proc_macro: Fix expand_expr expansion of bool literals

[mystor]

Previously, the expand_expr method would expand bool literals as a
Literal token containing a LitKind::Bool, rather than as an Ident.
This is not a valid token, and the LitKind::Bool case needs to be
handled seperately.

Tests were added to more deeply compare the streams in the expand-expr
test suite to catch mistakes like this in the future.

[rust-highfive]

r? @wesleywiser

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[mystor]

Oops, I did not mean to open this as a draft.

[wesleywiser]

This looks ok to me but I know very little about proc macros.

@mystor are there any compatibility issues with this change that you are aware of? Specifically, I'm imagining something like a proc macro that expects to get a token tree of Literal(..., "true", ...) instead of Ident("true", ...) and now fails to parse it correctly. Is that a concern?

[mystor]

I highly doubt that there are any major crates which are using this API, given that it was fairly recently introduced (last november, #87264), and hasn't even been exposed as an unstable API from proc-macro2 yet.

It appears that only 2 crates even enable the unstable feature (thanks @m-ou-se for helping me search!): https://crates.io/crates/nyar-macro, and https://crates.io/crates/include-transformed. nyar-macro doesn't appear to even call the method, and enables the feature unnecessarily, and include-transformed only uses the API to expand string literals, so won't notice any changes to how bools are handled.

[eddyb]

@bors r+

[bors]

📌 Commit fb5b7b4 has been approved by eddyb

It is now in the queue for this repository.

[bors]

⌛ Testing commit fb5b7b4 with merge 29554c0...

[bors]

☀️ Test successful - checks-actions
Approved by: eddyb
Pushing 29554c0 to master...

[rust-timer]

Finished benchmarking commit (29554c0): comparison url.

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: 😿 relevant regression found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.6%	2.6%	1
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	N/A	N/A	0

Cycles

Results

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: 🎉 relevant improvement found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-3.0%	-3.0%	1
Improvements 🎉 (secondary)	-2.9%	-2.9%	1
All 😿🎉 (primary)	-3.0%	-3.0%	1

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

@rustbot label: -perf-regression

Footnotes

1. the arithmetic mean of the percent change↩↩²

2. number of relevant changes↩↩²