Simplify `TokenTree` and fix `macro_rules!` bugs #39419

jseyfried · 2017-01-31T06:34:42Z

This PR

fixes macros: tt fragments treat $(foo)* like foo #39390, fixes macros: simplify tt matchers #39403, and fixes macros: syntax errors in matches should fail on definition, not use #39404 (each is a [breaking-change], see issues for examples),
fixes Regression in procedural macros emitting macro_rules macros #39889,
simplifies and optimizes macro invocation parsing,
cleans up ext::tt::transcribe,
removes tokenstream::TokenTree::Sequence and Token::MatchNt,
- instead, adds a new type ext::tt::quoted::TokenTree for use by macro_rules! (ext::tt)
removes parser.quote_depth and parser.parsing_token_tree, and
removes quote_matcher!.
- Instead, use quote_tokens! and ext::tt::quoted::parse the result with expect_matchers=true.
- I found no outside uses of quote_matcher! when searching Rust code on Github.

jseyfried · 2017-01-31T06:37:02Z

This is groundwork for procedural and declarative macros 2.0.
cc #38356 #39412

eddyb · 2017-01-31T07:08:12Z

src/libsyntax/ext/tt/quoted.rs

+    /// A kleene-style repetition sequence with a span
+    Sequence(Span, Rc<SequenceRepetition>),
+    /// Matches a nonterminal. This is only used in the left hand side of MBE macros.
+    Match(Span, ast::Ident /* name to bind */, ast::Ident /* kind of nonterminal */),


Can't this be done on the fly? (i.e in parsing not lexing)

Neither parsing nor lexing knows about sequences and matchers at all. We lex directly into a Vec<TokenTree> and consume the token trees in the parser directly (e.g. parsing a token tree is constant time). Sequences and matchers are parsed by ext::tt::quoted::parse.

nrc

I only got halfway through reviewing this PR before the (long) weekend, and then my browser crashed and lost my comments. There wasn't anything major. Anyway, here is a single comment and I'll finish the review on Tuesday. Sorry for the delay.

nrc · 2017-02-03T01:08:02Z

src/libsyntax/ext/tt/transcribe.rs

-    idx: usize,
-    dotdotdoted: bool,
-    sep: Option<Token>,
+enum Frame {


This would benefit from a comment

nrc · 2017-02-03T01:10:35Z

src/libsyntax/ext/tt/transcribe.rs

-    }
-}
+    let mut stack = SmallVector::one(Frame::Delimited {
+        forest: Rc::new(tokenstream::Delimited { delim: token::NoDelim, tts: src }),


I would factor this out into a ctor function

nrc · 2017-02-03T01:11:35Z

src/libsyntax/ext/tt/transcribe.rs

+enum LockstepIterSize {
+    LisUnconstrained,
+    LisConstraint(usize, Ident),
+    LisContradiction(String),


nit: I'd kill the Lis prefix

nrc · 2017-02-03T01:27:22Z

src/libsyntax/ext/tt/quoted.rs

@@ -0,0 +1,228 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT


Why make this module here? I'd have thought TTs were much more general than just quasi quoting

We still have tokenstream::{TokenStream, TokenTree, ...}.

quoted::TokenTree is more general than tokenstream::TokenTree since it also supports "$-quoted tokens" from the macro_rules! syntax -- $e, $e:expr, and $(...)*. In other words, quoted::TokenTree is the parse tree for macro_rules! syntax.

nrc · 2017-02-07T03:07:49Z

Oh, GH didn't lose my earlier comments. Good.

nrc

Just one more comment, and that can be done later

nrc · 2017-02-07T03:37:07Z

src/libsyntax/ext/tt/quoted.rs

@@ -76,6 +76,8 @@ pub enum TokenTree {
    Delimited(Span, Rc<Delimited>),
    /// A kleene-style repetition sequence with a span
    Sequence(Span, Rc<SequenceRepetition>),
+    /// Matches a nonterminal. This is only used in the left hand side of MBE macros.
+    Match(Span, ast::Ident /* name to bind */, ast::Ident /* kind of nonterminal */),


I think Match is a pretty bad name - it is not actually a match of a pattern to text (or anything to do with a match expression). Maybe PatternVariable or MacroVariable is better? Doesn't have to be done in this PR though.

With a bit more refactoring I could also move Nonterminal::SubstNt here -- I think MacroVariable would be a better fit for that. MacroVariableDeclaration is too long though (imo); how about MetaVarDecl?

