Make the test cfg a userspace check-cfg

compiler/rustc_session/src/config/cfg.rs

@@ -332,6 +332,11 @@ impl CheckCfg {
         // Note that symbols inserted conditionally in `default_configuration`
         // are inserted unconditionally here.
         //
+        // One exception is the `test` cfg which is consider to be a "user-space"
+        // cfg, despite being also set by in `default_configuration` above.
+        // It allows the build system to "deny" using the config by not marking it
+        // as expected (e.g. `lib.test = false` for Cargo).
+        //
         // When adding a new config here you should also update
         // `tests/ui/check-cfg/well-known-values.rs` (in order to test the
         // expected values of the new config) and bless the all directory.
@@ -453,8 +458,6 @@ impl CheckCfg {
 
         ins!(sym::target_thread_local, no_values);
 
-        ins!(sym::test, no_values);
-
         ins!(sym::ub_checks, no_values);
 
         ins!(sym::unix, no_values);

src/bootstrap/src/core/builder/cargo.rs

@@ -624,6 +624,8 @@ impl Builder<'_> {
         // get warnings about it being unexpected.
         hostflags.arg("-Zunstable-options");
         hostflags.arg("--check-cfg=cfg(bootstrap)");
+        // #[cfg(bootstrap)] as we are transition `test` to userspace cfg
+        hostflags.arg("--check-cfg=cfg(test)");
 
         // FIXME: It might be better to use the same value for both `RUSTFLAGS` and `RUSTDOCFLAGS`,
         // but this breaks CI. At the very least, stage0 `rustdoc` needs `--cfg bootstrap`. See

src/bootstrap/src/lib.rs

@@ -77,6 +77,8 @@ const LLD_FILE_NAMES: &[&str] = &["ld.lld", "ld64.lld", "lld-link", "wasm-ld"];
 #[allow(clippy::type_complexity)] // It's fine for hard-coded list and type is explained above.
 const EXTRA_CHECK_CFGS: &[(Option<Mode>, &str, Option<&[&'static str]>)] = &[
     (None, "bootstrap", None),
+    // #[cfg(bootstrap)] to be removed when Cargo is updated
+    (None, "test", None),
     (Some(Mode::Rustc), "llvm_enzyme", None),
     (Some(Mode::Codegen), "llvm_enzyme", None),
     (Some(Mode::ToolRustc), "llvm_enzyme", None),

src/doc/rustc/src/check-cfg.md

@@ -99,7 +99,7 @@ the need to specify them manually.
 Well known names and values are implicitly added as long as at least one `--check-cfg` argument
 is present.
 
-As of `2024-08-20T`, the list of known names is as follows:
+As of `2025-01-02T`, the list of known names is as follows:
 
 <!--- See CheckCfg::fill_well_known in compiler/rustc_session/src/config.rs -->
 
@@ -130,11 +130,13 @@ As of `2024-08-20T`, the list of known names is as follows:
  - `target_pointer_width`
  - `target_thread_local`
  - `target_vendor`
- - `test`
  - `ub_checks`
  - `unix`
  - `windows`
 
+> Starting with CURRENT_RUSTC_VERSION, the `test` cfg is consider to be a "userspace" config
+> despite being also set by `rustc` and should be managed by the build-system it-self.
+
 Like with `values(any())`, well known names checking can be disabled by passing `cfg(any())`
 as argument to `--check-cfg`.
 

src/tools/compiletest/src/runtest.rs

@@ -506,8 +506,9 @@ impl<'test> TestCx<'test> {
             // Generate `cfg(FALSE, REV1, ..., REVN)` (for all possible revisions)
             //
             // For compatibility reason we consider the `FALSE` cfg to be expected
-            // since it is extensively used in the testsuite.
-            check_cfg.push_str("cfg(FALSE");
+            // since it is extensively used in the testsuite, as well as the `test`
+            // cfg since we have tests that uses it.
+            check_cfg.push_str("cfg(test,FALSE");
             for revision in &self.props.revisions {
                 check_cfg.push(',');
                 check_cfg.push_str(&normalize_revision(revision));

