Auto merge of #98904 - matthiaskrgr:rollup-05owsx7, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #98738 (Clarify MIR semantics of checked binary operations)
 - #98782 (Improve spans for specialization error)
 - #98793 (Lint against executable files in the root directory)
 - #98814 (rustdoc: Censor certain complex unevaluated const exprs)
 - #98878 (add more `rustc_pass_by_value`)
 - #98879 (Fix "wrap closure in parenthesis" suggestion for `async` closure)
 - #98886 (incr.comp.: Make split-dwarf commandline options [TRACKED].)
 - #98898 (Add "no-div-regex" eslint rule)

Failed merges:

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

compiler/rustc_borrowck/src/constraint_generation.rs

@@ -149,7 +149,7 @@ impl<'cg, 'cx, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'cx, 'tcx> {
     fn visit_ascribe_user_ty(
         &mut self,
         _place: &Place<'tcx>,
-        _variance: &ty::Variance,
+        _variance: ty::Variance,
         _user_ty: &UserTypeProjection,
         _location: Location,
     ) {

compiler/rustc_middle/src/mir/syntax.rs

@@ -311,6 +311,7 @@ pub enum StatementKind<'tcx> {
 
 /// Describes what kind of retag is to be performed.
 #[derive(Copy, Clone, TyEncodable, TyDecodable, Debug, PartialEq, Eq, Hash, HashStable)]
+#[rustc_pass_by_value]
 pub enum RetagKind {
     /// The initial retag when entering a function.
     FnEntry,
@@ -990,11 +991,19 @@ pub enum Rvalue<'tcx> {
     ///   matching types and return a value of that type.
     BinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
 
-    /// Same as `BinaryOp`, but yields `(T, bool)` instead of `T`. In addition to performing the
-    /// same computation as the matching `BinaryOp`, checks if the infinite precison result would be
-    /// unequal to the actual result and sets the `bool` if this is the case.
+    /// Same as `BinaryOp`, but yields `(T, bool)` with a `bool` indicating an error condition.
     ///
-    /// This only supports addition, subtraction, multiplication, and shift operations on integers.
+    /// When overflow checking is disabled, the error condition is false. Otherwise, the error
+    /// condition is determined as described below.
+    ///
+    /// For addition, subtraction, and multiplication on integers the error condition is set when
+    /// the infinite precision result would be unequal to the actual result.
+    ///
+    /// For shift operations on integers the error condition is set when the value of right-hand
+    /// side is greater than or equal to the number of bits in the type of the left-hand side, or
+    /// when the value of right-hand side is negative.
+    ///
+    /// Other combinations of types and operators are unsupported.
     CheckedBinaryOp(BinOp, Box<(Operand<'tcx>, Operand<'tcx>)>),
 
     /// Computes a value as described by the operation.

compiler/rustc_middle/src/mir/visit.rs

@@ -147,7 +147,7 @@ macro_rules! make_mir_visitor {
             fn visit_ascribe_user_ty(
                 &mut self,
                 place: & $($mutability)? Place<'tcx>,
-                variance: & $($mutability)? ty::Variance,
+                variance: $(& $mutability)? ty::Variance,
                 user_ty: & $($mutability)? UserTypeProjection,
                 location: Location,
             ) {
@@ -164,7 +164,7 @@ macro_rules! make_mir_visitor {
 
             fn visit_retag(
                 &mut self,
-                kind: & $($mutability)? RetagKind,
+                kind: $(& $mutability)? RetagKind,
                 place: & $($mutability)? Place<'tcx>,
                 location: Location,
             ) {
@@ -425,7 +425,7 @@ macro_rules! make_mir_visitor {
                 self.visit_source_info(source_info);
                 match kind {
                     StatementKind::Assign(
-                        box(ref $($mutability)? place, ref $($mutability)? rvalue)
+                        box (place, rvalue)
                     ) => {
                         self.visit_assign(place, rvalue, location);
                     }
@@ -465,13 +465,13 @@ macro_rules! make_mir_visitor {
                         );
                     }
                     StatementKind::Retag(kind, place) => {
-                        self.visit_retag(kind, place, location);
+                        self.visit_retag($(& $mutability)? *kind, place, location);
                     }
                     StatementKind::AscribeUserType(
-                        box(ref $($mutability)? place, ref $($mutability)? user_ty),
+                        box (place, user_ty),
                         variance
                     ) => {
-                        self.visit_ascribe_user_ty(place, variance, user_ty, location);
+                        self.visit_ascribe_user_ty(place, $(& $mutability)? *variance, user_ty, location);
                     }
                     StatementKind::Coverage(coverage) => {
                         self.visit_coverage(
@@ -480,9 +480,9 @@ macro_rules! make_mir_visitor {
                         )
                     }
                     StatementKind::CopyNonOverlapping(box crate::mir::CopyNonOverlapping{
-                      ref $($mutability)? src,
-                      ref $($mutability)? dst,
-                      ref $($mutability)? count,
+                        src,
+                        dst,
+                        count,
                     }) => {
                       self.visit_operand(src, location);
                       self.visit_operand(dst, location);
@@ -517,8 +517,7 @@ macro_rules! make_mir_visitor {
                     TerminatorKind::GeneratorDrop |
                     TerminatorKind::Unreachable |
                     TerminatorKind::FalseEdge { .. } |
-                    TerminatorKind::FalseUnwind { .. } => {
-                    }
+                    TerminatorKind::FalseUnwind { .. } => {}
 
                     TerminatorKind::Return => {
                         // `return` logically moves from the return place `_0`. Note that the place
@@ -830,7 +829,7 @@ macro_rules! make_mir_visitor {
 
             fn super_ascribe_user_ty(&mut self,
                                      place: & $($mutability)? Place<'tcx>,
-                                     _variance: & $($mutability)? ty::Variance,
+                                     _variance: $(& $mutability)? ty::Variance,
                                      user_ty: & $($mutability)? UserTypeProjection,
                                      location: Location) {
                 self.visit_place(
@@ -847,7 +846,7 @@ macro_rules! make_mir_visitor {
             }
 
             fn super_retag(&mut self,
-                           _kind: & $($mutability)? RetagKind,
+                           _kind: $(& $mutability)? RetagKind,
                            place: & $($mutability)? Place<'tcx>,
                            location: Location) {
                 self.visit_place(

compiler/rustc_session/src/config.rs

@@ -2724,8 +2724,8 @@ pub(crate) mod dep_tracking {
     use super::{
         BranchProtection, CFGuard, CFProtection, CrateType, DebugInfo, ErrorOutputType,
         InstrumentCoverage, LdImpl, LinkerPluginLto, LocationDetail, LtoCli, OomStrategy, OptLevel,
-        OutputType, OutputTypes, Passes, SourceFileHashAlgorithm, SwitchWithOptPath,
-        SymbolManglingVersion, TrimmedDefPaths,
+        OutputType, OutputTypes, Passes, SourceFileHashAlgorithm, SplitDwarfKind,
+        SwitchWithOptPath, SymbolManglingVersion, TrimmedDefPaths,
     };
     use crate::lint;
     use crate::options::WasiExecModel;
@@ -2812,6 +2812,7 @@ pub(crate) mod dep_tracking {
         Edition,
         LinkerPluginLto,
         SplitDebuginfo,
+        SplitDwarfKind,
         StackProtector,
         SwitchWithOptPath,
         SymbolManglingVersion,

compiler/rustc_session/src/options.rs

@@ -1496,15 +1496,15 @@ options! {
         "control if mem::uninitialized and mem::zeroed panic on more UB"),
     strip: Strip = (Strip::None, parse_strip, [UNTRACKED],
         "tell the linker which information to strip (`none` (default), `debuginfo` or `symbols`)"),
-    split_dwarf_kind: SplitDwarfKind = (SplitDwarfKind::Split, parse_split_dwarf_kind, [UNTRACKED],
+    split_dwarf_kind: SplitDwarfKind = (SplitDwarfKind::Split, parse_split_dwarf_kind, [TRACKED],
         "split dwarf variant (only if -Csplit-debuginfo is enabled and on relevant platform)
         (default: `split`)
 
         `split`: sections which do not require relocation are written into a DWARF object (`.dwo`)
                  file which is ignored by the linker
         `single`: sections which do not require relocation are written into object file but ignored
                   by the linker"),
-    split_dwarf_inlining: bool = (true, parse_bool, [UNTRACKED],
+    split_dwarf_inlining: bool = (true, parse_bool, [TRACKED],
         "provide minimal debug info in the object/executable to facilitate online \
          symbolication/stack traces in the absence of .dwo/.dwp files when using Split DWARF"),
     symbol_mangling_version: Option<SymbolManglingVersion> = (None,

compiler/rustc_type_ir/src/lib.rs

@@ -599,6 +599,7 @@ impl UnifyKey for FloatVid {
 }
 
 #[derive(Copy, Clone, PartialEq, Decodable, Encodable, Hash)]
+#[rustc_pass_by_value]
 pub enum Variance {
     Covariant,     // T<A> <: T<B> iff A <: B -- e.g., function return type
     Invariant,     // T<A> <: T<B> iff B == A -- e.g., type of mutable cell

