stabilize cfg_select!

compiler/rustc_attr_parsing/src/attributes/cfg_select.rs

@@ -7,6 +7,8 @@ use rustc_hir::attrs::CfgEntry;
 use rustc_parse::exp;
 use rustc_parse::parser::Parser;
 use rustc_session::Session;
+use rustc_session::lint::BuiltinLintDiag;
+use rustc_session::lint::builtin::UNREACHABLE_CFGS;
 use rustc_span::{ErrorGuaranteed, Ident, Span};
 
 use crate::parser::MetaItemOrLitParser;
@@ -86,5 +88,16 @@ pub fn parse_cfg_select(
         }
     }
 
+    if let Some((underscore, _, _)) = branches.wildcard {
+        for (_, _, span) in &branches.unreachable {
+            p.psess.buffer_lint(
+                UNREACHABLE_CFGS,
+                *span,
+                lint_node_id,
+                BuiltinLintDiag::UnreachableCfg { span: *span, wildcard_span: underscore.span },
+            );
+        }
+    }
+
     Ok(branches)
 }

compiler/rustc_builtin_macros/messages.ftl

@@ -86,10 +86,6 @@ builtin_macros_cfg_accessible_unspecified_path = `cfg_accessible` path is not sp
 
 builtin_macros_cfg_select_no_matches = none of the predicates in this `cfg_select` evaluated to true
 
-builtin_macros_cfg_select_unreachable = unreachable predicate
-    .label = always matches
-    .label2 = this predicate is never reached
-
 builtin_macros_coerce_pointee_requires_maybe_sized = `derive(CoercePointee)` requires `{$name}` to be marked `?Sized`
 
 builtin_macros_coerce_pointee_requires_one_field = `CoercePointee` can only be derived on `struct`s with at least one field

compiler/rustc_builtin_macros/src/cfg_select.rs

@@ -1,12 +1,10 @@
 use rustc_ast::tokenstream::TokenStream;
 use rustc_attr_parsing as attr;
-use rustc_attr_parsing::{
-    CfgSelectBranches, CfgSelectPredicate, EvalConfigResult, parse_cfg_select,
-};
+use rustc_attr_parsing::{CfgSelectBranches, EvalConfigResult, parse_cfg_select};
 use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
 use rustc_span::{Ident, Span, sym};
 
-use crate::errors::{CfgSelectNoMatches, CfgSelectUnreachable};
+use crate::errors::CfgSelectNoMatches;
 
 /// Selects the first arm whose predicate evaluates to true.
 fn select_arm(ecx: &ExtCtxt<'_>, branches: CfgSelectBranches) -> Option<(TokenStream, Span)> {
@@ -32,18 +30,6 @@ pub(super) fn expand_cfg_select<'cx>(
             ecx.current_expansion.lint_node_id,
         ) {
             Ok(branches) => {
-                if let Some((underscore, _, _)) = branches.wildcard {
-                    // Warn for every unreachable predicate. We store the fully parsed branch for rustfmt.
-                    for (predicate, _, _) in &branches.unreachable {
-                        let span = match predicate {
-                            CfgSelectPredicate::Wildcard(underscore) => underscore.span,
-                            CfgSelectPredicate::Cfg(cfg) => cfg.span(),
-                        };
-                        let err = CfgSelectUnreachable { span, wildcard_span: underscore.span };
-                        ecx.dcx().emit_warn(err);
-                    }
-                }
-
                 if let Some((tts, arm_span)) = select_arm(ecx, branches) {
                     return ExpandResult::from_tts(
                         ecx,

compiler/rustc_builtin_macros/src/errors.rs

@@ -999,14 +999,3 @@ pub(crate) struct CfgSelectNoMatches {
     #[primary_span]
     pub span: Span,
 }
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_cfg_select_unreachable)]
-pub(crate) struct CfgSelectUnreachable {
-    #[primary_span]
-    #[label(builtin_macros_label2)]
-    pub span: Span,
-
-    #[label]
-    pub wildcard_span: Span,
-}

compiler/rustc_codegen_cranelift/patches/0027-sysroot_tests-128bit-atomic-operations.patch

@@ -17,9 +17,9 @@ index 1e336bf..35e6f54 100644
 @@ -2,5 +2,4 @@
  // tidy-alphabetical-start
 -#![cfg_attr(target_has_atomic = "128", feature(integer_atomics))]
- #![cfg_attr(test, feature(cfg_select))]
  #![feature(alloc_layout_extra)]
  #![feature(array_ptr_get)]
+ #![feature(array_try_from_fn)]
 diff --git a/coretests/tests/atomic.rs b/coretests/tests/atomic.rs
 index b735957..ea728b6 100644
 --- a/coretests/tests/atomic.rs

compiler/rustc_data_structures/src/lib.rs

@@ -11,13 +11,13 @@
 #![allow(rustc::default_hash_types)]
 #![allow(rustc::potential_query_instability)]
 #![cfg_attr(bootstrap, feature(array_windows))]
+#![cfg_attr(bootstrap, feature(cfg_select))]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![feature(allocator_api)]
 #![feature(ascii_char)]
 #![feature(ascii_char_variants)]
 #![feature(assert_matches)]
 #![feature(auto_traits)]
-#![feature(cfg_select)]
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(extend_one)]

compiler/rustc_lint/messages.ftl

@@ -916,6 +916,10 @@ lint_unpredictable_fn_pointer_comparisons = function pointer comparisons do not
 
 lint_unqualified_local_imports = `use` of a local item without leading `self::`, `super::`, or `crate::`
 
+lint_unreachable_cfg = unreachable configuration predicate
+    .label = always matches
+    .label2 = this configuration predicate is never reached
+
 lint_unsafe_attr_outside_unsafe = unsafe attribute used without unsafe
     .label = usage of unsafe attribute
 lint_unsafe_attr_outside_unsafe_suggestion = wrap the attribute in `unsafe(...)`

compiler/rustc_lint/src/early/diagnostics.rs

@@ -293,6 +293,10 @@ pub fn decorate_builtin_lint(
             }
             .decorate_lint(diag);
         }
+        BuiltinLintDiag::UnreachableCfg { span, wildcard_span } => {
+            lints::UnreachableCfg { span, wildcard_span }.decorate_lint(diag);
+        }
+
         BuiltinLintDiag::UnusedCrateDependency { extern_crate, local_crate } => {
             lints::UnusedCrateDependency { extern_crate, local_crate }.decorate_lint(diag)
         }

compiler/rustc_lint/src/lib.rs

@@ -295,6 +295,7 @@ fn register_builtins(store: &mut LintStore) {
         UNUSED_ASSIGNMENTS,
         DEAD_CODE,
         UNUSED_MUT,
+        UNREACHABLE_CFGS,
         UNREACHABLE_CODE,
         UNREACHABLE_PATTERNS,
         UNUSED_MUST_USE,

compiler/rustc_lint/src/lints.rs

@@ -3199,3 +3199,13 @@ pub(crate) struct UnusedVisibility {
     #[suggestion(style = "short", code = "", applicability = "machine-applicable")]
     pub span: Span,
 }
+
+#[derive(LintDiagnostic)]
+#[diag(lint_unreachable_cfg)]
+pub(crate) struct UnreachableCfg {
+    #[label(lint_label2)]
+    pub span: Span,
+
+    #[label]
+    pub wildcard_span: Span,
+}

compiler/rustc_lint_defs/src/builtin.rs

@@ -121,6 +121,7 @@ declare_lint_pass! {
         UNKNOWN_LINTS,
         UNNAMEABLE_TEST_ITEMS,
         UNNAMEABLE_TYPES,
+        UNREACHABLE_CFGS,
         UNREACHABLE_CODE,
         UNREACHABLE_PATTERNS,
         UNSAFE_ATTR_OUTSIDE_UNSAFE,
@@ -856,6 +857,32 @@ declare_lint! {
     "detects unreachable patterns"
 }
 
+declare_lint! {
+    /// The `unreachable_cfgs` lint detects unreachable configuration
+    /// predicates.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// cfg_select! {
+    ///     _ => (),
+    ///     windows => (),
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// This usually indicates a mistake in how the predicates are specified or
+    /// ordered. In this example, the `_` predicate will always match, so the
+    /// `windows` is impossible to reach. Remember, arms match in order, you
+    /// probably wanted to put the `windows` case above the `_` case.
+    pub UNREACHABLE_CFGS,
+    Warn,
+    "detects unreachable configuration predicates"
+}
+
 declare_lint! {
     /// The `overlapping_range_endpoints` lint detects `match` arms that have [range patterns] that
     /// overlap on their endpoints.

