compiler: Make Externally Implementable Item (eii) macros "semiopaque" #151046

Enselic · 2026-01-13T05:42:17Z

Otherwise eiis defined by std will produce large amounts of missing stability attribute errors. This problem is not eii specific, as can be seen in #146993 and which is demonstrated in #151022.

As can be seen with

$ git grep rustc_macro_transparency
compiler/rustc_arena/src/lib.rs:#[rustc_macro_transparency = "semiopaque"]
[...]

it is very common for macros to use "semiopaque".

r? @jdonszelmann

Tracking issue: #125418

Needed for: #150588

Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors.

jdonszelmann · 2026-01-13T10:57:31Z

what does opaque/semiopaque exactly mean? like what effect does that have? Is there a nice reference somewhere?

jdonszelmann · 2026-01-13T10:57:52Z

@rustbot author

Enselic · 2026-01-13T19:50:54Z

@jdonszelmann Hopefully the in-tree docs can help?

rust/compiler/rustc_span/src/hygiene.rs

Lines 182 to 200 in 3bdf45f

    
           /// A property of a macro expansion that determines how identifiers 
        
           /// produced by that expansion are resolved. 
        
           #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug, Encodable, Decodable)] 
        
           #[derive(HashStable_Generic)] 
        
           pub enum Transparency { 
        
               /// Identifier produced by a transparent expansion is always resolved at call-site. 
        
               /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this. 
        
               Transparent, 
        
               /// Identifier produced by a semi-opaque expansion may be resolved 
        
               /// either at call-site or at definition-site. 
        
               /// If it's a local variable, label or `$crate` then it's resolved at def-site. 
        
               /// Otherwise it's resolved at call-site. 
        
               /// `macro_rules` macros behave like this, built-in macros currently behave like this too, 
        
               /// but that's an implementation detail. 
        
               SemiOpaque, 
        
               /// Identifier produced by an opaque expansion is always resolved at definition-site. 
        
               /// Def-site spans in procedural macros, identifiers from `macro` by default use this. 
        
               Opaque, 
        
           }

Also, this seems to be the most important place for where the difference of the variants matter (but I don't understand the code myself):

rust/compiler/rustc_span/src/hygiene.rs

Lines 605 to 619 in 3bdf45f

    
           // Evaluate opaque and semi-opaque versions of the new syntax context. 
        
           let (opaque, opaque_and_semiopaque) = match transparency { 
        
               Transparency::Transparent => (parent_opaque, parent_opaque_and_semiopaque), 
        
               Transparency::SemiOpaque => ( 
        
                   parent_opaque, 
        
                   // Will be the same as `ctxt` if the expn chain contains only (semi-)opaques. 
        
                   self.alloc_ctxt(parent_opaque_and_semiopaque, expn_id, transparency), 
        
               ), 
        
               Transparency::Opaque => ( 
        
                   // Will be the same as `ctxt` if the expn chain contains only opaques. 
        
                   self.alloc_ctxt(parent_opaque, expn_id, transparency), 
        
                   // Will be the same as `ctxt` if the expn chain contains only (semi-)opaques. 
        
                   self.alloc_ctxt(parent_opaque_and_semiopaque, expn_id, transparency), 
        
               ), 
        
           };

I personally find the discussion that starts here interesting.

In the end, for me, it boils down to:

Doing this makes errors go away.
The same thing is done to a lot of other macros already.
We are making changes to an unstable feature and don't have to get everything perfect on the first try.

jdonszelmann · 2026-01-14T11:40:25Z

Yea, makes sense. Just wanted to understand what we were doing to it :3
Thanks for the explaination!

jdonszelmann · 2026-01-14T11:40:37Z

@bors r+ rollup

rust-bors · 2026-01-14T11:40:40Z

📌 Commit 8a8b31a has been approved by jdonszelmann

It is now in the queue for this repository.

