check-cfg: adjust expected names and values when useful

compiler/rustc_lint/src/context.rs

@@ -727,11 +727,14 @@ fn lookup_with_diagnostics(
                                 .collect::<Vec<_>>();
                             possibilities.sort();
 
+                            let mut should_print_possibilities = true;
                             if let Some((value, value_span)) = value {
                                 if best_match_values.contains(&Some(value)) {
                                     db.span_suggestion(name_span, "there is a config with a similar name and value", best_match, Applicability::MaybeIncorrect);
+                                    should_print_possibilities = false;
                                 } else if best_match_values.contains(&None) {
                                     db.span_suggestion(name_span.to(value_span), "there is a config with a similar name and no value", best_match, Applicability::MaybeIncorrect);
+                                    should_print_possibilities = false;
                                 } else if let Some(first_value) = possibilities.first() {
                                     db.span_suggestion(name_span.to(value_span), "there is a config with a similar name and different values", format!("{best_match} = \"{first_value}\""), Applicability::MaybeIncorrect);
                                 } else {
@@ -741,13 +744,21 @@ fn lookup_with_diagnostics(
                                 db.span_suggestion(name_span, "there is a config with a similar name", best_match, Applicability::MaybeIncorrect);
                             }
 
-                            if !possibilities.is_empty() {
+                            if !possibilities.is_empty() && should_print_possibilities {
                                 let possibilities = possibilities.join("`, `");
                                 db.help(format!("expected values for `{best_match}` are: `{possibilities}`"));
                             }
                         } else {
                             db.span_suggestion(name_span, "there is a config with a similar name", best_match, Applicability::MaybeIncorrect);
                         }
+                    } else if !possibilities.is_empty() {
+                        let mut possibilities = possibilities.iter()
+                            .map(Symbol::as_str)
+                            .collect::<Vec<_>>();
+                        possibilities.sort();
+                        let possibilities = possibilities.join("`, `");
+
+                        db.help(format!("expected names are: `{possibilities}`"));
                     }
                 },
                 BuiltinLintDiagnostics::UnexpectedCfgValue((name, name_span), value) => {

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

@@ -4,6 +4,7 @@ warning: unexpected `cfg` condition name
 LL | #[cfg(FALSE)]
    |       ^^^^^
    |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: 1 warning emitted

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

@@ -4,6 +4,7 @@ warning: unexpected `cfg` condition name
 LL | #[cfg(target(os = "linux", architecture = "arm"))]
    |                            ^^^^^^^^^^^^^^^^^^^^
    |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: 1 warning emitted

tests/ui/check-cfg/diagnotics.stderr

@@ -13,7 +13,6 @@ warning: unexpected `cfg` condition name
 LL | #[cfg(featur = "foo")]
    |       ^^^^^^^^^^^^^^
    |
-   = help: expected values for `feature` are: `foo`
 help: there is a config with a similar name and value
    |
 LL | #[cfg(feature = "foo")]

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

@@ -4,6 +4,7 @@ warning: unexpected `cfg` condition name
 LL | #[cfg(unknown_key = "value")]
    |       ^^^^^^^^^^^^^^^^^^^^^
    |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: 1 warning emitted

tests/ui/check-cfg/mix.stderr

@@ -35,6 +35,8 @@ warning: unexpected `cfg` condition name
    |
 LL | #[cfg_attr(uu, test)]
    |            ^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected condition value `bar` for condition name `feature`
    |
@@ -71,18 +73,24 @@ warning: unexpected `cfg` condition name
    |
 LL |     cfg!(xxx = "foo");
    |          ^^^^^^^^^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:48:10
    |
 LL |     cfg!(xxx);
    |          ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:50:14
    |
 LL |     cfg!(any(xxx, windows));
    |              ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition value
   --> $DIR/mix.rs:52:14
@@ -97,36 +105,48 @@ warning: unexpected `cfg` condition name
    |
 LL |     cfg!(any(windows, xxx));
    |                       ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:56:20
    |
 LL |     cfg!(all(unix, xxx));
    |                    ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:58:14
    |
 LL |     cfg!(all(aa, bb));
    |              ^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:58:18
    |
 LL |     cfg!(all(aa, bb));
    |                  ^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:61:14
    |
 LL |     cfg!(any(aa, bb));
    |              ^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:61:18
    |
 LL |     cfg!(any(aa, bb));
    |                  ^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition value
   --> $DIR/mix.rs:64:20
@@ -141,6 +161,8 @@ warning: unexpected `cfg` condition name
    |
 LL |     cfg!(any(xxx, feature = "zebra"));
    |              ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition value
   --> $DIR/mix.rs:66:19
@@ -155,12 +177,16 @@ warning: unexpected `cfg` condition name
    |
 LL |     cfg!(any(xxx, unix, xxx));
    |              ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition name
   --> $DIR/mix.rs:69:25
    |
 LL |     cfg!(any(xxx, unix, xxx));
    |                         ^^^
+   |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
 
 warning: unexpected `cfg` condition value
   --> $DIR/mix.rs:72:14

tests/ui/check-cfg/stmt-no-ice.stderr

@@ -4,6 +4,7 @@ warning: unexpected `cfg` condition name
 LL |     #[cfg(crossbeam_loom)]
    |           ^^^^^^^^^^^^^^
    |
+   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `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`
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: 1 warning emitted