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A scheme for more macro-matcher friendly pre-expansion gating #65974

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merged 2 commits into from
Nov 7, 2019

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@Centril Centril commented Oct 30, 2019

Pre-expansion gating will now avoid gating macro matchers that did not result in Success(...). That is, the following is now OK despite box 42 being a valid expr and that form being pre-expansion gated:

macro_rules! m {
    ($e:expr) => { 0 }; // This fails on the input below due to `, foo`.
    (box $e:expr, foo) => { 1 }; // Successful matcher, we should get `2`.
}

fn main() {
    assert_eq!(1, m!(box 42, foo));
}

Closes #65846.

r? @petrochenkov
cc @Mark-Simulacrum

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 30, 2019
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@petrochenkov 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 Nov 2, 2019
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@Centril Centril force-pushed the matcher-friendly-gating branch from e6d4cd6 to acbfe3f Compare November 6, 2019 10:24
@Centril Centril force-pushed the matcher-friendly-gating branch from 3dbf9fb to bceaba8 Compare November 6, 2019 11:30
@Centril Centril added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 6, 2019
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@bors r+

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bors commented Nov 6, 2019

📌 Commit bceaba8 has been approved by petrochenkov

@bors 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-review Status: Awaiting review from the assignee but also interested parties. labels Nov 6, 2019
Centril added a commit to Centril/rust that referenced this pull request Nov 7, 2019
…petrochenkov

A scheme for more macro-matcher friendly pre-expansion gating

Pre-expansion gating will now avoid gating macro matchers that did not result in `Success(...)`. That is, the following is now OK despite `box 42` being a valid `expr` and that form being pre-expansion gated:

```rust
macro_rules! m {
    ($e:expr) => { 0 }; // This fails on the input below due to `, foo`.
    (box $e:expr, foo) => { 1 }; // Successful matcher, we should get `2`.
}

fn main() {
    assert_eq!(1, m!(box 42, foo));
}
```

Closes rust-lang#65846.

r? @petrochenkov
cc @Mark-Simulacrum
bors added a commit that referenced this pull request Nov 7, 2019
Rollup of 5 pull requests

Successful merges:

 - #59789 (Revert two unapproved changes to rustc_typeck.)
 - #65752 (Use structured suggestions for missing associated items)
 - #65884 (syntax: ABI-oblivious grammar)
 - #65974 (A scheme for more macro-matcher friendly pre-expansion gating)
 - #66017 (Add future incompatibility lint for `array.into_iter()`)

Failed merges:

 - #66056 (rustc_metadata: Some reorganization of the module structure)

r? @ghost
@bors bors merged commit bceaba8 into rust-lang:master Nov 7, 2019
@Centril Centril deleted the matcher-friendly-gating branch November 7, 2019 11:40
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Pre-expansion gating collects spans from unSuccessful macro matchers
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