MetaVarDecl SGTM

bors · 2017-02-10T07:31:31Z

☔ The latest upstream changes (presumably #39712) made this pull request unmergeable. Please resolve the merge conflicts.

bors · 2017-02-13T01:59:32Z

☔ The latest upstream changes (presumably #39572) made this pull request unmergeable. Please resolve the merge conflicts.

jseyfried · 2017-02-16T23:51:31Z

@eddyb would you mind Cratering this?

bors · 2017-02-17T06:50:47Z

☔ The latest upstream changes (presumably #39752) made this pull request unmergeable. Please resolve the merge conflicts.

eddyb · 2017-02-17T08:21:34Z

@jseyfried Can you ping me after a rebase?

jseyfried · 2017-02-17T08:30:36Z

@eddyb rebased.

eddyb · 2017-02-17T22:18:19Z

The crater report shows 4 main regressions:

brotli (failure)
chipmunk (failure) - this one looks like a bug in chipmunk itself
clap (failure) - this is very bad, as clap has 454 other packages depending on it
multipart (failure)

These all look like macro-defining macros, and they seem like they should work, but something is perhaps doing too-eager parsing? I've never liked $foo:bar (or even just $foo) being a single token, it shouldn't.

jseyfried · 2017-02-18T03:08:12Z

It looks like all these errors are due to fixing #39404. That is, they are legitimate errors in the macro definition that didn't show up before because the erroneous pattern never ended up getting used to match anything. I'll start a warning cycle.

I've never liked $foo:bar (or even just $foo) being a single token, it shouldn't.

Agreed, that's one of the reasons for this PR. After this PR, $foo:bar is never a single token (it used to be Token::Interpolated(Nonterminal::MatchNt(..)) sometimes; this PR removes Nonterminal::MatchNt).
Also, $foo is never a single token in a tokenstream::TokenTree after this PR, except on certain error paths (planning on removing Nonterminal::SubstNt later after refactoring the relevant errors).

eddyb · 2017-02-18T09:14:18Z

~~Is it really #39404? It looked like the lone $foo was supposed to be interpolated from an outer macro, or am I imagining things?~~ The fallout looks pretty bad if it's their bug, multiple patch releases may be needed.

EDIT: No, you're right 😞

eddyb · 2017-02-18T10:07:47Z

Okay, this might not be that bad. clap is affected in 1.* and 2.* and since these are post-0.*, one release for each (of 1.* and 2.*) should be enough to fix most (ideally, all) of the regressions.
I've opened clap-rs/clap#857 and we can do another crater run once that's released.

jseyfried · 2017-02-28T22:18:46Z

@bors r=nrc

bors · 2017-02-28T22:18:47Z

📌 Commit 839398a has been approved by nrc

bors · 2017-02-28T22:19:48Z

⌛ Testing commit 839398a with merge d35bcfa...

bors · 2017-02-28T22:21:30Z

💔 Test failed - status-appveyor

alexcrichton · 2017-02-28T22:30:23Z

@bors: retry * network error

…

On Tue, Feb 28, 2017 at 4:21 PM, bors ***@***.***> wrote: 💔 Test failed - status-appveyor <https://ci.appveyor.com/project/rust-lang/rust/build/1.0.2168> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#39419 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD95GB7SjuZ5IPQajxpJNAzk0PKgfWqks5rhJ3sgaJpZM4LySVU> .

@nrc

Simplify `TokenTree` and fix `macro_rules!` bugs This PR - fixes rust-lang#39390, fixes rust-lang#39403, and fixes rust-lang#39404 (each is a [breaking-change], see issues for examples), - fixes rust-lang#39889, - simplifies and optimizes macro invocation parsing, - cleans up `ext::tt::transcribe`, - removes `tokenstream::TokenTree::Sequence` and `Token::MatchNt`, - instead, adds a new type `ext::tt::quoted::TokenTree` for use by `macro_rules!` (`ext::tt`) - removes `parser.quote_depth` and `parser.parsing_token_tree`, and - removes `quote_matcher!`. - Instead, use `quote_tokens!` and `ext::tt::quoted::parse` the result with `expect_matchers=true`. - I found no outside uses of `quote_matcher!` when searching Rust code on Github. r? @nrc

Rollup of 6 pull requests - Successful merges: #39419, #39936, #39944, #39960, #40028, #40128 - Failed merges:

bors · 2017-03-01T05:58:13Z

⌛ Testing commit 839398a with merge 7ce1fbe...

@nrc

Simplify `TokenTree` and fix `macro_rules!` bugs This PR - fixes #39390, fixes #39403, and fixes #39404 (each is a [breaking-change], see issues for examples), - fixes #39889, - simplifies and optimizes macro invocation parsing, - cleans up `ext::tt::transcribe`, - removes `tokenstream::TokenTree::Sequence` and `Token::MatchNt`, - instead, adds a new type `ext::tt::quoted::TokenTree` for use by `macro_rules!` (`ext::tt`) - removes `parser.quote_depth` and `parser.parsing_token_tree`, and - removes `quote_matcher!`. - Instead, use `quote_tokens!` and `ext::tt::quoted::parse` the result with `expect_matchers=true`. - I found no outside uses of `quote_matcher!` when searching Rust code on Github. r? @nrc

bors · 2017-03-01T07:57:04Z

☀️ Test successful - status-appveyor, status-travis
Approved by: nrc
Pushing 7ce1fbe to master...