compiler/rustc_typeck/src/check/callee.rs

@@ -280,15 +280,36 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         callee_node: &hir::ExprKind<'_>,
         callee_span: Span,
     ) {
-        let hir_id = self.tcx.hir().get_parent_node(hir_id);
-        let parent_node = self.tcx.hir().get(hir_id);
+        let hir = self.tcx.hir();
+        let parent_hir_id = hir.get_parent_node(hir_id);
+        let parent_node = hir.get(parent_hir_id);
         if let (
             hir::Node::Expr(hir::Expr {
-                kind: hir::ExprKind::Closure { fn_decl_span, .. }, ..
+                kind: hir::ExprKind::Closure { fn_decl_span, body, .. },
+                ..
             }),
             hir::ExprKind::Block(..),
         ) = (parent_node, callee_node)
         {
+            let fn_decl_span = if hir.body(*body).generator_kind
+                == Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Closure))
+            {
+                // Actually need to unwrap a few more layers of HIR to get to
+                // the _real_ closure...
+                let async_closure = hir.get_parent_node(hir.get_parent_node(parent_hir_id));
+                if let hir::Node::Expr(hir::Expr {
+                    kind: hir::ExprKind::Closure { fn_decl_span, .. },
+                    ..
+                }) = hir.get(async_closure)
+                {
+                    *fn_decl_span
+                } else {
+                    return;
+                }
+            } else {
+                *fn_decl_span
+            };
+
             let start = fn_decl_span.shrink_to_lo();
             let end = callee_span.shrink_to_hi();
             err.multipart_suggestion(

compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs

@@ -279,11 +279,16 @@ fn check_predicates<'tcx>(
     span: Span,
 ) {
     let tcx = infcx.tcx;
-    let impl1_predicates: Vec<_> = traits::elaborate_predicates(
+    let instantiated = tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs);
+    let impl1_predicates: Vec<_> = traits::elaborate_predicates_with_span(
         tcx,
-        tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs).predicates.into_iter(),
+        std::iter::zip(
+            instantiated.predicates,
+            // Don't drop predicates (unsound!) because `spans` is too short
+            instantiated.spans.into_iter().chain(std::iter::repeat(span)),
+        ),
     )
-    .map(|obligation| obligation.predicate)
+    .map(|obligation| (obligation.predicate, obligation.cause.span))
     .collect();
 
     let mut impl2_predicates = if impl2_node.is_from_trait() {
@@ -321,7 +326,7 @@ fn check_predicates<'tcx>(
     // which is sound because we forbid impls like the following
     //
     // impl<D: Debug> AlwaysApplicable for D { }
-    let always_applicable_traits = impl1_predicates.iter().copied().filter(|&predicate| {
+    let always_applicable_traits = impl1_predicates.iter().copied().filter(|&(predicate, _)| {
         matches!(
             trait_predicate_kind(tcx, predicate),
             Some(TraitSpecializationKind::AlwaysApplicable)
@@ -345,11 +350,11 @@ fn check_predicates<'tcx>(
         }
     }
     impl2_predicates.extend(
-        traits::elaborate_predicates(tcx, always_applicable_traits)
+        traits::elaborate_predicates_with_span(tcx, always_applicable_traits)
             .map(|obligation| obligation.predicate),
     );
 
-    for predicate in impl1_predicates {
+    for (predicate, span) in impl1_predicates {
         if !impl2_predicates.contains(&predicate) {
             check_specialization_on(tcx, predicate, span)
         }
@@ -384,9 +389,17 @@ fn check_specialization_on<'tcx>(tcx: TyCtxt<'tcx>, predicate: ty::Predicate<'tc
                     .emit();
             }
         }
+        ty::PredicateKind::Projection(ty::ProjectionPredicate { projection_ty, term }) => {
+            tcx.sess
+                .struct_span_err(
+                    span,
+                    &format!("cannot specialize on associated type `{projection_ty} == {term}`",),
+                )
+                .emit();
+        }
         _ => {
             tcx.sess
-                .struct_span_err(span, &format!("cannot specialize on `{:?}`", predicate))
+                .struct_span_err(span, &format!("cannot specialize on predicate `{}`", predicate))
                 .emit();
         }
     }

src/librustdoc/clean/utils.rs

@@ -340,17 +340,98 @@ pub(crate) fn is_literal_expr(tcx: TyCtxt<'_>, hir_id: hir::HirId) -> bool {
     false
 }
 
