Rollup of 6 pull requests

src/librustc/dep_graph/graph.rs

@@ -524,7 +524,7 @@ impl DepGraph {
             edge_list_indices.push((start, end));
         }
 
-        debug_assert!(edge_list_data.len() <= ::std::u32::MAX as usize);
+        debug_assert!(edge_list_data.len() <= u32::MAX as usize);
         debug_assert_eq!(edge_list_data.len(), total_edge_count);
 
         SerializedDepGraph { nodes, fingerprints, edge_list_indices, edge_list_data }

src/librustc/mir/interpret/allocation.rs

@@ -818,9 +818,9 @@ impl UndefMask {
             // First set all bits except the first `bita`,
             // then unset the last `64 - bitb` bits.
             let range = if bitb == 0 {
-                u64::max_value() << bita
+                u64::MAX << bita
             } else {
-                (u64::max_value() << bita) & (u64::max_value() >> (64 - bitb))
+                (u64::MAX << bita) & (u64::MAX >> (64 - bitb))
             };
             if new_state {
                 self.blocks[blocka] |= range;
@@ -832,21 +832,21 @@ impl UndefMask {
         // across block boundaries
         if new_state {
             // Set `bita..64` to `1`.
-            self.blocks[blocka] |= u64::max_value() << bita;
+            self.blocks[blocka] |= u64::MAX << bita;
             // Set `0..bitb` to `1`.
             if bitb != 0 {
-                self.blocks[blockb] |= u64::max_value() >> (64 - bitb);
+                self.blocks[blockb] |= u64::MAX >> (64 - bitb);
             }
             // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1)..blockb {
-                self.blocks[block] = u64::max_value();
+                self.blocks[block] = u64::MAX;
             }
         } else {
             // Set `bita..64` to `0`.
-            self.blocks[blocka] &= !(u64::max_value() << bita);
+            self.blocks[blocka] &= !(u64::MAX << bita);
             // Set `0..bitb` to `0`.
             if bitb != 0 {
-                self.blocks[blockb] &= !(u64::max_value() >> (64 - bitb));
+                self.blocks[blockb] &= !(u64::MAX >> (64 - bitb));
             }
             // Fill in all the other blocks (much faster than one bit at a time).
             for block in (blocka + 1)..blockb {

src/librustc/mir/interpret/pointer.rs

@@ -78,9 +78,9 @@ pub trait PointerArithmetic: layout::HasDataLayout {
     fn overflowing_signed_offset(&self, val: u64, i: i128) -> (u64, bool) {
         // FIXME: is it possible to over/underflow here?
         if i < 0 {
-            // Trickery to ensure that `i64::min_value()` works fine: compute `n = -i`.
+            // Trickery to ensure that `i64::MIN` works fine: compute `n = -i`.
             // This formula only works for true negative values; it overflows for zero!
-            let n = u64::max_value() - (i as u64) + 1;
+            let n = u64::MAX - (i as u64) + 1;
             let res = val.overflowing_sub(n);
             self.truncate_to_ptr(res)
         } else {

src/librustc/traits/structural_impls.rs

@@ -415,9 +415,9 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
             super::ReferenceOutlivesReferent(ty) => {
                 tcx.lift(&ty).map(super::ReferenceOutlivesReferent)
             }
-            super::ObjectTypeBound(ty, r) => tcx
-                .lift(&ty)
-                .and_then(|ty| tcx.lift(&r).and_then(|r| Some(super::ObjectTypeBound(ty, r)))),
+            super::ObjectTypeBound(ty, r) => {
+                tcx.lift(&ty).and_then(|ty| tcx.lift(&r).map(|r| super::ObjectTypeBound(ty, r)))
+            }
             super::ObjectCastObligation(ty) => tcx.lift(&ty).map(super::ObjectCastObligation),
             super::Coercion { source, target } => {
                 Some(super::Coercion { source: tcx.lift(&source)?, target: tcx.lift(&target)? })

src/librustc/ty/layout.rs

@@ -7,7 +7,6 @@ use rustc_span::DUMMY_SP;
 
 use std::cmp;
 use std::fmt;
-use std::i128;
 use std::iter;
 use std::mem;
 use std::ops::Bound;
@@ -1001,7 +1000,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     }
                 }
 
