Remove --check-cfg checking of --cfg args

compiler/rustc_lint/messages.ftl

@@ -128,12 +128,6 @@ lint_builtin_type_alias_generic_bounds = bounds on generic parameters are not en
 lint_builtin_type_alias_where_clause = where clauses are not enforced in type aliases
     .suggestion = the clause will not be checked when the type alias is used, and should be removed
 
-lint_builtin_unexpected_cli_config_name = unexpected `{$name}` as condition name
-    .help = was set with `--cfg` but isn't in the `--check-cfg` expected names
-
-lint_builtin_unexpected_cli_config_value = unexpected condition value `{$value}` for condition name `{$name}`
-    .help = was set with `--cfg` but isn't in the `--check-cfg` expected values
-
 lint_builtin_unpermitted_type_init_label = this code causes undefined behavior when executed
 lint_builtin_unpermitted_type_init_label_suggestion = help: use `MaybeUninit<T>` instead, and only call `assume_init` after initialization is done
 

compiler/rustc_lint/src/builtin.rs

@@ -33,7 +33,6 @@ use crate::{
         BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
         BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasGenericBounds,
         BuiltinTypeAliasGenericBoundsSuggestion, BuiltinTypeAliasWhereClause,
-        BuiltinUnexpectedCliConfigName, BuiltinUnexpectedCliConfigValue,
         BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
         BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
         BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
@@ -60,7 +59,6 @@ use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
-use rustc_session::config::ExpectedValues;
 use rustc_session::lint::{BuiltinLintDiagnostics, FutureIncompatibilityReason};
 use rustc_span::edition::Edition;
 use rustc_span::source_map::Spanned;
@@ -2889,26 +2887,3 @@ impl EarlyLintPass for SpecialModuleName {
         }
     }
 }
-
-pub use rustc_session::lint::builtin::UNEXPECTED_CFGS;
-
-declare_lint_pass!(UnexpectedCfgs => [UNEXPECTED_CFGS]);
-
-impl EarlyLintPass for UnexpectedCfgs {
-    fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
-        let cfg = &cx.sess().parse_sess.config;
-        let check_cfg = &cx.sess().parse_sess.check_config;
-        for &(name, value) in cfg {
-            match check_cfg.expecteds.get(&name) {
-                Some(ExpectedValues::Some(values)) if !values.contains(&value) => {
-                    let value = value.unwrap_or(kw::Empty);
-                    cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigValue { name, value });
-                }
-                None if check_cfg.exhaustive_names => {
-                    cx.emit_lint(UNEXPECTED_CFGS, BuiltinUnexpectedCliConfigName { name });
-                }
-                _ => { /* expected */ }
-            }
-        }
-    }
-}

compiler/rustc_lint/src/lib.rs

@@ -179,7 +179,6 @@ early_lint_methods!(
             IncompleteInternalFeatures: IncompleteInternalFeatures,
             RedundantSemicolons: RedundantSemicolons,
             UnusedDocComment: UnusedDocComment,
-            UnexpectedCfgs: UnexpectedCfgs,
         ]
     ]
 );

compiler/rustc_lint/src/lints.rs

@@ -553,21 +553,6 @@ pub enum BuiltinSpecialModuleNameUsed {
     Main,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(lint_builtin_unexpected_cli_config_name)]
-#[help]
-pub struct BuiltinUnexpectedCliConfigName {
-    pub name: Symbol,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(lint_builtin_unexpected_cli_config_value)]
-#[help]
-pub struct BuiltinUnexpectedCliConfigValue {
-    pub name: Symbol,
-    pub value: Symbol,
-}
-
 // deref_into_dyn_supertrait.rs
 #[derive(LintDiagnostic)]
 #[diag(lint_supertrait_as_deref_target)]

compiler/rustc_lint_defs/src/builtin.rs

@@ -3439,6 +3439,7 @@ declare_lint_pass! {
         UNCONDITIONAL_PANIC,
         UNCONDITIONAL_RECURSION,
         UNDEFINED_NAKED_FUNCTION_ABI,
+        UNEXPECTED_CFGS,
         UNFULFILLED_LINT_EXPECTATIONS,
         UNINHABITED_STATIC,
         UNKNOWN_CRATE_TYPES,

src/doc/unstable-book/src/compiler-flags/check-cfg.md

@@ -35,6 +35,9 @@ and `cfg!(name = "value")` call. It will check that the `"value"` specified is p
 list of expected values. If `"value"` is not in it, then `rustc` will report an `unexpected_cfgs`
 lint diagnostic. The default diagnostic level for this lint is `Warn`.
 
+The command line `--cfg` arguments are currently *NOT* checked but may very well be checked in
+the future.
+
 To enable checking of values, but to provide an empty set of expected values, use these forms:
 
 ```bash