@jdonszelmann

compiler: Make Externally Implementable Item (eii) macros "semiopaque" Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors. This problem is not eii specific, as can be seen in rust-lang#146993 and which is demonstrated in rust-lang#151022. As can be seen with ```console $ git grep rustc_macro_transparency compiler/rustc_arena/src/lib.rs:#[rustc_macro_transparency = "semiopaque"] [...] ``` it is very common for macros to use `"semiopaque"`. r? @jdonszelmann Tracking issue: rust-lang#125418 Needed for: rust-lang#150588

@jdonszelmann

compiler: Make Externally Implementable Item (eii) macros "semiopaque" Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors. This problem is not eii specific, as can be seen in rust-lang#146993 and which is demonstrated in rust-lang#151022. As can be seen with ```console $ git grep rustc_macro_transparency compiler/rustc_arena/src/lib.rs:#[rustc_macro_transparency = "semiopaque"] [...] ``` it is very common for macros to use `"semiopaque"`. r? @jdonszelmann Tracking issue: rust-lang#125418 Needed for: rust-lang#150588

@ghost

…uwer Rollup of 12 pull requests Successful merges: - #150585 (Add a context-consistency check before emitting redundant generic-argument suggestions) - #150586 (rustdoc: Fix intra-doc link bugs involving type aliases and associated items) - #150590 (Don't try to recover keyword as non-keyword identifier ) - #150817 (cleanup: remove borrowck handling for inline const patterns) - #150939 (resolve: Relax some asserts in glob overwriting and add tests) - #150966 (rustc_target: Remove unused Arch::PowerPC64LE) - #150971 (Disallow eii in statement position) - #151016 (fix: WASI threading regression by disabling pthread usage) - #151046 (compiler: Make Externally Implementable Item (eii) macros "semiopaque") - #151103 (mir_build: Simplify length-determination and indexing for array/slice patterns) - #151117 (Avoid serde dependency in build_helper when not necessary) - #151127 (Delete `MetaItemOrLitParser::Err`) r? @ghost

@jdonszelmann

compiler: Make Externally Implementable Item (eii) macros "semiopaque" Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors. This problem is not eii specific, as can be seen in rust-lang#146993 and which is demonstrated in rust-lang#151022. As can be seen with ```console $ git grep rustc_macro_transparency compiler/rustc_arena/src/lib.rs:#[rustc_macro_transparency = "semiopaque"] [...] ``` it is very common for macros to use `"semiopaque"`. r? @jdonszelmann Tracking issue: rust-lang#125418 Needed for: rust-lang#150588

@ghost

…uwer Rollup of 16 pull requests Successful merges: - #150585 (Add a context-consistency check before emitting redundant generic-argument suggestions) - #150586 (rustdoc: Fix intra-doc link bugs involving type aliases and associated items) - #150590 (Don't try to recover keyword as non-keyword identifier ) - #150817 (cleanup: remove borrowck handling for inline const patterns) - #150939 (resolve: Relax some asserts in glob overwriting and add tests) - #150962 (Remove `FeedConstTy` and provide ty when lowering const arg) - #150966 (rustc_target: Remove unused Arch::PowerPC64LE) - #150971 (Disallow eii in statement position) - #151016 (fix: WASI threading regression by disabling pthread usage) - #151046 (compiler: Make Externally Implementable Item (eii) macros "semiopaque") - #151099 (Recover parse gracefully from `<const N>`) - #151117 (Avoid serde dependency in build_helper when not necessary) - #151127 (Delete `MetaItemOrLitParser::Err`) - #151128 (Add temporary new bors e-mail address to the mailmap) - #151130 (resolve: Downgrade `ambiguous_glob_imports` to warn-by-default) - #151138 (Rename `rust.use-lld` to `rust.bootstrap-override-lld` in INSTALL.md) r? @ghost