tests/ui/check-cfg/allow-same-level.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `FALSE`
 LL | #[cfg(FALSE)]
    |       ^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(FALSE)`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default

tests/ui/check-cfg/cargo-build-script.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `has_foo`
 LL | #[cfg(has_foo)]
    |       ^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `has_bar`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `has_bar`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: consider using a Cargo feature instead
    = help: or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:
             [lints.rust]

tests/ui/check-cfg/cargo-feature.none.stderr

@@ -25,7 +25,7 @@ warning: unexpected `cfg` condition name: `tokio_unstable`
 LL | #[cfg(tokio_unstable)]
    |       ^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: consider using a Cargo feature instead
    = help: or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:
             [lints.rust]

tests/ui/check-cfg/cargo-feature.some.stderr

@@ -25,7 +25,7 @@ warning: unexpected `cfg` condition name: `tokio_unstable`
 LL | #[cfg(tokio_unstable)]
    |       ^^^^^^^^^^^^^^
    |
-   = help: expected names are: `CONFIG_NVME`, `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `CONFIG_NVME`, `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: consider using a Cargo feature instead
    = help: or consider adding in `Cargo.toml` the `check-cfg` lint config for the lint:
             [lints.rust]

tests/ui/check-cfg/cfg-value-for-cfg-name-duplicate.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `value`
 LL | #[cfg(value)]
    |       ^^^^^
    |
-   = help: expected names are: `bar`, `bee`, `clippy`, `cow`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `bar`, `bee`, `clippy`, `cow`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(value)`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default

tests/ui/check-cfg/cfg-value-for-cfg-name-multiple.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `my_value`
 LL | #[cfg(my_value)]
    |       ^^^^^^^^
    |
-   = help: expected names are: `bar`, `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `bar`, `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(my_value)`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default

tests/ui/check-cfg/cfg-value-for-cfg-name.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `linux`
 LL | #[cfg(linux)]
    |       ^^^^^ help: found config with similar value: `target_os = "linux"`
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(linux)`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default

tests/ui/check-cfg/compact-names.stderr

@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `target_architecture`
 LL | #[cfg(target(os = "linux", architecture = "arm"))]
    |                            ^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(target_architecture, values("arm"))`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default

tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr

@@ -4,20 +4,18 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(unknown_key, values("value"))`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: unexpected `cfg` condition value: `value`
   --> $DIR/exhaustive-names-values.rs:14:7
    |
-LL | #[cfg(test = "value")]
-   |       ^^^^----------
-   |           |
-   |           help: remove the value
+LL | #[cfg(target_vendor = "value")]
+   |       ^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: no expected value for `test`
+   = note: expected values for `target_vendor` are: `apple`, `espressif`, `fortanix`, `ibm`, `kmc`, `nintendo`, `nvidia`, `pc`, `risc0`, `sony`, `sun`, `unikraft`, `unknown`, `uwp`, `win7`, and `wrs`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition name: `feature`

tests/ui/check-cfg/exhaustive-names-values.feature.stderr

@@ -4,20 +4,18 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `ub_checks`, `unix`, and `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `fmt_debug`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `rustfmt`, `sanitize`, `sanitizer_cfi_generalize_pointers`, `sanitizer_cfi_normalize_integers`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `ub_checks`, `unix`, and `windows`
    = help: to expect this configuration use `--check-cfg=cfg(unknown_key, values("value"))`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: unexpected `cfg` condition value: `value`
   --> $DIR/exhaustive-names-values.rs:14:7
    |
-LL | #[cfg(test = "value")]
-   |       ^^^^----------
-   |           |
-   |           help: remove the value
+LL | #[cfg(target_vendor = "value")]
+   |       ^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: no expected value for `test`
+   = note: expected values for `target_vendor` are: `apple`, `espressif`, `fortanix`, `ibm`, `kmc`, `nintendo`, `nvidia`, `pc`, `risc0`, `sony`, `sun`, `unikraft`, `unknown`, `uwp`, `win7`, and `wrs`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `unk`