Fix instanceof narrowing #10194
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,184 @@ | ||
| //// [controlFlowInstanceof.ts] | ||
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| // Repros from #10167 | ||
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| function f1(s: Set<string> | Set<number>) { | ||
| s = new Set<number>(); | ||
| s; // Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<number> | ||
| } | ||
| s; // Set<number> | ||
| s.add(42); | ||
| } | ||
|
|
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| function f2(s: Set<string> | Set<number>) { | ||
| s = new Set<number>(); | ||
| s; // Set<number> | ||
| if (s instanceof Promise) { | ||
| s; // Set<number> & Promise<any> | ||
| } | ||
| s; // Set<number> | ||
| s.add(42); | ||
| } | ||
|
|
||
| function f3(s: Set<string> | Set<number>) { | ||
| s; // Set<string> | Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<string> | Set<number> | ||
| } | ||
| else { | ||
| s; // never | ||
| } | ||
| } | ||
|
|
||
| function f4(s: Set<string> | Set<number>) { | ||
| s = new Set<number>(); | ||
| s; // Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<number> | ||
| } | ||
| else { | ||
| s; // never | ||
| } | ||
| } | ||
|
|
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| // More tests | ||
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| class A { a: string } | ||
| class B extends A { b: string } | ||
| class C extends A { c: string } | ||
|
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| function foo(x: A | undefined) { | ||
| x; // A | undefined | ||
| if (x instanceof B || x instanceof C) { | ||
| x; // B | C | ||
| } | ||
| x; // A | undefined | ||
| if (x instanceof B && x instanceof C) { | ||
| x; // B & C | ||
| } | ||
| x; // A | undefined | ||
| if (!x) { | ||
| return; | ||
| } | ||
| x; // A | ||
| if (x instanceof B) { | ||
| x; // B | ||
| if (x instanceof C) { | ||
| x; // B & C | ||
| } | ||
| else { | ||
| x; // B | ||
| } | ||
| x; // B | ||
| } | ||
| else { | ||
| x; // A | ||
| } | ||
| x; // A | ||
| } | ||
|
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| // X is neither assignable to Y nor a subtype of Y | ||
| // Y is assignable to X, but not a subtype of X | ||
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| interface X { | ||
| x?: string; | ||
| } | ||
|
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| class Y { | ||
| y: string; | ||
| } | ||
|
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| function goo(x: X) { | ||
| x; | ||
| if (x instanceof Y) { | ||
| x.y; | ||
| } | ||
| x; | ||
| } | ||
|
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||
| //// [controlFlowInstanceof.js] | ||
| // Repros from #10167 | ||
| function f1(s) { | ||
| s = new Set(); | ||
| s; // Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<number> | ||
| } | ||
| s; // Set<number> | ||
| s.add(42); | ||
| } | ||
| function f2(s) { | ||
| s = new Set(); | ||
| s; // Set<number> | ||
| if (s instanceof Promise) { | ||
| s; // Set<number> & Promise<any> | ||
| } | ||
| s; // Set<number> | ||
| s.add(42); | ||
| } | ||
| function f3(s) { | ||
| s; // Set<string> | Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<string> | Set<number> | ||
| } | ||
| else { | ||
| s; // never | ||
| } | ||
| } | ||
| function f4(s) { | ||
| s = new Set(); | ||
| s; // Set<number> | ||
| if (s instanceof Set) { | ||
| s; // Set<number> | ||
| } | ||
| else { | ||
| s; // never | ||
| } | ||
| } | ||
| // More tests | ||
| class A { | ||
| } | ||
| class B extends A { | ||
| } | ||
| class C extends A { | ||
| } | ||
| function foo(x) { | ||
| x; // A | undefined | ||
| if (x instanceof B || x instanceof C) { | ||
| x; // B | C | ||
| } | ||
| x; // A | undefined | ||
| if (x instanceof B && x instanceof C) { | ||
| x; // B & C | ||
| } | ||
| x; // A | undefined | ||
| if (!x) { | ||
| return; | ||
| } | ||
| x; // A | ||
| if (x instanceof B) { | ||
| x; // B | ||
| if (x instanceof C) { | ||
| x; // B & C | ||
| } | ||
| else { | ||
| x; // B | ||
| } | ||
| x; // B | ||
| } | ||
| else { | ||
| x; // A | ||
| } | ||
| x; // A | ||
| } | ||
| class Y { | ||
| } | ||
| function goo(x) { | ||
| x; | ||
| if (x instanceof Y) { | ||
| x.y; | ||
| } | ||
| x; | ||
| } |
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I think there's a little more precision than the wording lends to here. If the candidate isn't a subtype, but is assignable, we keep the original type in place. (e.g. with
Array.isArray, you preserve the original type instead of giving backArray<any>).