Update strict-inference re: return types of setters, overriding methods #595
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See the change to the spec: dart-lang/language#595 Change-Id: I5aeb20eb175f7018ecc99f398ea4d463b1e7874e Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118920 Commit-Queue: Samuel Rawlins <[email protected]> Reviewed-by: Brian Wilkerson <[email protected]>
| local functions can always be inferred from downwards or upwards inference, as | ||
| it will have a body, and the return type of the body is known (even if there | ||
| are inference failures within). | ||
| Declaring a recursive local function, a top-level function, a static method, a |
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Is a recursive function always a problem?
Should it only be if the return type of the function depends on itself, and not, say:
foo(int x) => x <= 0 ? 0 : foo(x - 1).toString().length;The return type of this function is no harder to deduce than a non-recursive function.
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I thought type inference only calculated an omitted return type on a local function if that function was "non-recursive", as in, never references itself.
I don't see anything in the spec regarding this concept though...
| it will have a body, and the return type of the body is known (even if there | ||
| are inference failures within). | ||
| Declaring a recursive local function, a top-level function, a static method, a | ||
| non-overriding instance method, a typedef, a generic function type, or a |
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"a typedef" is traditionally called a "a type alias".
The "a generic function type" case is different from the rest. Every other thing you mention is the syntactic category of a declaration, which makes sense since the sentence starts with "Declaring a ...". A "generic function type" is not a declaration, so it's not as clear what it means to "declare" one.
Why is it important that the function type is generic?
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Hmm, I may just be abusing the analyzer's AST for this concept, GenericFunctionType. It's not important that it be declared with type arguments. E.g.
void f6(callback()) { // Inference failure
callback();
}The issue there is that the return type of callback is implicitly dynamic; no inference is carried out. Is this just called a "function type?"
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