Rollup of 10 pull requests

Cargo.lock

@@ -5295,7 +5295,6 @@ name = "tidy"
 version = "0.1.0"
 dependencies = [
  "cargo_metadata 0.14.0",
- "crossbeam-utils",
  "lazy_static",
  "regex",
  "walkdir",

compiler/rustc_ast/src/token.rs

@@ -436,6 +436,30 @@ impl Token {
             || self == &OpenDelim(Delimiter::Parenthesis)
     }
 
+    /// Returns `true` if the token can appear at the start of an item.
+    pub fn can_begin_item(&self) -> bool {
+        match self.kind {
+            Ident(name, _) => [
+                kw::Fn,
+                kw::Use,
+                kw::Struct,
+                kw::Enum,
+                kw::Pub,
+                kw::Trait,
+                kw::Extern,
+                kw::Impl,
+                kw::Unsafe,
+                kw::Static,
+                kw::Union,
+                kw::Macro,
+                kw::Mod,
+                kw::Type,
+            ]
+            .contains(&name),
+            _ => false,
+        }
+    }
+
     /// Returns `true` if the token is any literal.
     pub fn is_lit(&self) -> bool {
         matches!(self.kind, Literal(..))

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -798,58 +798,55 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             let mut op = self.codegen_operand(&mut bx, arg);
 
             if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
-                if let Pair(..) = op.val {
-                    // In the case of Rc<Self>, we need to explicitly pass a
-                    // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
-                    // that is understood elsewhere in the compiler as a method on
-                    // `dyn Trait`.
-                    // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
-                    // we get a value of a built-in pointer type
-                    'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
-                        && !op.layout.ty.is_region_ptr()
-                    {
-                        for i in 0..op.layout.fields.count() {
-                            let field = op.extract_field(&mut bx, i);
-                            if !field.layout.is_zst() {
-                                // we found the one non-zero-sized field that is allowed
-                                // now find *its* non-zero-sized field, or stop if it's a
-                                // pointer
-                                op = field;
-                                continue 'descend_newtypes;
+                match op.val {
+                    Pair(data_ptr, meta) => {
+                        // In the case of Rc<Self>, we need to explicitly pass a
+                        // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
+                        // that is understood elsewhere in the compiler as a method on
+                        // `dyn Trait`.
+                        // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
+                        // we get a value of a built-in pointer type
+                        'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
+                            && !op.layout.ty.is_region_ptr()
+                        {
+                            for i in 0..op.layout.fields.count() {
+                                let field = op.extract_field(&mut bx, i);
+                                if !field.layout.is_zst() {
+                                    // we found the one non-zero-sized field that is allowed
+                                    // now find *its* non-zero-sized field, or stop if it's a
+                                    // pointer
+                                    op = field;
+                                    continue 'descend_newtypes;
+                                }
                             }
+
+                            span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
                         }
 
-                        span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
+                        // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
+                        // data pointer and vtable. Look up the method in the vtable, and pass
+                        // the data pointer as the first argument
+                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
+                            &mut bx,
+                            meta,
+                            op.layout.ty,
+                            &fn_abi,
+                        ));
+                        llargs.push(data_ptr);
+                        continue 'make_args;
                     }
-
-                    // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
-                    // data pointer and vtable. Look up the method in the vtable, and pass
-                    // the data pointer as the first argument
-                    match op.val {
-                        Pair(data_ptr, meta) => {
-                            llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
-                                &mut bx,
-                                meta,
-                                op.layout.ty,
-                                &fn_abi,
-                            ));
-                            llargs.push(data_ptr);
-                            continue 'make_args;
-                        }
-                        other => bug!("expected a Pair, got {:?}", other),
+                    Ref(data_ptr, Some(meta), _) => {
+                        // by-value dynamic dispatch
+                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
+                            &mut bx,
+                            meta,
+                            op.layout.ty,
+                            &fn_abi,
+                        ));
+                        llargs.push(data_ptr);
+                        continue;
                     }
-                } else if let Ref(data_ptr, Some(meta), _) = op.val {
-                    // by-value dynamic dispatch
-                    llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
-                        &mut bx,
-                        meta,
-                        op.layout.ty,
-                        &fn_abi,
-                    ));
-                    llargs.push(data_ptr);
-                    continue;
-                } else {
-                    span_bug!(span, "can't codegen a virtual call on {:?}", op);
+                    _ => span_bug!(span, "can't codegen a virtual call on {:?}", op),
                 }
             }
 

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -81,7 +81,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
 }
 
 /// The `InterpCx` is only meant to be used to do field and index projections into constants for
-/// `simd_shuffle` and const patterns in match arms.
+/// `simd_shuffle` and const patterns in match arms. It never performs alignment checks.
 ///
 /// The function containing the `match` that is currently being analyzed may have generic bounds
 /// that inform us about the generic bounds of the constant. E.g., using an associated constant
@@ -98,7 +98,11 @@ pub(super) fn mk_eval_cx<'mir, 'tcx>(
         tcx,
         root_span,
         param_env,
-        CompileTimeInterpreter::new(tcx.const_eval_limit(), can_access_statics),
+        CompileTimeInterpreter::new(
+            tcx.const_eval_limit(),
+            can_access_statics,
+            /*check_alignment:*/ false,
+        ),
     )
 }
 
