
>"hello" : "hello"
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}
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
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>f1 : <T>(x: T | (string extends T ? null | undefined : never)) => void
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>x : T | (string extends T ? null : never)
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>null : null
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let z = x!; // NonNullable<T>
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>z : T | (string extends T ? null : never)
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>x! : T | (string extends T ? null : never)
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>x : T | (string extends T ? null : never)
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}
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function f2<T, U extends null | undefined>(x: T | U) {
41+
>f2 : <T, U extends null>(x: T | U) => void
42+
>null : null
43+
>x : T | U
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let z = x!; // NonNullable<T>
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>z : T | U
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>x! : T | U
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>x : T | U
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}
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‎tests/cases/compiler/nonNullableReduction.ts

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// @strict: true
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// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
9+
f1?.("hello");
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f2?.("hello");
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}
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
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let z = x!; // NonNullable<T>
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}
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function f2<T, U extends null | undefined>(x: T | U) {
18+
let z = x!; // NonNullable<T>
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}

‎tests/cases/compiler/nonNullableReductionNonStrict.ts

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// Repros from #43425
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type Transform1<T> = ((value: string) => T) | (string extends T ? undefined : never);
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type Transform2<T> = string extends T ? ((value: string) => T) | undefined : (value: string) => T;
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function test<T>(f1: Transform1<T>, f2: Transform2<T>) {
7+
f1?.("hello");
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f2?.("hello");
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}
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function f1<T>(x: T | (string extends T ? null | undefined : never)) {
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let z = x!; // NonNullable<T>
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}
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function f2<T, U extends null | undefined>(x: T | U) {
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let z = x!; // NonNullable<T>
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}

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