rustc: Stabilize much of the `proc_macro` feature

This commit stabilizes some of the `proc_macro` language feature as well as a
number of APIs in the `proc_macro` crate as [previously discussed][1]. This
means that on stable Rust you can now define custom procedural macros which
operate as attributes attached to items or `macro_rules!`-like bang-style
invocations. This extends the suite of currently stable procedural macros,
custom derives, with custom attributes and custom bang macros.

Note though that despite the stabilization in this commit procedural macros are
still not usable on stable Rust. To stabilize that we'll need to stabilize at
least part of the `use_extern_macros` feature. Currently you can define a
procedural macro attribute but you can't import it to call it!

A summary of the changes made in this PR (as well as the various consequences)
is:

* The `proc_macro` language and library features are now stable.
* Other APIs not stabilized in the `proc_macro` crate are now named under a
  different feature, such as `proc_macro_diagnostic` or `proc_macro_span`.
* A few checks in resolution for `proc_macro` being enabled have switched over
  to `use_extern_macros` being enabled. This means that code using
  `#![feature(proc_macro)]` today will likely need to move to
  `#![feature(use_extern_macros)]`.

It's intended that this PR, once landed, will be followed up with an attempt to
stabilize a small slice of `use_extern_macros` just for procedural macros to
make this feature 100% usable on stable.

[1]: https://internals.rust-lang.org/t/help-stabilize-a-subset-of-macros-2-0/7252

2 files changed, 130 insertions, 108 deletions

diff --git a/src/libproc_macro/diagnostic.rs b/src/libproc_macro/diagnostic.rs
index a82e3dcb060..06939a9d1e1 100644
--- a/src/libproc_macro/diagnostic.rs
+++ b/src/libproc_macro/diagnostic.rs
@@ -13,7 +13,7 @@ use Span;
 use rustc_errors as rustc;
 
 /// An enum representing a diagnostic level.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
 #[derive(Copy, Clone, Debug)]
 pub enum Level {
     /// An error.
@@ -30,7 +30,7 @@ pub enum Level {
 
 /// A structure representing a diagnostic message and associated children
 /// messages.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
 #[derive(Clone, Debug)]
 pub struct Diagnostic {
     level: Level,
@@ -43,7 +43,7 @@ macro_rules! diagnostic_child_methods {
     ($spanned:ident, $regular:ident, $level:expr) => (
         /// Add a new child diagnostic message to `self` with the level
         /// identified by this methods name with the given `span` and `message`.
-        #[unstable(feature = "proc_macro", issue = "38356")]
+        #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
         pub fn $spanned<T: Into<String>>(mut self, span: Span, message: T) -> Diagnostic {
             self.children.push(Diagnostic::spanned(span, $level, message));
             self
@@ -51,7 +51,7 @@ macro_rules! diagnostic_child_methods {
 
         /// Add a new child diagnostic message to `self` with the level
         /// identified by this method's name with the given `message`.
-        #[unstable(feature = "proc_macro", issue = "38356")]
+        #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
         pub fn $regular<T: Into<String>>(mut self, message: T) -> Diagnostic {
             self.children.push(Diagnostic::new($level, message));
             self
@@ -61,7 +61,7 @@ macro_rules! diagnostic_child_methods {
 
 impl Diagnostic {
     /// Create a new diagnostic with the given `level` and `message`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
     pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
         Diagnostic {
             level: level,
@@ -73,7 +73,7 @@ impl Diagnostic {
 
     /// Create a new diagnostic with the given `level` and `message` pointing to
     /// the given `span`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
     pub fn spanned<T: Into<String>>(span: Span, level: Level, message: T) -> Diagnostic {
         Diagnostic {
             level: level,
@@ -89,13 +89,13 @@ impl Diagnostic {
     diagnostic_child_methods!(span_help, help, Level::Help);
 
     /// Returns the diagnostic `level` for `self`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
     pub fn level(&self) -> Level {
         self.level
     }
 
     /// Emit the diagnostic.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
     pub fn emit(self) {
         ::__internal::with_sess(move |sess, _| {
             let handler = &sess.span_diagnostic;
diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index ecc66e869ae..f5a7c88a1b7 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -46,7 +46,7 @@ extern crate rustc_data_structures;
 
 mod diagnostic;
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
 pub use diagnostic::{Diagnostic, Level};
 
 use std::{ascii, fmt, iter};
@@ -94,13 +94,13 @@ impl !Sync for LexError {}
 
 impl TokenStream {
     /// Returns an empty `TokenStream` containing no token trees.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn new() -> TokenStream {
         TokenStream(tokenstream::TokenStream::empty())
     }
 
