Auto merge of #50968 - kennytm:rollup, r=kennytm

Rollup of 15 pull requests

Successful merges:

 - #50846 (Add E0665)
 - #50849 (CheckLoopVisitor: also visit closure arguments)
 - #50863 (Make `[T]::len` and `str::len` const fn)
 - #50875 (rustdoc: use "short form" doc(cfg) printing even when combined with other conditionals)
 - #50913 (Fix typo in cell.rs)
 - #50914 (Issue #50636: Improve error diagnostic with missing commas after struct fields.)
 - #50931 (Inline `try_get`.)
 - #50932 (Optimize seen Predicate filtering.)
 - #50945 (Stabilize feature from_ref)
 - #50946 (rustc: Fix procedural macros generating lifetime tokens)
 - #50947 (rustdoc: set tab width in rust source blocks)
 - #50952 (Add the 2018 edition of the book to doc.rust-lang.org)
 - #50958 (Micro-optimization on PR#50697)
 - #50961 (Fix FileCheck finding with MSVC)
 - #50963 (Right-size the `VecDeque` in `coerce_unsized`.)

Failed merges:

src/bootstrap/doc.rs

@@ -272,6 +272,12 @@ impl Step for TheBook {
             name: INTERNER.intern_string(format!("{}/second-edition", name)),
         });
 
+        // build book 2018 edition
+        builder.ensure(Rustbook {
+            target,
+            name: INTERNER.intern_string(format!("{}/2018-edition", name)),
+        });
+
         // build the version info page and CSS
         builder.ensure(Standalone {
             compiler,

src/bootstrap/lib.rs

@@ -592,12 +592,20 @@ impl Build {
             Path::new(llvm_bindir.trim()).join(exe("FileCheck", &*target))
         } else {
             let base = self.llvm_out(self.config.build).join("build");
-            let exe = exe("FileCheck", &*target);
-            if !self.config.ninja && self.config.build.contains("msvc") {
-                base.join("Release/bin").join(exe)
+            let base = if !self.config.ninja && self.config.build.contains("msvc") {
+                if self.config.llvm_optimize {
+                    if self.config.llvm_release_debuginfo {
+                        base.join("RelWithDebInfo")
+                    } else {
+                        base.join("Release")
+                    }
+                } else {
+                    base.join("Debug")
+                }
             } else {
-                base.join("bin").join(exe)
-            }
+                base
+            };
+            base.join("bin").join(exe("FileCheck", &*target))
         }
     }
 

src/liballoc/slice.rs

@@ -119,8 +119,8 @@ pub use core::slice::{SplitN, RSplitN, SplitNMut, RSplitNMut};
 pub use core::slice::{RSplit, RSplitMut};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::slice::{from_raw_parts, from_raw_parts_mut};
-#[unstable(feature = "from_ref", issue = "45703")]
-pub use core::slice::{from_ref, from_ref_mut};
+#[stable(feature = "from_ref", since = "1.28.0")]
+pub use core::slice::{from_ref, from_mut};
 #[unstable(feature = "slice_get_slice", issue = "35729")]
 pub use core::slice::SliceIndex;
 #[unstable(feature = "exact_chunks", issue = "47115")]

src/libcore/cell.rs

@@ -1257,7 +1257,7 @@ impl<'a, T: ?Sized + fmt::Display> fmt::Display for RefMut<'a, T> {
 /// To assist with proper design, the following scenarios are explicitly declared legal
 /// for single-threaded code:
 ///
-/// 1. A `&T` reference can be released to safe code and there it can co-exit with other `&T`
+/// 1. A `&T` reference can be released to safe code and there it can co-exist with other `&T`
 /// references, but not with a `&mut T`
 ///
 /// 2. A `&mut T` reference may be released to safe code provided neither other `&mut T` nor `&T`

src/libcore/lib.rs

@@ -119,6 +119,9 @@
 #![feature(powerpc_target_feature)]
 #![feature(mips_target_feature)]
 #![feature(aarch64_target_feature)]
+#![feature(const_slice_len)]
+#![feature(const_str_as_bytes)]
+#![feature(const_str_len)]
 
