fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself by ShE3py · Pull Request #152302 · rust-lang/rust

ShE3py · 2026-02-07T16:50:13Z

Some environment variables (e.g. CARGO_BIN_NAME) are only available for some targets (Cargo Targets, § Environment variables Cargo sets for crates), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing:

const _: &str = env!("CARGO_BIN_NAME");

Before:

error: environment variable `CARGO_BIN_NAME` not defined at compile time
 --> lib.rs:1:17
  |
1 | const _: &str = env!("CARGO_BIN_NAME");
  |                 ^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME`

After:

error: environment variable `CARGO_BIN_NAME` not defined at compile time
 --> lib.rs:1:17
  |
1 | const _: &str = env!("CARGO_BIN_NAME");
  |                 ^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: `CARGO_BIN_NAME` may not be available for the current Cargo target
  = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead

@rustbot label +T-compiler +A-diagnostics +D-confusing

rustbot · 2026-02-07T16:50:18Z

r? @davidtwco

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davidtwco

LGTM, one nit about the diagnostic wording but then we can merge

View changes since this review

davidtwco · 2026-02-16T13:40:20Z

compiler/rustc_builtin_macros/src/errors.rs

 #[derive(Diagnostic)]
 pub(crate) enum EnvNotDefined<'a> {
    #[diag("environment variable `{$var}` not defined at compile time")]
+    #[help("`{$var}` may not be available for the current Cargo target")]


"current Cargo target" reads strangely to me, I'm not entirely sure what I'd interpret this as referring to. Does this only come up with different crate types?

It's what the Cargo Book call them, but they don't really map 1:1 to crate types (cf. TargetKind::rustc_crate_types).

E.g. CARGO_BIN_NAME is only available for binaries and example binaries, CARGO_MANIFEST_LINKS only for build scripts, and both are compiled with --crate-type=bin.

I'll try to improve the message with TargetKind::description, but not sure if it is exposed to Rustc.

I've also updated the PR description.

It's fine for just now then, we can always adjust the wording later if we need to

davidtwco · 2026-03-10T11:52:49Z

@bors r+ rollup

rust-bors · 2026-03-10T11:52:52Z

📌 Commit 57650ee has been approved by davidtwco

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 1000. This pull request will be tested once the tree is reopened.

@rustbot

fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself Some environment variables (e.g. `CARGO_BIN_NAME`) are only available for some targets ([Cargo Targets](https://doc.rust-lang.org/cargo/reference/cargo-targets.html), [§ Environment variables Cargo sets for crates](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing: ```rs const _: &str = env!("CARGO_BIN_NAME"); ``` Before: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME` ``` After: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: `CARGO_BIN_NAME` may not be available for the current Cargo target = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead ``` @rustbot label +T-compiler +A-diagnostics +D-confusing

@rustbot

fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself Some environment variables (e.g. `CARGO_BIN_NAME`) are only available for some targets ([Cargo Targets](https://doc.rust-lang.org/cargo/reference/cargo-targets.html), [§ Environment variables Cargo sets for crates](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing: ```rs const _: &str = env!("CARGO_BIN_NAME"); ``` Before: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME` ``` After: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: `CARGO_BIN_NAME` may not be available for the current Cargo target = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead ``` @rustbot label +T-compiler +A-diagnostics +D-confusing

…uwer Rollup of 8 pull requests Successful merges: - #149130 (Implement coercions between `&pin (mut|const) T` and `&(mut) T` when `T: Unpin`) - #152457 (Pass -pg to linker when using -Zinstrument-mcount) - #153143 (Allow `./x test` to run tests without doc tests and without benchmarks) - #153653 (scalable vector: type renames and simple checks) - #152302 (fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself) - #153641 (Move `Spanned`.) - #153643 (Avoid projection-only suggestions for inherent assoc types) - #153657 (triagebot: remove myself from some mention groups)

@rustbot

fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself Some environment variables (e.g. `CARGO_BIN_NAME`) are only available for some targets ([Cargo Targets](https://doc.rust-lang.org/cargo/reference/cargo-targets.html), [§ Environment variables Cargo sets for crates](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing: ```rs const _: &str = env!("CARGO_BIN_NAME"); ``` Before: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME` ``` After: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: `CARGO_BIN_NAME` may not be available for the current Cargo target = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead ``` @rustbot label +T-compiler +A-diagnostics +D-confusing

…uwer Rollup of 13 pull requests Successful merges: - #149130 (Implement coercions between `&pin (mut|const) T` and `&(mut) T` when `T: Unpin`) - #152457 (Pass -pg to linker when using -Zinstrument-mcount) - #153143 (Allow `./x test` to run tests without doc tests and without benchmarks) - #153471 (Refactor `ActiveJobGuard`) - #153595 (`QueryLatch` cleanups) - #153653 (scalable vector: type renames and simple checks) - #152302 (fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself) - #153479 (Add rationale for intentional potential_query_instability allows) - #153600 (add test for proc-macros with custom panic payloads) - #153641 (Move `Spanned`.) - #153643 (Avoid projection-only suggestions for inherent assoc types) - #153657 (triagebot: remove myself from some mention groups) - #153659 (Mark an unreachable match arm as such)

