clippy::from_over_into: an implementation of `From` is preferred since it gives you `Into<_>` for free where the reverse isn't true

What you see

warning: an implementation of `From` is preferred since it gives you `Into<_>` for free where the reverse isn't true
 --> main.rs:5:1
  |
5 | impl Into<StringWrapper> for String {
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#from_over_into
  = note: `#[warn(clippy::from_over_into)]` on by default
help: replace the `Into` implementation with `From<std::string::String>`
  |
5 ~ impl From<String> for StringWrapper {
6 ~     fn from(val: String) -> Self {
7 ~         StringWrapper(val)
  |

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

According the std docs implementing From<..> is preferred since it gives you Into<..> for free where the reverse isn’t true.

Code that works but is not idiomatic Rust. Warns by default.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

struct StringWrapper(String);

impl Into<StringWrapper> for String {
    fn into(self) -> StringWrapper {
        StringWrapper(self)
    }
}

Write this instead

struct StringWrapper(String);

impl From<String> for StringWrapper {
    fn from(s: String) -> StringWrapper {
        StringWrapper(s)
    }
}

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::from_over_into)]
fn my_function() { /* ... */ }

[lints.clippy]
from_over_into = "allow"

cargo clippy -- -A clippy::from-over-into

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Settings in clippy.toml

• msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml