std: Rename Show/String to Debug/Display

This commit is an implementation of [RFC 565][rfc] which is a stabilization of
the `std::fmt` module and the implementations of various formatting traits.
Specifically, the following changes were performed:

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0565-show-string-guidelines.md

* The `Show` trait is now deprecated, it was renamed to `Debug`
* The `String` trait is now deprecated, it was renamed to `Display`
* Many `Debug` and `Display` implementations were audited in accordance with the
  RFC and audited implementations now have the `#[stable]` attribute
  * Integers and floats no longer print a suffix
  * Smart pointers no longer print details that they are a smart pointer
  * Paths with `Debug` are now quoted and escape characters
* The `unwrap` methods on `Result` now require `Display` instead of `Debug`
* The `Error` trait no longer has a `detail` method and now requires that
  `Display` must be implemented. With the loss of `String`, this has moved into
  libcore.
* `impl<E: Error> FromError<E> for Box<Error>` now exists
* `derive(Show)` has been renamed to `derive(Debug)`. This is not currently
  warned about due to warnings being emitted on stage1+

While backwards compatibility is attempted to be maintained with a blanket
implementation of `Display` for the old `String` trait (and the same for
`Show`/`Debug`) this is still a breaking change due to primitives no longer
implementing `String` as well as modifications such as `unwrap` and the `Error`
trait. Most code is fairly straightforward to update with a rename or tweaks of
method calls.

[breaking-change]
Closes #21436

13 files changed, 63 insertions, 70 deletions

diff --git a/src/libsyntax/abi.rs b/src/libsyntax/abi.rs
index 09235ee209c..7447e0b229e 100644
--- a/src/libsyntax/abi.rs
+++ b/src/libsyntax/abi.rs
@@ -15,7 +15,7 @@ pub use self::AbiArchitecture::*;
 
 use std::fmt;
 
-#[derive(Copy, PartialEq)]
+#[derive(Copy, PartialEq, Eq, Show)]
 pub enum Os {
     OsWindows,
     OsMacos,
@@ -26,7 +26,7 @@ pub enum Os {
     OsDragonfly,
 }
 
-#[derive(PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Clone, Copy)]
+#[derive(PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Clone, Copy, Show)]
 pub enum Abi {
     // NB: This ordering MUST match the AbiDatas array below.
     // (This is ensured by the test indices_are_correct().)
@@ -119,25 +119,13 @@ impl Abi {
     }
 }
 
-impl fmt::Show for Abi {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
-    }
-}
-
-impl fmt::String for Abi {
+impl fmt::Display for Abi {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "\"{}\"", self.name())
     }
 }
 
-impl fmt::Show for Os {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
-    }
-}
-
-impl fmt::String for Os {
+impl fmt::Display for Os {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             OsLinux => "linux".fmt(f),
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index fcf80410da2..6e2818bf267 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -100,28 +100,28 @@ impl Ident {
     }
 }
 
-impl fmt::Show for Ident {
+impl fmt::Debug for Ident {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}#{}", self.name, self.ctxt)
     }
 }
 
-impl fmt::String for Ident {
+impl fmt::Display for Ident {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(&self.name, f)
+        fmt::Display::fmt(&self.name, f)
     }
 }
 
-impl fmt::Show for Name {
+impl fmt::Debug for Name {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let Name(nm) = *self;
         write!(f, "{:?}({})", token::get_name(*self).get(), nm)
     }
 }
 
-impl fmt::String for Name {
+impl fmt::Display for Name {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(token::get_name(*self).get(), f)
+        fmt::Display::fmt(token::get_name(*self).get(), f)
     }
 }
 
@@ -1100,13 +1100,13 @@ impl PartialEq for IntTy {
     }
 }
 
-impl fmt::Show for IntTy {
+impl fmt::Debug for IntTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Display::fmt(self, f)
     }
 }
 
-impl fmt::String for IntTy {
+impl fmt::Display for IntTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", ast_util::int_ty_to_string(*self, None))
     }
@@ -1155,13 +1155,13 @@ impl UintTy {
     }
 }
 
-impl fmt::Show for UintTy {
+impl fmt::Debug for UintTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Display::fmt(self, f)
     }
 }
 
-impl fmt::String for UintTy {
+impl fmt::Display for UintTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", ast_util::uint_ty_to_string(*self, None))
     }
@@ -1173,13 +1173,13 @@ pub enum FloatTy {
     TyF64,
 }
 