-                let (mut min, mut max) = (i128::max_value(), i128::min_value());
+                let (mut min, mut max) = (i128::MAX, i128::MIN);
                 let discr_type = def.repr.discr_type();
                 let bits = Integer::from_attr(self, discr_type).size().bits();
                 for (i, discr) in def.discriminants(tcx) {
@@ -1021,7 +1020,7 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                     }
                 }
                 // We might have no inhabited variants, so pretend there's at least one.
-                if (min, max) == (i128::max_value(), i128::min_value()) {
+                if (min, max) == (i128::MAX, i128::MIN) {
                     min = 0;
                     max = 0;
                 }

src/librustc/ty/print/pretty.rs

@@ -920,7 +920,7 @@ pub trait PrettyPrinter<'tcx>:
             }
             (ConstValue::Scalar(Scalar::Raw { data, .. }), ty::Uint(ui)) => {
                 let bit_size = Integer::from_attr(&self.tcx(), UnsignedInt(*ui)).size();
-                let max = truncate(u128::max_value(), bit_size);
+                let max = truncate(u128::MAX, bit_size);
 
                 let ui_str = ui.name_str();
                 if data == max {

src/librustc/ty/query/on_disk_cache.rs

@@ -92,7 +92,7 @@ struct AbsoluteBytePos(u32);
 
 impl AbsoluteBytePos {
     fn new(pos: usize) -> AbsoluteBytePos {
-        debug_assert!(pos <= ::std::u32::MAX as usize);
+        debug_assert!(pos <= u32::MAX as usize);
         AbsoluteBytePos(pos as u32)
     }
 

src/librustc/ty/util.rs

@@ -50,11 +50,11 @@ fn signed_min(size: Size) -> i128 {
 }
 
 fn signed_max(size: Size) -> i128 {
-    i128::max_value() >> (128 - size.bits())
+    i128::MAX >> (128 - size.bits())
 }
 
 fn unsigned_max(size: Size) -> u128 {
-    u128::max_value() >> (128 - size.bits())
+    u128::MAX >> (128 - size.bits())
 }
 
 fn int_size_and_signed<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> (Size, bool) {
@@ -77,7 +77,7 @@ impl<'tcx> Discr<'tcx> {
             let min = signed_min(size);
             let max = signed_max(size);
             let val = sign_extend(self.val, size) as i128;
-            assert!(n < (i128::max_value() as u128));
+            assert!(n < (i128::MAX as u128));
             let n = n as i128;
             let oflo = val > max - n;
             let val = if oflo { min + (n - (max - val) - 1) } else { val + n };

src/librustc_codegen_llvm/back/write.rs

@@ -725,7 +725,7 @@ pub(crate) unsafe fn codegen(
                         Err(_) => return 0,
                     };
 
-                    if let Err(_) = write!(cursor, "{:#}", demangled) {
+                    if write!(cursor, "{:#}", demangled).is_err() {
                         // Possible only if provided buffer is not big enough
                         return 0;
                     }

src/librustc_codegen_llvm/context.rs

@@ -174,7 +174,6 @@ pub unsafe fn create_module(
 
         let llvm_data_layout = llvm::LLVMGetDataLayout(llmod);
         let llvm_data_layout = str::from_utf8(CStr::from_ptr(llvm_data_layout).to_bytes())
-            .ok()
             .expect("got a non-UTF8 data-layout from LLVM");
 
         // Unfortunately LLVM target specs change over time, and right now we

src/librustc_codegen_ssa/back/write.rs

@@ -1257,7 +1257,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
                 if main_thread_worker_state == MainThreadWorkerState::Idle {
                     if !queue_full_enough(work_items.len(), running, max_workers) {
                         // The queue is not full enough, codegen more items:
-                        if let Err(_) = codegen_worker_send.send(Message::CodegenItem) {
+                        if codegen_worker_send.send(Message::CodegenItem).is_err() {
                             panic!("Could not send Message::CodegenItem to main thread")
                         }
                         main_thread_worker_state = MainThreadWorkerState::Codegenning;

src/librustc_error_codes/error_codes/E0380.md

@@ -1,4 +1,14 @@
-Auto traits cannot have methods or associated items.
-For more information see the [opt-in builtin traits RFC][RFC 19].
+An auto trait was declared with a method or an associated item.
+
+Erroneous code example:
+
+```compile_fail,E0380
+unsafe auto trait Trait {
+    type Output; // error!
+}
+```
+
+Auto traits cannot have methods or associated items. For more information see
+the [opt-in builtin traits RFC][RFC 19].
 