Rollup of 6 pull requests - Successful merges: #39419, #39936, #39944, #39960, #40028, #40128 - Failed merges:

Updated AST as per <rust-lang/rust#39419>, thereby closing #19. Since those changes involved removing MathcNt and SubstNt, I've removed the unsafe parts of Quote that relied on that. Quote is now a safe module (where '$x' and '$x:ty' don't work), enabled by default. Difference tests now work on 'ast.rs' as well as 'parser.rs'. Additional work was done on cleaning up tests around macros and tokens. Closes #16.

rust-highfive assigned nrc Jan 31, 2017

jseyfried mentioned this pull request Jan 31, 2017

Tracking issue for RFC 1566: Procedural macros #38356

Closed

31 tasks

jseyfried mentioned this pull request Jan 31, 2017

Support nested macro_rules! #34925

Merged

jseyfried added A-macros Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..) S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Jan 31, 2017

eddyb reviewed Jan 31, 2017

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jseyfried force-pushed the simplify_tokentree branch 2 times, most recently from ca90c32 to 04b8382 Compare January 31, 2017 08:41

nrc reviewed Feb 3, 2017

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nrc approved these changes Feb 7, 2017

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jseyfried mentioned this pull request Feb 9, 2017

parser: fix ICE when parsing token trees after an error #39674

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jseyfried mentioned this pull request Feb 11, 2017

ICE with macro_rules! in block #39709

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jseyfried force-pushed the simplify_tokentree branch from a4e7704 to ea1f84c Compare February 12, 2017 04:18

jseyfried force-pushed the simplify_tokentree branch 3 times, most recently from 67be452 to 88716e7 Compare February 16, 2017 12:38

jseyfried force-pushed the simplify_tokentree branch from 88716e7 to f46907c Compare February 17, 2017 08:30

eddyb mentioned this pull request Feb 18, 2017

Add missing fragment specifier to a clap_app! rule. clap-rs/clap#857

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jseyfried force-pushed the simplify_tokentree branch from b6e60f9 to 839398a Compare February 28, 2017 22:15

frewsxcv mentioned this pull request Mar 1, 2017

Rollup of 6 pull requests #40167

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bors added a commit that referenced this pull request Mar 1, 2017

Auto merge of #40167 - frewsxcv:rollup, r=frewsxcv

88f7016

Rollup of 6 pull requests - Successful merges: #39419, #39936, #39944, #39960, #40028, #40128 - Failed merges:

bors added a commit that referenced this pull request Mar 1, 2017

Auto merge of #40167 - frewsxcv:rollup, r=frewsxcv

b671c32

Rollup of 6 pull requests - Successful merges: #39419, #39936, #39944, #39960, #40028, #40128 - Failed merges:

bors merged commit 839398a into rust-lang:master Mar 1, 2017

This was referenced Mar 1, 2017

Refactor parsing of trait object types #40043

Merged

Better tokentree pretty printer #39079

Closed

dtolnay mentioned this pull request Mar 2, 2017

No syntax variables matched as repeating at this depth dtolnay/proc-macro-hack#1

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sanmai-NL mentioned this pull request Mar 2, 2017

maud_macros build breaks with rustc 1.17.0-nightly (691eba135 2017-03-01) lambda-fairy/maud#77

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golddranks mentioned this pull request Mar 9, 2017

Regression in binary_macros-0.6.3, Rust 1.16 #40381

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jseyfried deleted the simplify_tokentree branch March 9, 2017 06:28

jseyfried mentioned this pull request Mar 10, 2017

[beta] macro: fix issue with sequence repetitions on beta #40411

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aidanhs mentioned this pull request Mar 11, 2017

Update to nightly 2017-03-03 SkylerLipthay/interpolate_idents#17

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harpocrates mentioned this pull request Apr 20, 2017

Fix macros harpocrates/language-rust#19

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jseyfried mentioned this pull request May 8, 2017

macro_rules attempts to expand tokens it needs to only pass through. #28415

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jseyfried mentioned this pull request May 18, 2017

Rust 1.17 regression - chipmunk-0.0.2, invalid fragment specifier #41795

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jseyfried mentioned this pull request Jul 18, 2017

missing_fragment_specifier future-compatibility warnings #40107

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ehuss mentioned this pull request Jul 29, 2020

Metavariables can be keywords rust-lang/reference#863

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ehuss mentioned this pull request Jun 12, 2022

mbe matchers can contain dollar ($) rust-lang/reference#1229

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Simplify `TokenTree` and fix `macro_rules!` bugs #39419

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		@@ -0,0 +1,228 @@
		// Copyright 2017 The Rust Project Developers. See the COPYRIGHT

Simplify TokenTree and fix macro_rules! bugs #39419

Simplify TokenTree and fix macro_rules! bugs #39419

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Simplify `TokenTree` and fix `macro_rules!` bugs #39419

Simplify `TokenTree` and fix `macro_rules!` bugs #39419

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