Auto merge of #64526 - Centril:rollup-k4cz2xn, r=Centril

Rollup of 4 pull requests

Successful merges:

 - #64357 (`AdtDef` is an algebraic data type, not abstract data type)
 - #64485 (update Miri)
 - #64509 (Make some adjustments to the documentation for `std::convert::identity`)
 - #64518 (Use while let slice_pattern instead of carrying an index around)

Failed merges:

r? @ghost

13 files changed, 54 insertions, 39 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 77e2ce07dbc..0fe31384274 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -234,9 +234,9 @@ dependencies = [
 
 [[package]]
 name = "byteorder"
-version = "1.2.7"
+version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "94f88df23a25417badc922ab0f5716cc1330e87f71ddd9203b3a3ccd9cedf75d"
+checksum = "a7c3dd8985a7111efc5c80b44e23ecdd8c007de8ade3b96595387e812b957cf5"
 
 [[package]]
 name = "bytes"
@@ -2067,7 +2067,7 @@ dependencies = [
  "hex",
  "log",
  "num-traits",
- "rand 0.6.1",
+ "rand 0.7.0",
  "rustc-workspace-hack",
  "rustc_version",
  "shell-escape",
@@ -3255,7 +3255,6 @@ dependencies = [
 name = "rustc-workspace-hack"
 version = "1.0.0"
 dependencies = [
- "byteorder",
  "crossbeam-utils 0.6.5",
  "serde",
  "serde_json",
diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs
index 402a7b2c95a..06f2b7bab12 100644
--- a/src/libcore/convert.rs
+++ b/src/libcore/convert.rs
@@ -42,11 +42,11 @@
 
 use crate::fmt;
 
-/// An identity function.
+/// The identity function.
 ///
 /// Two things are important to note about this function:
 ///
-/// - It is not always equivalent to a closure like `|x| x` since the
+/// - It is not always equivalent to a closure like `|x| x`, since the
 ///   closure may coerce `x` into a different type.
 ///
 /// - It moves the input `x` passed to the function.
@@ -56,31 +56,32 @@ use crate::fmt;
 ///
 /// # Examples
 ///
-/// Using `identity` to do nothing among other interesting functions:
+/// Using `identity` to do nothing in a sequence of other, interesting,
+/// functions:
 ///
 /// ```rust
 /// use std::convert::identity;
 ///
 /// fn manipulation(x: u32) -> u32 {
-///     // Let's assume that this function does something interesting.
+///     // Let's pretend that adding one is an interesting function.
 ///     x + 1
 /// }
 ///
 /// let _arr = &[identity, manipulation];
 /// ```
 ///
-/// Using `identity` to get a function that changes nothing in a conditional:
+/// Using `identity` as a "do nothing" base case in a conditional:
 ///
 /// ```rust
 /// use std::convert::identity;
 ///
 /// # let condition = true;
-///
+/// #
 /// # fn manipulation(x: u32) -> u32 { x + 1 }
-///
+/// #
 /// let do_stuff = if condition { manipulation } else { identity };
 ///
-/// // do more interesting stuff..
+/// // Do more interesting stuff...
 ///
 /// let _results = do_stuff(42);
 /// ```
diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
index d569573a5e9..0834faf1324 100644
--- a/src/librustc/Cargo.toml
+++ b/src/librustc/Cargo.toml
@@ -31,7 +31,7 @@ syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 backtrace = "0.3.3"
 parking_lot = "0.9"
-byteorder = { version = "1.1", features = ["i128"]}
+byteorder = { version = "1.3" }
 chalk-engine = { version = "0.9.0", default-features=false }
 rustc_fs_util = { path = "../librustc_fs_util" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 17eb4a8957f..5ca819e12f2 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -1938,9 +1938,15 @@ pub struct FieldDef {
     pub vis: Visibility,
 }
 
-/// The definition of an abstract data type -- a struct or enum.
+/// The definition of a user-defined type, e.g., a `struct`, `enum`, or `union`.
 ///
 /// These are all interned (by `intern_adt_def`) into the `adt_defs` table.
+///
+/// The initialism *"Adt"* stands for an [*algebraic data type (ADT)*][adt].
+/// This is slightly wrong because `union`s are not ADTs.
+/// Moreover, Rust only allows recursive data types through indirection.
+///
+/// [adt]: https://en.wikipedia.org/wiki/Algebraic_data_type
 pub struct AdtDef {
     /// `DefId` of the struct, enum or union item.
     pub did: DefId,
diff --git a/src/librustc_mir/Cargo.toml b/src/librustc_mir/Cargo.toml
index e02736078b5..0691390bead 100644
--- a/src/librustc_mir/Cargo.toml
+++ b/src/librustc_mir/Cargo.toml
@@ -24,6 +24,6 @@ rustc_lexer = { path = "../librustc_lexer" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
-byteorder = { version = "1.1", features = ["i128"] }
+byteorder = { version = "1.3" }
 rustc_apfloat = { path = "../librustc_apfloat" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
diff --git a/src/librustc_mir/borrow_check/conflict_errors.rs b/src/librustc_mir/borrow_check/conflict_errors.rs
index 4b4516d6bf2..81359c6a46e 100644
--- a/src/librustc_mir/borrow_check/conflict_errors.rs
+++ b/src/librustc_mir/borrow_check/conflict_errors.rs
@@ -614,8 +614,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     projection,
                 } = first_borrowed_place;
 
-                for (i, elem) in projection.iter().enumerate().rev() {
-                    let proj_base = &projection[..i];
+                let mut cursor = &**projection;
+                while let [proj_base @ .., elem] = cursor {
+                    cursor = proj_base;
 
                     match elem {
                         ProjectionElem::Field(field, _) if union_ty(base, proj_base).is_some() => {
@@ -637,8 +638,9 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     projection,
                 } = second_borrowed_place;
 
-                for (i, elem) in projection.iter().enumerate().rev() {
-                    let proj_base = &projection[..i];
+                let mut cursor = &**projection;
+                while let [proj_base @ .., elem] = cursor {
+                    cursor = proj_base;
 
                     if let ProjectionElem::Field(field, _) = elem {
                         if let Some(union_ty) = union_ty(base, proj_base) {
diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs
index 5ef70461296..1d3576244c4 100644
--- a/src/librustc_mir/borrow_check/mod.rs
+++ b/src/librustc_mir/borrow_check/mod.rs
@@ -1758,7 +1758,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         debug!("check_if_assigned_path_is_moved place: {:?}", place);
 
         // None case => assigning to `x` does not require `x` be initialized.
-        for (i, elem) in place.projection.iter().enumerate().rev() {
+        let mut cursor = &*place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
+
             match elem {
                 ProjectionElem::Index(_/*operand*/) |
                 ProjectionElem::ConstantIndex { .. } |
@@ -1771,8 +1774,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
                 // assigning to (*P) requires P to be initialized
                 ProjectionElem::Deref => {
-                    let proj_base = &place.projection[..i];
-
                     self.check_if_full_path_is_moved(
                         location, InitializationRequiringAction::Use,
                         (PlaceRef {
@@ -1790,7 +1791,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 }
 
                 ProjectionElem::Field(..) => {
-                    let proj_base = &place.projection[..i];
                     // if type of `P` has a dtor, then
                     // assigning to `P.f` requires `P` itself
                     // be already initialized
diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index 1d17bae559c..62bff3421a0 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -2417,9 +2417,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             "add_reborrow_constraint({:?}, {:?}, {:?})",
             location, borrow_region, borrowed_place
         );
-        for (i, elem) in borrowed_place.projection.iter().enumerate().rev() {
+
+        let mut cursor = &*borrowed_place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
+
             debug!("add_reborrow_constraint - iteration {:?}", elem);
-            let proj_base = &borrowed_place.projection[..i];
 
             match elem {
                 ProjectionElem::Deref => {
diff --git a/src/librustc_mir/build/matches/mod.rs b/src/librustc_mir/build/matches/mod.rs
index aa261f8eb6f..2b0237c7c08 100644
--- a/src/librustc_mir/build/matches/mod.rs
+++ b/src/librustc_mir/build/matches/mod.rs
@@ -1296,8 +1296,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // Insert a Shallow borrow of the prefixes of any fake borrows.
         for place in fake_borrows
         {
-            for (i, elem) in place.projection.iter().enumerate().rev() {
-                let proj_base = &place.projection[..i];
+            let mut cursor = &*place.projection;
+            while let [proj_base @ .., elem] = cursor {
+                cursor = proj_base;
 
                 if let ProjectionElem::Deref = elem {
                     // Insert a shallow borrow after a deref. For other
diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index f8af9b9fcbe..39aa5c717ac 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -407,8 +407,9 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
         place: &Place<'tcx>,
         is_mut_use: bool,
     ) {
-        for (i, elem) in place.projection.iter().enumerate().rev() {
-            let proj_base = &place.projection[..i];
+        let mut cursor = &*place.projection;
+        while let [proj_base @ .., elem] = cursor {
+            cursor = proj_base;
 
             match elem {
                 ProjectionElem::Field(..) => {
diff --git a/src/librustc_mir/util/alignment.rs b/src/librustc_mir/util/alignment.rs
index b4c97f91917..a75c1af04f0 100644
--- a/src/librustc_mir/util/alignment.rs
+++ b/src/librustc_mir/util/alignment.rs
@@ -38,8 +38,9 @@ fn is_within_packed<'tcx, L>(tcx: TyCtxt<'tcx>, local_decls: &L, place: &Place<'
 where
     L: HasLocalDecls<'tcx>,
 {
-    for (i, elem) in place.projection.iter().enumerate().rev() {
-        let proj_base = &place.projection[..i];
+    let mut cursor = &*place.projection;
+    while let [proj_base @ .., elem] = cursor {
+        cursor = proj_base;
 
         match elem {
             // encountered a Deref, which is ABI-aligned
diff --git a/src/tools/miri b/src/tools/miri
-Subproject dd94c7c5a32be2ee0adeeaf9d46f26f14925797
+Subproject d88138723780d11ca2c09560111223dc20b9d5f
diff --git a/src/tools/rustc-workspace-hack/Cargo.toml b/src/tools/rustc-workspace-hack/Cargo.toml
index d068e1cf307..930279c0ca2 100644
--- a/src/tools/rustc-workspace-hack/Cargo.toml
+++ b/src/tools/rustc-workspace-hack/Cargo.toml
@@ -62,7 +62,6 @@ crossbeam-utils = { version = "0.6.5", features = ["nightly"] }
 serde = { version = "1.0.82", features = ['derive'] }
 serde_json = { version = "1.0.31", features = ["raw_value"] }
 smallvec = { version = "0.6", features = ['union', 'may_dangle'] }
-byteorder = { version = "1.2.7", features = ["i128"] }
 
 
 [target.'cfg(not(windows))'.dependencies]