Auto merge of rust-lang#72187 - RalfJung:rollup-a7a9jdi, r=RalfJung

Rollup of 12 pull requests

Successful merges:

 - rust-lang#71525 (`prefix` should not be mutable.)
 - rust-lang#71741 (Pointer printing: do not print 0 offset)
 - rust-lang#71870 (Be slightly more precise about any::type_name()'s guarantees.)
 - rust-lang#71909 (Document From trait for Option implementations)
 - rust-lang#71964 (Fix bootstrap failing on win32)
 - rust-lang#72137 (Clean up E0581 explanation)
 - rust-lang#72138 (Add doc comment for `rustc_middle::mir::mono::Linkage`)
 - rust-lang#72150 (Remove UnnormalizedProjection)
 - rust-lang#72151 (Update books)
 - rust-lang#72163 (docs: remove comment referencing non-existent method)
 - rust-lang#72169 (Clean up E0582 explanation)
 - rust-lang#72183 (Fix Arc::decr_strong_count doc test)

Failed merges:

r? @ghost

src/bootstrap/bootstrap.py

@@ -180,13 +180,16 @@ def format_build_time(duration):
 def default_build_triple():
     """Build triple as in LLVM"""
     default_encoding = sys.getdefaultencoding()
-    required = not sys.platform == 'win32'
-    ostype = require(["uname", "-s"], exit=required).decode(default_encoding)
-    cputype = require(['uname', '-m'], exit=required).decode(default_encoding)
+    required = sys.platform != 'win32'
+    ostype = require(["uname", "-s"], exit=required)
+    cputype = require(['uname', '-m'], exit=required)
 
     if ostype is None or cputype is None:
         return 'x86_64-pc-windows-msvc'
 
+    ostype = ostype.decode(default_encoding)
+    cputype = cputype.decode(default_encoding)
+
     # The goal here is to come up with the same triple as LLVM would,
     # at least for the subset of platforms we're willing to target.
     ostype_mapper = {

src/liballoc/sync.rs

@@ -835,12 +835,14 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// unsafe {
     ///     let ptr = Arc::into_raw(five);
-    ///     Arc::decr_strong_count(ptr);
+    ///     Arc::incr_strong_count(ptr);
     ///
-    ///     // This assertion is deterministic because we haven't shared
+    ///     // Those assertions are deterministic because we haven't shared
     ///     // the `Arc` between threads.
     ///     let five = Arc::from_raw(ptr);
-    ///     assert_eq!(0, Arc::strong_count(&five));
+    ///     assert_eq!(2, Arc::strong_count(&five));
+    ///     Arc::decr_strong_count(ptr);
+    ///     assert_eq!(1, Arc::strong_count(&five));
     /// }
     /// ```
     #[inline]

src/libcore/any.rs

@@ -446,14 +446,16 @@ impl TypeId {
 /// # Note
 ///
 /// This is intended for diagnostic use. The exact contents and format of the
-/// string are not specified, other than being a best-effort description of the
-/// type. For example, `type_name::<Option<String>>()` could return the
-/// `"Option<String>"` or `"std::option::Option<std::string::String>"`, but not
-/// `"foobar"`. In addition, the output may change between versions of the
-/// compiler.
+/// string returned are not specified, other than being a best-effort
+/// description of the type. For example, amongst the strings
+/// that `type_name::<Option<String>>()` might return are `"Option<String>"` and
+/// `"std::option::Option<std::string::String>"`.
 ///
-/// The type name should not be considered a unique identifier of a type;
-/// multiple types may share the same type name.
+/// The returned string must not be considered to be a unique identifier of a
+/// type as multiple types may map to the same type name. Similarly, there is no
+/// guarantee that all parts of a type will appear in the returned string: for
+/// example, lifetime specifiers are currently not included. In addition, the
+/// output may change between versions of the compiler.
 ///
 /// The current implementation uses the same infrastructure as compiler
 /// diagnostics and debuginfo, but this is not guaranteed.

src/libcore/option.rs

@@ -1357,20 +1357,65 @@ impl<'a, T> IntoIterator for &'a mut Option<T> {
 
 #[stable(since = "1.12.0", feature = "option_from")]
 impl<T> From<T> for Option<T> {
+    /// Copies `val` into a new `Some`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let o: Option<u8> = Option::from(67);
+    ///
+    /// assert_eq!(Some(67), o);
+    /// ```
     fn from(val: T) -> Option<T> {
         Some(val)
     }
 }
 