compiler/rustc_lint_defs/src/lib.rs

@@ -696,6 +696,10 @@ pub enum BuiltinLintDiag {
     },
     UnusedVisibility(Span),
     AttributeLint(AttributeLintKind),
+    UnreachableCfg {
+        span: Span,
+        wildcard_span: Span,
+    },
 }
 
 #[derive(Debug, HashStable_Generic)]

compiler/rustc_span/src/lib.rs

@@ -18,8 +18,8 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![cfg_attr(bootstrap, feature(array_windows))]
+#![cfg_attr(bootstrap, feature(cfg_select))]
 #![cfg_attr(target_arch = "loongarch64", feature(stdarch_loongarch))]
-#![feature(cfg_select)]
 #![feature(core_io_borrowed_buf)]
 #![feature(if_let_guard)]
 #![feature(map_try_insert)]

library/core/src/lib.rs

@@ -100,7 +100,6 @@
 #![feature(bigint_helper_methods)]
 #![feature(bstr)]
 #![feature(bstr_internals)]
-#![feature(cfg_select)]
 #![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(const_carrying_mul_add)]
 #![feature(const_cmp)]
@@ -247,7 +246,7 @@ pub mod autodiff {
 #[unstable(feature = "contracts", issue = "128044")]
 pub mod contracts;
 
-#[unstable(feature = "cfg_select", issue = "115585")]
+#[stable(feature = "cfg_select", since = "CURRENT_RUSTC_VERSION")]
 pub use crate::macros::cfg_select;
 
 #[macro_use]

library/core/src/macros/mod.rs

@@ -208,8 +208,6 @@ pub macro assert_matches {
 /// # Example
 ///
 /// ```
-/// #![feature(cfg_select)]
-///
 /// cfg_select! {
 ///     unix => {
 ///         fn foo() { /* unix specific functionality */ }
@@ -227,14 +225,12 @@ pub macro assert_matches {
 /// right-hand side:
 ///
 /// ```
-/// #![feature(cfg_select)]
-///
 /// let _some_string = cfg_select! {
 ///     unix => "With great power comes great electricity bills",
 ///     _ => { "Behind every successful diet is an unwatched pizza" }
 /// };
 /// ```
-#[unstable(feature = "cfg_select", issue = "115585")]
+#[stable(feature = "cfg_select", since = "CURRENT_RUSTC_VERSION")]
 #[rustc_diagnostic_item = "cfg_select"]
 #[rustc_builtin_macro]
 pub macro cfg_select($($tt:tt)*) {

library/coretests/tests/lib.rs

@@ -1,6 +1,5 @@
 // tidy-alphabetical-start
 #![cfg_attr(target_has_atomic = "128", feature(integer_atomics))]
-#![cfg_attr(test, feature(cfg_select))]
 #![feature(alloc_layout_extra)]
 #![feature(array_ptr_get)]
 #![feature(array_try_from_fn)]

library/panic_unwind/src/lib.rs

@@ -15,7 +15,6 @@
 #![unstable(feature = "panic_unwind", issue = "32837")]
 #![doc(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![feature(cfg_emscripten_wasm_eh)]
-#![feature(cfg_select)]
 #![feature(core_intrinsics)]
 #![feature(lang_items)]
 #![feature(panic_unwind)]

library/std/src/lib.rs

@@ -319,7 +319,6 @@
 #![feature(bstr)]
 #![feature(bstr_internals)]
 #![feature(cast_maybe_uninit)]
-#![feature(cfg_select)]
 #![feature(char_internals)]
 #![feature(clone_to_uninit)]
 #![feature(const_convert)]
@@ -695,7 +694,7 @@ mod panicking;
 #[allow(dead_code, unused_attributes, fuzzy_provenance_casts, unsafe_op_in_unsafe_fn)]
 mod backtrace_rs;
 
-#[unstable(feature = "cfg_select", issue = "115585")]
+#[stable(feature = "cfg_select", since = "CURRENT_RUSTC_VERSION")]
 pub use core::cfg_select;
 #[unstable(
     feature = "concat_bytes",

library/std/tests/env_modify.rs

@@ -1,6 +1,5 @@
 // These tests are in a separate integration test as they modify the environment,
 // and would otherwise cause some other tests to fail.
-#![feature(cfg_select)]
 
 use std::env::*;
 use std::ffi::{OsStr, OsString};

library/std_detect/src/lib.rs

@@ -15,7 +15,7 @@
 //! * `s390x`: [`is_s390x_feature_detected`]
 
