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Allow drawing inferences to conditional type branches (#27012)
* Allow drawing inferences to conditional type branches * Fix lint
1 parent c3b4f72 commit a55c0b7

6 files changed

+287
-1
lines changed

‎src/compiler/checker.ts

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13508,6 +13508,9 @@ namespace ts {
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inferFromTypes(getTrueTypeFromConditionalType(<ConditionalType>source), getTrueTypeFromConditionalType(<ConditionalType>target));
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inferFromTypes(getFalseTypeFromConditionalType(<ConditionalType>source), getFalseTypeFromConditionalType(<ConditionalType>target));
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}
13511+
else if (target.flags & TypeFlags.Conditional) {
13512+
inferFromTypes(source, getUnionType([getTrueTypeFromConditionalType(<ConditionalType>target), getFalseTypeFromConditionalType(<ConditionalType>target)]));
13513+
}
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else if (target.flags & TypeFlags.UnionOrIntersection) {
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const targetTypes = (<UnionOrIntersectionType>target).types;
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let typeVariableCount = 0;
@@ -13754,7 +13757,7 @@ namespace ts {
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function hasPrimitiveConstraint(type: TypeParameter): boolean {
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const constraint = getConstraintOfTypeParameter(type);
13757-
return !!constraint && maybeTypeOfKind(constraint, TypeFlags.Primitive | TypeFlags.Index);
13760+
return !!constraint && maybeTypeOfKind(constraint.flags & TypeFlags.Conditional ? getDefaultConstraintOfConditionalType(constraint as ConditionalType) : constraint, TypeFlags.Primitive | TypeFlags.Index);
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}
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function isObjectLiteralType(type: Type) {

‎tests/baselines/reference/extractInferenceImprovement.errors.txt

Lines changed: 38 additions & 0 deletions
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@@ -0,0 +1,38 @@
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tests/cases/compiler/extractInferenceImprovement.ts(26,26): error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type 'never'.
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tests/cases/compiler/extractInferenceImprovement.ts(28,26): error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"first" | "second"'.
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==== tests/cases/compiler/extractInferenceImprovement.ts (2 errors) ====
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// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
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function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
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return obj[key];
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}
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function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
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return obj[key];
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}
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const s = Symbol();
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interface StrNum {
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first: string;
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second: number;
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[s]: string;
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}
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const obj: StrNum = {} as any;
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let prop: string;
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// should work
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prop = getProperty2(obj, 'first');
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prop = getProperty3(obj, 'first');
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// Should fail
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prop = getProperty2(obj, s);
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~
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!!! error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type 'never'.
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prop = getProperty3(obj, s);
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~
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!!! error TS2345: Argument of type 'unique symbol' is not assignable to parameter of type '"first" | "second"'.
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‎tests/baselines/reference/extractInferenceImprovement.js

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,48 @@
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//// [extractInferenceImprovement.ts]
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// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
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function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
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return obj[key];
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}
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function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
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return obj[key];
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}
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const s = Symbol();
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interface StrNum {
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first: string;
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second: number;
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[s]: string;
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}
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const obj: StrNum = {} as any;
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let prop: string;
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// should work
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prop = getProperty2(obj, 'first');
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prop = getProperty3(obj, 'first');
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// Should fail
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prop = getProperty2(obj, s);
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prop = getProperty3(obj, s);
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//// [extractInferenceImprovement.js]
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// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
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function getProperty2(obj, key) {
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return obj[key];
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}
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function getProperty3(obj, key) {
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return obj[key];
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}
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const s = Symbol();
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const obj = {};
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let prop;
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// should work
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prop = getProperty2(obj, 'first');
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prop = getProperty3(obj, 'first');
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// Should fail
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prop = getProperty2(obj, s);
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prop = getProperty3(obj, s);

