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Improve narrowing of generic types in control flow analysis (#43183)
* Narrow type variables with union constraints when merited by contextual type * Narrow generics with union type constraints as indicated by contextual type * Accept new baselines * Add tests * Fix circularity for JSX elements * Remove unnecessary isConstraintPosition information from flow cache key * Update comment * Add additional tests * Rename to getNarrowableTypeForReference, remove getConstraintForLocation * Add comment * Fix removal of undefined in destructurings with initializers * Use getContextFreeTypeOfExpression in discriminateContextualTypeByObjectMembers * In obj[x], use constraint of obj's type only when x's type is non-generic * Add comment
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152 changes: 152 additions & 0 deletions
152
tests/baselines/reference/controlFlowGenericTypes.errors.txt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,152 @@ | ||
| tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(49,15): error TS2345: Argument of type 'undefined' is not assignable to parameter of type 'Box<T>'. | ||
| tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(55,15): error TS2345: Argument of type 'undefined' is not assignable to parameter of type 'Box<unknown>'. | ||
| tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(81,11): error TS2339: Property 'foo' does not exist on type 'MyUnion'. | ||
| Property 'foo' does not exist on type 'AA'. | ||
| tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(90,44): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. | ||
| tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts(91,11): error TS2339: Property 'foo' does not exist on type 'MyUnion'. | ||
| Property 'foo' does not exist on type 'AA'. | ||
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| ==== tests/cases/conformance/controlFlow/controlFlowGenericTypes.ts (5 errors) ==== | ||
| function f1<T extends string | undefined>(x: T, y: { a: T }, z: [T]): string { | ||
| if (x) { | ||
| x; | ||
| x.length; | ||
| return x; | ||
| } | ||
| if (y.a) { | ||
| y.a.length; | ||
| return y.a; | ||
| } | ||
| if (z[0]) { | ||
| z[0].length; | ||
| return z[0]; | ||
| } | ||
| return "hello"; | ||
| } | ||
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| function f2<T>(x: Extract<T, string | undefined> | null): string { | ||
| if (x) { | ||
| x; | ||
| x.length; | ||
| return x; | ||
| } | ||
| return "hello"; | ||
| } | ||
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| interface Box<T> { | ||
| item: T; | ||
| } | ||
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| declare function isBox(x: any): x is Box<unknown>; | ||
| declare function isUndefined(x: unknown): x is undefined; | ||
| declare function unbox<T>(x: Box<T>): T; | ||
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| function g1<T extends Box<T> | undefined>(x: T) { | ||
| if (isBox(x)) { | ||
| unbox(x); | ||
| } | ||
| } | ||
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| function g2<T extends Box<T> | undefined>(x: T) { | ||
| if (!isUndefined(x)) { | ||
| unbox(x); | ||
| } | ||
| } | ||
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| function g3<T extends Box<T> | undefined>(x: T) { | ||
| if (!isBox(x)) { | ||
| unbox(x); // Error | ||
| ~ | ||
| !!! error TS2345: Argument of type 'undefined' is not assignable to parameter of type 'Box<T>'. | ||
| } | ||
| } | ||
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| function g4<T extends Box<T> | undefined>(x: T) { | ||
| if (isUndefined(x)) { | ||
| unbox(x); // Error | ||
| ~ | ||
| !!! error TS2345: Argument of type 'undefined' is not assignable to parameter of type 'Box<unknown>'. | ||
| } | ||
| } | ||
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| // Repro from #13995 | ||
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| declare function takeA(val: 'A'): void; | ||
| export function bounceAndTakeIfA<AB extends 'A' | 'B'>(value: AB): AB { | ||
| if (value === 'A') { | ||
| takeA(value); | ||
| return value; | ||
| } | ||
| else { | ||
| return value; | ||
| } | ||
| } | ||
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| // Repro from #13995 | ||
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| type Common = { id: number }; | ||
| type AA = { tag: 'A', id: number }; | ||
| type BB = { tag: 'B', id: number, foo: number }; | ||
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| type MyUnion = AA | BB; | ||
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| const fn = (value: MyUnion) => { | ||
| value.foo; // Error | ||
| ~~~ | ||
| !!! error TS2339: Property 'foo' does not exist on type 'MyUnion'. | ||
| !!! error TS2339: Property 'foo' does not exist on type 'AA'. | ||
| if ('foo' in value) { | ||
| value.foo; | ||
| } | ||
| if (value.tag === 'B') { | ||
| value.foo; | ||
| } | ||
| }; | ||
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| const fn2 = <T extends MyUnion>(value: T): MyUnion => { | ||
| ~~~~~~~ | ||
| !!! error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value. | ||
| value.foo; // Error | ||
| ~~~ | ||
| !!! error TS2339: Property 'foo' does not exist on type 'MyUnion'. | ||
| !!! error TS2339: Property 'foo' does not exist on type 'AA'. | ||
| if ('foo' in value) { | ||
| value.foo; | ||
| } | ||
| if (value.tag === 'B') { | ||
| value.foo; | ||
| } | ||
| }; | ||
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| // Repro from #13995 | ||
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| type A1 = { | ||
| testable: true | ||
| doTest: () => void | ||
| } | ||
| type B1 = { | ||
| testable: false | ||
| }; | ||
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| type Union = A1 | B1 | ||
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| function notWorking<T extends Union>(object: T) { | ||
| if (!object.testable) return; | ||
| object.doTest(); | ||
| } | ||
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| // Repro from #42939 | ||
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| interface A { | ||
| a: number | null; | ||
| }; | ||
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| function get<K extends keyof A>(key: K, obj: A): number { | ||
| const value = obj[key]; | ||
| if (value !== null) { | ||
| return value; | ||
| } | ||
| return 0; | ||
| }; | ||
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