Macros: Add a 'literal' fragment specifier #49835

da-x · 2018-04-10T09:25:43Z

macro_rules! test_literal {
    ($l:literal) => {
        println!("literal: {}", $l);
    };
    ($e:expr) => {
        println!("expr: {}", $e);
    };
}

fn main() {
    let a = 1;
    test_literal!(a);
    test_literal!(2);
    test_literal!(-3);
}

Output:

expr: 1
literal: 2
literal: -3

ToDo:

rust-highfive · 2018-04-10T09:25:48Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @petrochenkov (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

TimNN · 2018-04-10T10:13:34Z

Your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

Resolving deltas: 100% (613503/613503), completed with 4872 local objects.
---
[00:00:46] configure: rust.quiet-tests     := True
---
[00:43:58] ..............................................................................i.....................
[00:44:04] .....................i..............................................................................
---
[00:44:39] ..................................................F.................................................
[00:44:46] i.........................................................................i.........................
[00:44:52] ....................................................................................................
[00:45:00] ....................................................................................................
[00:45:08] ....................................................................................................
known-linux-gnu/test/ui" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/macro-invalid-fragment-spec.stage2-x86_64-unknown-linux-gnu" "-Crpath" "-O" "-Zmiri" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/macro-invalid-fragment-spec.stage2-x86_64-unknown-linux-gnu.aux" "-A" "unused"
---
[00:45:09] {"message":"invalid fragment specifier `foo`","code":null,"level":"error","spans":[{"file_name":"/checkout/src/test/ui/macro-invalid-fragment-spec.rs","byte_start":490,"byte_end":496,"line_start":12,"line_end":12,"column_start":6,"column_end":12,"is_primary":true,"text":[{"text":"    ($x:foo) => ()","highlight_start":6,"highlight_end":12}],"label":null,"suggested_replacement":null,"expansion":null}],"children":[{"message":"valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `literal`, `path`, `meta`, `tt`, `item` and `vis`","code":null,"level":"help","spans":[],"children":[],"rendered":null}],"rendered":"error: invalid fragment specifier `foo`\n  --> /checkout/src/test/ui/macro-invalid-fragment-spec.rs:12:6\n   |\nLL |     ($x:foo) => ()\n   |      ^^^^^^\n   |\n   = help: valid fragment specifiers are `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `literal`, `path`, `meta`, `tt` "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "3.9.1\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:45:09] expected success, got: exit code: 101
[00:45:09]
[00:45:09]
[00:45:09] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[00:45:09] Build completed unsuccessfully in 0:02:28
[00:45:09] make: *** [check] Error 1
[00:45:09] Makefile:58: recipe for target 'check' failed
---
$ ls -lat $HOME/Library/Logs/DiagnosticReports/
ls: cannot access /home/travis/Library/Logs/DiagnosticReports/: No such file or directory

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

petrochenkov · 2018-04-15T09:53:33Z

Could you add tests where literals of various kinds (integral, string, boolean) are used in expressions, patterns (including range patterns LIT ... LIT) and attributes (#[attr = LIT]).
After that we can discuss supporting -.
Docs are not mandatory, but they may be added into src/doc/unstable-book/src/language-features.

petrochenkov · 2018-04-16T10:06:48Z

This also needs to be feature gated, see b284419 for an example.

pietroalbini · 2018-04-23T10:29:28Z

Ping from triage @da-x! Will you have some time to work on this in the future?

da-x · 2018-04-23T10:36:53Z

@pietroalbini - Yes - I am planning to add tests, feature gating, and documentation. Hopefully soon!

bors · 2018-04-28T12:49:05Z

☔ The latest upstream changes (presumably #50155) made this pull request unmergeable. Please resolve the merge conflicts.

da-x · 2018-04-29T08:58:13Z

Added tests, feature gate, and docs.

Testing revealed that true and false are not recognized as literals. I'm working to fix it.

petrochenkov · 2018-04-29T18:28:31Z

src/test/run-pass/macro-literal.rs

+}
+
+macro_rules! match_attr {
+ (#[$attr:meta] $e:literal) => {


I meant literal inside the attribute produced by the macro, e.g. something like

macro_rules! match_attr { ($e: literal) => { // Struct with doc comment passed via $literal #[doc = $literal] struct S; } }

petrochenkov · 2018-04-29T18:30:56Z

src/test/run-pass/macro-literal.rs

+}
+
+macro_rules! test_user {
+ ($s:literal, $e:literal) => {


Could you add a case checking that $lit1 ... $lit2 is parsed as a range pattern in patterns?

petrochenkov · 2018-04-29T18:35:27Z

src/test/run-pass/macro-literal.rs

+}
+
+macro_rules! catch_range {
+ ($s:literal ... $e:literal) => {


Similarly to attributes, the range should rather be produced by a macro (1833a1f#r184891034), this test with ... on the left side of the macro is testing something entirely different and probably not useful.

bors · 2018-05-01T19:19:30Z

☔ The latest upstream changes (presumably #49789) made this pull request unmergeable. Please resolve the merge conflicts.

shepmaster · 2018-05-06T21:34:00Z

Ping from triage, @da-x ! You have review comments and merge conflicts to address!

da-x · 2018-05-06T21:35:59Z

Yes, will be on it!

