Auto merge of rust-lang#95702 - Dylan-DPC:rollup-793rz6v, r=Dylan-DPC

Rollup of 8 pull requests

Successful merges:

 - rust-lang#88025 (ScmCredentials netbsd implementation.)
 - rust-lang#95473 (track individual proc-macro expansions in the self-profiler)
 - rust-lang#95547 (caution against ptr-to-int transmutes)
 - rust-lang#95585 (Explain why `&T` is cloned when `T` is not `Clone`)
 - rust-lang#95591 (Use revisions to track NLL test output (part 1))
 - rust-lang#95663 (diagnostics: give a special note for unsafe fn / Fn/FnOnce/FnMut)
 - rust-lang#95673 (:arrow_up: rust-analyzer)
 - rust-lang#95681 (resolve: Fix resolution of empty paths passed from rustdoc)

Failed merges:

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

Author: bors

compiler/rustc_expand/src/base.rs

@@ -1047,6 +1047,12 @@ impl<'a> ExtCtxt<'a> {
         self.current_expansion.id.expn_data().call_site
     }
 
+    /// Returns the current expansion kind's description.
+    pub(crate) fn expansion_descr(&self) -> String {
+        let expn_data = self.current_expansion.id.expn_data();
+        expn_data.kind.descr()
+    }
+
     /// Equivalent of `Span::def_site` from the proc macro API,
     /// except that the location is taken from the span passed as an argument.
     pub fn with_def_site_ctxt(&self, span: Span) -> Span {

compiler/rustc_expand/src/proc_macro.rs

@@ -24,6 +24,8 @@ impl base::ProcMacro for BangProcMacro {
         span: Span,
         input: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {
+        let _timer =
+            ecx.sess.prof.generic_activity_with_arg("expand_proc_macro", ecx.expansion_descr());
         let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
         let server = proc_macro_server::Rustc::new(ecx);
         self.client.run(&EXEC_STRATEGY, server, input, proc_macro_backtrace).map_err(|e| {
@@ -48,6 +50,8 @@ impl base::AttrProcMacro for AttrProcMacro {
         annotation: TokenStream,
         annotated: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {
+        let _timer =
+            ecx.sess.prof.generic_activity_with_arg("expand_proc_macro", ecx.expansion_descr());
         let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
         let server = proc_macro_server::Rustc::new(ecx);
         self.client
@@ -97,17 +101,21 @@ impl MultiItemModifier for ProcMacroDerive {
             nt_to_tokenstream(&item, &ecx.sess.parse_sess, CanSynthesizeMissingTokens::No)
         };
 
-        let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
-        let server = proc_macro_server::Rustc::new(ecx);
-        let stream = match self.client.run(&EXEC_STRATEGY, server, input, proc_macro_backtrace) {
-            Ok(stream) => stream,
-            Err(e) => {
-                let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
-                if let Some(s) = e.as_str() {
-                    err.help(&format!("message: {}", s));
+        let stream = {
+            let _timer =
+                ecx.sess.prof.generic_activity_with_arg("expand_proc_macro", ecx.expansion_descr());
+            let proc_macro_backtrace = ecx.ecfg.proc_macro_backtrace;
+            let server = proc_macro_server::Rustc::new(ecx);
+            match self.client.run(&EXEC_STRATEGY, server, input, proc_macro_backtrace) {
+                Ok(stream) => stream,
+                Err(e) => {
+                    let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
+                    if let Some(s) = e.as_str() {
+                        err.help(&format!("message: {}", s));
+                    }
+                    err.emit();
+                    return ExpandResult::Ready(vec![]);
                 }
-                err.emit();
-                return ExpandResult::Ready(vec![]);
             }
         };
 

compiler/rustc_resolve/src/lib.rs

@@ -3298,7 +3298,9 @@ impl<'a> Resolver<'a> {
             PathResult::NonModule(path_res) if path_res.unresolved_segments() == 0 => {
                 Some(path_res.base_res())
             }
-            PathResult::NonModule(..) | PathResult::Failed { .. } => None,
+            PathResult::Module(ModuleOrUniformRoot::ExternPrelude)
+            | PathResult::NonModule(..)
+            | PathResult::Failed { .. } => None,
             PathResult::Module(..) | PathResult::Indeterminate => unreachable!(),
         }
     }

compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs

@@ -208,6 +208,15 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 flags.push((sym::_Self, Some("&[]".to_owned())));
             }
 
+            if self_ty.is_fn() {
+                let fn_sig = self_ty.fn_sig(self.tcx);
+                let shortname = match fn_sig.unsafety() {
+                    hir::Unsafety::Normal => "fn",
+                    hir::Unsafety::Unsafe => "unsafe fn",
+                };
+                flags.push((sym::_Self, Some(shortname.to_owned())));
+            }
+
             if let ty::Array(aty, len) = self_ty.kind() {
                 flags.push((sym::_Self, Some("[]".to_owned())));
                 flags.push((sym::_Self, Some(format!("[{}]", aty))));

compiler/rustc_typeck/src/check/demand.rs

@@ -40,6 +40,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty);
         self.suggest_missing_parentheses(err, expr);
         self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected);
+        self.note_type_is_not_clone(err, expected, expr_ty, expr);
         self.note_need_for_fn_pointer(err, expected, expr_ty);
         self.note_internal_mutation_in_method(err, expr, expected, expr_ty);
         self.report_closure_inferred_return_type(err, expected);
@@ -630,7 +631,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     Applicability::MachineApplicable,
                                     true,
                                 ));
-
                     }
                 }
                 _ => {}

compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs

@@ -2,8 +2,6 @@ use super::FnCtxt;
 use crate::astconv::AstConv;
 
 use rustc_ast::util::parser::ExprPrecedence;
-use rustc_span::{self, Span};
-
 use rustc_errors::{Applicability, Diagnostic, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorOf, DefKind};
@@ -13,12 +11,14 @@ use rustc_hir::{
     WherePredicate,
 };
 use rustc_infer::infer::{self, TyCtxtInferExt};
-
+use rustc_infer::traits;
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, Binder, Ty};
+use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::{self, Binder, ToPredicate, Ty};
 use rustc_span::symbol::{kw, sym};
+use rustc_span::Span;
+use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 
-use rustc_middle::ty::subst::GenericArgKind;
 use std::iter;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@@ -846,4 +846,53 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let node = self.tcx.hir().get(id);
         matches!(node, Node::Stmt(Stmt { kind: StmtKind::Local(..), .. }))
     }
+
+    /// Suggest that `&T` was cloned instead of `T` because `T` does not implement `Clone`,
+    /// which is a side-effect of autoref.
+    pub(crate) fn note_type_is_not_clone(
+        &self,
+        diag: &mut Diagnostic,
+        expected_ty: Ty<'tcx>,
+        found_ty: Ty<'tcx>,
+        expr: &hir::Expr<'_>,
+    ) {
+        let hir::ExprKind::MethodCall(segment, &[ref callee_expr], _) = expr.kind else { return; };
+        let Some(clone_trait_did) = self.tcx.lang_items().clone_trait() else { return; };
+        let ty::Ref(_, pointee_ty, _) = found_ty.kind() else { return };
+        let results = self.typeck_results.borrow();
+        // First, look for a `Clone::clone` call
+        if segment.ident.name == sym::clone
+            && results.type_dependent_def_id(expr.hir_id).map_or(
+                false,
+                |did| {
+                    self.tcx.associated_item(did).container
+                        == ty::AssocItemContainer::TraitContainer(clone_trait_did)
+                },
+            )
+            // If that clone call hasn't already dereferenced the self type (i.e. don't give this
+            // diagnostic in cases where we have `(&&T).clone()` and we expect `T`).
+            && !results.expr_adjustments(callee_expr).iter().any(|adj| matches!(adj.kind, ty::adjustment::Adjust::Deref(..)))
+            // Check that we're in fact trying to clone into the expected type
+            && self.can_coerce(*pointee_ty, expected_ty)
+            // And the expected type doesn't implement `Clone`
+            && !self.predicate_must_hold_considering_regions(&traits::Obligation {
+                cause: traits::ObligationCause::dummy(),
+                param_env: self.param_env,
+                recursion_depth: 0,
+                predicate: ty::Binder::dummy(ty::TraitRef {
+                    def_id: clone_trait_did,
+                    substs: self.tcx.mk_substs([expected_ty.into()].iter()),
+                })
+                .without_const()
+                .to_predicate(self.tcx),
+            })
+        {
+            diag.span_note(
+                callee_expr.span,
+                &format!(
+                    "`{expected_ty}` does not implement `Clone`, so `{found_ty}` was cloned instead"
+                ),
+            );
+        }
+    }
 }

library/core/src/intrinsics.rs

@@ -991,6 +991,16 @@ extern "rust-intrinsic" {
     /// let ptr_num_cast = ptr as *const i32 as usize;
     /// ```
     ///
+    /// Note that using `transmute` to turn a pointer to a `usize` is (as noted above) [undefined
+    /// behavior][ub] in `const` contexts. Also outside of consts, this operation might not behave
+    /// as expected -- this is touching on many unspecified aspects of the Rust memory model.
+    /// Depending on what the code is doing, the following alternatives are preferrable to
+    /// pointer-to-integer transmutation:
+    /// - If the code just wants to store data of arbitrary type in some buffer and needs to pick a
+    ///   type for that buffer, it can use [`MaybeUninit`][mem::MaybeUninit].
+    /// - If the code actually wants to work on the address the pointer points to, it can use `as`
+    ///   casts or [`ptr.addr()`][pointer::addr].
+    ///
     /// Turning a `*mut T` into an `&mut T`:
     ///
     /// ```

library/core/src/ops/function.rs

@@ -60,6 +60,12 @@
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{Fn}<{Args}>` closure, found `{Self}`",
     label = "expected an `Fn<{Args}>` closure, found `{Self}`"
 )]
@@ -141,6 +147,12 @@ pub trait Fn<Args>: FnMut<Args> {
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{FnMut}<{Args}>` closure, found `{Self}`",
     label = "expected an `FnMut<{Args}>` closure, found `{Self}`"
 )]
@@ -214,6 +226,12 @@ pub trait FnMut<Args>: FnOnce<Args> {
         Args = "()",
         note = "wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}`"
     ),
+    on(
+        _Self = "unsafe fn",
+        note = "unsafe function cannot be called generically without an unsafe block",
+        // SAFETY: tidy is not smart enough to tell that the below unsafe block is a string
+        label = "call the function in a closure: `|| unsafe {{ /* code */ }}`"
+    ),
     message = "expected a `{FnOnce}<{Args}>` closure, found `{Self}`",
     label = "expected an `FnOnce<{Args}>` closure, found `{Self}`"
 )]