Type annotations needed for closure with associated type

I tried this code:

use std::marker::PhantomData;

fn test_good() -> Builder<String> {
    // this compiles
    Builder::default().with_func(|s| drop(s))
}

fn test_bad() -> Builder<String> {
    // error[E0282]: type annotations needed
    Builder::default().with_func(|s| drop(s.len()))
}

#[derive(Default)]
pub struct Builder<Foo>(PhantomData<Foo>);

impl<Foo> Builder<Foo> {
    fn with_func(self, _: impl Fn(Foo)) -> Self {
        self
    }
}

I expect this to compile, but the test_bad function does not compile.

Meta

Rust Version: 1.86.0

Start by reproducing the provided test_good and test_bad examples with Rust 1.86.0 and compare the compiler diagnostics. No repository file or test is named in the report, so tracing the type-inference path will be necessary; done means the test_bad example compiles without requiring an explicit closure parameter type.