Auto merge of #42780 - frewsxcv:rollup, r=frewsxcv

Rollup of 6 pull requests

- Successful merges: #42271, #42717, #42728, #42749, #42756, #42772
- Failed merges:

src/doc/unstable-book/src/library-features/char-error-internals.md

@@ -0,0 +1,5 @@
+# `char_error_internals`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------

src/liballoc/vec.rs

@@ -2124,10 +2124,12 @@ impl<T> From<Box<[T]>> for Vec<T> {
     }
 }
 
-#[stable(feature = "box_from_vec", since = "1.18.0")]
-impl<T> Into<Box<[T]>> for Vec<T> {
-    fn into(self) -> Box<[T]> {
-        self.into_boxed_slice()
+// note: test pulls in libstd, which causes errors here
+#[cfg(not(test))]
+#[stable(feature = "box_from_vec", since = "1.20.0")]
+impl<T> From<Vec<T>> for Box<[T]> {
+    fn from(v: Vec<T>) -> Box<[T]> {
+        v.into_boxed_slice()
     }
 }
 

src/libcore/char.rs

@@ -19,7 +19,7 @@ use char_private::is_printable;
 use convert::TryFrom;
 use fmt::{self, Write};
 use slice;
-use str::from_utf8_unchecked_mut;
+use str::{from_utf8_unchecked_mut, FromStr};
 use iter::FusedIterator;
 use mem::transmute;
 
@@ -208,6 +208,63 @@ impl From<u8> for char {
     }
 }
 
+
+/// An error which can be returned when parsing a char.
+#[stable(feature = "char_from_str", since = "1.19.0")]
+#[derive(Clone, Debug)]
+pub struct ParseCharError {
+    kind: CharErrorKind,
+}
+
+impl ParseCharError {
+    #[unstable(feature = "char_error_internals",
+               reason = "this method should not be available publicly",
+               issue = "0")]
+    #[doc(hidden)]
+    pub fn __description(&self) -> &str {
+        match self.kind {
+            CharErrorKind::EmptyString => {
+                "cannot parse char from empty string"
+            },
+            CharErrorKind::TooManyChars => "too many characters in string"
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum CharErrorKind {
+    EmptyString,
+    TooManyChars,
+}
+
+#[stable(feature = "char_from_str", since = "1.19.0")]
+impl fmt::Display for ParseCharError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.__description().fmt(f)
+    }
+}
+
+
+#[stable(feature = "char_from_str", since = "1.19.0")]
+impl FromStr for char {
+    type Err = ParseCharError;
+
+    #[inline]
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut chars = s.chars();
+        match (chars.next(), chars.next()) {
+            (None, _) => {
+                Err(ParseCharError { kind: CharErrorKind::EmptyString })
+            },
+            (Some(c), None) => Ok(c),
+            _ => {
+                Err(ParseCharError { kind: CharErrorKind::TooManyChars })
+            }
+        }
+    }
+}
+
+
 #[unstable(feature = "try_from", issue = "33417")]
 impl TryFrom<u32> for char {
     type Error = CharTryFromError;

src/libcore/tests/char.rs

@@ -10,6 +10,7 @@
 
 use std::{char,str};
 use std::convert::TryFrom;
+use std::str::FromStr;
 
 #[test]
 fn test_convert() {
@@ -28,6 +29,16 @@ fn test_convert() {
     assert!(char::try_from(0xFFFF_FFFF_u32).is_err());
 }
 
+#[test]
+fn test_from_str() {
+    assert_eq!(char::from_str("a").unwrap(), 'a');
+    assert_eq!(char::try_from("a").unwrap(), 'a');
+    assert_eq!(char::from_str("\0").unwrap(), '\0');
+    assert_eq!(char::from_str("\u{D7FF}").unwrap(), '\u{d7FF}');
+    assert!(char::from_str("").is_err());
+    assert!(char::from_str("abc").is_err());
+}
+
 #[test]
 fn test_is_lowercase() {
     assert!('a'.is_lowercase());

src/librustc_lint/unused.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use rustc::hir::def_id::DefId;
 use rustc::ty;
 use rustc::ty::adjustment;
 use util::nodemap::FxHashMap;
@@ -144,20 +145,18 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
             ty::TyTuple(ref tys, _) if tys.is_empty() => return,
             ty::TyNever => return,
             ty::TyBool => return,
-            ty::TyAdt(def, _) => {
-                let attrs = cx.tcx.get_attrs(def.did);
-                check_must_use(cx, &attrs, s.span)
-            }
+            ty::TyAdt(def, _) => check_must_use(cx, def.did, s.span),
             _ => false,
         };
         if !warned {
             cx.span_lint(UNUSED_RESULTS, s.span, "unused result");
         }
 
-        fn check_must_use(cx: &LateContext, attrs: &[ast::Attribute], sp: Span) -> bool {
-            for attr in attrs {
+        fn check_must_use(cx: &LateContext, def_id: DefId, sp: Span) -> bool {
+            for attr in cx.tcx.get_attrs(def_id).iter() {
                 if attr.check_name("must_use") {
-                    let mut msg = "unused result which must be used".to_string();
+                    let mut msg = format!("unused `{}` which must be used",
+                                          cx.tcx.item_path_str(def_id));
                     // check for #[must_use="..."]
                     if let Some(s) = attr.value_str() {
                         msg.push_str(": ");

src/librustc_resolve/build_reduced_graph.rs

@@ -523,7 +523,10 @@ impl<'a> Resolver<'a> {
         };
 
         let kind = ModuleKind::Def(Def::Mod(def_id), name);
-        self.arenas.alloc_module(ModuleData::new(parent, kind, def_id, Mark::root(), DUMMY_SP))
+        let module =
+            self.arenas.alloc_module(ModuleData::new(parent, kind, def_id, Mark::root(), DUMMY_SP));
+        self.extern_module_map.insert((def_id, macros_only), module);
+        module
     }
 
     pub fn macro_def_scope(&mut self, expansion: Mark) -> Module<'a> {

src/libstd/env.rs

@@ -438,6 +438,35 @@ pub struct JoinPathsError {
 ///
 /// # Examples
 ///
+/// Joining paths on a Unix-like platform:
+///
+/// ```
+/// # if cfg!(unix) {
+/// use std::env;
+/// use std::ffi::OsString;
+/// use std::path::Path;
+///
+/// let paths = [Path::new("/bin"), Path::new("/usr/bin")];
+/// let path_os_string = env::join_paths(paths.iter()).unwrap();
+/// assert_eq!(path_os_string, OsString::from("/bin:/usr/bin"));
+/// # }
+/// ```
+///
+/// Joining a path containing a colon on a Unix-like platform results in an error:
+///
+/// ```
+/// # if cfg!(unix) {
+/// use std::env;
+/// use std::path::Path;
+///
+/// let paths = [Path::new("/bin"), Path::new("/usr/bi:n")];
+/// assert!(env::join_paths(paths.iter()).is_err());
+/// # }
+/// ```
+///
+/// Using `env::join_paths` with `env::spit_paths` to append an item to the `PATH` environment
+/// variable:
+///
 /// ```
 /// use std::env;
 /// use std::path::PathBuf;

src/libstd/error.rs

@@ -340,6 +340,14 @@ impl Error for char::CharTryFromError {
     }
 }
 
+#[stable(feature = "char_from_str", since = "1.19.0")]
+impl Error for char::ParseCharError {
+    fn description(&self) -> &str {
+        self.__description()
+    }
+}
+
+
 // copied from any.rs
 impl Error + 'static {
     /// Returns true if the boxed type is the same as `T`