不加vec!的话会有以下报错。

[514366607]

error[E0277]: a value of type Vec<i32> cannot be built from an iterator over elements of type &{integer}
--> main.rs:26:44
|
26 | let v4: Vec = [0; 10].into_iter().collect();
| ^^^^^^^ value of type Vec<i32> cannot be built from std::iter::Iterator<Item=&{integer}>
|
= help: the trait FromIterator<&{integer}> is not implemented for Vec<i32>
= help: the trait FromIterator<T> is implemented for Vec<T>
note: the method call chain might not have had the expected associated types
--> main.rs:26:32
|
26 | let v4: Vec = [0; 10].into_iter().collect();
| ------- ^^^^^^^^^^^ Iterator::Item is &{integer} here
| |
| this expression has type [{integer}; 10]
note: required by a bound in collect
--> /Users/hible/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:2049:19
|
2049 | fn collect<B: FromIteratorSelf::Item>(self) -> B
| ^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in Iterator::collect

error: aborting due to previous error

For more information about this error, try rustc --explain E0277.

[CAESIUS-TIM]

rust 2018 会有问题，但是 2021 以上就没有问题了。

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=6cdf7413bc6b5a593b5e18d865e302f9