Rollup merge of #124742 - Urgau:check-cfg-rustfmt, r=fmease

Add `rustfmt` cfg to well known cfgs list

This PR adds the `rustfmt` cfg to the well known cfgs list.

Related to https://github.com/rust-lang/rust/issues/124735

18 files changed, 56 insertions, 37 deletions

diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index 31badbd8692..2fa04bbe345 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -262,13 +262,15 @@ impl CheckCfg {
 
         ins!(sym::debug_assertions, no_values);
 
-        // These four are never set by rustc, but we set them anyway: they
-        // should not trigger a lint because `cargo clippy`, `cargo doc`,
-        // `cargo test` and `cargo miri run` (respectively) can set them.
+        // These four are never set by rustc, but we set them anyway; they
+        // should not trigger the lint because `cargo clippy`, `cargo doc`,
+        // `cargo test`, `cargo miri run` and `cargo fmt` (respectively)
+        // can set them.
         ins!(sym::clippy, no_values);
         ins!(sym::doc, no_values);
         ins!(sym::doctest, no_values);
         ins!(sym::miri, no_values);
+        ins!(sym::rustfmt, no_values);
 
         ins!(sym::overflow_checks, no_values);
 
diff --git a/src/doc/rustc/src/check-cfg.md b/src/doc/rustc/src/check-cfg.md
index 37708bda1f3..56198437ee9 100644
--- a/src/doc/rustc/src/check-cfg.md
+++ b/src/doc/rustc/src/check-cfg.md
@@ -71,7 +71,7 @@ Those well known names and values follows the same stability as what they refer
 Well known names and values checking is always enabled as long as at least one
 `--check-cfg` argument is present.
 
-As of `2024-04-06T`, the list of known names is as follows:
+As of `2024-05-06T`, the list of known names is as follows:
 
 <!--- See CheckCfg::fill_well_known in compiler/rustc_session/src/config.rs -->
 
@@ -84,6 +84,7 @@ As of `2024-04-06T`, the list of known names is as follows:
  - `panic`
  - `proc_macro`
  - `relocation_model`
+ - `rustfmt`
  - `sanitize`
  - `sanitizer_cfi_generalize_pointers`
  - `sanitizer_cfi_normalize_integers`
diff --git a/tests/ui/check-cfg/allow-same-level.stderr b/tests/ui/check-cfg/allow-same-level.stderr
index 99e81d3bba6..ae4c1605f01 100644
--- a/tests/ui/check-cfg/allow-same-level.stderr
+++ b/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`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/cargo-feature.none.stderr b/tests/ui/check-cfg/cargo-feature.none.stderr
index ae2351b82ce..627f03ddf55 100644
--- a/tests/ui/check-cfg/cargo-feature.none.stderr
+++ b/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`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `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`, `windows`
    = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(tokio_unstable)");` to the top of the `build.rs`
    = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
 
diff --git a/tests/ui/check-cfg/cargo-feature.some.stderr b/tests/ui/check-cfg/cargo-feature.some.stderr
index 191efbf2d54..9cc5fb6aca0 100644
--- a/tests/ui/check-cfg/cargo-feature.some.stderr
+++ b/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`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `CONFIG_NVME`, `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `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`, `windows`
    = help: consider using a Cargo feature instead or adding `println!("cargo::rustc-check-cfg=cfg(tokio_unstable)");` to the top of the `build.rs`
    = note: see <https://doc.rust-lang.org/nightly/cargo/reference/build-scripts.html#rustc-check-cfg> for more information about checking conditional configuration
 
