Perform `cfg` attribute processing during macro expansion and fix bugs #33706

jseyfried · 2016-05-18T03:45:42Z

This PR refactors cfg attribute processing and fixes bugs. More specifically:

It merges gated feature checking for stmt/expr attributes, cfg_attr processing, and cfg processing into a single fold.
- This allows feature gated cfg variables to be used in cfg_attr on unconfigured items. All other feature gated attributes can already be used on unconfigured items.
It performs cfg attribute processing during macro expansion instead of after expansion so that macro-expanded items are configured the same as ordinary items. In particular, to match their non-expanded counterparts,
- macro-expanded unconfigured macro invocations are no longer expanded,
- macro-expanded unconfigured macro definitions are no longer usable, and
- feature gated cfg variables on macro-expanded macro definitions/invocations are now errors.

This is a [breaking-change]. For example, the following would break:

macro_rules! m {
    () => {
        #[cfg(attr)]
        macro_rules! foo { () => {} }
        foo!(); // This will be an error

        macro_rules! bar { () => { fn f() {} } }
        #[cfg(attr)] bar!(); // This will no longer be expanded ...
        fn g() { f(); } // ... so that `f` will be unresolved.

        #[cfg(target_thread_local)] // This will be a gated feature error
        macro_rules! baz { () => {} }
    }
}

m!();

EDIT: fixes #22250, fixes #31369.

r? @nrc

jseyfried · 2016-05-18T12:43:19Z

cc @nikomatsakis

bors · 2016-05-19T20:56:28Z

☔ The latest upstream changes (presumably #33742) made this pull request unmergeable. Please resolve the merge conflicts.

jseyfried · 2016-05-19T23:25:57Z

Rebased.

nrc · 2016-05-23T02:47:52Z

src/libsyntax/config.rs


+pub trait CfgFolder: fold::Folder {
+    fn in_cfg(&mut self, attrs: &[ast::Attribute]) -> bool;
+    fn visit_unconfigurable_expr(&mut self, _expr: &ast::Expr) {}


Could you document these methods please?

nrc · 2016-05-23T03:08:57Z

r+ with the comment added

jseyfried · 2016-05-24T05:32:27Z

@nrc I made sure we process cfg_attr attributes on non-optional expressions and added comments.

jseyfried · 2016-05-24T21:14:31Z

@nrc also, some process questions:

Should this PR be tagged relnotes? (c.f. #33458)
Do you intend "r+ with the comment added" to have the same meaning as "r=me with the comment added"? Currently, I don't approve on behalf of a reviewer unless they say "r=me".

bors · 2016-05-26T18:35:03Z

☔ The latest upstream changes (presumably #33766) made this pull request unmergeable. Please resolve the merge conflicts.

…_items`

…ng into `StripUnconfigured`

…ured item is allowed

jseyfried · 2016-05-27T00:12:06Z

Rebased.

nrc · 2016-05-27T00:59:49Z

@bors: r+

@jseyfried yes and yes

bors · 2016-05-27T00:59:50Z

📌 Commit 9d84921 has been approved by nrc

bors · 2016-05-27T03:03:59Z

⌛ Testing commit 9d84921 with merge 4d92f83...

bors · 2016-05-27T04:25:20Z

💔 Test failed - auto-win-gnu-32-opt-rustbuild

jseyfried · 2016-05-27T11:22:51Z

@bors retry

bors · 2016-05-27T15:08:16Z

⌛ Testing commit 9d84921 with merge 8be1128...

bors · 2016-05-27T16:21:01Z

💔 Test failed - auto-win-gnu-32-opt-rustbuild

…ded.

jseyfried · 2016-05-27T23:58:48Z

@bors r=nrc

bors · 2016-05-27T23:58:49Z

📌 Commit 53ab137 has been approved by nrc

bors · 2016-05-28T00:46:15Z

⌛ Testing commit 53ab137 with merge 8b012ed...

