Fix error recovery in format macro parsing

[FabianWolff]

Fixes #88770. Basically, the assumption in the following comment is incorrect:

rust/compiler/rustc_builtin_macros/src/format.rs

Lines 167 to 172 in b69fe57

	// `Parser::expect` tries to recover using the
	// `Parser::unexpected_try_recover` function. This function is able
	// to recover if the expected token is a closing delimiter.
	//
	// As `,` is not a closing delimiter, it will always return an `Err`
	// variant.

This is only true in the first iteration of the loop, when p.clear_expected_tokens() is called. In subsequent iterations, p.expected_tokens won't be empty, so p.expect() won't actually call unexpected_try_recover():

rust/compiler/rustc_parse/src/parser/mod.rs

Lines 487 to 498 in b69fe57

	pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
	if self.expected_tokens.is_empty() {
	if self.token == *t {
	self.bump();
	Ok(false)
	} else {
	self.unexpected_try_recover(t)
	}
	} else {
	self.expect_one_of(slice::from_ref(t), &[])
	}
	}

Instead, it will call expect_one_of(), which can recover and return Ok(). This PR handles this case to fix the ICE in #88770.

[FabianWolff]

It seems that @rustbot somehow passed over this PR and did not assign anybody. Therefore (feel free to reassign):

r? @petrochenkov

[petrochenkov]

Thanks!
@bors r+

[bors]

📌 Commit a8421ca has been approved by petrochenkov

[bors]

⌛ Testing commit a8421ca with merge 43cb20b43f165d2be40c99326f383feffd2eea94...

[bors]

💔 Test failed - checks-actions

[rust-log-analyzer]

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[petrochenkov]

Looks like some infra issue.
@bors retry

[bors]

⌛ Testing commit a8421ca with merge a0648ea...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing a0648ea to master...

[rust-timer]

Finished benchmarking commit (a0648ea): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression