Add more suggestions to unexpected cfg names and values

compiler/rustc_lint/src/context.rs

@@ -706,9 +706,13 @@ pub trait LintContext {
                 },
                 BuiltinLintDiagnostics::UnexpectedCfgName((name, name_span), value) => {
                     let possibilities: Vec<Symbol> = sess.parse_sess.check_config.expecteds.keys().copied().collect();
+                    let is_from_cargo = std::env::var_os("CARGO").is_some();
+                    let mut is_feature_cfg = name == sym::feature;
 
+                    if is_feature_cfg && is_from_cargo {
+                        db.help("consider defining some features in `Cargo.toml`");
                     // Suggest the most probable if we found one
-                    if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
+                    } else if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
                         if let Some(ExpectedValues::Some(best_match_values)) =
                             sess.parse_sess.check_config.expecteds.get(&best_match) {
                             let mut possibilities = best_match_values.iter()
@@ -741,8 +745,8 @@ pub trait LintContext {
                         } else {
                             db.span_suggestion(name_span, "there is a config with a similar name", best_match, Applicability::MaybeIncorrect);
                         }
-                    } else if name == sym::feature && std::env::var_os("CARGO").is_some() {
-                        db.help("consider defining some features in `Cargo.toml`");
+
+                        is_feature_cfg |= best_match == sym::feature;
                     } else if !possibilities.is_empty() {
                         let mut possibilities = possibilities.iter()
                             .map(Symbol::as_str)
@@ -756,6 +760,23 @@ pub trait LintContext {
                         // once.
                         db.help_once(format!("expected names are: `{possibilities}`"));
                     }
+
+                    let inst = if let Some((value, _value_span)) = value {
+                        let pre = if is_from_cargo { "\\" } else { "" };
+                        format!("cfg({name}, values({pre}\"{value}{pre}\"))")
+                    } else {
+                        format!("cfg({name})")
+                    };
+
+                    if is_from_cargo {
+                        if !is_feature_cfg {
+                            db.help(format!("consider using a Cargo feature instead or adding `println!(\"cargo:rustc-check-cfg={inst}\");` to the top of a `build.rs`"));
+                        }
+                        db.note("see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration");
+                    } else {
+                        db.help(format!("to expect this configuration use `--check-cfg={inst}`"));
+                        db.note("see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration");
+                    }
                 },
                 BuiltinLintDiagnostics::UnexpectedCfgValue((name, name_span), value) => {
                     let Some(ExpectedValues::Some(values)) = &sess.parse_sess.check_config.expecteds.get(&name) else {
@@ -767,6 +788,7 @@ pub trait LintContext {
                         .copied()
                         .flatten()
                         .collect();
+                    let is_from_cargo = std::env::var_os("CARGO").is_some();
 
                     // Show the full list if all possible values for a given name, but don't do it
                     // for names as the possibilities could be very long
@@ -787,6 +809,8 @@ pub trait LintContext {
                                 db.span_suggestion(value_span, "there is a expected value with a similar name", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
 
                             }
+                        } else if name == sym::feature && is_from_cargo {
+                            db.help(format!("consider defining `{name}` as feature in `Cargo.toml`"));
                         } else if let &[first_possibility] = &possibilities[..] {
                             db.span_suggestion(name_span.shrink_to_hi(), "specify a config value", format!(" = \"{first_possibility}\""), Applicability::MaybeIncorrect);
                         }
@@ -796,6 +820,27 @@ pub trait LintContext {
                             db.span_suggestion(name_span.shrink_to_hi().to(value_span), "remove the value", "", Applicability::MaybeIncorrect);
                         }
                     }
+
+                    let inst = if let Some((value, _value_span)) = value {
+                        let pre = if is_from_cargo { "\\" } else { "" };
+                        format!("cfg({name}, values({pre}\"{value}{pre}\"))")
+                    } else {
+                        format!("cfg({name})")
+                    };
+
+                    if is_from_cargo {
+                        if name == sym::feature {
+                            if let Some((value, _value_span)) = value {
+                                db.help(format!("consider adding `{value}` as a feature in `Cargo.toml`"));
+                            }
+                        } else {
+                            db.help(format!("consider using a Cargo feature instead or adding `println!(\"cargo:rustc-check-cfg={inst}\");` to the top of a `build.rs`"));
+                        }
+                        db.note("see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration");
+                    } else {
+                        db.help(format!("to expect this configuration use `--check-cfg={inst}`"));
+                        db.note("see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration");
+                    }
                 },
                 BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(new_span, suggestion) => {
                     db.multipart_suggestion(