@nrc

Perform `cfg` attribute processing during macro expansion and fix bugs This PR refactors `cfg` attribute processing and fixes bugs. More specifically: - It merges gated feature checking for stmt/expr attributes, `cfg_attr` processing, and `cfg` processing into a single fold. - This allows feature gated `cfg` variables to be used in `cfg_attr` on unconfigured items. All other feature gated attributes can already be used on unconfigured items. - It performs `cfg` attribute processing during macro expansion instead of after expansion so that macro-expanded items are configured the same as ordinary items. In particular, to match their non-expanded counterparts, - macro-expanded unconfigured macro invocations are no longer expanded, - macro-expanded unconfigured macro definitions are no longer usable, and - feature gated `cfg` variables on macro-expanded macro definitions/invocations are now errors. This is a [breaking-change]. For example, the following would break: ```rust macro_rules! m { () => { #[cfg(attr)] macro_rules! foo { () => {} } foo!(); // This will be an error macro_rules! bar { () => { fn f() {} } } #[cfg(attr)] bar!(); // This will no longer be expanded ... fn g() { f(); } // ... so that `f` will be unresolved. #[cfg(target_thread_local)] // This will be a gated feature error macro_rules! baz { () => {} } } } m!(); ``` r? @nrc

bors · 2016-05-28T03:45:44Z

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-32cross-opt, auto-linux-64-cargotest, auto-linux-64-cross-armhf, auto-linux-64-cross-armsf, auto-linux-64-cross-freebsd, auto-linux-64-cross-netbsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-cross-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild

jseyfried · 2016-05-29T01:00:28Z

Fixes #22250.

jseyfried · 2016-06-01T08:45:27Z

Fixes #31369.

@nrc

Fix a regression in the configuration folder This fixes #34028, a regression caused by #33706 in which unconfigured impl items generated by a macro in an impl item position are not removed. r? @nrc

rust-highfive assigned nrc May 18, 2016

jseyfried force-pushed the refactor_cfg branch 2 times, most recently from 61e9e91 to aa36f63 Compare May 18, 2016 10:22

jseyfried force-pushed the refactor_cfg branch from aa36f63 to b6e3247 Compare May 19, 2016 22:17

jseyfried force-pushed the refactor_cfg branch from b6e3247 to c71e5aa Compare May 22, 2016 03:11

nrc reviewed May 23, 2016
View reviewed changes

jseyfried force-pushed the refactor_cfg branch from 71193c4 to e2c4ebf Compare May 24, 2016 20:05

jseyfried added 11 commits May 26, 2016 23:23

Add and use HasAttrs trait

29c1059

Refactor the syntax::config::fold_* functions into methods

7a42e46

Introduce CfgFolder trait

7985439

Refactor CfgFolder::in_cfg -> CfgFolder::configure

f3e8076

Implement CfgFolder directly instead of passing a closure to `strip…

a306f85

…_items`

Move cfg_attr processing and stmt/expr attribute gated feature checki…

d3a0e17

…ng into `StripUnconfigured`

Process cfg_attr attributes on non-optional expressions

15d5074

Test that a feature gated cfg variable in a cfg_attr on an unconfig…

3636ce7

…ured item is allowed

Update spans' expn_id during the marking fold

25c7333

Strip unconfigured items during macro expansion

1aa34e0

Refactor expand_expr

0558df2

jseyfried force-pushed the refactor_cfg branch 4 times, most recently from 9d84921 to 3636ce7 Compare May 27, 2016 00:11

jseyfried force-pushed the refactor_cfg branch from 9d84921 to ae61e31 Compare May 27, 2016 23:25

jseyfried added 2 commits May 27, 2016 23:57

Test that unconfigured macro-expanded macro invocations are not expan…

6b3edc2

…ded.

Comment methods in CfgFolder

53ab137

jseyfried force-pushed the refactor_cfg branch from ae61e31 to 53ab137 Compare May 27, 2016 23:57

bors merged commit 53ab137 into rust-lang:master May 28, 2016

bors mentioned this pull request May 28, 2016

Allow syntax extensions which modify and decorate #33738

Closed

jseyfried mentioned this pull request May 29, 2016

Process cfg_attr during expansion #22250

Closed

This was referenced Jun 1, 2016

cfg attributes appear are improperly applied inside of include! #31369

Closed

Fix a regression in the configuration folder #34031

Merged

Macro hygiene regression #34028

Closed

jseyfried mentioned this pull request Jun 9, 2016

regression: ICE on an unconfigured interpolated item in a macro invocation #34171

Closed

jseyfried deleted the refactor_cfg branch February 15, 2017 08:21

Mark-Simulacrum mentioned this pull request May 20, 2017

Utilize cfg_attr instead of a build script. rust-lang/backtrace-rs#48

Merged

Perform cfg attribute processing during macro expansion and fix bugs #33706

Perform cfg attribute processing during macro expansion and fix bugs #33706

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Perform `cfg` attribute processing during macro expansion and fix bugs #33706

Perform `cfg` attribute processing during macro expansion and fix bugs #33706

jseyfried commented May 18, 2016 •

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