-impl fmt::Show for FloatTy {
+impl fmt::Debug for FloatTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Display::fmt(self, f)
     }
 }
 
-impl fmt::String for FloatTy {
+impl fmt::Display for FloatTy {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", ast_util::float_ty_to_string(*self))
     }
@@ -1222,24 +1222,15 @@ pub enum PrimTy {
     TyChar
 }
 
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy)]
+#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Copy, Show)]
 pub enum Onceness {
     Once,
     Many
 }
 
-impl fmt::Show for Onceness {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(match *self {
-            Once => "once",
-            Many => "many",
-        }, f)
-    }
-}
-
-impl fmt::String for Onceness {
+impl fmt::Display for Onceness {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(match *self {
+        fmt::Display::fmt(match *self {
             Once => "once",
             Many => "many",
         }, f)
@@ -1358,9 +1349,9 @@ pub enum Unsafety {
     Normal,
 }
 
-impl fmt::String for Unsafety {
+impl fmt::Display for Unsafety {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(match *self {
+        fmt::Display::fmt(match *self {
             Unsafety::Normal => "normal",
             Unsafety::Unsafe => "unsafe",
         }, f)
@@ -1375,7 +1366,7 @@ pub enum ImplPolarity {
     Negative,
 }
 
-impl fmt::Show for ImplPolarity {
+impl fmt::Debug for ImplPolarity {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             ImplPolarity::Positive => "positive".fmt(f),
diff --git a/src/libsyntax/ast_map/mod.rs b/src/libsyntax/ast_map/mod.rs
index f462a730d3a..fcdcd9d8263 100644
--- a/src/libsyntax/ast_map/mod.rs
+++ b/src/libsyntax/ast_map/mod.rs
@@ -46,7 +46,7 @@ impl PathElem {
     }
 }
 
-impl fmt::String for PathElem {
+impl fmt::Display for PathElem {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let slot = token::get_name(self.name());
         write!(f, "{}", slot)
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index 6f57c06d33e..856237f2155 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -358,9 +358,9 @@ pub enum StabilityLevel {
     Locked
 }
 
-impl fmt::String for StabilityLevel {
+impl fmt::Display for StabilityLevel {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::Show::fmt(self, f)
+        fmt::Debug::fmt(self, f)
     }
 }
 
diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index 7213b0fa955..e8c2b0318ce 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -235,9 +235,9 @@ pub enum Level {
     Help,
 }
 
-impl fmt::String for Level {
+impl fmt::Display for Level {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use std::fmt::String;
+        use std::fmt::Display;
 
         match *self {
             Bug => "error: internal compiler error".fmt(f),
diff --git a/src/libsyntax/ext/deriving/mod.rs b/src/libsyntax/ext/deriving/mod.rs
index 603c4478007..e52a2b513ce 100644
--- a/src/libsyntax/ext/deriving/mod.rs
+++ b/src/libsyntax/ext/deriving/mod.rs
@@ -99,7 +99,9 @@ pub fn expand_meta_derive(cx: &mut ExtCtxt,
 
                             "Rand" => expand!(rand::expand_deriving_rand),
 
+                            // NOTE(stage0): remove "Show"
                             "Show" => expand!(show::expand_deriving_show),
+                            "Debug" => expand!(show::expand_deriving_show),
 
                             "Default" => expand!(default::expand_deriving_default),
 
diff --git a/src/libsyntax/ext/deriving/show.rs b/src/libsyntax/ext/deriving/show.rs
index 48034ce50ab..f5b5d4dda19 100644
--- a/src/libsyntax/ext/deriving/show.rs
+++ b/src/libsyntax/ext/deriving/show.rs
@@ -35,7 +35,7 @@ pub fn expand_deriving_show<F>(cx: &mut ExtCtxt,
     let trait_def = TraitDef {
         span: span,
         attributes: Vec::new(),
-        path: Path::new(vec!("std", "fmt", "Show")),
+        path: Path::new(vec!("std", "fmt", "Debug")),
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         methods: vec!(
@@ -67,7 +67,7 @@ fn show_substructure(cx: &mut ExtCtxt, span: Span,
         Struct(_) => substr.type_ident,
         EnumMatching(_, v, _) => v.node.name,
         EnumNonMatchingCollapsed(..) | StaticStruct(..) | StaticEnum(..) => {
-            cx.span_bug(span, "nonsensical .fields in `#[derive(Show)]`")
+            cx.span_bug(span, "nonsensical .fields in `#[derive(Debug)]`")
         }
     };
 
