Auto merge of #94061 - matthiaskrgr:rollup-oduekp5, r=matthiaskrgr

Rollup of 10 pull requests

Successful merges:

 - #92366 (Resolve concern of `derive_default_enum`)
 - #93382 (Add a bit more padding in search box)
 - #93962 (Make [u8]::cmp implementation branchless)
 - #94015 (rustdoc --check option documentation)
 - #94017 (Clarify confusing UB statement in MIR)
 - #94020 (Support pretty printing of invalid constants)
 - #94027 (Update browser UI test version)
 - #94037 (Fix inconsistent symbol mangling with -Zverbose)
 - #94045 (Update books)
 - #94054 (:arrow_up: rust-analyzer)

Failed merges:

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

Author: bors

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -222,9 +222,6 @@ fn validate_default_attribute(
             "this method must only be called with a variant that has a `#[default]` attribute",
         ),
         [first, rest @ ..] => {
-            // FIXME(jhpratt) Do we want to perform this check? It doesn't exist
-            // for `#[inline]`, `#[non_exhaustive]`, and presumably others.
-
             let suggestion_text =
                 if rest.len() == 1 { "try removing this" } else { "try removing these" };
 

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -11,7 +11,8 @@ use rustc_middle::{
 use rustc_span::{source_map::DUMMY_SP, symbol::Symbol};
 
 use crate::interpret::{
-    intern_const_alloc_recursive, ConstValue, InternKind, InterpCx, MPlaceTy, MemPlaceMeta, Scalar,
+    intern_const_alloc_recursive, ConstValue, InternKind, InterpCx, InterpResult, MPlaceTy,
+    MemPlaceMeta, Scalar,
 };
 
 mod error;
@@ -132,42 +133,39 @@ fn const_to_valtree_inner<'tcx>(
     }
 }
 
-/// This function uses `unwrap` copiously, because an already validated constant
-/// must have valid fields and can thus never fail outside of compiler bugs. However, it is
-/// invoked from the pretty printer, where it can receive enums with no variants and e.g.
-/// `read_discriminant` needs to be able to handle that.
-pub(crate) fn destructure_const<'tcx>(
+/// This function should never fail for validated constants. However, it is also invoked from the
+/// pretty printer which might attempt to format invalid constants and in that case it might fail.
+pub(crate) fn try_destructure_const<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     val: ty::Const<'tcx>,
-) -> mir::DestructuredConst<'tcx> {
+) -> InterpResult<'tcx, mir::DestructuredConst<'tcx>> {
     trace!("destructure_const: {:?}", val);
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
-    let op = ecx.const_to_op(val, None).unwrap();
+    let op = ecx.const_to_op(val, None)?;
 
     // We go to `usize` as we cannot allocate anything bigger anyway.
     let (field_count, variant, down) = match val.ty().kind() {
         ty::Array(_, len) => (usize::try_from(len.eval_usize(tcx, param_env)).unwrap(), None, op),
-        ty::Adt(def, _) if def.variants.is_empty() => {
-            return mir::DestructuredConst { variant: None, fields: &[] };
-        }
         ty::Adt(def, _) => {
-            let variant = ecx.read_discriminant(&op).unwrap().1;
-            let down = ecx.operand_downcast(&op, variant).unwrap();
+            let variant = ecx.read_discriminant(&op)?.1;
+            let down = ecx.operand_downcast(&op, variant)?;
             (def.variants[variant].fields.len(), Some(variant), down)
         }
         ty::Tuple(substs) => (substs.len(), None, op),
         _ => bug!("cannot destructure constant {:?}", val),
     };
 
-    let fields_iter = (0..field_count).map(|i| {
-        let field_op = ecx.operand_field(&down, i).unwrap();
-        let val = op_to_const(&ecx, &field_op);
-        ty::Const::from_value(tcx, val, field_op.layout.ty)
-    });
-    let fields = tcx.arena.alloc_from_iter(fields_iter);
+    let fields = (0..field_count)
+        .map(|i| {
+            let field_op = ecx.operand_field(&down, i)?;
+            let val = op_to_const(&ecx, &field_op);
+            Ok(ty::Const::from_value(tcx, val, field_op.layout.ty))
+        })
+        .collect::<InterpResult<'tcx, Vec<_>>>()?;
+    let fields = tcx.arena.alloc_from_iter(fields);
 
-    mir::DestructuredConst { variant, fields }
+    Ok(mir::DestructuredConst { variant, fields })
 }
 
 pub(crate) fn deref_const<'tcx>(

compiler/rustc_const_eval/src/lib.rs

@@ -41,9 +41,9 @@ pub fn provide(providers: &mut Providers) {
     providers.eval_to_const_value_raw = const_eval::eval_to_const_value_raw_provider;
     providers.eval_to_allocation_raw = const_eval::eval_to_allocation_raw_provider;
     providers.const_caller_location = const_eval::const_caller_location;
-    providers.destructure_const = |tcx, param_env_and_value| {
+    providers.try_destructure_const = |tcx, param_env_and_value| {
         let (param_env, value) = param_env_and_value.into_parts();
-        const_eval::destructure_const(tcx, param_env, value)
+        const_eval::try_destructure_const(tcx, param_env, value).ok()
     };
     providers.const_to_valtree = |tcx, param_env_and_value| {
         let (param_env, raw) = param_env_and_value.into_parts();

