Rollup of 7 pull requests

src/ci/scripts/install-msys2.sh

@@ -12,10 +12,14 @@ IFS=$'\n\t'
 source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"
 
 if isWindows; then
-    for RETRY_COUNT in 1 2 3 4 5 6 7 8 9 10; do
-        choco install msys2 \
-            --params="/InstallDir:$(ciCheckoutPath)/msys2 /NoPath" -y --no-progress \
-            && mkdir -p "$(ciCheckoutPath)/msys2/home/${USERNAME}" \
-            && ciCommandAddPath "$(ciCheckoutPath)/msys2/usr/bin" && break
-    done
+    # Pre-followed the api/v2 URL to the CDN since the API can be a bit flakey
+    curl -sSL https://packages.chocolatey.org/msys2.20190524.0.0.20191030.nupkg > \
+        msys2.nupkg
+    curl -sSL https://packages.chocolatey.org/chocolatey-core.extension.1.3.5.1.nupkg > \
+        chocolatey-core.extension.nupkg
+    choco install -s . msys2 \
+        --params="/InstallDir:$(ciCheckoutPath)/msys2 /NoPath" -y --no-progress
+    rm msys2.nupkg chocolatey-core.extension.nupkg
+    mkdir -p "$(ciCheckoutPath)/msys2/home/${USERNAME}"
+    ciCommandAddPath "$(ciCheckoutPath)/msys2/usr/bin"
 fi

src/libcore/char/methods.rs

@@ -434,36 +434,35 @@ impl char {
     #[inline]
     pub fn encode_utf8(self, dst: &mut [u8]) -> &mut str {
         let code = self as u32;
-        // SAFETY: each arm checks the size of the slice and only uses `get_unchecked` unsafe ops
-        unsafe {
-            let len = if code < MAX_ONE_B && !dst.is_empty() {
-                *dst.get_unchecked_mut(0) = code as u8;
-                1
-            } else if code < MAX_TWO_B && dst.len() >= 2 {
-                *dst.get_unchecked_mut(0) = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
-                *dst.get_unchecked_mut(1) = (code & 0x3F) as u8 | TAG_CONT;
-                2
-            } else if code < MAX_THREE_B && dst.len() >= 3 {
-                *dst.get_unchecked_mut(0) = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
-                *dst.get_unchecked_mut(1) = (code >> 6 & 0x3F) as u8 | TAG_CONT;
-                *dst.get_unchecked_mut(2) = (code & 0x3F) as u8 | TAG_CONT;
-                3
-            } else if dst.len() >= 4 {
-                *dst.get_unchecked_mut(0) = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
-                *dst.get_unchecked_mut(1) = (code >> 12 & 0x3F) as u8 | TAG_CONT;
-                *dst.get_unchecked_mut(2) = (code >> 6 & 0x3F) as u8 | TAG_CONT;
-                *dst.get_unchecked_mut(3) = (code & 0x3F) as u8 | TAG_CONT;
-                4
-            } else {
-                panic!(
-                    "encode_utf8: need {} bytes to encode U+{:X}, but the buffer has {}",
-                    from_u32_unchecked(code).len_utf8(),
-                    code,
-                    dst.len(),
-                )
-            };
-            from_utf8_unchecked_mut(dst.get_unchecked_mut(..len))
-        }
+        let len = self.len_utf8();
+        match (len, &mut dst[..]) {
+            (1, [a, ..]) => {
+                *a = code as u8;
+            }
+            (2, [a, b, ..]) => {
+                *a = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
+                *b = (code & 0x3F) as u8 | TAG_CONT;
+            }
+            (3, [a, b, c, ..]) => {
+                *a = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
+                *b = (code >> 6 & 0x3F) as u8 | TAG_CONT;
+                *c = (code & 0x3F) as u8 | TAG_CONT;
+            }
+            (4, [a, b, c, d, ..]) => {
+                *a = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
+                *b = (code >> 12 & 0x3F) as u8 | TAG_CONT;
+                *c = (code >> 6 & 0x3F) as u8 | TAG_CONT;
+                *d = (code & 0x3F) as u8 | TAG_CONT;
+            }
+            _ => panic!(
+                "encode_utf8: need {} bytes to encode U+{:X}, but the buffer has {}",
+                len,
+                code,
+                dst.len(),
+            ),
+        };
+        // SAFETY: We just wrote UTF-8 content in, so converting to str is fine.
+        unsafe { from_utf8_unchecked_mut(&mut dst[..len]) }
     }
 
