Reduce HIR debug output

[Noratrieb]

HIR debug output is currently very verbose, especially when used with the alternate (#) flag. This commit reduces the amount of noisy newlines by forcing a few small key types to stay on one line, which makes the output easier to read and scroll by.

$ rustc +after hello_world.rs -Zunpretty=hir-tree | wc -l
582
$ rustc +before hello_world.rs -Zunpretty=hir-tree | wc -l
932

[rustbot]

r? @cjgillot

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[Noratrieb]

                    parents: [
                        "(0, Some(4294967040))",
                        "(1, Some(0))",
                        "(2, Some(0))",
                        "(3, Some(0))",
                        "(4, Some(0))",
                    ],

it's not great that this looks like a string now. I wasn't able to use format_args itself because of the local copy that it can't capture :/

[SkiFire13]

it's not great that this looks like a string now. I wasn't able to use format_args itself because of the local copy that it can't capture :/

You can create a new local struct with two fields and manually implement Debug for it which does write!(fmt, "({}, {})"), self.id, self.parented_node). In my projects I often define a function like this to simplify the code (however with Display instead of Debug), though I'm not sure where to put it in rustc:

fn debug_fn(f: impl Fn(&mut fmt::Formatter<'_>) -> fmt::Result) -> impl fmt::Debug {
    struct DebugFn<F>(F);
    impl<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result> fmt::Debug for DebugFn<F> {
        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
            (self.0)(fmt)
        }
    }
    DebugFn(f)
}

Rustdoc seems to also have something similar already:

rust/src/librustdoc/html/format.rs

Lines 1665 to 1680 in f34356e

	pub(crate) fn display_fn(
	f: impl FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
	) -> impl fmt::Display {
	struct WithFormatter<F>(Cell<Option<F>>);
	impl<F> fmt::Display for WithFormatter<F>
	where
	F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
	{
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
	(self.0.take()).unwrap()(f)
	}
	}
	WithFormatter(Cell::new(Some(f)))
	}

[Noratrieb]

I didn't think of that, thanks! No idea where the best place would be to put the function, I just put it at the bottom of the file (which is probably a bad idea).

[cjgillot]

Thanks. That will definitely be useful. Can we pull this thread a bit more?

[cjgillot]

@bors r+

[bors]

📌 Commit e1787f5 has been approved by cjgillot

It is now in the queue for this repository.