Summary

The fix for from_over_into fails if the Into implementation includes a self.<expr>.clone() if the cloned type implements Copy. The fix for clone_on_copy keeps self, but the fix for from_over_into means self is no longer valid. Using #[allow(...)] to apply the suggestions serially (in either order) works fine.

Reproducer

Here's a simple example that triggers the error:

struct Foo(i64); 
impl Into<i64> for Foo {
    fn into(self) -> i64 {
        self.0.clone()
    }
}

I expected to see the code transformed into this:

struct Foo(i64); 
impl From<Foo> for i64 {
    fn from(val: Foo) -> Self {
        val.0
    }
}

Instead, it produces invalid code that results in the following compiler error:

struct Foo(i64); 
impl From<Foo> for i64 {
    fn from(val: Foo) -> Self {
        self.0
    }
}

error[E0424]: expected value, found module `self`
    --> example/src/foo.rs:1000:9
     |
999  |     fn from(val: Foo) -> Self {
     |        ---- this function doesn't have a `self` parameter
1000 |         self.0
     |         ^^^^ `self` value is a keyword only available in methods with a `self` parameter
     |
help: add a `self` receiver parameter to make the associated `fn` a method
     |
999  |     fn from(&self, val: Foo) -> Self {
     |             ++++++

error: aborting due to 1 previous error

Version

rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7

Additional Labels

@rustbot label +I-suggestion-causes-error