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Handle attempts to have multiple cfgd tail expressions #117988

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merged 1 commit into from
Nov 20, 2023

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estebank
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When encountering code that seems like it might be trying to have multiple tail expressions depending on cfg information, suggest alternatives that will success to parse.

fn foo() -> String {
    #[cfg(feature = "validation")]
    [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
    #[cfg(not(feature = "validation"))]
    String::new()
}
error: expected `;`, found `#`
  --> $DIR/multiple-tail-expr-behind-cfg.rs:5:64
   |
LL |     #[cfg(feature = "validation")]
   |     ------------------------------ only `;` terminated statements or tail expressions are allowed after this attribute
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
   |                                                                ^ expected `;` here
LL |     #[cfg(not(feature = "validation"))]
   |     - unexpected token
   |
help: add `;` here
   |
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
   |                                                                +
help: alternatively, consider surrounding the expression with a block
   |
LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
   |     +                                                             +
help: it seems like you are trying to provide different expressions depending on `cfg`, consider using `if cfg!(..)`
   |
LL ~     if cfg!(feature = "validation") {
LL ~         [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
LL ~     } else if cfg!(not(feature = "validation")) {
LL ~         String::new()
LL +     }
   |

Fix #106020.

r? @oli-obk

When encountering code that seems like it might be trying to have
multiple tail expressions depending on `cfg` information, suggest
alternatives that will success to parse.

```rust
fn foo() -> String {
    #[cfg(feature = "validation")]
    [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
    #[cfg(not(feature = "validation"))]
    String::new()
}
```

```
error: expected `;`, found `#`
  --> $DIR/multiple-tail-expr-behind-cfg.rs:5:64
   |
LL |     #[cfg(feature = "validation")]
   |     ------------------------------ only `;` terminated statements or tail expressions are allowed after this attribute
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
   |                                                                ^ expected `;` here
LL |     #[cfg(not(feature = "validation"))]
   |     - unexpected token
   |
help: add `;` here
   |
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
   |                                                                +
help: alternatively, consider surrounding the expression with a block
   |
LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
   |     +                                                             +
help: it seems like you are trying to provide different expressions depending on `cfg`, consider using `if cfg!(..)`
   |
LL ~     if cfg!(feature = "validation") {
LL ~         [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
LL ~     } else if cfg!(not(feature = "validation")) {
LL ~         String::new()
LL +     }
   |
```

Fix rust-lang#106020.
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rustbot commented Nov 16, 2023

Could not assign reviewer from: oli-obk.
User(s) oli-obk are either the PR author, already assigned, or on vacation, and there are no other candidates.
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rustbot commented Nov 16, 2023

r? @cjgillot

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 16, 2023
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@bors r+

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bors commented Nov 19, 2023

📌 Commit a16722d has been approved by cjgillot

It is now in the queue for this repository.

@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 19, 2023
bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 20, 2023
…mpiler-errors

Rollup of 8 pull requests

Successful merges:

 - rust-lang#117828 (Avoid iterating over hashmaps in astconv)
 - rust-lang#117832 (interpret: simplify handling of shifts by no longer trying to handle signed and unsigned shift amounts in the same branch)
 - rust-lang#117891 (Recover `dyn` and `impl` after `for<...>`)
 - rust-lang#117957 (if available use a Child's pidfd for kill/wait)
 - rust-lang#117988 (Handle attempts to have multiple `cfg`d tail expressions)
 - rust-lang#117994 (Ignore but do not assume region obligations from unifying headers in negative coherence)
 - rust-lang#118000 (Make regionck care about placeholders in outlives components)
 - rust-lang#118068 (subtree update cg_gcc 2023/11/17)

r? `@ghost`
`@rustbot` modify labels: rollup
bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 20, 2023
…tthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#117828 (Avoid iterating over hashmaps in astconv)
 - rust-lang#117832 (interpret: simplify handling of shifts by no longer trying to handle signed and unsigned shift amounts in the same branch)
 - rust-lang#117891 (Recover `dyn` and `impl` after `for<...>`)
 - rust-lang#117957 (if available use a Child's pidfd for kill/wait)
 - rust-lang#117988 (Handle attempts to have multiple `cfg`d tail expressions)
 - rust-lang#117994 (Ignore but do not assume region obligations from unifying headers in negative coherence)
 - rust-lang#118000 (Make regionck care about placeholders in outlives components)
 - rust-lang#118068 (subtree update cg_gcc 2023/11/17)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit e6a3ca0 into rust-lang:master Nov 20, 2023
11 checks passed
@rustbot rustbot added this to the 1.76.0 milestone Nov 20, 2023
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Nov 20, 2023
Rollup merge of rust-lang#117988 - estebank:issue-106020, r=cjgillot

Handle attempts to have multiple `cfg`d tail expressions

When encountering code that seems like it might be trying to have multiple tail expressions depending on `cfg` information, suggest alternatives that will success to parse.

```rust
fn foo() -> String {
    #[cfg(feature = "validation")]
    [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
    #[cfg(not(feature = "validation"))]
    String::new()
}
```

```
error: expected `;`, found `#`
  --> $DIR/multiple-tail-expr-behind-cfg.rs:5:64
   |
LL |     #[cfg(feature = "validation")]
   |     ------------------------------ only `;` terminated statements or tail expressions are allowed after this attribute
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
   |                                                                ^ expected `;` here
LL |     #[cfg(not(feature = "validation"))]
   |     - unexpected token
   |
help: add `;` here
   |
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
   |                                                                +
help: alternatively, consider surrounding the expression with a block
   |
LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
   |     +                                                             +
help: it seems like you are trying to provide different expressions depending on `cfg`, consider using `if cfg!(..)`
   |
LL ~     if cfg!(feature = "validation") {
LL ~         [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
LL ~     } else if cfg!(not(feature = "validation")) {
LL ~         String::new()
LL +     }
   |
```

Fix rust-lang#106020.

r? `@oli-obk`
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Unexpected token: expected ;, found #.
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