Don't print newlines in APITs

[compiler-errors]

This is kind of a hack, but it gets the job done because the only "special" formatting that (afaict) rustc_ast_pretty does is break with newlines sometimes.

Fixes rust-lang/measureme#207

[rustbot]

r? @wesleywiser

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[jyn514]

Can we change this in pprust instead? I don't know why we'd want it to add the newline ... if it's just for -Zunpretty=expanded that doesn't seem worth adding hacks for.

[compiler-errors]

This newline is not impl Trait specifically. This is just the regular line breaking that pprust does for code that is too long:

rust/compiler/rustc_ast_pretty/src/pp.rs

Lines 417 to 435 in 096309e

	fn print_break(&mut self, token: BreakToken, size: isize) {
	let fits = match self.get_top() {
	PrintFrame::Fits => true,
	PrintFrame::Broken { breaks: Breaks::Consistent, .. } => false,
	PrintFrame::Broken { breaks: Breaks::Inconsistent, .. } => size <= self.space,
	};
	if fits {
	self.pending_indentation += token.blank_space;
	self.space -= token.blank_space;
	} else {
	if let Some(pre_break) = token.pre_break {
	self.out.push(pre_break);
	}
	self.out.push('\n');
	let indent = self.indent as isize + token.offset;
	self.pending_indentation = indent;
	self.space = cmp::max(MARGIN - indent, MIN_SPACE);
	}
	}

I don't think we should remove pprust's ability to break lines, and I don't think it's worth it to introduce extra configurables (like breaking only with spaces). I'd rather have the hack be as localized as possible, or else rewrite this formatting code to no longer rely on pprust at all.

[wesleywiser]

@bors r+ rollup

[bors]

📌 Commit 4692375 has been approved by wesleywiser

It is now in the queue for this repository.