     /// Encodes this character as UTF-16 into the provided `u16` buffer,

src/libcore/lib.rs

@@ -129,6 +129,7 @@
 #![feature(associated_type_bounds)]
 #![feature(const_type_id)]
 #![feature(const_caller_location)]
+#![feature(slice_patterns)]
 
 #[prelude_import]
 #[allow(unused)]

src/librustc/mir/interpret/error.rs

@@ -432,6 +432,7 @@ pub enum UnsupportedOpInfo<'tcx> {
     HeapAllocNonPowerOfTwoAlignment(u64),
     ReadFromReturnPointer,
     PathNotFound(Vec<String>),
+    TransmuteSizeDiff(Ty<'tcx>, Ty<'tcx>),
 }
 
 impl fmt::Debug for UnsupportedOpInfo<'tcx> {
@@ -460,6 +461,11 @@ impl fmt::Debug for UnsupportedOpInfo<'tcx> {
                            passing data of type {:?}",
                 callee_ty, caller_ty
             ),
+            TransmuteSizeDiff(from_ty, to_ty) => write!(
+                f,
+                "tried to transmute from {:?} to {:?}, but their sizes differed",
+                from_ty, to_ty
+            ),
             FunctionRetMismatch(caller_ty, callee_ty) => write!(
                 f,
                 "tried to call a function with return type {:?} \

src/librustc/mir/interpret/value.rs

@@ -367,8 +367,9 @@ impl<'tcx, Tag> Scalar<Tag> {
     }
 
     /// Do not call this method!  Use either `assert_ptr` or `force_ptr`.
+    /// This method is intentionally private, do not make it public.
     #[inline]
-    pub fn to_ptr(self) -> InterpResult<'tcx, Pointer<Tag>> {
+    fn to_ptr(self) -> InterpResult<'tcx, Pointer<Tag>> {
         match self {
             Scalar::Raw { data: 0, .. } => throw_unsup!(InvalidNullPointerUsage),
             Scalar::Raw { .. } => throw_unsup!(ReadBytesAsPointer),
@@ -544,12 +545,6 @@ impl<'tcx, Tag> ScalarMaybeUndef<Tag> {
         }
     }
 
-    /// Do not call this method!  Use either `assert_ptr` or `force_ptr`.
-    #[inline(always)]
-    pub fn to_ptr(self) -> InterpResult<'tcx, Pointer<Tag>> {
-        self.not_undef()?.to_ptr()
-    }
-
     /// Do not call this method!  Use either `assert_bits` or `force_bits`.
     #[inline(always)]
     pub fn to_bits(self, target_size: Size) -> InterpResult<'tcx, u128> {

src/librustc/traits/error_reporting.rs

@@ -2373,7 +2373,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let span = self.tcx.def_span(generator_did);
 
         // Do not ICE on closure typeck (#66868).
-        if let None = self.tcx.hir().as_local_hir_id(generator_did) {
+        if self.tcx.hir().as_local_hir_id(generator_did).is_none() {
             return false;
         }
 

src/librustc/ty/relate.rs

@@ -537,8 +537,8 @@ pub fn super_relate_consts<R: TypeRelation<'tcx>>(
                         Ok(ConstValue::Scalar(a_val))
                     } else if let ty::FnPtr(_) = a.ty.kind {
                         let alloc_map = tcx.alloc_map.lock();
-                        let a_instance = alloc_map.unwrap_fn(a_val.to_ptr().unwrap().alloc_id);
-                        let b_instance = alloc_map.unwrap_fn(b_val.to_ptr().unwrap().alloc_id);
+                        let a_instance = alloc_map.unwrap_fn(a_val.assert_ptr().alloc_id);
+                        let b_instance = alloc_map.unwrap_fn(b_val.assert_ptr().alloc_id);
                         if a_instance == b_instance {
                             Ok(ConstValue::Scalar(a_val))
                         } else {

src/librustc_error_codes/error_codes.rs

@@ -346,6 +346,7 @@ E0622: include_str!("./error_codes/E0622.md"),
 E0623: include_str!("./error_codes/E0623.md"),
 E0624: include_str!("./error_codes/E0624.md"),
 E0626: include_str!("./error_codes/E0626.md"),
+E0627: include_str!("./error_codes/E0627.md"),
 E0631: include_str!("./error_codes/E0631.md"),
 E0633: include_str!("./error_codes/E0633.md"),
 E0635: include_str!("./error_codes/E0635.md"),
@@ -574,7 +575,6 @@ E0745: include_str!("./error_codes/E0745.md"),
 //  E0612, // merged into E0609
 //  E0613, // Removed (merged with E0609)
     E0625, // thread-local statics cannot be accessed at compile-time
-    E0627, // yield statement outside of generator literal
     E0628, // generators cannot have explicit parameters
     E0629, // missing 'feature' (rustc_const_unstable)
     // rustc_const_unstable attribute must be paired with stable/unstable