 #![unstable(feature = "stdarch_internal", issue = "none")]
-#![feature(staged_api, cfg_select, doc_cfg, allow_internal_unstable)]
+#![feature(staged_api, doc_cfg, allow_internal_unstable)]
 #![deny(rust_2018_idioms)]
 #![allow(clippy::shadow_reuse)]
 #![cfg_attr(test, allow(unused_imports))]

library/unwind/src/lib.rs

@@ -1,7 +1,6 @@
 #![no_std]
 #![unstable(feature = "panic_unwind", issue = "32837")]
 #![feature(cfg_emscripten_wasm_eh)]
-#![feature(cfg_select)]
 #![feature(link_cfg)]
 #![feature(staged_api)]
 #![cfg_attr(not(target_env = "msvc"), feature(libc))]

src/tools/miri/src/lib.rs

@@ -1,5 +1,4 @@
 #![feature(abort_unwind)]
-#![feature(cfg_select)]
 #![feature(rustc_private)]
 #![feature(float_gamma)]
 #![feature(float_erf)]
@@ -17,6 +16,7 @@
 #![feature(derive_coerce_pointee)]
 #![feature(arbitrary_self_types)]
 #![feature(iter_advance_by)]
+#![cfg_attr(bootstrap, feature(cfg_select))]
 #![cfg_attr(bootstrap, feature(duration_from_nanos_u128))]
 // Configure clippy and other lints
 #![allow(

src/tools/miri/tests/pass/float_extra_rounding_error.rs

@@ -2,7 +2,6 @@
 //@revisions: random max none
 //@[max]compile-flags: -Zmiri-max-extra-rounding-error
 //@[none]compile-flags: -Zmiri-no-extra-rounding-error
-#![feature(cfg_select)]
 
 use std::collections::HashSet;
 use std::hint::black_box;

tests/run-make/c-link-to-rust-va-list-fn/checkrust.rs

@@ -1,6 +1,5 @@
 #![crate_type = "staticlib"]
 #![feature(c_variadic)]
-#![feature(cfg_select)]
 
 use std::ffi::{CStr, CString, VaList, c_char, c_double, c_int, c_long, c_longlong};
 

tests/ui/asm/cfg.rs

@@ -3,7 +3,6 @@
 //@ revisions: reva revb
 //@ only-x86_64
 //@ run-pass
-#![feature(cfg_select)]
 
 use std::arch::{asm, naked_asm};
 

tests/ui/check-cfg/cfg-select.rs

@@ -1,6 +1,5 @@
 //@ check-pass
 
-#![feature(cfg_select)]
 #![crate_type = "lib"]
 
 cfg_select! {

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

@@ -1,5 +1,5 @@
 warning: unexpected `cfg` condition name: `invalid_cfg1`
-  --> $DIR/cfg-select.rs:8:5
+  --> $DIR/cfg-select.rs:7:5
    |
 LL |     invalid_cfg1 => {}
    |     ^^^^^^^^^^^^
@@ -10,7 +10,7 @@ LL |     invalid_cfg1 => {}
    = note: `#[warn(unexpected_cfgs)]` on by default
 
 warning: unexpected `cfg` condition name: `invalid_cfg2`
-  --> $DIR/cfg-select.rs:14:5
+  --> $DIR/cfg-select.rs:13:5
    |
 LL |     invalid_cfg2 => {}
    |     ^^^^^^^^^^^^

tests/ui/lint/issue-70819-dont-override-forbid-in-same-scope.stderr

@@ -431,3 +431,21 @@ note: the lint level is defined here
 LL | #![forbid(forbidden_lint_groups)]
    |           ^^^^^^^^^^^^^^^^^^^^^
 
+Future breakage diagnostic:
+error: warn(unused) incompatible with previous forbid
+  --> $DIR/issue-70819-dont-override-forbid-in-same-scope.rs:22:13
+   |
+LL |     #![forbid(unused)]
+   |               ------ `forbid` level set here
+LL |     #![deny(unused)]
+LL |     #![warn(unused)]
+   |             ^^^^^^ overruled by previous forbid
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #81670 <https://github.com/rust-lang/rust/issues/81670>
+note: the lint level is defined here
+  --> $DIR/issue-70819-dont-override-forbid-in-same-scope.rs:17:11
+   |
+LL | #![forbid(forbidden_lint_groups)]
+   |           ^^^^^^^^^^^^^^^^^^^^^
+