@@ -203,7 +207,13 @@ pub(crate) fn turn_into_const_value<'tcx>(
     let cid = key.value;
     let def_id = cid.instance.def.def_id();
     let is_static = tcx.is_static(def_id);
-    let ecx = mk_eval_cx(tcx, tcx.def_span(key.value.instance.def_id()), key.param_env, is_static);
+    // This is just accessing an already computed constant, so no need to check alginment here.
+    let ecx = mk_eval_cx(
+        tcx,
+        tcx.def_span(key.value.instance.def_id()),
+        key.param_env,
+        /*can_access_statics:*/ is_static,
+    );
 
     let mplace = ecx.raw_const_to_mplace(constant).expect(
         "can only fail if layout computation failed, \
@@ -300,7 +310,11 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
         key.param_env,
         // Statics (and promoteds inside statics) may access other statics, because unlike consts
         // they do not have to behave "as if" they were evaluated at runtime.
-        CompileTimeInterpreter::new(tcx.const_eval_limit(), /*can_access_statics:*/ is_static),
+        CompileTimeInterpreter::new(
+            tcx.const_eval_limit(),
+            /*can_access_statics:*/ is_static,
+            /*check_alignment:*/ tcx.sess.opts.unstable_opts.extra_const_ub_checks,
+        ),
     );
 
     let res = ecx.load_mir(cid.instance.def, cid.promoted);

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -101,14 +101,22 @@ pub struct CompileTimeInterpreter<'mir, 'tcx> {
     /// * Pointers to allocations inside of statics can never leak outside, to a non-static global.
     /// This boolean here controls the second part.
     pub(super) can_access_statics: bool,
+
+    /// Whether to check alignment during evaluation.
+    check_alignment: bool,
 }
 
 impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> {
-    pub(crate) fn new(const_eval_limit: Limit, can_access_statics: bool) -> Self {
+    pub(crate) fn new(
+        const_eval_limit: Limit,
+        can_access_statics: bool,
+        check_alignment: bool,
+    ) -> Self {
         CompileTimeInterpreter {
             steps_remaining: const_eval_limit.0,
             stack: Vec::new(),
             can_access_statics,
+            check_alignment,
         }
     }
 }
@@ -238,7 +246,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
 
     #[inline(always)]
     fn enforce_alignment(ecx: &InterpCx<'mir, 'tcx, Self>) -> bool {
-        ecx.tcx.sess.opts.unstable_opts.extra_const_ub_checks
+        ecx.machine.check_alignment
     }
 
     #[inline(always)]

compiler/rustc_const_eval/src/might_permit_raw_init.rs

@@ -13,7 +13,11 @@ pub fn might_permit_raw_init<'tcx>(
     let strict = tcx.sess.opts.unstable_opts.strict_init_checks;
 
     if strict {
-        let machine = CompileTimeInterpreter::new(Limit::new(0), false);
+        let machine = CompileTimeInterpreter::new(
+            Limit::new(0),
+            /*can_access_statics:*/ false,
+            /*check_alignment:*/ true,
+        );
 
         let mut cx = InterpCx::new(tcx, rustc_span::DUMMY_SP, ParamEnv::reveal_all(), machine);
 

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1588,9 +1588,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             Mismatch::Variable(infer::ExpectedFound { expected, found }),
                         )
                     }
+                    ValuePairs::Terms(infer::ExpectedFound {
+                        expected: ty::Term::Const(_),
+                        found: ty::Term::Const(_),
+                    }) => (false, Mismatch::Fixed("constant")),
                     ValuePairs::TraitRefs(_) | ValuePairs::PolyTraitRefs(_) => {
                         (false, Mismatch::Fixed("trait"))
                     }
+                    ValuePairs::Regions(_) => (false, Mismatch::Fixed("lifetime")),
                     _ => (false, Mismatch::Fixed("type")),
                 };
                 let vals = match self.values_str(values) {

compiler/rustc_middle/src/traits/mod.rs

@@ -469,6 +469,13 @@ impl<'tcx> ObligationCauseCode<'tcx> {
             _ => None,
         }
     }
+
+    pub fn peel_match_impls(&self) -> &Self {
+        match self {
+            MatchImpl(cause, _) => cause.code(),
+            _ => self,
+        }
+    }
 }
 
 // `ObligationCauseCode` is used a lot. Make sure it doesn't unintentionally get bigger.