diff --git a/src/libsyntax/ext/format.rs b/src/libsyntax/ext/format.rs
index f512b33f024..84f2ef0678d 100644
--- a/src/libsyntax/ext/format.rs
+++ b/src/libsyntax/ext/format.rs
@@ -603,8 +603,8 @@ impl<'a, 'b> Context<'a, 'b> {
         let trait_ = match *ty {
             Known(ref tyname) => {
                 match &tyname[] {
-                    ""  => "String",
-                    "?" => "Show",
+                    ""  => "Display",
+                    "?" => "Debug",
                     "e" => "LowerExp",
                     "E" => "UpperExp",
                     "o" => "Octal",
diff --git a/src/libsyntax/owned_slice.rs b/src/libsyntax/owned_slice.rs
index 707e540a17b..872354024e9 100644
--- a/src/libsyntax/owned_slice.rs
+++ b/src/libsyntax/owned_slice.rs
@@ -22,7 +22,7 @@ pub struct OwnedSlice<T> {
     data: Box<[T]>
 }
 
-impl<T:fmt::Show> fmt::Show for OwnedSlice<T> {
+impl<T:fmt::Debug> fmt::Debug for OwnedSlice<T> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
         self.data.fmt(fmt)
     }
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 4cdafb36eec..f9de55756b5 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -586,10 +586,10 @@ impl<'a> StringReader<'a> {
     /// `\x00` marker.
     #[inline(never)]
     fn scan_embedded_hygienic_ident(&mut self) -> ast::Ident {
-        fn bump_expecting_char<'a,D:fmt::Show>(r: &mut StringReader<'a>,
-                                               c: char,
-                                               described_c: D,
-                                               whence: &str) {
+        fn bump_expecting_char<'a,D:fmt::Debug>(r: &mut StringReader<'a>,
+                                                c: char,
+                                                described_c: D,
+                                                whence: &str) {
             match r.curr {
                 Some(r_c) if r_c == c => r.bump(),
                 Some(r_c) => panic!("expected {:?}, hit {:?}, {}", described_c, r_c, whence),
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index e5aef12e827..6112ee851ac 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -375,7 +375,7 @@ pub enum Nonterminal {
     NtTT(P<ast::TokenTree>), // needs P'ed to break a circularity
 }
 
-impl fmt::Show for Nonterminal {
+impl fmt::Debug for Nonterminal {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             NtItem(..) => f.pad("NtItem(..)"),
@@ -651,15 +651,15 @@ impl BytesContainer for InternedString {
     }
 }
 
-impl fmt::Show for InternedString {
+impl fmt::Debug for InternedString {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt::String::fmt(self, f)
+        fmt::Debug::fmt(&self.string[], f)
     }
 }
 
-impl fmt::String for InternedString {
+impl fmt::Display for InternedString {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", &self.string[])
+        fmt::Display::fmt(&self.string[], f)
     }
 }
 
diff --git a/src/libsyntax/ptr.rs b/src/libsyntax/ptr.rs
index 37fa8703706..01f3839b039 100644
--- a/src/libsyntax/ptr.rs
+++ b/src/libsyntax/ptr.rs
@@ -36,7 +36,7 @@
 //!   implementation changes (using a special thread-local heap, for example).
 //!   Moreover, a switch to, e.g. `P<'a, T>` would be easy and mostly automated.
 
-use std::fmt::{self, Show};
+use std::fmt::{self, Display, Debug};
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
 use std::ptr;
@@ -100,9 +100,14 @@ impl<T: PartialEq> PartialEq for P<T> {
 
 impl<T: Eq> Eq for P<T> {}
 
-impl<T: Show> Show for P<T> {
+impl<T: Debug> Debug for P<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        (**self).fmt(f)
+        Debug::fmt(&**self, f)
+    }
+}
+impl<T: Display> Display for P<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&**self, f)
     }
 }
 
diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index 5dca39f1aea..35654ae0598 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -114,9 +114,16 @@ impl Ord for RcStr {
     }
 }
 
-impl fmt::Show for RcStr {
+impl fmt::Debug for RcStr {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use std::fmt::Show;
+        use std::fmt::Debug;
+        self[].fmt(f)
+    }
+}
+
+impl fmt::Display for RcStr {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use std::fmt::Display;
         self[].fmt(f)
     }
 }