 #[stable(feature = "option_ref_from_ref_option", since = "1.30.0")]
 impl<'a, T> From<&'a Option<T>> for Option<&'a T> {
+    /// Converts from `&Option<T>` to `Option<&T>`.
+    ///
+    /// # Examples
+    ///
+    /// Converts an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, preserving the original.
+    /// The [`map`] method takes the `self` argument by value, consuming the original,
+    /// so this technique uses `as_ref` to first take an `Option` to a reference
+    /// to the value inside the original.
+    ///
+    /// [`map`]: ../../std/option/enum.Option.html#method.map
+    /// [`String`]: ../../std/string/struct.String.html
+    /// [`usize`]: ../../std/primitive.usize.html
+    ///
+    /// ```
+    /// let s: Option<String> = Some(String::from("Hello, Rustaceans!"));
+    /// let o: Option<usize> = Option::from(&s).map(|ss: &String| ss.len());
+    ///
+    /// println!("Can still print s: {:?}", s);
+    ///
+    /// assert_eq!(o, Some(18));
+    /// ```
     fn from(o: &'a Option<T>) -> Option<&'a T> {
         o.as_ref()
     }
 }
 
 #[stable(feature = "option_ref_from_ref_option", since = "1.30.0")]
 impl<'a, T> From<&'a mut Option<T>> for Option<&'a mut T> {
+    /// Converts from `&mut Option<T>` to `Option<&mut T>`
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut s = Some(String::from("Hello"));
+    /// let o: Option<&mut String> = Option::from(&mut s);
+    ///
+    /// match o {
+    ///     Some(t) => *t = String::from("Hello, Rustaceans!"),
+    ///     None => (),
+    /// }
+    ///
+    /// assert_eq!(s, Some(String::from("Hello, Rustaceans!")));
+    /// ```
     fn from(o: &'a mut Option<T>) -> Option<&'a mut T> {
         o.as_mut()
     }

src/librustc_codegen_ssa/debuginfo/type_names.rs

@@ -198,7 +198,6 @@ pub fn push_debuginfo_type_name<'tcx>(
         ty::Error
         | ty::Infer(_)
         | ty::Placeholder(..)
-        | ty::UnnormalizedProjection(..)
         | ty::Projection(..)
         | ty::Bound(..)
         | ty::Opaque(..)

src/librustc_error_codes/error_codes/E0581.md

@@ -1,4 +1,4 @@
-In a `fn` type, a lifetime appears only in the return type,
+In a `fn` type, a lifetime appears only in the return type
 and not in the arguments types.
 
 Erroneous code example:
@@ -10,8 +10,11 @@ fn main() {
 }
 ```
 
-To fix this issue, either use the lifetime in the arguments, or use
-`'static`. Example:
+The problem here is that the lifetime isn't contrained by any of the arguments,
+making it impossible to determine how long it's supposed to live.
+
+To fix this issue, either use the lifetime in the arguments, or use the
+`'static` lifetime. Example:
 
 ```
 fn main() {

src/librustc_error_codes/error_codes/E0582.md

@@ -1,5 +1,5 @@
-A lifetime appears only in an associated-type binding,
-and not in the input types to the trait.
+A lifetime is only present in an associated-type binding, and not in the input
+types to the trait.
 
 Erroneous code example:
 

src/librustc_infer/infer/canonical/canonicalizer.rs

@@ -415,7 +415,6 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
             | ty::Never
             | ty::Tuple(..)
             | ty::Projection(..)
-            | ty::UnnormalizedProjection(..)
             | ty::Foreign(..)
             | ty::Param(..)
             | ty::Opaque(..) => {

src/librustc_infer/infer/error_reporting/need_type_info.rs

@@ -554,7 +554,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                     let output = bound_output.skip_binder();
                     err.span_label(e.span, &format!("this method call resolves to `{:?}`", output));
                     let kind = &output.kind;
-                    if let ty::Projection(proj) | ty::UnnormalizedProjection(proj) = kind {
+                    if let ty::Projection(proj) = kind {
                         if let Some(span) = self.tcx.hir().span_if_local(proj.item_def_id) {
                             err.span_label(span, &format!("`{:?}` defined here", output));
                         }

src/librustc_infer/infer/freshen.rs

@@ -204,7 +204,6 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             | ty::Never
             | ty::Tuple(..)
             | ty::Projection(..)
-            | ty::UnnormalizedProjection(..)
             | ty::Foreign(..)
             | ty::Param(..)
             | ty::Closure(..)

