Rollup of 12 pull requests

compiler/rustc_ast/src/attr/mod.rs

@@ -526,7 +526,7 @@ impl MetaItemKind {
     fn list_from_tokens(tokens: TokenStream) -> Option<MetaItemKind> {
         let mut tokens = tokens.into_trees().peekable();
         let mut result = Vec::new();
-        while let Some(..) = tokens.peek() {
+        while tokens.peek().is_some() {
             let item = NestedMetaItem::from_tokens(&mut tokens)?;
             result.push(item);
             match tokens.next() {

compiler/rustc_data_structures/src/steal.rs

@@ -30,17 +30,19 @@ impl<T> Steal<T> {
         Steal { value: RwLock::new(Some(value)) }
     }
 
+    #[track_caller]
     pub fn borrow(&self) -> MappedReadGuard<'_, T> {
         ReadGuard::map(self.value.borrow(), |opt| match *opt {
             None => panic!("attempted to read from stolen value"),
             Some(ref v) => v,
         })
     }
 
+    #[track_caller]
     pub fn steal(&self) -> T {
         let value_ref = &mut *self.value.try_write().expect("stealing value which is locked");
         let value = value_ref.take();
-        value.expect("attempt to read from stolen value")
+        value.expect("attempt to steal from stolen value")
     }
 }
 

compiler/rustc_middle/src/ty/cast.rs

@@ -22,15 +22,16 @@ pub enum CastTy<'tcx> {
     /// Various types that are represented as ints and handled mostly
     /// in the same way, merged for easier matching.
     Int(IntTy),
-    /// Floating-Point types
+    /// Floating-point types.
     Float,
-    /// Function Pointers
+    /// Function pointers.
     FnPtr,
-    /// Raw pointers
+    /// Raw pointers.
     Ptr(ty::TypeAndMut<'tcx>),
 }
 
-/// Cast Kind. See RFC 401 (or librustc_typeck/check/cast.rs)
+/// Cast Kind. See [RFC 401](https://rust-lang.github.io/rfcs/0401-coercions.html)
+/// (or librustc_typeck/check/cast.rs).
 #[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum CastKind {
     CoercionCast,
@@ -48,7 +49,7 @@ pub enum CastKind {
 
 impl<'tcx> CastTy<'tcx> {
     /// Returns `Some` for integral/pointer casts.
-    /// casts like unsizing casts will return `None`
+    /// Casts like unsizing casts will return `None`.
     pub fn from_ty(t: Ty<'tcx>) -> Option<CastTy<'tcx>> {
         match *t.kind() {
             ty::Bool => Some(CastTy::Int(IntTy::Bool)),

compiler/rustc_middle/src/ty/codec.rs

@@ -18,7 +18,6 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::{CrateNum, DefId};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use rustc_span::Span;
-use std::convert::{TryFrom, TryInto};
 use std::hash::Hash;
 use std::intrinsics;
 use std::marker::DiscriminantKind;
@@ -81,7 +80,8 @@ where
     E: TyEncoder<'tcx>,
     M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
     T: EncodableWithShorthand<'tcx, E>,
-    <T::Variant as DiscriminantKind>::Discriminant: Ord + TryFrom<usize>,
+    // The discriminant and shorthand must have the same size.
+    T::Variant: DiscriminantKind<Discriminant = isize>,
 {
     let existing_shorthand = cache(encoder).get(value).copied();
     if let Some(shorthand) = existing_shorthand {
@@ -97,7 +97,7 @@ where
     // The shorthand encoding uses the same usize as the
     // discriminant, with an offset so they can't conflict.
     let discriminant = intrinsics::discriminant_value(variant);
-    assert!(discriminant < SHORTHAND_OFFSET.try_into().ok().unwrap());
+    assert!(SHORTHAND_OFFSET > discriminant as usize);
 
     let shorthand = start + SHORTHAND_OFFSET;
 

compiler/rustc_mir/src/shim.rs

@@ -165,7 +165,7 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
     let mut body =
         new_body(source, blocks, local_decls_for_sig(&sig, span), sig.inputs().len(), span);
 
-    if let Some(..) = ty {
+    if ty.is_some() {
         // The first argument (index 0), but add 1 for the return value.
         let dropee_ptr = Place::from(Local::new(1 + 0));
         if tcx.sess.opts.debugging_opts.mir_emit_retag {

compiler/rustc_mir/src/transform/const_prop.rs

@@ -139,7 +139,7 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
             Default::default(),
             body.arg_count,
             Default::default(),
-            tcx.def_span(def_id),
+            body.span,
             body.generator_kind,
         );
 

compiler/rustc_mir/src/transform/simplify.rs

@@ -61,7 +61,7 @@ impl<'tcx> MirPass<'tcx> for SimplifyCfg {
     }
 
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        debug!("SimplifyCfg({:?}) - simplifying {:?}", self.label, body);
+        debug!("SimplifyCfg({:?}) - simplifying {:?}", self.label, body.source);
         simplify_cfg(body);
     }
 }

compiler/rustc_parse_format/src/lib.rs

@@ -736,7 +736,7 @@ fn find_skips_from_snippet(
 
     fn find_skips(snippet: &str, is_raw: bool) -> Vec<usize> {
         let mut eat_ws = false;
-        let mut s = snippet.chars().enumerate().peekable();
+        let mut s = snippet.char_indices().peekable();
         let mut skips = vec![];
         while let Some((pos, c)) = s.next() {
             match (c, s.peek()) {