 [RFC 19]: https://github.com/rust-lang/rfcs/blob/master/text/0019-opt-in-builtin-traits.md

src/librustc_errors/lib.rs

@@ -163,7 +163,7 @@ impl CodeSuggestion {
                         None => buf.push_str(&line[lo..]),
                     }
                 }
-                if let None = hi_opt {
+                if hi_opt.is_none() {
                     buf.push('\n');
                 }
             }

src/librustc_errors/registry.rs

@@ -27,6 +27,6 @@ impl Registry {
         if !self.long_descriptions.contains_key(code) {
             return Err(InvalidErrorCode);
         }
-        Ok(self.long_descriptions.get(code).unwrap().clone())
+        Ok(*self.long_descriptions.get(code).unwrap())
     }
 }

src/librustc_interface/util.rs

@@ -426,7 +426,7 @@ pub(crate) fn check_attr_crate_type(attrs: &[ast::Attribute], lint_buffer: &mut
     for a in attrs.iter() {
         if a.check_name(sym::crate_type) {
             if let Some(n) = a.value_str() {
-                if let Some(_) = categorize_crate_type(n) {
+                if categorize_crate_type(n).is_some() {
                     return;
                 }
 

src/librustc_lint/context.rs

@@ -335,7 +335,7 @@ impl LintStore {
             lint_name.to_string()
         };
         // If the lint was scoped with `tool::` check if the tool lint exists
-        if let Some(_) = tool_name {
+        if tool_name.is_some() {
             match self.by_name.get(&complete_name) {
                 None => match self.lint_groups.get(&*complete_name) {
                     None => return CheckLintNameResult::Tool(Err((None, String::new()))),

src/librustc_mir/borrow_check/type_check/mod.rs

@@ -1905,7 +1905,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             // expressions evaluate through `as_temp` or `into` a return
             // slot or local, so to find all unsized rvalues it is enough
             // to check all temps, return slots and locals.
-            if let None = self.reported_errors.replace((ty, span)) {
+            if self.reported_errors.replace((ty, span)).is_none() {
                 let mut diag = struct_span_err!(
                     self.tcx().sess,
                     span,

src/librustc_mir/borrow_check/type_check/relate_tys.rs

@@ -64,7 +64,7 @@ impl TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
     }
 
     fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> {
-        if let Some(_) = &mut self.borrowck_context {
+        if self.borrowck_context.is_some() {
             let origin = NLLRegionVariableOrigin::Existential { from_forall };
             self.infcx.next_nll_region_var(origin)
         } else {

src/librustc_mir/dataflow/generic/engine.rs

@@ -239,23 +239,26 @@ where
             }
 
             SwitchInt { ref targets, ref values, ref discr, .. } => {
-                // If this is a switch on an enum discriminant, a custom effect may be applied
-                // along each outgoing edge.
-                if let Some(place) = discr.place() {
-                    let enum_def = switch_on_enum_discriminant(self.tcx, self.body, bb_data, place);
-                    if let Some(enum_def) = enum_def {
+                let Engine { tcx, body, .. } = *self;
+                let enum_ = discr
+                    .place()
+                    .and_then(|discr| switch_on_enum_discriminant(tcx, body, bb_data, discr));
+                match enum_ {
+                    // If this is a switch on an enum discriminant, a custom effect may be applied
+                    // along each outgoing edge.
+                    Some((enum_place, enum_def)) => {
                         self.propagate_bits_into_enum_discriminant_switch_successors(
-                            in_out, bb, enum_def, place, dirty_list, &*values, &*targets,
+                            in_out, bb, enum_def, enum_place, dirty_list, &*values, &*targets,
                         );
-
-                        return;
                     }
-                }
 
-                // Otherwise, it's just a normal `SwitchInt`, and every successor sees the same
-                // exit state.
-                for target in targets.iter().copied() {
-                    self.propagate_bits_into_entry_set_for(&in_out, target, dirty_list);
+                    // Otherwise, it's just a normal `SwitchInt`, and every successor sees the same
+                    // exit state.
+                    None => {
+                        for target in targets.iter().copied() {
+                            self.propagate_bits_into_entry_set_for(&in_out, target, dirty_list);
+                        }
+                    }
                 }
             }
 