diff --git a/tests/ui/check-cfg/cfg-value-for-cfg-name-duplicate.stderr b/tests/ui/check-cfg/cfg-value-for-cfg-name-duplicate.stderr
index f1393c55819..4975129802b 100644
--- a/tests/ui/check-cfg/cfg-value-for-cfg-name-duplicate.stderr
+++ b/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`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `bar`, `bee`, `clippy`, `cow`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/cfg-value-for-cfg-name-multiple.stderr b/tests/ui/check-cfg/cfg-value-for-cfg-name-multiple.stderr
index 3d4f430c2bb..6404556f46c 100644
--- a/tests/ui/check-cfg/cfg-value-for-cfg-name-multiple.stderr
+++ b/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`, `foo`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `bar`, `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/cfg-value-for-cfg-name.stderr b/tests/ui/check-cfg/cfg-value-for-cfg-name.stderr
index 142d10076e9..bda1a601410 100644
--- a/tests/ui/check-cfg/cfg-value-for-cfg-name.stderr
+++ b/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`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/compact-names.stderr b/tests/ui/check-cfg/compact-names.stderr
index dd19f606620..079be8d08c2 100644
--- a/tests/ui/check-cfg/compact-names.stderr
+++ b/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`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr b/tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr
index 91afe766c8d..c196f607376 100644
--- a/tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr
+++ b/tests/ui/check-cfg/exhaustive-names-values.empty_cfg.stderr
@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/exhaustive-names-values.feature.stderr b/tests/ui/check-cfg/exhaustive-names-values.feature.stderr
index 93b0621e224..6344739ae76 100644
--- a/tests/ui/check-cfg/exhaustive-names-values.feature.stderr
+++ b/tests/ui/check-cfg/exhaustive-names-values.feature.stderr
@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `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`, `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
diff --git a/tests/ui/check-cfg/exhaustive-names-values.full.stderr b/tests/ui/check-cfg/exhaustive-names-values.full.stderr
index 93b0621e224..6344739ae76 100644
--- a/tests/ui/check-cfg/exhaustive-names-values.full.stderr
+++ b/tests/ui/check-cfg/exhaustive-names-values.full.stderr
@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `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`, `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
diff --git a/tests/ui/check-cfg/exhaustive-names.stderr b/tests/ui/check-cfg/exhaustive-names.stderr
index f4eb5a640ae..605825cd4e5 100644
--- a/tests/ui/check-cfg/exhaustive-names.stderr
+++ b/tests/ui/check-cfg/exhaustive-names.stderr
@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `unknown_key`
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `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
diff --git a/tests/ui/check-cfg/mix.stderr b/tests/ui/check-cfg/mix.stderr
index 1ccdd10d123..54591699145 100644
--- a/tests/ui/check-cfg/mix.stderr
+++ b/tests/ui/check-cfg/mix.stderr
@@ -44,7 +44,7 @@ warning: unexpected `cfg` condition name: `uu`
 LL | #[cfg_attr(uu, test)]
    |            ^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `feature`, `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`, `windows`
    = help: to expect this configuration use `--check-cfg=cfg(uu)`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
diff --git a/tests/ui/check-cfg/stmt-no-ice.stderr b/tests/ui/check-cfg/stmt-no-ice.stderr
index a6c72b0e6bf..ab0deae428d 100644
--- a/tests/ui/check-cfg/stmt-no-ice.stderr
+++ b/tests/ui/check-cfg/stmt-no-ice.stderr
@@ -4,7 +4,7 @@ warning: unexpected `cfg` condition name: `crossbeam_loom`
 LL |     #[cfg(crossbeam_loom)]
    |           ^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `windows`
    = help: to expect this configuration use `--check-cfg=cfg(crossbeam_loom)`
    = 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
diff --git a/tests/ui/check-cfg/well-known-names.stderr b/tests/ui/check-cfg/well-known-names.stderr
index 2f07174b905..2ce6fe80ef2 100644
--- a/tests/ui/check-cfg/well-known-names.stderr
+++ b/tests/ui/check-cfg/well-known-names.stderr
@@ -18,7 +18,7 @@ warning: unexpected `cfg` condition name: `features`
 LL | #[cfg(features = "foo")]
    |       ^^^^^^^^^^^^^^^^
    |
-   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `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`, `windows`
+   = help: expected names are: `clippy`, `debug_assertions`, `doc`, `doctest`, `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`, `windows`
    = help: to expect this configuration use `--check-cfg=cfg(features, values("foo"))`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
diff --git a/tests/ui/check-cfg/well-known-values.rs b/tests/ui/check-cfg/well-known-values.rs
index b821f8092dd..d5fe7464792 100644
--- a/tests/ui/check-cfg/well-known-values.rs
+++ b/tests/ui/check-cfg/well-known-values.rs
@@ -43,6 +43,8 @@
     //~^ WARN unexpected `cfg` condition value
     relocation_model = "_UNEXPECTED_VALUE",
     //~^ WARN unexpected `cfg` condition value
+    rustfmt = "_UNEXPECTED_VALUE",
+    //~^ WARN unexpected `cfg` condition value
     sanitize = "_UNEXPECTED_VALUE",
     //~^ WARN unexpected `cfg` condition value
     target_abi = "_UNEXPECTED_VALUE",
@@ -115,4 +117,7 @@ fn doc() {}
 #[cfg(clippy)]
 fn clippy() {}
 