+/// Build a textual representation of an unevaluated constant expression.
+///
+/// If the const expression is too complex, an underscore `_` is returned.
+/// For const arguments, it's `{ _ }` to be precise.
+/// This means that the output is not necessarily valid Rust code.
+///
+/// Currently, only
+///
+/// * literals (optionally with a leading `-`)
+/// * unit `()`
+/// * blocks (`{ … }`) around simple expressions and
+/// * paths without arguments
+///
+/// are considered simple enough. Simple blocks are included since they are
+/// necessary to disambiguate unit from the unit type.
+/// This list might get extended in the future.
+///
+/// Without this censoring, in a lot of cases the output would get too large
+/// and verbose. Consider `match` expressions, blocks and deeply nested ADTs.
+/// Further, private and `doc(hidden)` fields of structs would get leaked
+/// since HIR datatypes like the `body` parameter do not contain enough
+/// semantic information for this function to be able to hide them –
+/// at least not without significant performance overhead.
+///
+/// Whenever possible, prefer to evaluate the constant first and try to
+/// use a different method for pretty-printing. Ideally this function
+/// should only ever be used as a fallback.
 pub(crate) fn print_const_expr(tcx: TyCtxt<'_>, body: hir::BodyId) -> String {
     let hir = tcx.hir();
     let value = &hir.body(body).value;
 
-    let snippet = if !value.span.from_expansion() {
-        tcx.sess.source_map().span_to_snippet(value.span).ok()
-    } else {
-        None
-    };
+    #[derive(PartialEq, Eq)]
+    enum Classification {
+        Literal,
+        Simple,
+        Complex,
+    }
 
-    snippet.unwrap_or_else(|| rustc_hir_pretty::id_to_string(&hir, body.hir_id))
+    use Classification::*;
+
+    fn classify(expr: &hir::Expr<'_>) -> Classification {
+        match &expr.kind {
+            hir::ExprKind::Unary(hir::UnOp::Neg, expr) => {
+                if matches!(expr.kind, hir::ExprKind::Lit(_)) { Literal } else { Complex }
+            }
+            hir::ExprKind::Lit(_) => Literal,
+            hir::ExprKind::Tup([]) => Simple,
+            hir::ExprKind::Block(hir::Block { stmts: [], expr: Some(expr), .. }, _) => {
+                if classify(expr) == Complex { Complex } else { Simple }
+            }
+            // Paths with a self-type or arguments are too “complex” following our measure since
+            // they may leak private fields of structs (with feature `adt_const_params`).
+            // Consider: `<Self as Trait<{ Struct { private: () } }>>::CONSTANT`.
+            // Paths without arguments are definitely harmless though.
+            hir::ExprKind::Path(hir::QPath::Resolved(_, hir::Path { segments, .. })) => {
+                if segments.iter().all(|segment| segment.args.is_none()) { Simple } else { Complex }
+            }
+            // FIXME: Claiming that those kinds of QPaths are simple is probably not true if the Ty
+            //        contains const arguments. Is there a *concise* way to check for this?
+            hir::ExprKind::Path(hir::QPath::TypeRelative(..)) => Simple,
+            // FIXME: Can they contain const arguments and thus leak private struct fields?
+            hir::ExprKind::Path(hir::QPath::LangItem(..)) => Simple,
+            _ => Complex,
+        }
+    }
+
+    let classification = classify(value);
+
+    if classification == Literal
+    && !value.span.from_expansion()
+    && let Ok(snippet) = tcx.sess.source_map().span_to_snippet(value.span) {
+        // For literals, we avoid invoking the pretty-printer and use the source snippet instead to
+        // preserve certain stylistic choices the user likely made for the sake legibility like
+        //
+        // * hexadecimal notation
+        // * underscores
+        // * character escapes
+        //
+        // FIXME: This passes through `-/*spacer*/0` verbatim.
+        snippet
+    } else if classification == Simple {
+        // Otherwise we prefer pretty-printing to get rid of extraneous whitespace, comments and
+        // other formatting artifacts.
+        rustc_hir_pretty::id_to_string(&hir, body.hir_id)
+    } else if tcx.def_kind(hir.body_owner_def_id(body).to_def_id()) == DefKind::AnonConst {
+        // FIXME: Omit the curly braces if the enclosing expression is an array literal
+        //        with a repeated element (an `ExprKind::Repeat`) as in such case it
+        //        would not actually need any disambiguation.
+        "{ _ }".to_owned()
+    } else {
+        "_".to_owned()
+    }
 }
 
 /// Given a type Path, resolve it to a Type using the TyCtxt

src/librustdoc/html/render/mod.rs

@@ -716,12 +716,14 @@ fn assoc_const(
         ty = ty.print(cx),
     );
     if let Some(default) = default {
+        write!(w, " = ");
+
         // FIXME: `.value()` uses `clean::utils::format_integer_with_underscore_sep` under the
         //        hood which adds noisy underscores and a type suffix to number literals.
         //        This hurts readability in this context especially when more complex expressions
         //        are involved and it doesn't add much of value.
         //        Find a way to print constants here without all that jazz.
-        write!(w, " = {}", default.value(cx.tcx()).unwrap_or_else(|| default.expr(cx.tcx())));
+        write!(w, "{}", Escape(&default.value(cx.tcx()).unwrap_or_else(|| default.expr(cx.tcx()))));
     }
 }