Skip to content

1.100 beta regression: the Self constructor can only be used with tuple or unit structs #163800

New issue
New issue
Closed
#163863
Closed
1.100 beta regression: the Self constructor can only be used with tuple or unit structs#163800
#163863
Assignees
cyrgani
Labels
A-macrosArea: All kinds of macros (custom derive, macro_rules!, proc macros, ..)A-proc-macrosArea: Procedural macrosA-resolveArea: Name/path resolution done by `rustc_resolve` specificallyC-bugCategory: This is a bug.P-highHigh priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.T-langRelevant to the language teamregression-from-stable-to-betaPerformance or correctness regression from stable to beta.

Description

@mejrs
mejrs
opened on Oct 5, 2026

Found in #163482:

I tried this code:

#[derive(Clone, Copy)]
#[ghost::phantom]
pub struct Spooky<T>;

I expected to see this happen: compiles successfully on stable

Instead, this happened: compile error on beta:

error: the `Self` constructor can only be used with tuple or unit structs                                                                                                                                                                                                                                            
 --> src\lib.rs:1:10
  |
1 | #[derive(Clone, Copy)]
  |          ^^^^^

Meta

rustc --version --verbose:

1.100-beta
Backtrace 

<backtrace>

Activity

  1. mejrs
    added
    C-bugCategory: This is a bug.
    on Oct 5, 2026
  2. rustbot
    added
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on Oct 5, 2026
  3. theemathas
    added
    regression-from-stable-to-betaPerformance or correctness regression from stable to beta.
    on Oct 5, 2026
  4. rustbot
    added
    I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}
    on Oct 5, 2026
  5. theemathas
    added a parent issue on Oct 5, 2026
  6. theemathas
    added
    E-needs-bisectionCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc
    E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example
    on Oct 5, 2026

  7. mejrs commented on Oct 5, 2026

    @mejrs
    mejrs
    on Oct 5, 2026
    MemberAuthor

    Most likely #163080, cc @cyrgani @nnethercote

    The phantom macro rewrites the struct to en enum, so Self is no longer valid. that PR rewrote the macro to emit Self rather than the name of the struct, which is also re-exported by the phantom macro as an enum variant.

  8. cyrgani
    self-assigned this
    on Oct 5, 2026
  9. theemathas
    added
    A-resolveArea: Name/path resolution done by `rustc_resolve` specifically
    A-macrosArea: All kinds of macros (custom derive, macro_rules!, proc macros, ..)
    T-langRelevant to the language team
    T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.
    A-proc-macrosArea: Procedural macros
    and removed
    E-needs-bisectionCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc
    E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example
    needs-triageThis issue may need triage. Remove when done. See docs forge.rust-lang.org/release/issue-triaging
    on Oct 5, 2026
  10. JonathanBrouwer
    added 4 commits that reference this issue on Oct 6, 2026

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    3a16dae

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    c63f7d6

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    fa001aa

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    7d339ef
  11. rustbot
    removed
    I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}
    on Oct 6, 2026

  12. rustbot commented on Oct 6, 2026

    @rustbot
    rustbot
    on Oct 6, 2026
    Collaborator

    Assigning P-high (discussion on Zulip).

  13. rustbot
    added
    P-highHigh priority
    on Oct 6, 2026
  14. JonathanBrouwer
    added 3 commits that reference this issue on Oct 7, 2026

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    c254f7f

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    66f85b3

    Rollup merge of rust-lang#163863 - cyrgani:annoying-attr-macros, r=nn…

    49ccb54
  15. rust-bors
    closed this as completedin 49ccb54on Oct 8, 2026
  16. rust-bors
    added a commit that references this issue on Oct 8, 2026

    Unrolled build for #163863 in rollup 163957

    8f3ba4b
  17. github-actions
    added a commit that references this issue on Oct 10, 2026

    Rollup merge of #163863 - cyrgani:annoying-attr-macros, r=nnethercote

    66ffbb4
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Metadata

Metadata

Assignees

Labels

A-macrosArea: All kinds of macros (custom derive, macro_rules!, proc macros, ..)A-proc-macrosArea: Procedural macrosA-resolveArea: Name/path resolution done by `rustc_resolve` specificallyC-bugCategory: This is a bug.P-highHigh priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.T-langRelevant to the language teamregression-from-stable-to-betaPerformance or correctness regression from stable to beta.

Type

No type

Projects

No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions