Rollup of 9 pull requests

Cargo.lock

@@ -221,7 +221,6 @@ dependencies = [
  "getopts",
  "ignore",
  "libc",
- "num_cpus",
  "once_cell",
  "opener",
  "pretty_assertions",
@@ -249,7 +248,6 @@ dependencies = [
  "anyhow",
  "flate2",
  "hex 0.4.2",
- "num_cpus",
  "rayon",
  "serde",
  "serde_json",
@@ -4241,7 +4239,6 @@ name = "rustc_session"
 version = "0.0.0"
 dependencies = [
  "getopts",
- "num_cpus",
  "rustc_ast",
  "rustc_data_structures",
  "rustc_errors",

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -5,16 +5,21 @@ use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind};
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::traits::ObligationCause;
 use rustc_middle::mir::{
     self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory,
     FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef,
     ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm,
 };
-use rustc_middle::ty::{self, suggest_constraining_type_param, Ty};
+use rustc_middle::ty::{
+    self, suggest_constraining_type_param, suggest_constraining_type_params, PredicateKind, Ty,
+};
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::symbol::sym;
 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
 use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::TraitEngineExt as _;
 
 use crate::borrow_set::TwoPhaseActivation;
 use crate::borrowck_errors;
@@ -423,7 +428,63 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                             None,
                         );
                     }
+                } else {
+                    // Try to find predicates on *generic params* that would allow copying `ty`
+
+                    let tcx = self.infcx.tcx;
+                    let generics = tcx.generics_of(self.mir_def_id());
+                    if let Some(hir_generics) = tcx
+                        .typeck_root_def_id(self.mir_def_id().to_def_id())
+                        .as_local()
+                        .and_then(|def_id| tcx.hir().get_generics(def_id))
+                    {
+                        let predicates: Result<Vec<_>, _> = tcx.infer_ctxt().enter(|infcx| {
+                            let mut fulfill_cx =
+                                <dyn rustc_infer::traits::TraitEngine<'_>>::new(infcx.tcx);
+
+                            let copy_did = infcx.tcx.lang_items().copy_trait().unwrap();
+                            let cause = ObligationCause::new(
+                                span,
+                                self.mir_hir_id(),
+                                rustc_infer::traits::ObligationCauseCode::MiscObligation,
+                            );
+                            fulfill_cx.register_bound(&infcx, self.param_env, ty, copy_did, cause);
+                            let errors = fulfill_cx.select_where_possible(&infcx);
+
+                            // Only emit suggestion if all required predicates are on generic
+                            errors
+                                .into_iter()
+                                .map(|err| match err.obligation.predicate.kind().skip_binder() {
+                                    PredicateKind::Trait(predicate) => {
+                                        match predicate.self_ty().kind() {
+                                            ty::Param(param_ty) => Ok((
+                                                generics.type_param(param_ty, tcx),
+                                                predicate
+                                                    .trait_ref
+                                                    .print_only_trait_path()
+                                                    .to_string(),
+                                            )),
+                                            _ => Err(()),
+                                        }
+                                    }
+                                    _ => Err(()),
+                                })
+                                .collect()
+                        });
+
+                        if let Ok(predicates) = predicates {
+                            suggest_constraining_type_params(
+                                tcx,
+                                hir_generics,
+                                &mut err,
+                                predicates.iter().map(|(param, constraint)| {
+                                    (param.name.as_str(), &**constraint, None)
+                                }),
+                            );
+                        }
+                    }
                 }
+
                 let span = if let Some(local) = place.as_local() {
                     let decl = &self.body.local_decls[local];
                     Some(decl.source_info.span)

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -576,12 +576,12 @@ pub enum PassKind {
     Module,
 }
 
-/// LLVMRustThinLTOData
+// LLVMRustThinLTOData
 extern "C" {
     pub type ThinLTOData;
 }
 
-/// LLVMRustThinLTOBuffer
+// LLVMRustThinLTOBuffer
 extern "C" {
     pub type ThinLTOBuffer;
 }

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -500,15 +500,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`.
         // First, check x % y != 0 (or if that computation overflows).
         let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, &a, &b)?;
-        if overflow || res.assert_bits(a.layout.size) != 0 {
-            // Then, check if `b` is -1, which is the "MIN / -1" case.
-            let minus1 = Scalar::from_int(-1, dest.layout.size);
-            let b_scalar = b.to_scalar().unwrap();
-            if b_scalar == minus1 {
-                throw_ub_format!("exact_div: result of dividing MIN by -1 cannot be represented")
-            } else {
-                throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b,)
-            }
+        assert!(!overflow); // All overflow is UB, so this should never return on overflow.
+        if res.assert_bits(a.layout.size) != 0 {
+            throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b)
         }
         // `Rem` says this is all right, so we can let `Div` do its job.
         self.binop_ignore_overflow(BinOp::Div, &a, &b, dest)

compiler/rustc_const_eval/src/interpret/operator.rs

@@ -196,16 +196,20 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 _ => None,
             };
             if let Some(op) = op {
+                let l = self.sign_extend(l, left_layout) as i128;
                 let r = self.sign_extend(r, right_layout) as i128;
-                // We need a special check for overflowing remainder:
-                // "int_min % -1" overflows and returns 0, but after casting things to a larger int
-                // type it does *not* overflow nor give an unrepresentable result!
-                if bin_op == Rem {
-                    if r == -1 && l == (1 << (size.bits() - 1)) {
-                        return Ok((Scalar::from_int(0, size), true, left_layout.ty));
+
+                // We need a special check for overflowing Rem and Div since they are *UB*
+                // on overflow, which can happen with "int_min $OP -1".
+                if matches!(bin_op, Rem | Div) {
+                    if l == size.signed_int_min() && r == -1 {
+                        if bin_op == Rem {
+                            throw_ub!(RemainderOverflow)
+                        } else {
+                            throw_ub!(DivisionOverflow)
+                        }
                     }
                 }
-                let l = self.sign_extend(l, left_layout) as i128;
 
                 let (result, oflo) = op(l, r);
                 // This may be out-of-bounds for the result type, so we have to truncate ourselves.

compiler/rustc_lint/src/builtin.rs

@@ -1086,6 +1086,16 @@ impl EarlyLintPass for UnusedDocComment {
     fn check_generic_param(&mut self, cx: &EarlyContext<'_>, param: &ast::GenericParam) {
         warn_if_doc(cx, param.ident.span, "generic parameters", &param.attrs);
     }
+
+    fn check_block(&mut self, cx: &EarlyContext<'_>, block: &ast::Block) {
+        warn_if_doc(cx, block.span, "block", &block.attrs());
+    }
+
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+        if let ast::ItemKind::ForeignMod(_) = item.kind {
+            warn_if_doc(cx, item.span, "extern block", &item.attrs);
+        }
+    }
 }
 
 declare_lint! {

compiler/rustc_middle/src/lib.rs

@@ -56,6 +56,7 @@
 #![feature(nonzero_ops)]
 #![feature(unwrap_infallible)]
 #![feature(decl_macro)]
+#![feature(drain_filter)]
 #![recursion_limit = "512"]
 #![allow(rustc::potential_query_instability)]
 

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

@@ -233,6 +233,10 @@ pub enum UndefinedBehaviorInfo<'tcx> {
     DivisionByZero,
     /// Something was "remainded" by 0 (x % 0).
     RemainderByZero,
+    /// Signed division overflowed (INT_MIN / -1).
+    DivisionOverflow,
+    /// Signed remainder overflowed (INT_MIN % -1).
+    RemainderOverflow,
     /// Overflowing inbounds pointer arithmetic.
     PointerArithOverflow,
     /// Invalid metadata in a wide pointer (using `str` to avoid allocations).
@@ -310,6 +314,8 @@ impl fmt::Display for UndefinedBehaviorInfo<'_> {
             }
             DivisionByZero => write!(f, "dividing by zero"),
             RemainderByZero => write!(f, "calculating the remainder with a divisor of zero"),
+            DivisionOverflow => write!(f, "overflow in signed division (dividing MIN by -1)"),
+            RemainderOverflow => write!(f, "overflow in signed remainder (dividing MIN by -1)"),
             PointerArithOverflow => write!(f, "overflowing in-bounds pointer arithmetic"),
             InvalidMeta(msg) => write!(f, "invalid metadata in wide pointer: {}", msg),
             InvalidVtableDropFn(sig) => write!(