@rustbot

fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself Some environment variables (e.g. `CARGO_BIN_NAME`) are only available for some targets ([Cargo Targets](https://doc.rust-lang.org/cargo/reference/cargo-targets.html), [§ Environment variables Cargo sets for crates](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing: ```rs const _: &str = env!("CARGO_BIN_NAME"); ``` Before: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME` ``` After: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: `CARGO_BIN_NAME` may not be available for the current Cargo target = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead ``` @rustbot label +T-compiler +A-diagnostics +D-confusing

…uwer Rollup of 14 pull requests Successful merges: - #149130 (Implement coercions between `&pin (mut|const) T` and `&(mut) T` when `T: Unpin`) - #152457 (Pass -pg to linker when using -Zinstrument-mcount) - #153143 (Allow `./x test` to run tests without doc tests and without benchmarks) - #153471 (Refactor `ActiveJobGuard`) - #153595 (`QueryLatch` cleanups) - #153653 (scalable vector: type renames and simple checks) - #152302 (fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself) - #153283 (feat(rustdoc-json): Add optional support for rkyv (de)serialization) - #153479 (Add rationale for intentional potential_query_instability allows) - #153533 (Fix LegacyKeyValueFormat report from docker build: miscellaneous) - #153600 (add test for proc-macros with custom panic payloads) - #153643 (Avoid projection-only suggestions for inherent assoc types) - #153657 (triagebot: remove myself from some mention groups) - #153659 (Mark an unreachable match arm as such)

…uwer Rollup of 13 pull requests Successful merges: - #149130 (Implement coercions between `&pin (mut|const) T` and `&(mut) T` when `T: Unpin`) - #153143 (Allow `./x test` to run tests without doc tests and without benchmarks) - #153471 (Refactor `ActiveJobGuard`) - #153595 (`QueryLatch` cleanups) - #153653 (scalable vector: type renames and simple checks) - #152302 (fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself) - #153283 (feat(rustdoc-json): Add optional support for rkyv (de)serialization) - #153479 (Add rationale for intentional potential_query_instability allows) - #153533 (Fix LegacyKeyValueFormat report from docker build: miscellaneous) - #153600 (add test for proc-macros with custom panic payloads) - #153643 (Avoid projection-only suggestions for inherent assoc types) - #153657 (triagebot: remove myself from some mention groups) - #153659 (Mark an unreachable match arm as such)

@rustbot

Rollup merge of #152302 - ShE3py:cargo-envs, r=davidtwco fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself Some environment variables (e.g. `CARGO_BIN_NAME`) are only available for some targets ([Cargo Targets](https://doc.rust-lang.org/cargo/reference/cargo-targets.html), [§ Environment variables Cargo sets for crates](https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates)), and the current diagnostic when copy-pasting code from a binary to a library is kinda confusing: ```rs const _: &str = env!("CARGO_BIN_NAME"); ``` Before: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: there is a similar Cargo environment variable: `CARGO_BIN_NAME` ``` After: ``` error: environment variable `CARGO_BIN_NAME` not defined at compile time --> lib.rs:1:17 | 1 | const _: &str = env!("CARGO_BIN_NAME"); | ^^^^^^^^^^^^^^^^^^^^^^ | = help: `CARGO_BIN_NAME` may not be available for the current Cargo target = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_BIN_NAME")` instead ``` @rustbot label +T-compiler +A-diagnostics +D-confusing

…nathanBrouwer Rollup of 13 pull requests Successful merges: - rust-lang#149130 (Implement coercions between `&pin (mut|const) T` and `&(mut) T` when `T: Unpin`) - rust-lang#153143 (Allow `./x test` to run tests without doc tests and without benchmarks) - rust-lang#153471 (Refactor `ActiveJobGuard`) - rust-lang#153595 (`QueryLatch` cleanups) - rust-lang#153653 (scalable vector: type renames and simple checks) - rust-lang#152302 (fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself) - rust-lang#153283 (feat(rustdoc-json): Add optional support for rkyv (de)serialization) - rust-lang#153479 (Add rationale for intentional potential_query_instability allows) - rust-lang#153533 (Fix LegacyKeyValueFormat report from docker build: miscellaneous) - rust-lang#153600 (add test for proc-macros with custom panic payloads) - rust-lang#153643 (Avoid projection-only suggestions for inherent assoc types) - rust-lang#153657 (triagebot: remove myself from some mention groups) - rust-lang#153659 (Mark an unreachable match arm as such)

fix: don't suggest replacing env!("CARGO_BIN_NAME") with itself

57650ee

rustbot assigned davidtwco Feb 7, 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 Feb 7, 2026

rustbot added A-diagnostics Area: Messages for errors, warnings, and lints D-confusing Diagnostics: Confusing error or lint that should be reworked. labels Feb 7, 2026

davidtwco approved these changes Feb 16, 2026

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davidtwco approved these changes Mar 10, 2026

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rust-bors bot 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 Mar 10, 2026

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Rollup of 4 pull requests #153654

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Rollup of 8 pull requests #153658

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Rollup of 13 pull requests #153665

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Rollup of 14 pull requests #153669

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Rollup of 13 pull requests #153672

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rust-bors bot merged commit 8606308 into rust-lang:main Mar 11, 2026
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fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself#152302

fix: don't suggest replacing `env!("CARGO_BIN_NAME")` with itself#152302
rust-bors[bot] merged 1 commit intorust-lang:mainfrom
ShE3py:cargo-envs

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