src/librustc_error_codes/error_codes/E0124.md

@@ -1,5 +1,6 @@
-You declared two fields of a struct with the same name. Erroneous code
-example:
+A struct was declared with two fields having the same name.
+
+Erroneous code example:
 
 ```compile_fail,E0124
 struct Foo {

src/librustc_error_codes/error_codes/E0128.md

@@ -1,4 +1,5 @@
-Type parameter defaults can only use parameters that occur before them.
+A type parameter with default value is using forward declared identifier.
+
 Erroneous code example:
 
 ```compile_fail,E0128
@@ -7,11 +8,11 @@ struct Foo<T = U, U = ()> {
     field2: U,
 }
 // error: type parameters with a default cannot use forward declared
-// identifiers
+//        identifiers
 ```
 
-Since type parameters are evaluated in-order, you may be able to fix this issue
-by doing:
+Type parameter defaults can only use parameters that occur before them. Since
+type parameters are evaluated in-order, this issue could be fixed by doing:
 
 ```
 struct Foo<U = (), T = U> {

src/librustc_error_codes/error_codes/E0627.md

@@ -0,0 +1,30 @@
+A yield expression was used outside of the generator literal.
+
+Erroneous code example:
+
+```compile_fail,E0627
+#![feature(generators, generator_trait)]
+
+fn fake_generator() -> &'static str {
+    yield 1;
+    return "foo"
+}
+
+fn main() {
+    let mut generator = fake_generator;
+}
+```
+
+The error occurs because keyword `yield` can only be used inside the generator
+literal. This can be fixed by constructing the generator correctly.
+
+```
+#![feature(generators, generator_trait)]
+
+fn main() {
+    let mut generator = || {
+        yield 1;
+        return "foo"
+    };
+}
+```

src/librustc_mir/borrow_check/mod.rs

@@ -1424,7 +1424,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     /// Reports an error if this is a borrow of local data.
-    /// This is called for all Yield statements on movable generators
+    /// This is called for all Yield expressions on movable generators
     fn check_for_local_borrow(&mut self, borrow: &BorrowData<'tcx>, yield_span: Span) {
         debug!("check_for_local_borrow({:?})", borrow);
 

src/librustc_mir/borrow_check/path_utils.rs

@@ -131,7 +131,7 @@ pub(super) fn is_active<'tcx>(
 }
 
 /// Determines if a given borrow is borrowing local data
-/// This is called for all Yield statements on movable generators
+/// This is called for all Yield expressions on movable generators
 pub(super) fn borrow_of_local_data(place: &Place<'_>) -> bool {
     match place.base {
         PlaceBase::Static(_) => false,

src/librustc_mir/const_eval.rs

@@ -85,7 +85,7 @@ fn op_to_const<'tcx>(
     };
     let val = match immediate {
         Ok(mplace) => {
-            let ptr = mplace.ptr.to_ptr().unwrap();
+            let ptr = mplace.ptr.assert_ptr();
             let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
             ConstValue::ByRef { alloc, offset: ptr.offset }
         },
@@ -99,7 +99,7 @@ fn op_to_const<'tcx>(
                 // comes from a constant so it can happen have `Undef`, because the indirect
                 // memory that was read had undefined bytes.
                 let mplace = op.assert_mem_place();
-                let ptr = mplace.ptr.to_ptr().unwrap();
+                let ptr = mplace.ptr.assert_ptr();
                 let alloc = ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id);
                 ConstValue::ByRef { alloc, offset: ptr.offset }
             },
@@ -626,7 +626,7 @@ fn validate_and_turn_into_const<'tcx>(
         // whether they become immediates.
         let def_id = cid.instance.def.def_id();
         if tcx.is_static(def_id) || cid.promoted.is_some() {
-            let ptr = mplace.ptr.to_ptr()?;
+            let ptr = mplace.ptr.assert_ptr();
             Ok(tcx.mk_const(ty::Const {
                 val: ty::ConstKind::Value(ConstValue::ByRef {
                     alloc: ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id),

src/librustc_mir/hair/pattern/_match.rs

@@ -252,6 +252,7 @@ use syntax_pos::{Span, DUMMY_SP};
 use arena::TypedArena;
 
