Suggest name value cfg when only value is used for check-cfg

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

@@ -0,0 +1,12 @@
+// #120427
+// This test checks that when a single cfg has a value for user's specified name
+//
+// check-pass
+// compile-flags: -Z unstable-options
+// compile-flags: --check-cfg=cfg(foo,values("my_value")) --check-cfg=cfg(bar,values("my_value"))
+
+#[cfg(my_value)]
+//~^ WARNING unexpected `cfg` condition name: `my_value`
+fn x() {}
+
+fn main() {}

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

@@ -0,0 +1,21 @@
+warning: unexpected `cfg` condition name: `my_value`
+  --> $DIR/cfg-value-for-cfg-name-multiple.rs:8:7
+   |
+LL | #[cfg(my_value)]
+   |       ^^^^^^^^
+   |
+   = help: expected names are: `bar`, `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`, `unix`, `windows`
+   = help: to expect this configuration use `--check-cfg=cfg(my_value)`
+   = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+help: found config with similar value
+   |
+LL | #[cfg(foo = "my_value")]
+   |       ~~~~~~~~~~~~~~~~
+help: found config with similar value
+   |
+LL | #[cfg(bar = "my_value")]
+   |       ~~~~~~~~~~~~~~~~
+
+warning: 1 warning emitted
+

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

@@ -0,0 +1,18 @@
+// #120427
+// This test checks that when a single cfg has a value for user's specified name
+// suggest to use `#[cfg(target_os = "linux")]` instead of `#[cfg(linux)]`
+//
+// check-pass
+// compile-flags: -Z unstable-options
+// compile-flags: --check-cfg=cfg()
+
+#[cfg(linux)]
+//~^ WARNING unexpected `cfg` condition name: `linux`
+fn x() {}
+
+// will not suggest if the cfg has a value
+#[cfg(linux = "os-name")]
+//~^ WARNING unexpected `cfg` condition name: `linux`
+fn y() {}
+
+fn main() {}

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

@@ -0,0 +1,22 @@
+warning: unexpected `cfg` condition name: `linux`
+  --> $DIR/cfg-value-for-cfg-name.rs:9:7
+   |
+LL | #[cfg(linux)]
+   |       ^^^^^ help: found config with similar value: `target_os = "linux"`
+   |
+   = help: expected names are: `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`, `unix`, `windows`
+   = help: to expect this configuration use `--check-cfg=cfg(linux)`
+   = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: unexpected `cfg` condition name: `linux`
+  --> $DIR/cfg-value-for-cfg-name.rs:14:7
+   |
+LL | #[cfg(linux = "os-name")]
+   |       ^^^^^^^^^^^^^^^^^
+   |
+   = help: to expect this configuration use `--check-cfg=cfg(linux, values("os-name"))`
+   = note: see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration
+
+warning: 2 warnings emitted
+