rustfmt does not format this code

[xobs]

I tried this code:

struct Test;
impl Test {
    fn callit<T, F: FnOnce() -> T>(&self, f: F) -> T {
        f()
    }
    fn test(&self) {
        self.callit(|| {
if true {
if true {
if true {
let r#type = 1;
println!("      {type:?}                   {}           {}                  {:?}", 1,1,1);
}}}
});
    }
}
fn main() {}

I expected to see this happen: rustfmt should format the document

Instead, this happened: rustfmt did nothing and reported no error

Meta

rustc --version --verbose:

rustc 1.91.0-nightly (898aff704 2025-08-14)
binary: rustc
commit-hash: 898aff704d6f0d00343f21d31b8b9bfac8e43007
commit-date: 2025-08-14
host: x86_64-unknown-linux-gnu
release: 1.91.0-nightly
LLVM version: 21.1.0

Removing any single character from the println!() block allows it to format. Changing the name of r#type allows it to format. Removing one of the if true {} blocks or the closure allows it to format.

Link to playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=cee93ebcb8c17a2b8c989101d4a5f5fa

[fmease]

@rustbot transfer rustfmt

[seritools]

golfed minimal failing code:

fn c() {
    a.b(|| {
"                                                                                       "
})
}

the maximum length of the string that causes it to fail gets reduced with indentation, which is why it happens with a shorter string in the OP example.

changing a.b( to a( or a::b( doesn't repro anymore.