 use smallvec::{smallvec, SmallVec};
+use std::borrow::Cow;
 use std::cmp::{self, max, min, Ordering};
 use std::convert::TryInto;
 use std::fmt;
@@ -260,11 +261,12 @@ use std::ops::RangeInclusive;
 use std::u128;
 
 pub fn expand_pattern<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>, pat: Pat<'tcx>) -> Pat<'tcx> {
-    LiteralExpander { tcx: cx.tcx }.fold_pattern(&pat)
+    LiteralExpander { tcx: cx.tcx, param_env: cx.param_env }.fold_pattern(&pat)
 }
 
 struct LiteralExpander<'tcx> {
     tcx: TyCtxt<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
 }
 
 impl LiteralExpander<'tcx> {
@@ -284,9 +286,23 @@ impl LiteralExpander<'tcx> {
         debug!("fold_const_value_deref {:?} {:?} {:?}", val, rty, crty);
         match (val, &crty.kind, &rty.kind) {
             // the easy case, deref a reference
-            (ConstValue::Scalar(Scalar::Ptr(p)), x, y) if x == y => {
-                let alloc = self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id);
-                ConstValue::ByRef { alloc, offset: p.offset }
+            (ConstValue::Scalar(p), x, y) if x == y => {
+                match p {
+                    Scalar::Ptr(p) => {
+                        let alloc = self.tcx.alloc_map.lock().unwrap_memory(p.alloc_id);
+                        ConstValue::ByRef { alloc, offset: p.offset }
+                    }
+                    Scalar::Raw { .. } => {
+                        let layout = self.tcx.layout_of(self.param_env.and(rty)).unwrap();
+                        if layout.is_zst() {
+                            // Deref of a reference to a ZST is a nop.
+                            ConstValue::Scalar(Scalar::zst())
+                        } else {
+                            // FIXME(oli-obk): this is reachable for `const FOO: &&&u32 = &&&42;`
+                            bug!("cannot deref {:#?}, {} -> {}", val, crty, rty);
+                        }
+                    }
+                }
             }
             // unsize array to slice if pattern is array but match value or other patterns are slice
             (ConstValue::Scalar(Scalar::Ptr(p)), ty::Array(t, n), ty::Slice(u)) => {
@@ -2348,16 +2364,30 @@ fn specialize_one_pattern<'p, 'tcx>(
             // just integers. The only time they should be pointing to memory
             // is when they are subslices of nonzero slices.
             let (alloc, offset, n, ty) = match value.ty.kind {
-                ty::Array(t, n) => match value.val {
-                    ty::ConstKind::Value(ConstValue::ByRef { offset, alloc, .. }) => {
-                        (alloc, offset, n.eval_usize(cx.tcx, cx.param_env), t)
+                ty::Array(t, n) => {
+                    let n = n.eval_usize(cx.tcx, cx.param_env);
+                    // Shortcut for `n == 0` where no matter what `alloc` and `offset` we produce,
+                    // the result would be exactly what we early return here.
+                    if n == 0 {
+                        if ctor_wild_subpatterns.len() as u64 == 0 {
+                            return Some(PatStack::from_slice(&[]));
+                        } else {
+                            return None;
+                        }
                     }
-                    _ => span_bug!(pat.span, "array pattern is {:?}", value,),
-                },
+                    match value.val {
+                        ty::ConstKind::Value(ConstValue::ByRef { offset, alloc, .. }) => {
+                            (Cow::Borrowed(alloc), offset, n, t)
+                        }
+                        _ => span_bug!(pat.span, "array pattern is {:?}", value,),
+                    }
+                }
                 ty::Slice(t) => {
                     match value.val {
                         ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => {
-                            (data, Size::from_bytes(start as u64), (end - start) as u64, t)
+                            let offset = Size::from_bytes(start as u64);
+                            let n = (end - start) as u64;
+                            (Cow::Borrowed(data), offset, n, t)
                         }
                         ty::ConstKind::Value(ConstValue::ByRef { .. }) => {
                             // FIXME(oli-obk): implement `deref` for `ConstValue`

src/librustc_mir/hair/pattern/mod.rs

@@ -993,6 +993,12 @@ pub fn compare_const_vals<'tcx>(
         return fallback();
     }
 
+    // Early return for equal constants (so e.g. references to ZSTs can be compared, even if they
+    // are just integer addresses).
+    if a.val == b.val {
+        return from_bool(true);
+    }
+
     let a_bits = a.try_eval_bits(tcx, param_env, ty);
     let b_bits = b.try_eval_bits(tcx, param_env, ty);