Auto merge of #128835 - matthiaskrgr:rollup-apzlbxy, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #128306 (Update NonNull::align_offset quarantees)
 - #128612 (Make `validate_mir` ensure the final MIR for all bodies)
 - #128648 (Add regression test)
 - #128749 (Mark `{f32,f64}::{next_up,next_down,midpoint}` inline)
 - #128795 (Update E0517 message to reflect RFC 2195.)
 - #128825 (rm `declared_features` field in resolver)
 - #128826 (Only suggest `#[allow]` for `--warn` and `--deny` lint level flags)

r? `@ghost`
`@rustbot` modify labels: rollup

5 files changed, 26 insertions, 16 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0517.md b/compiler/rustc_error_codes/src/error_codes/E0517.md
index ae802245bd1..5354a08bf31 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0517.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0517.md
@@ -25,14 +25,17 @@ impl Foo {
 These attributes do not work on typedefs, since typedefs are just aliases.
 
 Representations like `#[repr(u8)]`, `#[repr(i64)]` are for selecting the
-discriminant size for enums with no data fields on any of the variants, e.g.
-`enum Color {Red, Blue, Green}`, effectively setting the size of the enum to
-the size of the provided type. Such an enum can be cast to a value of the same
-type as well. In short, `#[repr(u8)]` makes the enum behave like an integer
-with a constrained set of allowed values.
+discriminant size for enums. For enums with no data fields on any of the
+variants, e.g. `enum Color {Red, Blue, Green}`, this effectively sets the size
+of the enum to the size of the provided type. Such an enum can be cast to a
+value of the same type as well. In short, `#[repr(u8)]` makes a field-less enum
+behave like an integer with a constrained set of allowed values.
 
-Only field-less enums can be cast to numerical primitives, so this attribute
-will not apply to structs.
+For a description of how `#[repr(C)]` and representations like `#[repr(u8)]`
+affect the layout of enums with data fields, see [RFC 2195][rfc2195].
+
+Only field-less enums can be cast to numerical primitives. Representations like
+`#[repr(u8)]` will not apply to structs.
 
 `#[repr(packed)]` reduces padding to make the struct size smaller. The
 representation of enums isn't strictly defined in Rust, and this attribute
@@ -42,3 +45,5 @@ won't work on enums.
 types (i.e., `u8`, `i32`, etc) a representation that permits vectorization via
 SIMD. This doesn't make much sense for enums since they don't consist of a
 single list of data.
+
+[rfc2195]: https://github.com/rust-lang/rfcs/blob/master/text/2195-really-tagged-unions.md
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 8c99b1f4447..023352156eb 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -818,6 +818,13 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
     });
     sess.time("layout_testing", || layout_test::test_layout(tcx));
     sess.time("abi_testing", || abi_test::test_abi(tcx));
+    if tcx.sess.opts.unstable_opts.validate_mir {
+        sess.time("ensuring_optimized_MIR_is_computable", || {
+            tcx.hir().par_body_owners(|def_id| {
+                tcx.instance_mir(ty::InstanceKind::Item(def_id.into()));
+            });
+        });
+    }
 }
 
 /// Runs the type-checking, region checking and other miscellaneous analysis
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 6a9e67f74da..8c27cac1ea8 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -228,9 +228,11 @@ pub fn explain_lint_level_source(
                 err.note_once(format!(
                     "`{flag} {hyphen_case_lint_name}` implied by `{flag} {hyphen_case_flag_val}`"
                 ));
-                err.help_once(format!(
-                    "to override `{flag} {hyphen_case_flag_val}` add `#[allow({name})]`"
-                ));
+                if matches!(orig_level, Level::Warn | Level::Deny) {
+                    err.help_once(format!(
+                        "to override `{flag} {hyphen_case_flag_val}` add `#[allow({name})]`"
+                    ));
+                }
             }
         }
         LintLevelSource::Node { name: lint_attr_name, span, reason, .. } => {
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 023e428dc1b..89ac839651f 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -1129,9 +1129,6 @@ pub struct Resolver<'a, 'tcx> {
     /// Also includes of list of each fields visibility
     struct_constructors: LocalDefIdMap<(Res, ty::Visibility<DefId>, Vec<ty::Visibility<DefId>>)>,
 
-    /// Features declared for this crate.
-    declared_features: FxHashSet<Symbol>,
-
     lint_buffer: LintBuffer,
 
     next_node_id: NodeId,
@@ -1402,7 +1399,6 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
         let registered_tools = tcx.registered_tools(());
 
-        let features = tcx.features();
         let pub_vis = ty::Visibility::<DefId>::Public;
         let edition = tcx.sess.edition();
 
@@ -1506,7 +1502,6 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             multi_segment_macro_resolutions: Default::default(),
             builtin_attrs: Default::default(),
             containers_deriving_copy: Default::default(),
-            declared_features: features.declared_features.clone(),
             lint_buffer: LintBuffer::default(),
             next_node_id: CRATE_NODE_ID,
             node_id_to_def_id,
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index a6301a367a4..da7278175e9 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -1001,7 +1001,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 let feature = stability.feature;
 
                 let is_allowed = |feature| {
-                    self.declared_features.contains(&feature) || span.allows_unstable(feature)
+                    self.tcx.features().declared_features.contains(&feature)
+                        || span.allows_unstable(feature)
                 };
                 let allowed_by_implication = implied_by.is_some_and(|feature| is_allowed(feature));
                 if !is_allowed(feature) && !allowed_by_implication {