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Add rustc_on_unimplemented to Sum and Product trait.

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This commit is contained in:
Nixon Enraght-Moony 2022-12-04 18:46:57 +00:00
parent 7632db0e87
commit 5626df9c90
3 changed files with 56 additions and 0 deletions
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8
library/core/src/iter/traits/accum.rs
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@ -10,6 +10,10 @@ use crate::num::Wrapping;
/// [`sum()`]: Iterator::sum
/// [`FromIterator`]: iter::FromIterator
#[stable(feature = "iter_arith_traits", since = "1.12.0")]
#[rustc_on_unimplemented(
message = "a value of type `{Self}` cannot be made by summing an iterator over elements of type `{A}`",
label = "value of type `{Self}` cannot be made by summing a `std::iter::Iterator<Item={A}>`"
)]
pub trait Sum<A = Self>: Sized {
/// Method which takes an iterator and generates `Self` from the elements by
/// "summing up" the items.
@ -27,6 +31,10 @@ pub trait Sum<A = Self>: Sized {
/// [`product()`]: Iterator::product
/// [`FromIterator`]: iter::FromIterator
#[stable(feature = "iter_arith_traits", since = "1.12.0")]
#[rustc_on_unimplemented(
message = "a value of type `{Self}` cannot be made by multiplying all elements of type `{A}` from an iterator",
label = "value of type `{Self}` cannot be made by multiplying all elements from a `std::iter::Iterator<Item={A}>`"
)]
pub trait Product<A = Self>: Sized {
/// Method which takes an iterator and generates `Self` from the elements by
/// multiplying the items.

9
src/test/ui/on-unimplemented/sum.rs Normal file
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@ -0,0 +1,9 @@
// <https://github.com/rust-lang/rust/issues/105184>
fn main() {
vec![(), ()].iter().sum::<i32>();
//~^ ERROR
vec![(), ()].iter().product::<i32>();
//~^ ERROR
}

39
src/test/ui/on-unimplemented/sum.stderr Normal file
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@ -0,0 +1,39 @@
error[E0277]: a value of type `i32` cannot be made by summing an iterator over elements of type `&()`
--> $DIR/sum.rs:4:5
|
LL | vec![(), ()].iter().sum::<i32>();
| ^^^^^^^^^^^^^^^^^^^ --- required by a bound introduced by this call
| |
| value of type `i32` cannot be made by summing a `std::iter::Iterator<Item=&()>`
|
= help: the trait `Sum<&()>` is not implemented for `i32`
= help: the following other types implement trait `Sum<A>`:
<i32 as Sum<&'a i32>>
<i32 as Sum>
note: required by a bound in `std::iter::Iterator::sum`
--> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
|
LL | S: Sum<Self::Item>,
| ^^^^^^^^^^^^^^^ required by this bound in `std::iter::Iterator::sum`
error[E0277]: a value of type `i32` cannot be made by multiplying all elements of type `&()` from an iterator
--> $DIR/sum.rs:7:5
|
LL | vec![(), ()].iter().product::<i32>();
| ^^^^^^^^^^^^^^^^^^^ ------- required by a bound introduced by this call
| |
| value of type `i32` cannot be made by multiplying all elements from a `std::iter::Iterator<Item=&()>`
|
= help: the trait `Product<&()>` is not implemented for `i32`
= help: the following other types implement trait `Product<A>`:
<i32 as Product<&'a i32>>
<i32 as Product>
note: required by a bound in `std::iter::Iterator::product`
--> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
|
LL | P: Product<Self::Item>,
| ^^^^^^^^^^^^^^^^^^^ required by this bound in `std::iter::Iterator::product`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0277`.