compiler/rustc_middle/src/mir/interpret/queries.rs

@@ -98,4 +98,12 @@ impl<'tcx> TyCtxt<'tcx> {
         let raw_const = self.eval_to_allocation_raw(param_env.and(gid))?;
         Ok(self.global_alloc(raw_const.alloc_id).unwrap_memory())
     }
+
+    /// Destructure a constant ADT or array into its variant index and its field values.
+    pub fn destructure_const(
+        self,
+        param_env_and_val: ty::ParamEnvAnd<'tcx, ty::Const<'tcx>>,
+    ) -> mir::DestructuredConst<'tcx> {
+        self.try_destructure_const(param_env_and_val).unwrap()
+    }
 }

compiler/rustc_middle/src/mir/mod.rs

@@ -2270,11 +2270,13 @@ pub enum BinOp {
     Mul,
     /// The `/` operator (division)
     ///
-    /// Division by zero is UB.
+    /// Division by zero is UB, because the compiler should have inserted checks
+    /// prior to this.
     Div,
     /// The `%` operator (modulus)
     ///
-    /// Using zero as the modulus (second operand) is UB.
+    /// Using zero as the modulus (second operand) is UB, because the compiler
+    /// should have inserted checks prior to this.
     Rem,
     /// The `^` operator (bitwise xor)
     BitXor,

compiler/rustc_middle/src/query/mod.rs

@@ -924,10 +924,12 @@ rustc_queries! {
     }
 
     /// Destructure a constant ADT or array into its variant index and its
-    /// field values.
-    query destructure_const(
+    /// field values or return `None` if constant is invalid.
+    ///
+    /// Use infallible `TyCtxt::destructure_const` when you know that constant is valid.
+    query try_destructure_const(
         key: ty::ParamEnvAnd<'tcx, ty::Const<'tcx>>
-    ) -> mir::DestructuredConst<'tcx> {
+    ) -> Option<mir::DestructuredConst<'tcx>> {
         desc { "destructure constant" }
         remap_env_constness
     }

compiler/rustc_middle/src/ty/print/mod.rs

@@ -188,11 +188,6 @@ pub trait Printer<'tcx>: Sized {
             own_params.start = 1;
         }
 
-        // If we're in verbose mode, then print default-equal args too
-        if self.tcx().sess.verbose() {
-            return &substs[own_params];
-        }
-
         // Don't print args that are the defaults of their respective parameters.
         own_params.end -= generics
             .params

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1459,10 +1459,18 @@ pub trait PrettyPrinter<'tcx>:
             // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
             // correct `ty::ParamEnv` to allow printing *all* constant values.
             (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_param_types_or_consts() => {
-                let contents =
-                    self.tcx().destructure_const(ty::ParamEnv::reveal_all().and(
-                        self.tcx().mk_const(ty::ConstS { val: ty::ConstKind::Value(ct), ty }),
-                    ));
+                let Some(contents) = self.tcx().try_destructure_const(
+                    ty::ParamEnv::reveal_all()
+                        .and(self.tcx().mk_const(ty::ConstS { val: ty::ConstKind::Value(ct), ty })),
+                ) else {
+                    // Fall back to debug pretty printing for invalid constants.
+                    p!(write("{:?}", ct));
+                    if print_ty {
+                        p!(": ", print(ty));
+                    }
+                    return Ok(self);
+                };
+
                 let fields = contents.fields.iter().copied();
 
                 match *ty.kind() {

library/core/src/slice/cmp.rs

@@ -1,7 +1,6 @@
 //! Comparison traits for `[T]`.
 
-use crate::cmp;
-use crate::cmp::Ordering::{self, Greater, Less};
+use crate::cmp::{self, Ordering};
 use crate::mem;
 
 use super::from_raw_parts;
@@ -189,18 +188,18 @@ impl<A: Ord> SliceOrd for A {
 impl SliceOrd for u8 {
     #[inline]
     fn compare(left: &[Self], right: &[Self]) -> Ordering {
-        let order =
-            // SAFETY: `left` and `right` are references and are thus guaranteed to be valid.
-            // We use the minimum of both lengths which guarantees that both regions are
-            // valid for reads in that interval.
-            unsafe { memcmp(left.as_ptr(), right.as_ptr(), cmp::min(left.len(), right.len())) };
+        // Since the length of a slice is always less than or equal to isize::MAX, this never underflows.
+        let diff = left.len() as isize - right.len() as isize;
+        // This comparison gets optimized away (on x86_64 and ARM) because the subtraction updates flags.
+        let len = if left.len() < right.len() { left.len() } else { right.len() };
+        // SAFETY: `left` and `right` are references and are thus guaranteed to be valid.
+        // We use the minimum of both lengths which guarantees that both regions are
+        // valid for reads in that interval.
+        let mut order = unsafe { memcmp(left.as_ptr(), right.as_ptr(), len) as isize };
         if order == 0 {
-            left.len().cmp(&right.len())
-        } else if order < 0 {
-            Less
-        } else {
-            Greater
+            order = diff;
         }
+        order.cmp(&0)
     }
 }
 

src/ci/docker/host-x86_64/x86_64-gnu-tools/Dockerfile

@@ -72,7 +72,7 @@ ENV PATH="/node-v14.4.0-linux-x64/bin:${PATH}"
 # https://github.com/puppeteer/puppeteer/issues/375
 #
 # We also specify the version in case we need to update it to go around cache limitations.
-RUN npm install -g browser-ui-test@0.7.1 --unsafe-perm=true
+RUN npm install -g browser-ui-test@0.7.2 --unsafe-perm=true
 
 ENV RUST_CONFIGURE_ARGS \
   --build=x86_64-unknown-linux-gnu \