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -927,10 +927,12 @@ impl<'a> Parser<'a> {
                 return Ok(true);
             } else if self.look_ahead(0, |t| {
                 t == &token::CloseDelim(Delimiter::Brace)
-                    || (t.can_begin_expr() && t != &token::Semi && t != &token::Pound)
+                    || ((t.can_begin_expr() || t.can_begin_item())
+                        && t != &token::Semi
+                        && t != &token::Pound)
                     // Avoid triggering with too many trailing `#` in raw string.
                     || (sm.is_multiline(
-                        self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo())
+                        self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
                     ) && t == &token::Pound)
             }) && !expected.contains(&TokenType::Token(token::Comma))
             {

compiler/rustc_target/src/spec/mod.rs

@@ -1028,6 +1028,7 @@ supported_targets! {
     ("mipsel-sony-psp", mipsel_sony_psp),
     ("mipsel-unknown-none", mipsel_unknown_none),
     ("thumbv4t-none-eabi", thumbv4t_none_eabi),
+    ("armv4t-none-eabi", armv4t_none_eabi),
 
     ("aarch64_be-unknown-linux-gnu", aarch64_be_unknown_linux_gnu),
     ("aarch64-unknown-linux-gnu_ilp32", aarch64_unknown_linux_gnu_ilp32),

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -342,10 +342,8 @@ fn equate<'cx, 'tcx>(
     };
 
     let selcx = &mut SelectionContext::new(&infcx);
-    let opt_failing_obligation = obligations
-        .into_iter()
-        .chain(more_obligations)
-        .find(|o| negative_impl_exists(selcx, impl_env, o));
+    let opt_failing_obligation =
+        obligations.into_iter().chain(more_obligations).find(|o| negative_impl_exists(selcx, o));
 
     if let Some(failing_obligation) = opt_failing_obligation {
         debug!("overlap: obligation unsatisfiable {:?}", failing_obligation);
@@ -359,18 +357,15 @@ fn equate<'cx, 'tcx>(
 #[instrument(level = "debug", skip(selcx))]
 fn negative_impl_exists<'cx, 'tcx>(
     selcx: &SelectionContext<'cx, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
     o: &PredicateObligation<'tcx>,
 ) -> bool {
-    let infcx = &selcx.infcx().fork();
-
-    if resolve_negative_obligation(infcx, param_env, o) {
+    if resolve_negative_obligation(selcx.infcx().fork(), o) {
         return true;
     }
 
     // Try to prove a negative obligation exists for super predicates
-    for o in util::elaborate_predicates(infcx.tcx, iter::once(o.predicate)) {
-        if resolve_negative_obligation(infcx, param_env, &o) {
+    for o in util::elaborate_predicates(selcx.tcx(), iter::once(o.predicate)) {
+        if resolve_negative_obligation(selcx.infcx().fork(), &o) {
             return true;
         }
     }
@@ -380,8 +375,7 @@ fn negative_impl_exists<'cx, 'tcx>(
 
 #[instrument(level = "debug", skip(infcx))]
 fn resolve_negative_obligation<'cx, 'tcx>(
-    infcx: &InferCtxt<'cx, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
+    infcx: InferCtxt<'cx, 'tcx>,
     o: &PredicateObligation<'tcx>,
 ) -> bool {
     let tcx = infcx.tcx;
@@ -390,7 +384,8 @@ fn resolve_negative_obligation<'cx, 'tcx>(
         return false;
     };
 
-    let errors = super::fully_solve_obligation(infcx, o);
+    let param_env = o.param_env;
+    let errors = super::fully_solve_obligation(&infcx, o);
     if !errors.is_empty() {
         return false;
     }

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

@@ -1506,13 +1506,26 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
                 .emit();
             }
             FulfillmentErrorCode::CodeConstEquateError(ref expected_found, ref err) => {
-                self.report_mismatched_consts(
+                let mut diag = self.report_mismatched_consts(
                     &error.obligation.cause,
                     expected_found.expected,
                     expected_found.found,
                     err.clone(),
-                )
-                .emit();
+                );
+                let code = error.obligation.cause.code().peel_derives().peel_match_impls();
+                if let ObligationCauseCode::BindingObligation(..)
+                | ObligationCauseCode::ItemObligation(..) = code
+                {
+                    self.note_obligation_cause_code(
+                        &mut diag,
+                        &error.obligation.predicate,
+                        error.obligation.param_env,
+                        code,
+                        &mut vec![],
+                        &mut Default::default(),
+                    );
+                }
+                diag.emit();
             }
         }
     }

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -387,7 +387,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRe
                             tcx,
                             param_env,
                             item_hir_id,
-                            sig.output(),
+                            sig.inputs_and_output,
                             // We also assume that all of the function signature's parameter types
                             // are well formed.
                             &sig.inputs().iter().copied().collect(),

library/core/src/mem/maybe_uninit.rs

@@ -130,11 +130,8 @@ use crate::slice;
 ///         MaybeUninit::uninit().assume_init()
 ///     };
 ///
-///     // Dropping a `MaybeUninit` does nothing. Thus using raw pointer
-///     // assignment instead of `ptr::write` does not cause the old
-///     // uninitialized value to be dropped. Also if there is a panic during
-///     // this loop, we have a memory leak, but there is no memory safety
-///     // issue.
+///     // Dropping a `MaybeUninit` does nothing, so if there is a panic during this loop,
+///     // we have a memory leak, but there is no memory safety issue.
 ///     for elem in &mut data[..] {
 ///         elem.write(vec![42]);
 ///     }