‎tests/baselines/reference/extractInferenceImprovement.symbols

Lines changed: 86 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,86 @@
1+
=== tests/cases/compiler/extractInferenceImprovement.ts ===
2+
// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
3+
function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
4+
>getProperty2 : Symbol(getProperty2, Decl(extractInferenceImprovement.ts, 0, 0))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 1, 22))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 1, 24))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 1, 22))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 1, 44))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 1, 22))
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>key : Symbol(key, Decl(extractInferenceImprovement.ts, 1, 51))
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>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 1, 24))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 1, 22))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 1, 24))
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return obj[key];
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 1, 44))
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>key : Symbol(key, Decl(extractInferenceImprovement.ts, 1, 51))
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}
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function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
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>getProperty3 : Symbol(getProperty3, Decl(extractInferenceImprovement.ts, 3, 1))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 5, 22))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 5, 24))
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>Extract : Symbol(Extract, Decl(lib.es5.d.ts, --, --))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 5, 22))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 5, 61))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 5, 22))
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>key : Symbol(key, Decl(extractInferenceImprovement.ts, 5, 68))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 5, 24))
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>T : Symbol(T, Decl(extractInferenceImprovement.ts, 5, 22))
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>K : Symbol(K, Decl(extractInferenceImprovement.ts, 5, 24))
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return obj[key];
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 5, 61))
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>key : Symbol(key, Decl(extractInferenceImprovement.ts, 5, 68))
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}
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const s = Symbol();
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>s : Symbol(s, Decl(extractInferenceImprovement.ts, 9, 5))
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>Symbol : Symbol(Symbol, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
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interface StrNum {
44+
>StrNum : Symbol(StrNum, Decl(extractInferenceImprovement.ts, 9, 19))
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first: string;
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>first : Symbol(StrNum.first, Decl(extractInferenceImprovement.ts, 10, 18))
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second: number;
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>second : Symbol(StrNum.second, Decl(extractInferenceImprovement.ts, 11, 18))
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[s]: string;
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>[s] : Symbol(StrNum[s], Decl(extractInferenceImprovement.ts, 12, 19))
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>s : Symbol(s, Decl(extractInferenceImprovement.ts, 9, 5))
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}
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const obj: StrNum = {} as any;
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 15, 5))
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>StrNum : Symbol(StrNum, Decl(extractInferenceImprovement.ts, 9, 19))
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let prop: string;
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>prop : Symbol(prop, Decl(extractInferenceImprovement.ts, 17, 3))
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// should work
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prop = getProperty2(obj, 'first');
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>prop : Symbol(prop, Decl(extractInferenceImprovement.ts, 17, 3))
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>getProperty2 : Symbol(getProperty2, Decl(extractInferenceImprovement.ts, 0, 0))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 15, 5))
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prop = getProperty3(obj, 'first');
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>prop : Symbol(prop, Decl(extractInferenceImprovement.ts, 17, 3))
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>getProperty3 : Symbol(getProperty3, Decl(extractInferenceImprovement.ts, 3, 1))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 15, 5))
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// Should fail
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prop = getProperty2(obj, s);
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>prop : Symbol(prop, Decl(extractInferenceImprovement.ts, 17, 3))
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>getProperty2 : Symbol(getProperty2, Decl(extractInferenceImprovement.ts, 0, 0))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 15, 5))
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>s : Symbol(s, Decl(extractInferenceImprovement.ts, 9, 5))
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prop = getProperty3(obj, s);
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>prop : Symbol(prop, Decl(extractInferenceImprovement.ts, 17, 3))
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>getProperty3 : Symbol(getProperty3, Decl(extractInferenceImprovement.ts, 3, 1))
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>obj : Symbol(obj, Decl(extractInferenceImprovement.ts, 15, 5))
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>s : Symbol(s, Decl(extractInferenceImprovement.ts, 9, 5))
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‎tests/baselines/reference/extractInferenceImprovement.types

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@@ -0,0 +1,82 @@
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=== tests/cases/compiler/extractInferenceImprovement.ts ===
2+
// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
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function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
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>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
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>obj : T
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>key : Extract<K, string>
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return obj[key];
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>obj[key] : T[Extract<K, string>]
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>obj : T
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>key : Extract<K, string>
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}
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function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
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>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
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>obj : T
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>key : K
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return obj[key];
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>obj[key] : T[K]
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>obj : T
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>key : K
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}
24+
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const s = Symbol();
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>s : unique symbol
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>Symbol() : unique symbol
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>Symbol : SymbolConstructor
29+
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interface StrNum {
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first: string;
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>first : string
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second: number;
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>second : number
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[s]: string;
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>[s] : string
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>s : unique symbol
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}
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const obj: StrNum = {} as any;
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>obj : StrNum
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>{} as any : any
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>{} : {}
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let prop: string;
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>prop : string
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// should work
50+
prop = getProperty2(obj, 'first');
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>prop = getProperty2(obj, 'first') : string
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>prop : string
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>getProperty2(obj, 'first') : string
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>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
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>obj : StrNum
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>'first' : "first"
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prop = getProperty3(obj, 'first');
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>prop = getProperty3(obj, 'first') : string
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>prop : string
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>getProperty3(obj, 'first') : string
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>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
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>obj : StrNum
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>'first' : "first"
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// Should fail
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prop = getProperty2(obj, s);
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>prop = getProperty2(obj, s) : any
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>prop : string
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>getProperty2(obj, s) : any
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>getProperty2 : <T, K extends keyof T>(obj: T, key: Extract<K, string>) => T[K]
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>obj : StrNum
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>s : unique symbol
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prop = getProperty3(obj, s);
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>prop = getProperty3(obj, s) : any
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>prop : string
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>getProperty3(obj, s) : any
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>getProperty3 : <T, K extends Extract<keyof T, string>>(obj: T, key: K) => T[K]
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>obj : StrNum
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>s : unique symbol
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‎tests/cases/compiler/extractInferenceImprovement.ts

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// @target: es6
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// repro mostly from https://github.com/Microsoft/TypeScript/issues/25065
3+
function getProperty2<T, K extends keyof T>(obj: T, key: Extract<K, string>): T[K] {
4+
return obj[key];
5+
}
6+
7+
function getProperty3<T, K extends Extract<keyof T, string>>(obj: T, key: K): T[K] {
8+
return obj[key];
9+
}
10+
11+
const s = Symbol();
12+
interface StrNum {
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first: string;
14+
second: number;
15+
[s]: string;
16+
}
17+
const obj: StrNum = {} as any;
18+
19+
let prop: string;
20+
21+
// should work
22+
prop = getProperty2(obj, 'first');
23+
24+
prop = getProperty3(obj, 'first');
25+
26+
// Should fail
27+
prop = getProperty2(obj, s);
28+
29+
prop = getProperty3(obj, s);

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