Simplify `TokenStream` some more #57486

nnethercote · 2019-01-10T03:42:14Z

These commits simplify TokenStream, remove ThinTokenStream, and avoid some clones. The end result is simpler code and a slight perf win on some benchmarks.

r? @petrochenkov

nnethercote · 2019-01-10T03:42:32Z

(Note that the first commit is from #57004, and will be removed before landing.)

src/libsyntax/tokenstream.rs

src/libsyntax/parse/parser.rs

nnethercote · 2019-01-11T00:56:06Z

I added a new commit that changes TokenStream to uses Option.

petrochenkov · 2019-01-11T09:41:42Z

src/libsyntax/tokenstream.rs

+            None => true,
+            Some(ref stream) => {
+                // An empty stream should be represented as `None`, not as an empty `Vec`.
+                debug_assert!(stream.len() > 0);


Hmm, do we have operations that remove trees from the stream's vector?
It's correct that we should not create new empty streams as Some, but perhaps previously non-empty streams can turn into empty?

Not that I know of. But if it does happen, the old code for this function would silently do the wrong thing, while the new code will assert. I could change it to check for a length of zero in the Some case.

Yes, could you use the correct Some(ref stream) => stream.is_empty(), that would be more future-proof.

petrochenkov · 2019-01-11T09:41:56Z

@bors r+

bors · 2019-01-11T09:41:57Z

📌 Commit ea2784b8701bfd63dada95ea12bd854479b88e45 has been approved by petrochenkov

petrochenkov · 2019-01-13T11:08:52Z

@bors r-

petrochenkov · 2019-01-13T11:10:13Z

Also, it would be nice to make a perf run once #57004 is merged and this PR contains only the following diff.

bors · 2019-01-13T19:59:02Z

☔ The latest upstream changes (presumably #57577) made this pull request unmergeable. Please resolve the merge conflicts.

`TokenStream::Stream` can represent a token stream containing any number of token trees. `TokenStream::Tree` is the special case representing a single token tree. The latter doesn't occur all that often dynamically, so this commit removes it, which simplifies the code quite a bit. This change has mixed performance effects. - The size of `TokenStream` drops from 32 bytes to 8 bytes, and there is one less case for all the match statements. - The conversion of a `TokenTree` to a `TokenStream` now requires two allocations, for the creation of a single element Lrc<Vec<_>>. (But a subsequent commit in this PR will reduce the main source of such conversions.)

`TokenStream` is now almost identical to `ThinTokenStream`. This commit removes the latter, replacing it with the former.

This avoids some allocations.

Because that's the more typical way of representing an all-or-nothing type.

nnethercote · 2019-01-14T00:06:46Z

I updated is_empty and added a comment about empty streams not necessarily being represented with Empty.

nnethercote · 2019-01-14T00:06:51Z

@bors try

bors · 2019-01-14T00:07:07Z

⌛ Trying commit 7285724 with merge ad694da89a85d9e7fa5f5eee94b1159f186c2778...

petrochenkov · 2019-01-14T09:50:58Z

Travis says the build completed successfully, but this wasn't reported to this thread for some reason.
Let's see if rust-timer works with it or not.

@rust-timer build ad694da89a85d9e7fa5f5eee94b1159f186c2778

rust-timer · 2019-01-14T09:50:59Z

Insufficient permissions to issue commands to rust-timer.

petrochenkov · 2019-01-14T17:30:28Z

@bors r-

petrochenkov · 2019-01-14T17:32:40Z

(The "comparison URL" didn't work for me previously and showed "missing commit" or something like that, but now it seems ok.)

@bors r+

bors · 2019-01-14T17:32:41Z

📌 Commit 7285724 has been approved by petrochenkov

@petrochenkov

…re, r=petrochenkov Simplify `TokenStream` some more These commits simplify `TokenStream`, remove `ThinTokenStream`, and avoid some clones. The end result is simpler code and a slight perf win on some benchmarks. r? @petrochenkov

Centril · 2019-01-15T09:03:21Z

Failed in rollup #57624 (comment) due to toolstate change.

@bors r-

petrochenkov · 2019-01-15T09:18:57Z

Marking as blocked, we'll be able to merge this in few days when 1.32 is released and the pre-release toolstate restriction is lifted.

nnethercote · 2019-01-15T09:22:03Z

What is toolstate?

petrochenkov · 2019-01-15T09:24:18Z

@nnethercote
Build status of things like clippy/rustfmt/... that depend on compiler internals.
The restriction is that compiler changes must not break tools during the week before release.

nnethercote · 2019-01-17T23:04:18Z

Rust 1.32 has been released.

@bors r=petrochenkov

bors · 2019-01-17T23:04:19Z

📌 Commit 7285724 has been approved by petrochenkov

@petrochenkov

…re, r=petrochenkov Simplify `TokenStream` some more These commits simplify `TokenStream`, remove `ThinTokenStream`, and avoid some clones. The end result is simpler code and a slight perf win on some benchmarks. r? @petrochenkov

@ghost

Rollup of 7 pull requests Successful merges: - #57486 (Simplify `TokenStream` some more) - #57502 (make trait-aliases work across crates) - #57598 (Add missing unpretty option help message) - #57649 (privacy: Account for associated existential types) - #57659 (Fix release manifest generation) - #57699 (add applicability to remaining suggestions) - #57719 (Tweak `expand_node`) Failed merges: r? @ghost

rust-highfive assigned petrochenkov Jan 10, 2019

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nnethercote added 4 commits January 14, 2019 09:10

Remove ThinTokenStream.

ce0d994

`TokenStream` is now almost identical to `ThinTokenStream`. This commit removes the latter, replacing it with the former.

Avoid some TokenTree-to-TokenStream conversions.

ba31d83

This avoids some allocations.

Make TokenStream use Option.

7285724

Because that's the more typical way of representing an all-or-nothing type.

nnethercote force-pushed the simplify-TokenStream-more branch from ea2784b to 7285724 Compare January 14, 2019 00:06

petrochenkov added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jan 14, 2019

petrochenkov closed this Jan 14, 2019

petrochenkov reopened this Jan 14, 2019

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 14, 2019

Centril mentioned this pull request Jan 15, 2019

Rollup of 8 pull requests #57624

Closed

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jan 15, 2019

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-blocked Status: Blocked on something else such as an RFC or other implementation work. labels Jan 17, 2019

Centril mentioned this pull request Jan 19, 2019

Rollup of 7 pull requests #57755

Merged

bors merged commit 7285724 into rust-lang:master Jan 19, 2019

nnethercote deleted the simplify-TokenStream-more branch January 21, 2019 20:41

nnethercote mentioned this pull request Jan 30, 2019

proc_macro: make TokenStream::from_streams pre-allocate its vector. #58001

Merged

nnethercote mentioned this pull request Feb 15, 2019

Remove LazyTokenStream. #58476

Merged

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Simplify `TokenStream` some more #57486

Simplify `TokenStream` some more #57486

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Simplify TokenStream some more #57486

Simplify TokenStream some more #57486

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Simplify `TokenStream` some more #57486

Simplify `TokenStream` some more #57486

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