tests/rustdoc-ui/check-cfg/check-cfg.stderr

@@ -4,6 +4,8 @@ warning: unexpected `cfg` condition name: `uniz`
 LL | #[cfg(uniz)]
    |       ^^^^ help: there is a config with a similar name: `unix`
    |
+   = help: to expect this configuration use `--check-cfg=cfg(uniz)`
+   = 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: 1 warning emitted

tests/rustdoc-ui/doctest/check-cfg-test.stderr

@@ -5,6 +5,8 @@ LL | #[cfg(feature = "invalid")]
    |       ^^^^^^^^^^^^^^^^^^^
    |
    = note: expected values for `feature` are: `test`
+   = help: to expect this configuration use `--check-cfg=cfg(feature, values("invalid"))`
+   = 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: 1 warning emitted

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

@@ -5,6 +5,8 @@ LL | #[cfg(FALSE)]
    |       ^^^^^
    |
    = 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(FALSE)`
+   = 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: 1 warning emitted

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

@@ -0,0 +1,31 @@
+warning: unexpected `cfg` condition name: `feature`
+  --> $DIR/cargo-feature.rs:13:7
+   |
+LL | #[cfg(feature = "serde")]
+   |       ^^^^^^^^^^^^^^^^^
+   |
+   = help: consider defining some features in `Cargo.toml`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: unexpected `cfg` condition name: `tokio_unstable`
+  --> $DIR/cargo-feature.rs:18:7
+   |
+LL | #[cfg(tokio_unstable)]
+   |       ^^^^^^^^^^^^^^
+   |
+   = 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: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(tokio_unstable)");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: unexpected `cfg` condition name: `CONFIG_NVME`
+  --> $DIR/cargo-feature.rs:22:7
+   |
+LL | #[cfg(CONFIG_NVME = "m")]
+   |       ^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(CONFIG_NVME, values(\"m\"))");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: 3 warnings emitted
+

tests/ui/check-cfg/cargo-feature.rs

@@ -3,12 +3,25 @@
 // list of all the expected names
 //
 // check-pass
+// revisions: some none
 // rustc-env:CARGO=/usr/bin/cargo
 // compile-flags: --check-cfg=cfg() -Z unstable-options
-// error-pattern:Cargo.toml
+// [some]compile-flags: --check-cfg=cfg(feature,values("bitcode"))
+// [some]compile-flags: --check-cfg=cfg(CONFIG_NVME,values("y"))
+// [none]error-pattern:Cargo.toml
 
 #[cfg(feature = "serde")]
-//~^ WARNING unexpected `cfg` condition name
+//[none]~^ WARNING unexpected `cfg` condition name
+//[some]~^^ WARNING unexpected `cfg` condition value
 fn ser() {}
 
+#[cfg(tokio_unstable)]
+//~^ WARNING unexpected `cfg` condition name
+fn tokio() {}
+
+#[cfg(CONFIG_NVME = "m")]
+//[none]~^ WARNING unexpected `cfg` condition name
+//[some]~^^ WARNING unexpected `cfg` condition value
+fn tokio() {}
+
 fn main() {}

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

@@ -0,0 +1,35 @@
+warning: unexpected `cfg` condition value: `serde`
+  --> $DIR/cargo-feature.rs:13:7
+   |
+LL | #[cfg(feature = "serde")]
+   |       ^^^^^^^^^^^^^^^^^
+   |
+   = note: expected values for `feature` are: `bitcode`
+   = help: consider adding `serde` as a feature in `Cargo.toml`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: unexpected `cfg` condition name: `tokio_unstable`
+  --> $DIR/cargo-feature.rs:18:7
+   |
+LL | #[cfg(tokio_unstable)]
+   |       ^^^^^^^^^^^^^^
+   |
+   = help: expected names are: `CONFIG_NVME`, `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`, `unix`, `windows`
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(tokio_unstable)");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: unexpected `cfg` condition value: `m`
+  --> $DIR/cargo-feature.rs:22:7
+   |
+LL | #[cfg(CONFIG_NVME = "m")]
+   |       ^^^^^^^^^^^^^^---
+   |                     |
+   |                     help: there is a expected value with a similar name: `"y"`
+   |
+   = note: expected values for `CONFIG_NVME` are: `y`
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(CONFIG_NVME, values(\"m\"))");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: 3 warnings emitted
+