src/librustc_lint/types.rs

@@ -888,7 +888,6 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             | ty::Generator(..)
             | ty::GeneratorWitness(..)
             | ty::Placeholder(..)
-            | ty::UnnormalizedProjection(..)
             | ty::Projection(..)
             | ty::Opaque(..)
             | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),

src/librustc_middle/mir/interpret/pointer.rs

@@ -89,27 +89,35 @@ pub struct Pointer<Tag = ()> {
 
 static_assert_size!(Pointer, 16);
 
+/// Print the address of a pointer (without the tag)
+fn print_ptr_addr<Tag>(ptr: &Pointer<Tag>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+    // Forward `alternate` flag to `alloc_id` printing.
+    if f.alternate() {
+        write!(f, "{:#?}", ptr.alloc_id)?;
+    } else {
+        write!(f, "{:?}", ptr.alloc_id)?;
+    }
+    // Print offset only if it is non-zero.
+    if ptr.offset.bytes() > 0 {
+        write!(f, "+0x{:x}", ptr.offset.bytes())?;
+    }
+    Ok(())
+}
+
 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
 // all the Miri types.
 // We have to use `Debug` output for the tag, because `()` does not implement
 // `Display` so we cannot specialize that.
 impl<Tag: fmt::Debug> fmt::Debug for Pointer<Tag> {
     default fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if f.alternate() {
-            write!(f, "{:#?}+0x{:x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
-        } else {
-            write!(f, "{:?}+0x{:x}[{:?}]", self.alloc_id, self.offset.bytes(), self.tag)
-        }
+        print_ptr_addr(self, f)?;
+        write!(f, "[{:?}]", self.tag)
     }
 }
 // Specialization for no tag
 impl fmt::Debug for Pointer<()> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if f.alternate() {
-            write!(f, "{:#?}+0x{:x}", self.alloc_id, self.offset.bytes())
-        } else {
-            write!(f, "{:?}+0x{:x}", self.alloc_id, self.offset.bytes())
-        }
+        print_ptr_addr(self, f)
     }
 }
 

src/librustc_middle/mir/mono.rs

@@ -239,6 +239,9 @@ pub struct CodegenUnit<'tcx> {
     size_estimate: Option<usize>,
 }
 
+/// Specifies the linkage type for a `MonoItem`.
+///
+/// See https://llvm.org/docs/LangRef.html#linkage-types for more details about these variants.
 #[derive(Copy, Clone, PartialEq, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub enum Linkage {
     External,

src/librustc_middle/traits/query.rs

@@ -255,8 +255,6 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
         | ty::Infer(_)
         | ty::Bound(..)
         | ty::Generator(..) => false,
-
-        ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
     }
 }
 

src/librustc_middle/ty/context.rs

@@ -1878,7 +1878,6 @@ impl<'tcx> TyCtxt<'tcx> {
             Bound,
             Param,
             Infer,
-            UnnormalizedProjection,
             Projection,
             Opaque,
             Foreign

src/librustc_middle/ty/error.rs

@@ -284,7 +284,6 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
             ty::Projection(_) => "associated type".into(),
-            ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
             ty::Param(p) => format!("type parameter `{}`", p).into(),
             ty::Opaque(..) => "opaque type".into(),
             ty::Error => "type error".into(),
@@ -323,7 +322,6 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::Placeholder(..) => "higher-ranked type".into(),
             ty::Bound(..) => "bound type variable".into(),
             ty::Projection(_) => "associated type".into(),
-            ty::UnnormalizedProjection(_) => "associated type".into(),
             ty::Param(_) => "type parameter".into(),
             ty::Opaque(..) => "opaque type".into(),
         }

src/librustc_middle/ty/fast_reject.rs

@@ -90,7 +90,6 @@ pub fn simplify_type(
         ty::Never => Some(NeverSimplifiedType),
         ty::Tuple(ref tys) => Some(TupleSimplifiedType(tys.len())),
         ty::FnPtr(ref f) => Some(FunctionSimplifiedType(f.skip_binder().inputs().len())),
-        ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
         ty::Projection(_) | ty::Param(_) => {
             if can_simplify_params {
                 // In normalized types, projections don't unify with

src/librustc_middle/ty/flags.rs

@@ -121,11 +121,6 @@ impl FlagComputation {
                 self.add_projection_ty(data);
             }
 