 #[prelude_import]
 #[allow(unused)]

src/libcore/slice/mod.rs

@@ -59,9 +59,16 @@ mod rotate;
 mod sort;
 
 #[repr(C)]
-struct Repr<T> {
-    pub data: *const T,
-    pub len: usize,
+union Repr<'a, T: 'a> {
+    rust: &'a [T],
+    rust_mut: &'a mut [T],
+    raw: FatPtr<T>,
+}
+
+#[repr(C)]
+struct FatPtr<T> {
+    data: *const T,
+    len: usize,
 }
 
 //
@@ -119,9 +126,10 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn len(&self) -> usize {
+    #[rustc_const_unstable(feature = "const_slice_len")]
+    pub const fn len(&self) -> usize {
         unsafe {
-            mem::transmute::<&[T], Repr<T>>(self).len
+            Repr { rust: self }.raw.len
         }
     }
 
@@ -135,7 +143,8 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn is_empty(&self) -> bool {
+    #[rustc_const_unstable(feature = "const_slice_len")]
+    pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
 
@@ -418,7 +427,8 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn as_ptr(&self) -> *const T {
+    #[rustc_const_unstable(feature = "const_slice_as_ptr")]
+    pub const fn as_ptr(&self) -> *const T {
         self as *const [T] as *const T
     }
 
@@ -3856,8 +3866,8 @@ unsafe impl<'a, T> TrustedRandomAccess for ExactChunksMut<'a, T> {
 /// ```
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn from_raw_parts<'a, T>(p: *const T, len: usize) -> &'a [T] {
-    mem::transmute(Repr { data: p, len: len })
+pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
+    Repr { raw: FatPtr { data, len } }.rust
 }
 
 /// Performs the same functionality as `from_raw_parts`, except that a mutable
@@ -3869,21 +3879,21 @@ pub unsafe fn from_raw_parts<'a, T>(p: *const T, len: usize) -> &'a [T] {
 /// `from_raw_parts`.
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
-pub unsafe fn from_raw_parts_mut<'a, T>(p: *mut T, len: usize) -> &'a mut [T] {
-    mem::transmute(Repr { data: p, len: len })
+pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
+    Repr { raw: FatPtr { data, len} }.rust_mut
 }
 
 /// Converts a reference to T into a slice of length 1 (without copying).
-#[unstable(feature = "from_ref", issue = "45703")]
+#[stable(feature = "from_ref", since = "1.28.0")]
 pub fn from_ref<T>(s: &T) -> &[T] {
     unsafe {
         from_raw_parts(s, 1)
     }
 }
 
 /// Converts a reference to T into a slice of length 1 (without copying).
-#[unstable(feature = "from_ref", issue = "45703")]
-pub fn from_ref_mut<T>(s: &mut T) -> &mut [T] {
+#[stable(feature = "from_ref", since = "1.28.0")]
+pub fn from_mut<T>(s: &mut T) -> &mut [T] {
     unsafe {
         from_raw_parts_mut(s, 1)
     }

src/libcore/str/mod.rs

@@ -2166,7 +2166,8 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn len(&self) -> usize {
+    #[rustc_const_unstable(feature = "const_str_len")]
+    pub const fn len(&self) -> usize {
         self.as_bytes().len()
     }
 
@@ -2185,7 +2186,8 @@ impl str {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn is_empty(&self) -> bool {
+    #[rustc_const_unstable(feature = "const_str_len")]
+    pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }
 
@@ -2242,8 +2244,15 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline(always)]
-    pub fn as_bytes(&self) -> &[u8] {
-        unsafe { &*(self as *const str as *const [u8]) }
+    #[rustc_const_unstable(feature="const_str_as_bytes")]
+    pub const fn as_bytes(&self) -> &[u8] {
+        unsafe {
+            union Slices<'a> {
+                str: &'a str,
+                slice: &'a [u8],
+            }
+            Slices { str: self }.slice
+        }
     }
 