+#[cfg_attr(rustfmt, rustfmt::skip)]
+fn rustfmt() {}
+
 fn main() {}
diff --git a/tests/ui/check-cfg/well-known-values.stderr b/tests/ui/check-cfg/well-known-values.stderr
index cd5cdf3df3c..db4a5fd49e6 100644
--- a/tests/ui/check-cfg/well-known-values.stderr
+++ b/tests/ui/check-cfg/well-known-values.stderr
@@ -97,6 +97,17 @@ LL |     relocation_model = "_UNEXPECTED_VALUE",
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
   --> $DIR/well-known-values.rs:46:5
    |
+LL |     rustfmt = "_UNEXPECTED_VALUE",
+   |     ^^^^^^^----------------------
+   |            |
+   |            help: remove the value
+   |
+   = note: no expected value for `rustfmt`
+   = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
+
+warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
+  --> $DIR/well-known-values.rs:48:5
+   |
 LL |     sanitize = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
@@ -104,7 +115,7 @@ LL |     sanitize = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:48:5
+  --> $DIR/well-known-values.rs:50:5
    |
 LL |     target_abi = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -113,7 +124,7 @@ LL |     target_abi = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:50:5
+  --> $DIR/well-known-values.rs:52:5
    |
 LL |     target_arch = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -122,7 +133,7 @@ LL |     target_arch = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:52:5
+  --> $DIR/well-known-values.rs:54:5
    |
 LL |     target_endian = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -131,7 +142,7 @@ LL |     target_endian = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:54:5
+  --> $DIR/well-known-values.rs:56:5
    |
 LL |     target_env = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -140,7 +151,7 @@ LL |     target_env = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:56:5
+  --> $DIR/well-known-values.rs:58:5
    |
 LL |     target_family = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -149,7 +160,7 @@ LL |     target_family = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:58:5
+  --> $DIR/well-known-values.rs:60:5
    |
 LL |     target_feature = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -158,7 +169,7 @@ LL |     target_feature = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:60:5
+  --> $DIR/well-known-values.rs:62:5
    |
 LL |     target_has_atomic = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -167,7 +178,7 @@ LL |     target_has_atomic = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:62:5
+  --> $DIR/well-known-values.rs:64:5
    |
 LL |     target_has_atomic_equal_alignment = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -176,7 +187,7 @@ LL |     target_has_atomic_equal_alignment = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:64:5
+  --> $DIR/well-known-values.rs:66:5
    |
 LL |     target_has_atomic_load_store = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -185,7 +196,7 @@ LL |     target_has_atomic_load_store = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:66:5
+  --> $DIR/well-known-values.rs:68:5
    |
 LL |     target_os = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -194,7 +205,7 @@ LL |     target_os = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:68:5
+  --> $DIR/well-known-values.rs:70:5
    |
 LL |     target_pointer_width = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -203,7 +214,7 @@ LL |     target_pointer_width = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:70:5
+  --> $DIR/well-known-values.rs:72:5
    |
 LL |     target_thread_local = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^----------------------
@@ -214,7 +225,7 @@ LL |     target_thread_local = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:72:5
+  --> $DIR/well-known-values.rs:74:5
    |
 LL |     target_vendor = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -223,7 +234,7 @@ LL |     target_vendor = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:74:5
+  --> $DIR/well-known-values.rs:76:5
    |
 LL |     test = "_UNEXPECTED_VALUE",
    |     ^^^^----------------------
@@ -234,7 +245,7 @@ LL |     test = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:76:5
+  --> $DIR/well-known-values.rs:78:5
    |
 LL |     ub_checks = "_UNEXPECTED_VALUE",
    |     ^^^^^^^^^----------------------
@@ -245,7 +256,7 @@ LL |     ub_checks = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:78:5
+  --> $DIR/well-known-values.rs:80:5
    |
 LL |     unix = "_UNEXPECTED_VALUE",
    |     ^^^^----------------------
@@ -256,7 +267,7 @@ LL |     unix = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `_UNEXPECTED_VALUE`
-  --> $DIR/well-known-values.rs:80:5
+  --> $DIR/well-known-values.rs:82:5
    |
 LL |     windows = "_UNEXPECTED_VALUE",
    |     ^^^^^^^----------------------
@@ -267,7 +278,7 @@ LL |     windows = "_UNEXPECTED_VALUE",
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
 warning: unexpected `cfg` condition value: `linuz`
-  --> $DIR/well-known-values.rs:86:7
+  --> $DIR/well-known-values.rs:88:7
    |
 LL | #[cfg(target_os = "linuz")] // testing that we suggest `linux`
    |       ^^^^^^^^^^^^-------
@@ -277,5 +288,5 @@ LL | #[cfg(target_os = "linuz")] // testing that we suggest `linux`
    = note: expected values for `target_os` are: `aix`, `android`, `cuda`, `dragonfly`, `emscripten`, `espidf`, `freebsd`, `fuchsia`, `haiku`, `hermit`, `horizon`, `hurd`, `illumos`, `ios`, `l4re`, `linux`, `macos`, `netbsd`, `none`, `nto`, `openbsd`, `psp`, `redox`, `solaris`, `solid_asp3`, `teeos`, `tvos`, `uefi`, `unknown`, `visionos`, `vita`, `vxworks`, `wasi`, `watchos`, `windows`, `xous`, `zkvm`
    = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
 
-warning: 28 warnings emitted
+warning: 29 warnings emitted