Auto merge of rust-lang#136448 - matthiaskrgr:rollup-pdim5di, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#134272 (Remove rustc_encodable_decodable feature)
 - rust-lang#136283 (Update encode_utf16 to mention it is native endian)
 - rust-lang#136394 (Clean up MonoItem::instantiation_mode)
 - rust-lang#136402 (diagnostics: fix borrowck suggestions for if/while let conditionals)
 - rust-lang#136415 (Highlight clarifying information in "expected/found" error)
 - rust-lang#136422 (Convert two `rustc_middle::lint` functions to `Span` methods.)
 - rust-lang#136434 (rustc_allowed_through_unstable_modules: require deprecation message)

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

Author: bors

compiler/rustc_attr_data_structures/src/stability.rs

@@ -101,16 +101,6 @@ impl PartialConstStability {
     }
 }
 
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub enum AllowedThroughUnstableModules {
-    /// This does not get a deprecation warning. We still generally would prefer people to use the
-    /// fully stable path, and a warning will likely be emitted in the future.
-    WithoutDeprecation,
-    /// Emit the given deprecation warning.
-    WithDeprecation(Symbol),
-}
-
 /// The available stability levels.
 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 #[derive(HashStable_Generic)]
@@ -147,8 +137,9 @@ pub enum StabilityLevel {
     Stable {
         /// Rust release which stabilized this feature.
         since: StableSince,
-        /// This is `Some` if this item allowed to be referred to on stable via unstable modules.
-        allowed_through_unstable_modules: Option<AllowedThroughUnstableModules>,
+        /// This is `Some` if this item allowed to be referred to on stable via unstable modules;
+        /// the `Symbol` is the deprecation message printed in that case.
+        allowed_through_unstable_modules: Option<Symbol>,
     },
 }
 

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -6,12 +6,12 @@ use rustc_ast::MetaItem;
 use rustc_ast::attr::AttributeExt;
 use rustc_ast_pretty::pprust;
 use rustc_attr_data_structures::{
-    AllowedThroughUnstableModules, ConstStability, DefaultBodyStability, Stability, StabilityLevel,
-    StableSince, UnstableReason, VERSION_PLACEHOLDER,
+    ConstStability, DefaultBodyStability, Stability, StabilityLevel, StableSince, UnstableReason,
+    VERSION_PLACEHOLDER,
 };
 use rustc_errors::ErrorGuaranteed;
 use rustc_session::Session;
-use rustc_span::{Span, Symbol, sym};
+use rustc_span::{Span, Symbol, kw, sym};
 
 use crate::attributes::util::UnsupportedLiteralReason;
 use crate::{parse_version, session_diagnostics};
@@ -29,10 +29,14 @@ pub fn find_stability(
     for attr in attrs {
         match attr.name_or_empty() {
             sym::rustc_allowed_through_unstable_modules => {
-                allowed_through_unstable_modules = Some(match attr.value_str() {
-                    Some(msg) => AllowedThroughUnstableModules::WithDeprecation(msg),
-                    None => AllowedThroughUnstableModules::WithoutDeprecation,
-                })
+                // The value is mandatory, but avoid ICEs in case such code reaches this function.
+                allowed_through_unstable_modules = Some(attr.value_str().unwrap_or_else(|| {
+                    sess.dcx().span_delayed_bug(
+                        item_sp,
+                        "`#[rustc_allowed_through_unstable_modules]` without deprecation message",
+                    );
+                    kw::Empty
+                }))
             }
             sym::unstable => {
                 if stab.is_some() {

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -248,7 +248,98 @@ impl<'tcx> BorrowExplanation<'tcx> {
                         );
                         err.span_label(body.source_info(drop_loc).span, message);
 
