[globals] Remove global shape for Array.from
Type inference currently assumes that a `FunctionSignature`'s effects have no false positives. If a `mutate` effect is observed on a read-only place, Forget currently assumes this is an user error and [throws](https://github.com/facebook/react-forget/blob/207595e04e2be08b8f62bf21dac9d846b9651e43/forget/src/Inference/InferReferenceEffects.ts#L275-L281). Array.from is polymorphic -- its effects are dependent on the type of its parameters
mofeiZ committed
Apr 5, 2023 at 12:53 UTC
9d97015236b8f19bbf313e98065aaeb4d0322cbc
1 file changed
+9
-10
compiler/forget/src/HIR/Globals.ts
+9
-10
@@ -87,16 +87,15 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
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calleeEffect: Effect.Read,
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}),
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],
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- [
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- "from",
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- // Array.from(arrayLike, optionalFn, optionalThis)
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- addFunction(DEFAULT_SHAPES, [], {
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- positionalParams: [Effect.Mutate],
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- restParam: Effect.Read,
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- returnType: { kind: "Object", shapeId: BuiltInArrayId },
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- calleeEffect: Effect.Read,
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- }),
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- ],
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+ // https://tc39.es/ecma262/multipage/indexed-collections.html#sec-array.from
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+ // Array.from(arrayLike, optionalFn, optionalThis) not added because
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+ // the Effect of `arrayLike` is polymorphic i.e.
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+ // - Effect.read if
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+ // - it does not have an @iterator property and is array-like
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+ // (i.e. has a length property)
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+ /// - it is an iterable object whose iterator does not mutate itself
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+ // - Effect.mutate if it is a self-mutative iterator (e.g. a generator
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+ // function)
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[
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"of",
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// Array.of(element0, ..., elementN)