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

@@ -5,6 +5,8 @@ LL | #[cfg(target(os = "linux", architecture = "arm"))]
    |                            ^^^^^^^^^^^^^^^^^^^^
    |
    = 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(target_architecture, values("arm"))`
+   = 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: 1 warning emitted

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

@@ -5,6 +5,8 @@ LL | #[cfg(target(os = "linux", pointer_width = "X"))]
    |                            ^^^^^^^^^^^^^^^^^^^
    |
    = note: expected values for `target_pointer_width` are: `16`, `32`, `64`
+   = help: to expect this configuration use `--check-cfg=cfg(target_pointer_width, values("X"))`
+   = 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: 1 warning emitted

tests/ui/check-cfg/concat-values.stderr

@@ -5,6 +5,8 @@ LL | #[cfg(my_cfg)]
    |       ^^^^^^
    |
    = note: expected values for `my_cfg` are: `bar`, `foo`
+   = help: to expect this configuration use `--check-cfg=cfg(my_cfg)`
+   = 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 value: `unk`
@@ -14,6 +16,8 @@ LL | #[cfg(my_cfg = "unk")]
    |       ^^^^^^^^^^^^^^
    |
    = note: expected values for `my_cfg` are: `bar`, `foo`
+   = help: to expect this configuration use `--check-cfg=cfg(my_cfg, values("unk"))`
+   = 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
 

tests/ui/check-cfg/diagnotics.cargo.stderr

@@ -0,0 +1,71 @@
+warning: unexpected `cfg` condition name: `featur`
+  --> $DIR/diagnotics.rs:7:7
+   |
+LL | #[cfg(featur)]
+   |       ^^^^^^ help: there is a config with a similar name: `feature`
+   |
+   = help: expected values for `feature` are: `foo`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+   = note: `#[warn(unexpected_cfgs)]` on by default
+
+warning: unexpected `cfg` condition name: `featur`
+  --> $DIR/diagnotics.rs:11:7
+   |
+LL | #[cfg(featur = "foo")]
+   |       ^^^^^^^^^^^^^^
+   |
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+help: there is a config with a similar name and value
+   |
+LL | #[cfg(feature = "foo")]
+   |       ~~~~~~~
+
+warning: unexpected `cfg` condition name: `featur`
+  --> $DIR/diagnotics.rs:15:7
+   |
+LL | #[cfg(featur = "fo")]
+   |       ^^^^^^^^^^^^^
+   |
+   = help: expected values for `feature` are: `foo`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+help: there is a config with a similar name and different values
+   |
+LL | #[cfg(feature = "foo")]
+   |       ~~~~~~~~~~~~~~~
+
+warning: unexpected `cfg` condition name: `no_value`
+  --> $DIR/diagnotics.rs:22:7
+   |
+LL | #[cfg(no_value)]
+   |       ^^^^^^^^ help: there is a config with a similar name: `no_values`
+   |
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(no_value)");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: unexpected `cfg` condition name: `no_value`
+  --> $DIR/diagnotics.rs:26:7
+   |
+LL | #[cfg(no_value = "foo")]
+   |       ^^^^^^^^^^^^^^^^
+   |
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(no_value, values(\"foo\"))");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+help: there is a config with a similar name and no value
+   |
+LL | #[cfg(no_values)]
+   |       ~~~~~~~~~
+
+warning: unexpected `cfg` condition value: `bar`
+  --> $DIR/diagnotics.rs:30:7
+   |
+LL | #[cfg(no_values = "bar")]
+   |       ^^^^^^^^^--------
+   |                |
+   |                help: remove the value
+   |
+   = note: no expected value for `no_values`
+   = help: consider using a Cargo feature instead or adding `println!("cargo:rustc-check-cfg=cfg(no_values, values(\"bar\"))");` to the top of a `build.rs`
+   = note: see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration
+
+warning: 6 warnings emitted
+

tests/ui/check-cfg/diagnotics.rs

@@ -1,4 +1,7 @@
 // check-pass
+// revisions: cargo rustc
+// [rustc]unset-rustc-env:CARGO
+// [cargo]rustc-env:CARGO=/usr/bin/cargo
 // compile-flags: --check-cfg=cfg(feature,values("foo")) --check-cfg=cfg(no_values) -Z unstable-options
 
 #[cfg(featur)]