da-x · 2018-05-08T19:16:53Z

@petrochenkov Tried to address your comments. Thanks.

da-x · 2018-05-09T20:53:15Z

Also fixed for true/false to pass as literals rather than expressions.

petrochenkov · 2018-05-10T23:53:11Z

src/libsyntax/parse/token.rs

+ match *self {
+ Literal(..) => true,
+ Ident(ident, false) if ident.name == "true" => true,
+ Ident(ident, false) if ident.name == "false" => true,


Nit: keywords::True.name()/keywords::False.name() instead of "true"/"false".

petrochenkov · 2018-05-10T23:59:15Z

@da-x
Do you prefer to add support for - in this PR or in a separate one?
It will need changing ast::Lit in NtLiteral into ast::Expr and replacing the parse_lit logic for "literal" in macro_parser with something like fn parse_pat_literal_maybe_minus currently used in patterns.

da-x · 2018-05-11T20:26:39Z

I've added a fix for negative literals. Thanks for the help.

petrochenkov · 2018-05-13T12:26:08Z

src/libsyntax/parse/token.rs

@@ -310,6 +315,14 @@ impl Token {
 }
 }

+ /// Returns true if this token can begin a two-token literal (i.e. negative numbers)
+ pub fn can_begin_literal(&self) -> bool {


Could you merge this with is_lit_or_bool?

petrochenkov · 2018-05-13T12:30:45Z

src/libsyntax/ext/tt/macro_rules.rs

- "ident" | "lifetime" => {
- // being a single token, idents and lifetimes are harmless
+ "ident" | "lifetime" | "literal" => {
+ // being a single token, idents, literals and lifetimes are harmless


Hmm, literals are no longer necessarily single-token, but it shouldn't change anything with regards to follow set.

petrochenkov · 2018-05-13T12:31:25Z

src/libsyntax/fold.rs

@@ -156,6 +156,10 @@ pub trait Folder : Sized {
 noop_fold_ident(i, self)
 }

+ fn fold_lit(&mut self, i: P<Expr>) -> P<Expr> {


fold_lit and noop_fold_lit are no longer necessary.

petrochenkov · 2018-05-13T12:33:13Z

Excellent, thanks!
r=me after addressing the remaining comments and squashing commits.

Implements RFC 1576. See: https://github.com/rust-lang/rfcs/blob/master/text/1576-macros-literal-matcher.md Changes are mostly in libsyntax, docs, and tests. Feature gate is enabled for 1.27.0. Many thanks to Vadim Petrochenkov for following through code reviews and suggestions. Example: ````rust macro_rules! test_literal { ($l:literal) => { println!("literal: {}", $l); }; ($e:expr) => { println!("expr: {}", $e); }; } fn main() { let a = 1; test_literal!(a); test_literal!(2); test_literal!(-3); } ``` Output: ``` expr: 1 literal: 2 literal: -3 ```

petrochenkov · 2018-05-13T16:39:26Z

@bors r+

bors · 2018-05-13T16:39:26Z

📌 Commit 37ed2ab has been approved by petrochenkov

bors · 2018-05-13T17:07:46Z

⌛ Testing commit 37ed2ab with merge 9fae153...

Macros: Add a 'literal' fragment specifier See: #35625 ```rust macro_rules! test_literal { ($l:literal) => { println!("literal: {}", $l); }; ($e:expr) => { println!("expr: {}", $e); }; } fn main() { let a = 1; test_literal!(a); test_literal!(2); test_literal!(-3); } ``` Output: ``` expr: 1 literal: 2 literal: -3 ``` ToDo: * [x] Feature gate * [x] Basic tests * [x] Tests for range patterns * [x] Tests for attributes * [x] Documentation * [x] Fix for `true`/`false` * [x] Fix for negative number literals

bors · 2018-05-13T19:26:34Z

☀️ Test successful - status-appveyor, status-travis
Approved by: petrochenkov
Pushing 9fae153 to master...

rust-highfive assigned petrochenkov Apr 10, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Apr 10, 2018

Centril added T-lang Relevant to the language team, which will review and decide on the PR/issue. C-enhancement Category: An issue proposing an enhancement or a PR with one. labels Apr 15, 2018

petrochenkov 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-review Status: Awaiting review from the assignee but also interested parties. labels Apr 15, 2018

petrochenkov reviewed Apr 29, 2018

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da-x force-pushed the literal-fragment-pr branch from 3b0cc96 to 37ed2ab Compare May 13, 2018 16:19

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 May 13, 2018

bors merged commit 37ed2ab into rust-lang:master May 13, 2018

This was referenced May 13, 2018

stabilize macro_lifetime_matcher #50385

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Implementation of RFC 2086 - Allow Irrefutable Let patterns #49469

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Implement RFC 2056 trivial constraints in where clauses #48557

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Implement label break value (RFC 2046) #50045

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da-x deleted the literal-fragment-pr branch June 5, 2018 21:51

vlad20012 mentioned this pull request Jun 12, 2018

Add a 'literal' & lifetime fragment specifier intellij-rust/intellij-rust#2581

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Macros: Add a 'literal' fragment specifier #49835

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Macros: Add a 'literal' fragment specifier #49835

Macros: Add a 'literal' fragment specifier #49835

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