Auto merge of #132099 - matthiaskrgr:rollup-myi94r8, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #129248 (Taking a raw ref (`&raw (const|mut)`) of a deref of pointer (`*ptr`) is always safe)
 - #131906 (rustdoc: adjust spacing and typography in header)
 - #132084 (Consider param-env candidates even if they have errors)
 - #132096 (Replace an FTP link in comments with an equivalent HTTPS link)
 - #132098 (rustc_feature::Features: explain what that 'Option<Symbol>' is about)

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

5 files changed, 27 insertions, 22 deletions

diff --git a/compiler/rustc_data_structures/src/graph/dominators/mod.rs b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
index 85b030c1a48..53ff67f60e3 100644
--- a/compiler/rustc_data_structures/src/graph/dominators/mod.rs
+++ b/compiler/rustc_data_structures/src/graph/dominators/mod.rs
@@ -2,7 +2,7 @@
 //!
 //! Algorithm based on Loukas Georgiadis,
 //! "Linear-Time Algorithms for Dominators and Related Problems",
-//! <ftp://ftp.cs.princeton.edu/techreports/2005/737.pdf>
+//! <https://www.cs.princeton.edu/techreports/2005/737.pdf>
 //!
 //! Additionally useful is the original Lengauer-Tarjan paper on this subject,
 //! "A Fast Algorithm for Finding Dominators in a Flowgraph"
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 8f4c208f1fb..8182eb1e973 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -44,6 +44,8 @@ pub struct Features {
 }
 
 impl Features {
+    /// `since` should be set for stable features that are nevertheless enabled with a `#[feature]`
+    /// attribute, indicating since when they are stable.
     pub fn set_enabled_lang_feature(&mut self, name: Symbol, span: Span, since: Option<Symbol>) {
         self.enabled_lang_features.push((name, span, since));
         self.enabled_features.insert(name);
@@ -54,6 +56,10 @@ impl Features {
         self.enabled_features.insert(name);
     }
 
+    /// Returns a list of triples with:
+    /// - feature gate name
+    /// - the span of the `#[feature]` attribute
+    /// - (for already stable features) the version since which it is stable
     pub fn enabled_lang_features(&self) -> &Vec<(Symbol, Span, Option<Symbol>)> {
         &self.enabled_lang_features
     }
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 71c667b2cd6..5c5cd99345e 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -2657,8 +2657,8 @@ declare_lint! {
     ///
     /// ### Explanation
     ///
-    /// Dereferencing a null pointer causes [undefined behavior] even as a place expression,
-    /// like `&*(0 as *const i32)` or `addr_of!(*(0 as *const i32))`.
+    /// Dereferencing a null pointer causes [undefined behavior] if it is accessed
+    /// (loaded from or stored to).
     ///
     /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html
     pub DEREF_NULLPTR,
@@ -2673,14 +2673,14 @@ impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
         /// test if expression is a null ptr
         fn is_null_ptr(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
             match &expr.kind {
-                rustc_hir::ExprKind::Cast(expr, ty) => {
-                    if let rustc_hir::TyKind::Ptr(_) = ty.kind {
+                hir::ExprKind::Cast(expr, ty) => {
+                    if let hir::TyKind::Ptr(_) = ty.kind {
                         return is_zero(expr) || is_null_ptr(cx, expr);
                     }
                 }
                 // check for call to `core::ptr::null` or `core::ptr::null_mut`
-                rustc_hir::ExprKind::Call(path, _) => {
-                    if let rustc_hir::ExprKind::Path(ref qpath) = path.kind {
+                hir::ExprKind::Call(path, _) => {
+                    if let hir::ExprKind::Path(ref qpath) = path.kind {
                         if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id() {
                             return matches!(
                                 cx.tcx.get_diagnostic_name(def_id),
@@ -2697,7 +2697,7 @@ impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
         /// test if expression is the literal `0`
         fn is_zero(expr: &hir::Expr<'_>) -> bool {
             match &expr.kind {
-                rustc_hir::ExprKind::Lit(lit) => {
+                hir::ExprKind::Lit(lit) => {
                     if let LitKind::Int(a, _) = lit.node {
                         return a == 0;
                     }
@@ -2707,8 +2707,16 @@ impl<'tcx> LateLintPass<'tcx> for DerefNullPtr {
             false
         }
 
-        if let rustc_hir::ExprKind::Unary(rustc_hir::UnOp::Deref, expr_deref) = expr.kind {
-            if is_null_ptr(cx, expr_deref) {
+        if let hir::ExprKind::Unary(hir::UnOp::Deref, expr_deref) = expr.kind
+            && is_null_ptr(cx, expr_deref)
+        {
+            if let hir::Node::Expr(hir::Expr {
+                kind: hir::ExprKind::AddrOf(hir::BorrowKind::Raw, ..),
+                ..
+            }) = cx.tcx.parent_hir_node(expr.hir_id)
+            {
+                // `&raw *NULL` is ok.
+            } else {
                 cx.emit_span_lint(DEREF_NULLPTR, expr.span, BuiltinDerefNullptr {
                     label: expr.span,
                 });
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index 8512763a595..f3e6301d9d1 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -509,20 +509,12 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             }
             ExprKind::RawBorrow { arg, .. } => {
                 if let ExprKind::Scope { value: arg, .. } = self.thir[arg].kind
-                // THIR desugars UNSAFE_STATIC into *UNSAFE_STATIC_REF, where
-                // UNSAFE_STATIC_REF holds the addr of the UNSAFE_STATIC, so: take two steps
                     && let ExprKind::Deref { arg } = self.thir[arg].kind
-                    // FIXME(workingjubiee): we lack a clear reason to reject ThreadLocalRef here,
-                    // but we also have no conclusive reason to allow it either!
-                    && let ExprKind::StaticRef { .. } = self.thir[arg].kind
                 {
-                    // A raw ref to a place expr, even an "unsafe static", is okay!
-                    // We short-circuit to not recursively traverse this expression.
+                    // Taking a raw ref to a deref place expr is always safe.
+                    // Make sure the expression we're deref'ing is safe, though.
+                    visit::walk_expr(self, &self.thir[arg]);
                     return;
-                    // note: const_mut_refs enables this code, and it currently remains unsafe:
-                    // static mut BYTE: u8 = 0;
-                    // static mut BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(BYTE) };
-                    // static mut DEREF_BYTE_PTR: *mut u8 = unsafe { addr_of_mut!(*BYTE_PTR) };
                 }
             }
             ExprKind::Deref { arg } => {
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index eea3867190d..c0122d3d552 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -244,7 +244,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .param_env
             .caller_bounds()
             .iter()
-            .filter(|p| !p.references_error())
             .filter_map(|p| p.as_trait_clause())
             // Micro-optimization: filter out predicates relating to different traits.
             .filter(|p| p.def_id() == stack.obligation.predicate.def_id())