Auto merge of #94802 - matthiaskrgr:rollup-4plu0fi, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #92150 (Improve suggestion when casting usize to (possibly) wide pointer)
 - #94635 (Merge `#[deprecated]` and `#[rustc_deprecated]`)
 - #94657 (Constify `Index{,Mut}` for `[T]`, `str`, and `[T; N]`)
 - #94746 (diagnostics: use rustc_on_unimplemented to recommend `[].iter()`)
 - #94788 (Account for suggestions for complete removal of lines)

Failed merges:

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

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -437,13 +437,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 )
                 .emit();
             }
-        } else {
-            if attr.has_name(sym::deprecated) {
-                self.sess
-                    .struct_span_err(attr.span, "`#[deprecated]` cannot be used in staged API")
-                    .span_label(attr.span, "use `#[rustc_deprecated]` instead")
-                    .emit();
-            }
         }
     }
 

compiler/rustc_attr/src/builtin.rs

@@ -664,6 +664,7 @@ where
 {
     let mut depr: Option<(Deprecation, Span)> = None;
     let diagnostic = &sess.parse_sess.span_diagnostic;
+    let is_rustc = sess.features_untracked().staged_api;
 
     'outer: for attr in attrs_iter {
         if !(attr.has_name(sym::deprecated) || attr.has_name(sym::rustc_deprecated)) {
@@ -728,17 +729,31 @@ where
                                     continue 'outer;
                                 }
                             }
-                            sym::note if attr.has_name(sym::deprecated) => {
+                            sym::note => {
                                 if !get(mi, &mut note) {
                                     continue 'outer;
                                 }
                             }
+                            // FIXME(jhpratt) remove this after a bootstrap occurs. Emitting an
+                            // error specific to the renaming would be a good idea as well.
                             sym::reason if attr.has_name(sym::rustc_deprecated) => {
                                 if !get(mi, &mut note) {
                                     continue 'outer;
                                 }
                             }
-                            sym::suggestion if attr.has_name(sym::rustc_deprecated) => {
+                            sym::suggestion => {
+                                if !sess.features_untracked().deprecated_suggestion {
+                                    let mut diag = sess.struct_span_err(
+                                        mi.span,
+                                        "suggestions on deprecated items are unstable",
+                                    );
+                                    if sess.is_nightly_build() {
+                                        diag.help("add `#![feature(deprecated_suggestion)]` to the crate root");
+                                    }
+                                    // FIXME(jhpratt) change this to an actual tracking issue
+                                    diag.note("see #XXX for more details").emit();
+                                }
+
                                 if !get(mi, &mut suggestion) {
                                     continue 'outer;
                                 }
@@ -752,7 +767,7 @@ where
                                         if attr.has_name(sym::deprecated) {
                                             &["since", "note"]
                                         } else {
-                                            &["since", "reason", "suggestion"]
+                                            &["since", "note", "suggestion"]
                                         },
                                     ),
                                 );
@@ -775,24 +790,22 @@ where
             }
         }
 
-        if suggestion.is_some() && attr.has_name(sym::deprecated) {
-            unreachable!("only allowed on rustc_deprecated")
-        }
-
-        if attr.has_name(sym::rustc_deprecated) {
+        if is_rustc {
             if since.is_none() {
                 handle_errors(&sess.parse_sess, attr.span, AttrError::MissingSince);
                 continue;
             }
 
             if note.is_none() {
-                struct_span_err!(diagnostic, attr.span, E0543, "missing 'reason'").emit();
+                struct_span_err!(diagnostic, attr.span, E0543, "missing 'note'").emit();
                 continue;
             }
         }
 
-        let is_since_rustc_version = attr.has_name(sym::rustc_deprecated);
-        depr = Some((Deprecation { since, note, suggestion, is_since_rustc_version }, attr.span));
+        depr = Some((
+            Deprecation { since, note, suggestion, is_since_rustc_version: is_rustc },
+            attr.span,
+        ));
     }
 
     depr

compiler/rustc_errors/src/emitter.rs

@@ -1657,6 +1657,31 @@ impl EmitterWriter {
             let line_start = sm.lookup_char_pos(parts[0].span.lo()).line;
             draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
             let mut lines = complete.lines();
+            if lines.clone().next().is_none() {
+                // Account for a suggestion to completely remove a line(s) with whitespace (#94192).
+                let line_end = sm.lookup_char_pos(parts[0].span.hi()).line;
+                for line in line_start..=line_end {
+                    buffer.puts(
+                        row_num - 1 + line - line_start,
+                        0,
+                        &self.maybe_anonymized(line),
+                        Style::LineNumber,
+                    );
+                    buffer.puts(
+                        row_num - 1 + line - line_start,
+                        max_line_num_len + 1,
+                        "- ",
+                        Style::Removal,
+                    );
+                    buffer.puts(
+                        row_num - 1 + line - line_start,
+                        max_line_num_len + 3,
+                        &normalize_whitespace(&*file_lines.file.get_line(line - 1).unwrap()),
+                        Style::Removal,
+                    );
+                }
+                row_num += line_end - line_start;
+            }
             for (line_pos, (line, highlight_parts)) in
                 lines.by_ref().zip(highlights).take(MAX_SUGGESTION_HIGHLIGHT_LINES).enumerate()
             {

compiler/rustc_feature/src/active.rs

@@ -362,6 +362,8 @@ declare_features! (
     (active, default_alloc_error_handler, "1.48.0", Some(66741), None),
     /// Allows default type parameters to influence type inference.
     (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
+    /// Allows having using `suggestion` in the `#[deprecated]` attribute.
+    (active, deprecated_suggestion, "1.61.0", Some(94785), None),
     /// Allows `#[derive(Default)]` and `#[default]` on enums.
     (active, derive_default_enum, "1.56.0", Some(86985), None),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.