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -1398,12 +1398,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
     fn lifetime_deletion_span(&self, name: Ident, generics: &hir::Generics<'_>) -> Option<Span> {
         generics.params.iter().enumerate().find_map(|(i, param)| {
             if param.name.ident() == name {
-                let mut in_band = false;
-                if let hir::GenericParamKind::Lifetime { kind } = param.kind {
-                    if let hir::LifetimeParamKind::InBand = kind {
-                        in_band = true;
-                    }
-                }
+                let in_band = matches!(
+                    param.kind,
+                    hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::InBand }
+                );
                 if in_band {
                     Some(param.span)
                 } else if generics.params.len() == 1 {
@@ -1433,12 +1431,11 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
         lifetime: &hir::Lifetime,
     ) {
         let name = lifetime.name.ident();
-        let mut remove_decl = None;
-        if let Some(parent_def_id) = self.tcx.parent(def_id) {
-            if let Some(generics) = self.tcx.hir().get_generics(parent_def_id) {
-                remove_decl = self.lifetime_deletion_span(name, generics);
-            }
-        }
+        let remove_decl = self
+            .tcx
+            .parent(def_id)
+            .and_then(|parent_def_id| self.tcx.hir().get_generics(parent_def_id))
+            .and_then(|generics| self.lifetime_deletion_span(name, generics));
 
         let mut remove_use = None;
         let mut elide_use = None;

library/core/src/cmp.rs

@@ -541,7 +541,7 @@ impl Ordering {
     /// assert_eq!(result, Ordering::Equal);
     ///
     /// let x: (i64, i64, i64) = (1, 2, 7);
-    /// let y: (i64, i64, i64)  = (1, 5, 3);
+    /// let y: (i64, i64, i64) = (1, 5, 3);
     /// let result = x.0.cmp(&y.0).then_with(|| x.1.cmp(&y.1)).then_with(|| x.2.cmp(&y.2));
     ///
     /// assert_eq!(result, Ordering::Less);

src/test/ui/consts/const-eval/ub-wide-ptr.rs

@@ -8,6 +8,12 @@ use std::mem;
 // normalize-stderr-test "alloc\d+" -> "allocN"
 // normalize-stderr-test "size \d+" -> "size N"
 
+/// A newtype wrapper to prevent MIR generation from inserting reborrows that would affect the error
+/// message. Use this whenever the message is "any use of this value will cause an error" instead of
+/// "it is undefined behavior to use this value".
+#[repr(transparent)]
+struct W<T>(T);
+
 #[repr(C)]
 union MaybeUninit<T: Copy> {
     uninit: (),
@@ -95,26 +101,22 @@ const RAW_SLICE_LENGTH_UNINIT: *const [u8] = unsafe {
 
 // # trait object
 // bad trait object
-#[warn(const_err)]
-const TRAIT_OBJ_SHORT_VTABLE_1: &dyn Trait = unsafe { mem::transmute((&92u8, &3u8)) };
-//~^ WARN any use of this value will cause an error [const_err]
+const TRAIT_OBJ_SHORT_VTABLE_1: W<&dyn Trait> = unsafe { mem::transmute(W((&92u8, &3u8))) };
+//~^ ERROR it is undefined behavior to use this value
 // bad trait object
-#[warn(const_err)]
-const TRAIT_OBJ_SHORT_VTABLE_2: &dyn Trait = unsafe { mem::transmute((&92u8, &3u64)) };
-//~^ WARN any use of this value will cause an error [const_err]
+const TRAIT_OBJ_SHORT_VTABLE_2: W<&dyn Trait> = unsafe { mem::transmute(W((&92u8, &3u64))) };
+//~^ ERROR it is undefined behavior to use this value
 // bad trait object
-#[warn(const_err)]
-const TRAIT_OBJ_INT_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, 4usize)) };
-//~^ WARN any use of this value will cause an error [const_err]
+const TRAIT_OBJ_INT_VTABLE: W<&dyn Trait> = unsafe { mem::transmute(W((&92u8, 4usize))) };
+//~^ ERROR it is undefined behavior to use this value
 const TRAIT_OBJ_UNALIGNED_VTABLE: &dyn Trait = unsafe { mem::transmute((&92u8, &[0u8; 128])) };
 //~^ ERROR it is undefined behavior to use this value
 const TRAIT_OBJ_BAD_DROP_FN_NULL: &dyn Trait = unsafe { mem::transmute((&92u8, &[0usize; 8])) };
 //~^ ERROR it is undefined behavior to use this value
 const TRAIT_OBJ_BAD_DROP_FN_INT: &dyn Trait = unsafe { mem::transmute((&92u8, &[1usize; 8])) };
 //~^ ERROR it is undefined behavior to use this value
-#[warn(const_err)]
-const TRAIT_OBJ_BAD_DROP_FN_NOT_FN_PTR: &dyn Trait = unsafe { mem::transmute((&92u8, &[&42u8; 8])) };
-//~^ WARN any use of this value will cause an error [const_err]
+const TRAIT_OBJ_BAD_DROP_FN_NOT_FN_PTR: W<&dyn Trait> = unsafe { mem::transmute(W((&92u8, &[&42u8; 8]))) };
+//~^ ERROR it is undefined behavior to use this value
 
 // bad data *inside* the trait object
 const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = unsafe { mem::transmute::<_, &bool>(&3u8) };