@ghost

…uwer Rollup of 15 pull requests Successful merges: - #150585 (Add a context-consistency check before emitting redundant generic-argument suggestions) - #150586 (rustdoc: Fix intra-doc link bugs involving type aliases and associated items) - #150590 (Don't try to recover keyword as non-keyword identifier ) - #150817 (cleanup: remove borrowck handling for inline const patterns) - #150939 (resolve: Relax some asserts in glob overwriting and add tests) - #150962 (Remove `FeedConstTy` and provide ty when lowering const arg) - #150966 (rustc_target: Remove unused Arch::PowerPC64LE) - #150971 (Disallow eii in statement position) - #151016 (fix: WASI threading regression by disabling pthread usage) - #151046 (compiler: Make Externally Implementable Item (eii) macros "semiopaque") - #151099 (Recover parse gracefully from `<const N>`) - #151117 (Avoid serde dependency in build_helper when not necessary) - #151127 (Delete `MetaItemOrLitParser::Err`) - #151128 (Add temporary new bors e-mail address to the mailmap) - #151138 (Rename `rust.use-lld` to `rust.bootstrap-override-lld` in INSTALL.md) r? @ghost

@jdonszelmann

Rollup merge of #151046 - semiopaque-eii-fix, r=jdonszelmann compiler: Make Externally Implementable Item (eii) macros "semiopaque" Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors. This problem is not eii specific, as can be seen in #146993 and which is demonstrated in #151022. As can be seen with ```console $ git grep rustc_macro_transparency compiler/rustc_arena/src/lib.rs:#[rustc_macro_transparency = "semiopaque"] [...] ``` it is very common for macros to use `"semiopaque"`. r? @jdonszelmann Tracking issue: #125418 Needed for: #150588

@ghost

…uwer Rollup of 15 pull requests Successful merges: - rust-lang/rust#150585 (Add a context-consistency check before emitting redundant generic-argument suggestions) - rust-lang/rust#150586 (rustdoc: Fix intra-doc link bugs involving type aliases and associated items) - rust-lang/rust#150590 (Don't try to recover keyword as non-keyword identifier ) - rust-lang/rust#150817 (cleanup: remove borrowck handling for inline const patterns) - rust-lang/rust#150939 (resolve: Relax some asserts in glob overwriting and add tests) - rust-lang/rust#150962 (Remove `FeedConstTy` and provide ty when lowering const arg) - rust-lang/rust#150966 (rustc_target: Remove unused Arch::PowerPC64LE) - rust-lang/rust#150971 (Disallow eii in statement position) - rust-lang/rust#151016 (fix: WASI threading regression by disabling pthread usage) - rust-lang/rust#151046 (compiler: Make Externally Implementable Item (eii) macros "semiopaque") - rust-lang/rust#151099 (Recover parse gracefully from `<const N>`) - rust-lang/rust#151117 (Avoid serde dependency in build_helper when not necessary) - rust-lang/rust#151127 (Delete `MetaItemOrLitParser::Err`) - rust-lang/rust#151128 (Add temporary new bors e-mail address to the mailmap) - rust-lang/rust#151138 (Rename `rust.use-lld` to `rust.bootstrap-override-lld` in INSTALL.md) r? @ghost

compiler: Make Externally Implementable Item (eii) macros "semiopaque"

8a8b31a

Otherwise eiis defined by std will produce large amounts of `missing stability attribute` errors.

rustbot assigned jdonszelmann Jan 13, 2026

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 Jan 13, 2026

This was referenced Jan 13, 2026

REPRODUCER: Change thread_local_inner macro transparency to "opaque" #151022

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compiler: Make Externally Implementable Items (eii) in std build #150592

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Tracking Issue for externally implementable items #125418

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Rollup of 10 pull requests #151125

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Rollup of 12 pull requests #151129

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Rollup of 16 pull requests #151139

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Rollup of 15 pull requests #151144

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rust-bors bot merged commit daae660 into rust-lang:main Jan 15, 2026
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Enselic mentioned this pull request Jan 15, 2026

Hundreds of missing stability attribute errors with trivial Externally Implementable Item (eii) function in library/std #150514

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compiler: Make Externally Implementable Item (eii) macros "semiopaque" #151046

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