compiler/rustc_feature/src/builtin_attrs.rs

@@ -461,7 +461,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     // DuplicatesOk since it has its own validation
     ungated!(
         rustc_deprecated, Normal,
-        template!(List: r#"since = "version", reason = "...""#), DuplicatesOk // See E0550
+        template!(List: r#"since = "version", note = "...""#), DuplicatesOk // See E0550
     ),
     // DuplicatesOk since it has its own validation
     ungated!(

compiler/rustc_middle/src/ty/sty.rs

@@ -1886,6 +1886,15 @@ impl<'tcx> Ty<'tcx> {
         }
     }
 
+    #[inline]
+    pub fn is_array_slice(self) -> bool {
+        match self.kind() {
+            Slice(_) => true,
+            RawPtr(TypeAndMut { ty, .. }) | Ref(_, ty, _) => matches!(ty.kind(), Slice(_)),
+            _ => false,
+        }
+    }
+
     #[inline]
     pub fn is_array(self) -> bool {
         matches!(self.kind(), Array(..))

compiler/rustc_passes/src/stability.rs

@@ -202,7 +202,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
                     self.tcx.sess,
                     *span,
                     E0549,
-                    "rustc_deprecated attribute must be paired with \
+                    "deprecated attribute must be paired with \
                     either stable or unstable attribute"
                 )
                 .emit();

compiler/rustc_span/src/symbol.rs

@@ -562,6 +562,7 @@ symbols! {
         delay_span_bug_from_inside_query,
         deny,
         deprecated,
+        deprecated_suggestion,
         deref,
         deref_method,
         deref_mut,

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

@@ -11,7 +11,7 @@ use std::iter;
 
 use super::InferCtxtPrivExt;
 
-crate trait InferCtxtExt<'tcx> {
+pub trait InferCtxtExt<'tcx> {
     /*private*/
     fn impl_similar_to(
         &self,
@@ -204,6 +204,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 flags.push((sym::_Self, Some("{integral}".to_owned())));
             }
 
+            if self_ty.is_array_slice() {
+                flags.push((sym::_Self, Some("&[]".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/cast.rs

@@ -165,6 +165,12 @@ pub enum CastError {
     NonScalar,
     UnknownExprPtrKind,
     UnknownCastPtrKind,
+    /// Cast of int to (possibly) fat raw pointer.
+    ///
+    /// Argument is the specific name of the metadata in plain words, such as "a vtable"
+    /// or "a length". If this argument is None, then the metadata is unknown, for example,
+    /// when we're typechecking a type parameter with a ?Sized bound.
+    IntToFatCast(Option<&'static str>),
 }
 
 impl From<ErrorGuaranteed> for CastError {
@@ -522,6 +528,35 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                 .diagnostic()
                 .emit();
             }
+            CastError::IntToFatCast(known_metadata) => {
+                let mut err = struct_span_err!(
+                    fcx.tcx.sess,
+                    self.cast_span,
+                    E0606,
+                    "cannot cast `{}` to a pointer that {} wide",
+                    fcx.ty_to_string(self.expr_ty),
+                    if known_metadata.is_some() { "is" } else { "may be" }
+                );
+
+                err.span_label(
+                    self.cast_span,
+                    format!(
+                        "creating a `{}` requires both an address and {}",
+                        self.cast_ty,
+                        known_metadata.unwrap_or("type-specific metadata"),
+                    ),
+                );
+
+                if fcx.tcx.sess.is_nightly_build() {
+                    err.span_label(
+                        self.expr.span,
+                        "consider casting this expression to `*const ()`, \
+                        then using `core::ptr::from_raw_parts`",
+                    );
+                }
+
+                err.emit();
+            }
             CastError::UnknownCastPtrKind | CastError::UnknownExprPtrKind => {
                 let unknown_cast_to = match e {
                     CastError::UnknownCastPtrKind => true,
@@ -900,7 +935,13 @@ impl<'a, 'tcx> CastCheck<'tcx> {
         match fcx.pointer_kind(m_cast.ty, self.span)? {
             None => Err(CastError::UnknownCastPtrKind),
             Some(PointerKind::Thin) => Ok(CastKind::AddrPtrCast),
-            _ => Err(CastError::IllegalCast),
+            Some(PointerKind::Vtable(_)) => Err(CastError::IntToFatCast(Some("a vtable"))),
+            Some(PointerKind::Length) => Err(CastError::IntToFatCast(Some("a length"))),
+            Some(
+                PointerKind::OfProjection(_)
+                | PointerKind::OfOpaque(_, _)
+                | PointerKind::OfParam(_),
+            ) => Err(CastError::IntToFatCast(None)),
         }
     }