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Don't refer to 'this tail expression' in expansion.#142024

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m-ou-se:what-tail-expression
Jun 5, 2025
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Don't refer to 'this tail expression' in expansion.#142024
bors merged 1 commit intorust-lang:masterfrom
m-ou-se:what-tail-expression

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@m-ou-se m-ou-se commented Jun 4, 2025 •
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The user has no clue what the compiler is talking about when it says "this tail expression". It is an implementation detail of the macro that it uses a block with tail expression.

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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 Jun 4, 2025
@m-ou-se m-ou-se added the A-diagnostics Area: Messages for errors, warnings, and lints label Jun 4, 2025
jieyouxu
jieyouxu reviewed Jun 4, 2025
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tests/ui/never_type/feature-gate-never_type_fallback.stderr
Comment on lines -5 to -8
| --- ^^^^^^^^
| | |
| | the trait `T` is not implemented for `()`
| | this tail expression is of type `()`
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Remark: what's slightly amusing is that the Reference calls the tail expr of an block expr the "final operand"

The syntax for a block is [...] then an optional expression, called the final operand, and finally a }.
-- https://doc.rust-lang.org/reference/expressions/block-expr.html#r-expr.block.inner-attributes

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bjorn3 commented Jun 4, 2025

nit: s/hase/has in the commit message and PR description

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petrochenkov commented Jun 4, 2025

r=me after #142024 (comment) is addressed and CI is green.
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@rustbot rustbot 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 Jun 4, 2025
@m-ou-se
Don't refer to 'this tail expression' in expansion.
da2e33b 
The user has no clue what tail expression the compiler is talking
about: it is an implementation detail of the macro that it uses a block
with tail expression.
@m-ou-se m-ou-se force-pushed the what-tail-expression branch from f19d2fe to da2e33b Compare June 4, 2025 13:43
@m-ou-se m-ou-se mentioned this pull request Jun 4, 2025
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m-ou-se commented Jun 4, 2025

@bors r=petrochenkov rollup

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bors commented Jun 4, 2025

📌 Commit da2e33b has been approved by petrochenkov

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jun 4, 2025
@matthiaskrgr matthiaskrgr mentioned this pull request Jun 4, 2025
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bors added a commit that referenced this pull request Jun 5, 2025
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Auto merge of #142033 - matthiaskrgr:rollup-99lvg0j, r=matthiaskrgr
81a964c 
Rollup of 11 pull requests

Successful merges:

 - #141890 (Add link to correct documentation in htmldocck.py)
 - #141932 (Fix for async drop inside async gen fn)
 - #141960 (Use non-2015 edition paths in tests that do not test for their resolution)
 - #141968 (Run wfcheck in one big loop instead of per module)
 - #141969 (Triagebot: Remove `assign.users_on_vacation`)
 - #141985 (Ensure query keys are printed with reduced queries)
 - #141999 (Visit the ident in `PreciseCapturingNonLifetimeArg`.)
 - #142005 (Change `tag_field` to `FieldIdx` in `Variants::Multiple`)
 - #142017 (Fix incorrect use of "recommend" over "recommended")
 - #142024 (Don't refer to 'this tail expression' in expansion.)
 - #142025 (Don't refer to 'local binding' in extern macro.)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit e081588 into rust-lang:master Jun 5, 2025
10 checks passed
@rustbot rustbot added this to the 1.89.0 milestone Jun 5, 2025
rust-timer added a commit that referenced this pull request Jun 5, 2025
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Unrolled build for #142024
96e60ab 
Rollup merge of #142024 - m-ou-se:what-tail-expression, r=petrochenkov

Don't refer to 'this tail expression' in expansion.

The user has no clue what the compiler is talking about when it says "this tail expression". It is an implementation detail of the macro that it uses a block with tail expression.
@m-ou-se m-ou-se deleted the what-tail-expression branch June 5, 2025 08:08
christian-schilling pushed a commit to christian-schilling/rustc_codegen_cranelift that referenced this pull request Jan 27, 2026
@bors
Auto merge of #142033 - matthiaskrgr:rollup-99lvg0j, r=matthiaskrgr
bd1ff92 
Rollup of 11 pull requests

Successful merges:

 - rust-lang/rust#141890 (Add link to correct documentation in htmldocck.py)
 - rust-lang/rust#141932 (Fix for async drop inside async gen fn)
 - rust-lang/rust#141960 (Use non-2015 edition paths in tests that do not test for their resolution)
 - rust-lang/rust#141968 (Run wfcheck in one big loop instead of per module)
 - rust-lang/rust#141969 (Triagebot: Remove `assign.users_on_vacation`)
 - rust-lang/rust#141985 (Ensure query keys are printed with reduced queries)
 - rust-lang/rust#141999 (Visit the ident in `PreciseCapturingNonLifetimeArg`.)
 - rust-lang/rust#142005 (Change `tag_field` to `FieldIdx` in `Variants::Multiple`)
 - rust-lang/rust#142017 (Fix incorrect use of "recommend" over "recommended")
 - rust-lang/rust#142024 (Don't refer to 'this tail expression' in expansion.)
 - rust-lang/rust#142025 (Don't refer to 'local binding' in extern macro.)

r? `@ghost`
`@rustbot` modify labels: rollup
christian-schilling pushed a commit to christian-schilling/rustc_codegen_cranelift that referenced this pull request Jan 27, 2026
@bors
Auto merge of #142033 - matthiaskrgr:rollup-99lvg0j, r=matthiaskrgr
99c29ec 
Rollup of 11 pull requests

Successful merges:

 - rust-lang/rust#141890 (Add link to correct documentation in htmldocck.py)
 - rust-lang/rust#141932 (Fix for async drop inside async gen fn)
 - rust-lang/rust#141960 (Use non-2015 edition paths in tests that do not test for their resolution)
 - rust-lang/rust#141968 (Run wfcheck in one big loop instead of per module)
 - rust-lang/rust#141969 (Triagebot: Remove `assign.users_on_vacation`)
 - rust-lang/rust#141985 (Ensure query keys are printed with reduced queries)
 - rust-lang/rust#141999 (Visit the ident in `PreciseCapturingNonLifetimeArg`.)
 - rust-lang/rust#142005 (Change `tag_field` to `FieldIdx` in `Variants::Multiple`)
 - rust-lang/rust#142017 (Fix incorrect use of "recommend" over "recommended")
 - rust-lang/rust#142024 (Don't refer to 'this tail expression' in expansion.)
 - rust-lang/rust#142025 (Don't refer to 'local binding' in extern macro.)

r? `@ghost`
`@rustbot` modify labels: rollup
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