@@ -342,22 +345,27 @@ where
     }
 }
 
-/// Look at the last statement of a block that ends with  to see if it is an assignment of an enum
-/// discriminant to the local that determines the target of a `SwitchInt` like so:
-///   _42 = discriminant(..)
+/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
+/// an enum discriminant.
+///
+/// We expect such blocks to have a call to `discriminant` as their last statement like so:
+///   _42 = discriminant(_1)
 ///   SwitchInt(_42, ..)
+///
+/// If the basic block matches this pattern, this function returns the place corresponding to the
+/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
 fn switch_on_enum_discriminant(
     tcx: TyCtxt<'tcx>,
-    body: &mir::Body<'tcx>,
-    block: &mir::BasicBlockData<'tcx>,
+    body: &'mir mir::Body<'tcx>,
+    block: &'mir mir::BasicBlockData<'tcx>,
     switch_on: &mir::Place<'tcx>,
-) -> Option<&'tcx ty::AdtDef> {
+) -> Option<(&'mir mir::Place<'tcx>, &'tcx ty::AdtDef)> {
     match block.statements.last().map(|stmt| &stmt.kind) {
         Some(mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated))))
             if lhs == switch_on =>
         {
             match &discriminated.ty(body, tcx).ty.kind {
-                ty::Adt(def, _) => Some(def),
+                ty::Adt(def, _) => Some((discriminated, def)),
 
                 // `Rvalue::Discriminant` is also used to get the active yield point for a
                 // generator, but we do not need edge-specific effects in that case. This may

src/librustc_mir/dataflow/mod.rs

@@ -16,7 +16,6 @@ use std::borrow::Borrow;
 use std::fmt;
 use std::io;
 use std::path::PathBuf;
-use std::usize;
 
 pub use self::at_location::{FlowAtLocation, FlowsAtLocation};
 pub(crate) use self::drop_flag_effects::*;

src/librustc_mir/interpret/intrinsics.rs

@@ -203,7 +203,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         if is_add {
                             // max unsigned
                             Scalar::from_uint(
-                                u128::max_value() >> (128 - num_bits),
+                                u128::MAX >> (128 - num_bits),
                                 Size::from_bits(num_bits),
                             )
                         } else {
@@ -381,11 +381,11 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
         // Performs an exact division, resulting in undefined behavior where
-        // `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`.
+        // `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_value / -1" case.
+            // 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 {

src/librustc_mir/interpret/memory.rs

@@ -565,7 +565,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
 
         // # Function pointers
         // (both global from `alloc_map` and local from `extra_fn_ptr_map`)
-        if let Some(_) = self.get_fn_alloc(id) {
+        if self.get_fn_alloc(id).is_some() {
             return if let AllocCheck::Dereferenceable = liveness {
                 // The caller requested no function pointers.
                 throw_unsup!(DerefFunctionPointer)

src/librustc_mir/interpret/validity.rs

@@ -463,7 +463,7 @@ impl<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M
         let (lo, hi) = valid_range.clone().into_inner();
         // Determine the allowed range
         // `max_hi` is as big as the size fits
-        let max_hi = u128::max_value() >> (128 - op.layout.size.bits());
+        let max_hi = u128::MAX >> (128 - op.layout.size.bits());
         assert!(hi <= max_hi);
         // We could also write `(hi + 1) % (max_hi + 1) == lo` but `max_hi + 1` overflows for `u128`
         if (lo == 0 && hi == max_hi) || (hi + 1 == lo) {

src/librustc_parse/parser/attr.rs

@@ -37,7 +37,7 @@ impl<'a> Parser<'a> {
                     let inner_parse_policy = InnerAttributeParsePolicy::NotPermitted {
                         reason: inner_error_reason,
                         saw_doc_comment: just_parsed_doc_comment,
-                        prev_attr_sp: attrs.last().and_then(|a| Some(a.span)),
+                        prev_attr_sp: attrs.last().map(|a| a.span),
                     };
                     let attr = self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?;
                     attrs.push(attr);

src/librustc_passes/entry.rs

@@ -196,7 +196,7 @@ fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) {
     // The file may be empty, which leads to the diagnostic machinery not emitting this
     // note. This is a relatively simple way to detect that case and emit a span-less
     // note instead.
-    if let Ok(_) = tcx.sess.source_map().lookup_line(sp.lo()) {
+    if tcx.sess.source_map().lookup_line(sp.lo()).is_ok() {
         err.set_span(sp);
         err.span_label(sp, &note);
     } else {