Is it possible to create a type alias that has trait bounds on a generic type for a function?
This code:
pub type Foo<T: Read> = fn(bar: T);
yields error E0122 (in newer versions of Rust, it is only a warning):
An attempt was made to add a generic constraint to a type alias. This
constraint is entirely ignored. For backwards compatibility, Rust
still allows this with a warning. Consider the example below:
trait Foo {}
type MyType<R: Foo> = (R, ());
fn main() {
let t: MyType<u32>;
}
We're able to declare a variable of type
MyType<u32>, despite the fact
thatu32does not implementFoo. As a result, one should avoid using
generic constraints in concert with type aliases.
Is it possible to create a type alias that contains trait requirements on a function pointer? Obviously the compiler is telling me no for types, but didn't know if there was another option for functions that I wasn't thinking of.
generics rust function-pointers traits type-alias
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
add a comment |
This code:
pub type Foo<T: Read> = fn(bar: T);
yields error E0122 (in newer versions of Rust, it is only a warning):
An attempt was made to add a generic constraint to a type alias. This
constraint is entirely ignored. For backwards compatibility, Rust
still allows this with a warning. Consider the example below:
trait Foo {}
type MyType<R: Foo> = (R, ());
fn main() {
let t: MyType<u32>;
}
We're able to declare a variable of type
MyType<u32>, despite the fact
thatu32does not implementFoo. As a result, one should avoid using
generic constraints in concert with type aliases.
Is it possible to create a type alias that contains trait requirements on a function pointer? Obviously the compiler is telling me no for types, but didn't know if there was another option for functions that I wasn't thinking of.
generics rust function-pointers traits type-alias
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
1
This doesn't seem to be possible, as the error says. Experimenting withFn(T)as well didn't get me anywhere.
– Chris Emerson
Jun 17 '16 at 8:25
add a comment |
This code:
pub type Foo<T: Read> = fn(bar: T);
yields error E0122 (in newer versions of Rust, it is only a warning):
An attempt was made to add a generic constraint to a type alias. This
constraint is entirely ignored. For backwards compatibility, Rust
still allows this with a warning. Consider the example below:
trait Foo {}
type MyType<R: Foo> = (R, ());
fn main() {
let t: MyType<u32>;
}
We're able to declare a variable of type
MyType<u32>, despite the fact
thatu32does not implementFoo. As a result, one should avoid using
generic constraints in concert with type aliases.
Is it possible to create a type alias that contains trait requirements on a function pointer? Obviously the compiler is telling me no for types, but didn't know if there was another option for functions that I wasn't thinking of.
generics rust function-pointers traits type-alias
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
This code:
pub type Foo<T: Read> = fn(bar: T);
yields error E0122 (in newer versions of Rust, it is only a warning):
An attempt was made to add a generic constraint to a type alias. This
constraint is entirely ignored. For backwards compatibility, Rust
still allows this with a warning. Consider the example below:
trait Foo {}
type MyType<R: Foo> = (R, ());
fn main() {
let t: MyType<u32>;
}
We're able to declare a variable of type
MyType<u32>, despite the fact
thatu32does not implementFoo. As a result, one should avoid using
generic constraints in concert with type aliases.
Is it possible to create a type alias that contains trait requirements on a function pointer? Obviously the compiler is telling me no for types, but didn't know if there was another option for functions that I wasn't thinking of.
generics rust function-pointers traits type-alias
generics rust function-pointers traits type-alias
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
edited Dec 30 '18 at 0:15
Shepmaster
151k14296433
151k14296433
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
asked Jun 17 '16 at 0:14
nathansizemorenathansizemore
1,37522346
1,37522346
1
This doesn't seem to be possible, as the error says. Experimenting withFn(T)as well didn't get me anywhere.
– Chris Emerson
Jun 17 '16 at 8:25
add a comment |
1
This doesn't seem to be possible, as the error says. Experimenting withFn(T)as well didn't get me anywhere.
– Chris Emerson
Jun 17 '16 at 8:25
1
1
This doesn't seem to be possible, as the error says. Experimenting with
Fn(T) as well didn't get me anywhere.– Chris Emerson
Jun 17 '16 at 8:25
This doesn't seem to be possible, as the error says. Experimenting with
Fn(T) as well didn't get me anywhere.– Chris Emerson
Jun 17 '16 at 8:25
add a comment |
1 Answer
1
active
oldest
votes
At this time, it does not seem to be possible and no workarounds exist.
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
add a comment |
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1 Answer
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1 Answer
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active
oldest
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At this time, it does not seem to be possible and no workarounds exist.
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
add a comment |
At this time, it does not seem to be possible and no workarounds exist.
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
add a comment |
At this time, it does not seem to be possible and no workarounds exist.
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
At this time, it does not seem to be possible and no workarounds exist.
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
answered Jun 20 '16 at 18:14
nathansizemorenathansizemore
1,37522346
1,37522346
add a comment |
add a comment |
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This doesn't seem to be possible, as the error says. Experimenting with
Fn(T)as well didn't get me anywhere.– Chris Emerson
Jun 17 '16 at 8:25