-            &ty::UnnormalizedProjection(ref data) => {
-                self.add_flags(TypeFlags::HAS_TY_PROJECTION);
-                self.add_projection_ty(data);
-            }
-
             &ty::Opaque(_, substs) => {
                 self.add_flags(TypeFlags::HAS_TY_OPAQUE);
                 self.add_substs(substs);

src/librustc_middle/ty/layout.rs

@@ -1241,11 +1241,9 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
                 tcx.layout_raw(param_env.and(normalized))?
             }
 
-            ty::Bound(..)
-            | ty::Placeholder(..)
-            | ty::UnnormalizedProjection(..)
-            | ty::GeneratorWitness(..)
-            | ty::Infer(_) => bug!("Layout::compute: unexpected type `{}`", ty),
+            ty::Bound(..) | ty::Placeholder(..) | ty::GeneratorWitness(..) | ty::Infer(_) => {
+                bug!("Layout::compute: unexpected type `{}`", ty)
+            }
 
             ty::Param(_) | ty::Error => {
                 return Err(LayoutError::Unknown(ty));
@@ -2138,7 +2136,6 @@ where
             }
 
             ty::Projection(_)
-            | ty::UnnormalizedProjection(..)
             | ty::Bound(..)
             | ty::Placeholder(..)
             | ty::Opaque(..)

src/librustc_middle/ty/mod.rs

@@ -555,7 +555,7 @@ bitflags! {
                                           | TypeFlags::HAS_CT_PLACEHOLDER.bits
                                           | TypeFlags::HAS_FREE_LOCAL_REGIONS.bits;
 
-        /// Does this have [Projection] or [UnnormalizedProjection]?
+        /// Does this have [Projection]?
         const HAS_TY_PROJECTION           = 1 << 10;
         /// Does this have [Opaque]?
         const HAS_TY_OPAQUE               = 1 << 11;

src/librustc_middle/ty/outlives.rs

@@ -135,8 +135,6 @@ fn compute_components(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, out: &mut SmallVec<[Compo
                 }
             }
 
-            ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
-
             // We assume that inference variables are fully resolved.
             // So, if we encounter an inference variable, just record
             // the unresolved variable as a component.

src/librustc_middle/ty/print/mod.rs

@@ -294,7 +294,6 @@ pub fn characteristic_def_id_of_type(ty: Ty<'_>) -> Option<DefId> {
         | ty::FnPtr(_)
         | ty::Projection(_)
         | ty::Placeholder(..)
-        | ty::UnnormalizedProjection(..)
         | ty::Param(_)
         | ty::Opaque(..)
         | ty::Infer(_)

src/librustc_middle/ty/print/obsolete.rs

@@ -148,7 +148,6 @@ impl DefPathBasedNames<'tcx> {
             | ty::Bound(..)
             | ty::Infer(_)
             | ty::Placeholder(..)
-            | ty::UnnormalizedProjection(..)
             | ty::Projection(..)
             | ty::Param(_)
             | ty::GeneratorWitness(_)

src/librustc_middle/ty/print/pretty.rs

@@ -540,9 +540,6 @@ pub trait PrettyPrinter<'tcx>:
                 p!(print_def_path(def_id, &[]));
             }
             ty::Projection(ref data) => p!(print(data)),
-            ty::UnnormalizedProjection(ref data) => {
-                p!(write("Unnormalized("), print(data), write(")"))
-            }
             ty::Placeholder(placeholder) => p!(write("Placeholder({:?})", placeholder)),
             ty::Opaque(def_id, substs) => {
                 // FIXME(eddyb) print this with `print_def_path`.