-                        if let LocalInfo::BlockTailTemp(info) = local_decl.local_info() {
+                        struct FindLetExpr<'hir> {
+                            span: Span,
+                            result: Option<(Span, &'hir hir::Pat<'hir>, &'hir hir::Expr<'hir>)>,
+                            tcx: TyCtxt<'hir>,
+                        }
+
+                        impl<'hir> rustc_hir::intravisit::Visitor<'hir> for FindLetExpr<'hir> {
+                            type NestedFilter = rustc_middle::hir::nested_filter::OnlyBodies;
+                            fn nested_visit_map(&mut self) -> Self::Map {
+                                self.tcx.hir()
+                            }
+                            fn visit_expr(&mut self, expr: &'hir hir::Expr<'hir>) {
+                                if let hir::ExprKind::If(cond, _conseq, _alt)
+                                | hir::ExprKind::Loop(
+                                    hir::Block {
+                                        expr:
+                                            Some(&hir::Expr {
+                                                kind: hir::ExprKind::If(cond, _conseq, _alt),
+                                                ..
+                                            }),
+                                        ..
+                                    },
+                                    _,
+                                    hir::LoopSource::While,
+                                    _,
+                                ) = expr.kind
+                                    && let hir::ExprKind::Let(hir::LetExpr {
+                                        init: let_expr_init,
+                                        span: let_expr_span,
+                                        pat: let_expr_pat,
+                                        ..
+                                    }) = cond.kind
+                                    && let_expr_init.span.contains(self.span)
+                                {
+                                    self.result =
+                                        Some((*let_expr_span, let_expr_pat, let_expr_init))
+                                } else {
+                                    hir::intravisit::walk_expr(self, expr);
+                                }
+                            }
+                        }
+
+                        if let &LocalInfo::IfThenRescopeTemp { if_then } = local_decl.local_info()
+                            && let hir::Node::Expr(expr) = tcx.hir_node(if_then)
+                            && let hir::ExprKind::If(cond, conseq, alt) = expr.kind
+                            && let hir::ExprKind::Let(&hir::LetExpr {
+                                span: _,
+                                pat,
+                                init,
+                                // FIXME(#101728): enable rewrite when type ascription is
+                                // stabilized again.
+                                ty: None,
+                                recovered: _,
+                            }) = cond.kind
+                            && pat.span.can_be_used_for_suggestions()
+                            && let Ok(pat) = tcx.sess.source_map().span_to_snippet(pat.span)
+                        {
+                            suggest_rewrite_if_let(tcx, expr, &pat, init, conseq, alt, err);
+                        } else if let Some((old, new)) = multiple_borrow_span
+                            && let def_id = body.source.def_id()
+                            && let Some(node) = tcx.hir().get_if_local(def_id)
+                            && let Some(body_id) = node.body_id()
+                            && let hir_body = tcx.hir().body(body_id)
+                            && let mut expr_finder = (FindLetExpr { span: old, result: None, tcx })
+                            && let Some((let_expr_span, let_expr_pat, let_expr_init)) = {
+                                expr_finder.visit_expr(hir_body.value);
+                                expr_finder.result
+                            }
+                            && !let_expr_span.contains(new)
+                        {
+                            // #133941: The `old` expression is at the conditional part of an
+                            // if/while let expression. Adding a semicolon won't work.
+                            // Instead, try suggesting the `matches!` macro or a temporary.
+                            if let_expr_pat
+                                .walk_short(|pat| !matches!(pat.kind, hir::PatKind::Binding(..)))
+                            {
+                                if let Ok(pat_snippet) =
+                                    tcx.sess.source_map().span_to_snippet(let_expr_pat.span)
+                                    && let Ok(init_snippet) =
+                                        tcx.sess.source_map().span_to_snippet(let_expr_init.span)
+                                {
+                                    err.span_suggestion_verbose(
+                                        let_expr_span,
+                                        "consider using the `matches!` macro",
+                                        format!("matches!({init_snippet}, {pat_snippet})"),
+                                        Applicability::MaybeIncorrect,
+                                    );
+                                } else {
+                                    err.note("consider using the `matches!` macro");
+                                }
+                            }
+                        } else if let LocalInfo::BlockTailTemp(info) = local_decl.local_info() {
                             if info.tail_result_is_ignored {
                                 // #85581: If the first mutable borrow's scope contains
                                 // the second borrow, this suggestion isn't helpful.
@@ -281,23 +372,6 @@ impl<'tcx> BorrowExplanation<'tcx> {
                                     Applicability::MaybeIncorrect,
                                 );
                             };
-                        } else if let &LocalInfo::IfThenRescopeTemp { if_then } =
-                            local_decl.local_info()
-                            && let hir::Node::Expr(expr) = tcx.hir_node(if_then)
-                            && let hir::ExprKind::If(cond, conseq, alt) = expr.kind
-                            && let hir::ExprKind::Let(&hir::LetExpr {
-                                span: _,
-                                pat,
-                                init,
-                                // FIXME(#101728): enable rewrite when type ascription is
-                                // stabilized again.
-                                ty: None,
-                                recovered: _,
-                            }) = cond.kind
-                            && pat.span.can_be_used_for_suggestions()
-                            && let Ok(pat) = tcx.sess.source_map().span_to_snippet(pat.span)
-                        {
-                            suggest_rewrite_if_let(tcx, expr, &pat, init, conseq, alt, err);
                         }
                     }
                 }

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -56,7 +56,7 @@ fn show_substructure(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) ->
 
     let (ident, vdata, fields) = match substr.fields {
         Struct(vdata, fields) => (substr.type_ident, *vdata, fields),
-        EnumMatching(_, v, fields) => (v.ident, &v.data, fields),
+        EnumMatching(v, fields) => (v.ident, &v.data, fields),
         AllFieldlessEnum(enum_def) => return show_fieldless_enum(cx, span, enum_def, substr),
         EnumDiscr(..) | StaticStruct(..) | StaticEnum(..) => {
             cx.dcx().span_bug(span, "nonsensical .fields in `#[derive(Debug)]`")