     /// Converts a mutable string slice to a mutable byte slice. To convert the
@@ -2303,7 +2312,8 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn as_ptr(&self) -> *const u8 {
+    #[rustc_const_unstable(feature = "const_str_as_ptr")]
+    pub const fn as_ptr(&self) -> *const u8 {
         self as *const str as *const u8
     }
 

src/librustc/mir/mod.rs

@@ -948,7 +948,7 @@ impl<'tcx> TerminatorKind<'tcx> {
             Drop { target: ref mut t, unwind: Some(ref mut u), .. } |
             Assert { target: ref mut t, cleanup: Some(ref mut u), .. } |
             FalseUnwind { real_target: ref mut t, unwind: Some(ref mut u) } => {
-                Some(t).into_iter().chain(slice::from_ref_mut(u))
+                Some(t).into_iter().chain(slice::from_mut(u))
             }
             SwitchInt { ref mut targets, .. } => {
                 None.into_iter().chain(&mut targets[..])

src/librustc/traits/select.rs

@@ -3356,13 +3356,28 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     predicate: predicate.value
                 }))
         }).collect();
+
         // We are performing deduplication here to avoid exponential blowups
         // (#38528) from happening, but the real cause of the duplication is
         // unknown. What we know is that the deduplication avoids exponential
-        // amount of predicates being propogated when processing deeply nested
+        // amount of predicates being propagated when processing deeply nested
         // types.
-        let mut seen = FxHashSet();
-        predicates.retain(|i| seen.insert(i.clone()));
+        //
+        // This code is hot enough that it's worth avoiding the allocation
+        // required for the FxHashSet when possible. Special-casing lengths 0,
+        // 1 and 2 covers roughly 75--80% of the cases.
+        if predicates.len() <= 1 {
+            // No possibility of duplicates.
+        } else if predicates.len() == 2 {
+            // Only two elements. Drop the second if they are equal.
+            if predicates[0] == predicates[1] {
+                predicates.truncate(1);
+            }
+        } else {
+            // Three or more elements. Use a general deduplication process.
+            let mut seen = FxHashSet();
+            predicates.retain(|i| seen.insert(i.clone()));
+        }
         self.infcx().plug_leaks(skol_map, snapshot, predicates)
     }
 }

src/librustc/ty/maps/plumbing.rs

@@ -105,6 +105,10 @@ impl<'a, 'tcx, Q: QueryDescription<'tcx>> JobOwner<'a, 'tcx, Q> {
     /// start executing the query, or it returns with the result of the query.
     /// If the query is executing elsewhere, this will wait for it.
     /// If the query panicked, this will silently panic.
+    ///
+    /// This function is inlined because that results in a noticeable speedup
+    /// for some compile-time benchmarks.
+    #[inline(always)]
     pub(super) fn try_get(
         tcx: TyCtxt<'a, 'tcx, '_>,
         span: Span,

src/librustc_mir/borrow_check/mod.rs

@@ -1853,6 +1853,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                     for index in ii {
                         if flow_state.ever_inits.contains(index) {
                             self.used_mut.insert(*local);
+                            break;
                         }
                     }
                 }

src/librustc_passes/loops.rs

@@ -82,7 +82,8 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
             hir::ExprLoop(ref b, _, source) => {
                 self.with_context(Loop(LoopKind::Loop(source)), |v| v.visit_block(&b));
             }
-            hir::ExprClosure(.., b, _, _) => {
+            hir::ExprClosure(_, ref function_decl, b, _, _) => {
+                self.visit_fn_decl(&function_decl);
                 self.with_context(Closure, |v| v.visit_nested_body(b));
             }
             hir::ExprBlock(ref b, Some(_label)) => {

src/librustc_typeck/check/coercion.rs

@@ -537,8 +537,9 @@ impl<'f, 'gcx, 'tcx> Coerce<'f, 'gcx, 'tcx> {
 
         let mut selcx = traits::SelectionContext::new(self);
 
-        // Use a FIFO queue for this custom fulfillment procedure.
-        let mut queue = VecDeque::new();
+        // Use a FIFO queue for this custom fulfillment procedure. (The maximum
+        // length is almost always 1.)
+        let mut queue = VecDeque::with_capacity(1);
 
         // Create an obligation for `Source: CoerceUnsized<Target>`.
         let cause = ObligationCause::misc(self.cause.span, self.body_id);