     /// Checks if this `TokenStream` is empty.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn is_empty(&self) -> bool {
         self.0.is_empty()
     }
@@ -146,7 +146,7 @@ impl fmt::Debug for TokenStream {
 }
 
 /// Creates a token stream containing a single token tree.
-#[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl From<TokenTree> for TokenStream {
     fn from(tree: TokenTree) -> TokenStream {
         TokenStream(tree.to_internal())
@@ -154,7 +154,7 @@ impl From<TokenTree> for TokenStream {
 }
 
 /// Collects a number of token trees into a single stream.
-#[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl iter::FromIterator<TokenTree> for TokenStream {
     fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
         trees.into_iter().map(TokenStream::from).collect()
@@ -175,7 +175,7 @@ impl iter::FromIterator<TokenStream> for TokenStream {
 }
 
 /// Public implementation details for the `TokenStream` type, such as iterators.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub mod token_stream {
     use syntax::tokenstream;
     use {TokenTree, TokenStream, Delimiter};
@@ -184,13 +184,13 @@ pub mod token_stream {
     /// The iteration is "shallow", e.g. the iterator doesn't recurse into delimited groups,
     /// and returns whole groups as token trees.
     #[derive(Clone)]
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub struct IntoIter {
         cursor: tokenstream::Cursor,
         stack: Vec<TokenTree>,
     }
 
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     impl Iterator for IntoIter {
         type Item = TokenTree;
 
@@ -219,7 +219,7 @@ pub mod token_stream {
         }
     }
 
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     impl IntoIterator for TokenStream {
         type Item = TokenTree;
         type IntoIter = IntoIter;
@@ -238,7 +238,7 @@ pub mod token_stream {
 /// To quote `$` itself, use `$$`.
 ///
 /// This is a dummy macro, the actual implementation is in quote::Quoter
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_quote", issue = "38356")]
 #[macro_export]
 macro_rules! quote { () => {} }
 
@@ -248,26 +248,26 @@ mod quote;
 
 /// Quote a `Span` into a `TokenStream`.
 /// This is needed to implement a custom quoter.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_quote", issue = "38356")]
 pub fn quote_span(span: Span) -> TokenStream {
     quote::Quote::quote(span)
 }
 
 /// A region of source code, along with macro expansion information.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Copy, Clone)]
 pub struct Span(syntax_pos::Span);
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for Span {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for Span {}
 
 macro_rules! diagnostic_method {
     ($name:ident, $level:expr) => (
         /// Create a new `Diagnostic` with the given `message` at the span
         /// `self`.
-        #[unstable(feature = "proc_macro", issue = "38356")]
+        #[unstable(feature = "proc_macro_diagnostic", issue = "38356")]
         pub fn $name<T: Into<String>>(self, message: T) -> Diagnostic {
             Diagnostic::spanned(self, $level, message)
         }
@@ -276,7 +276,7 @@ macro_rules! diagnostic_method {
 
 impl Span {
     /// A span that resolves at the macro definition site.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn def_site() -> Span {
         ::__internal::with_sess(|_, data| data.def_site)
     }
@@ -285,13 +285,13 @@ impl Span {
     /// Identifiers created with this span will be resolved as if they were written
     /// directly at the macro call location (call-site hygiene) and other code
     /// at the macro call site will be able to refer to them as well.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn call_site() -> Span {
         ::__internal::with_sess(|_, data| data.call_site)
     }
 
     /// The original source file into which this span points.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn source_file(&self) -> SourceFile {
         SourceFile {
             filemap: __internal::lookup_char_pos(self.0.lo()).file,
@@ -300,7 +300,7 @@ impl Span {
 
     /// The `Span` for the tokens in the previous macro expansion from which
     /// `self` was generated from, if any.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn parent(&self) -> Option<Span> {
         self.0.parent().map(Span)
     }
@@ -308,13 +308,13 @@ impl Span {
     /// The span for the origin source code that `self` was generated from. If
     /// this `Span` wasn't generated from other macro expansions then the return
     /// value is the same as `*self`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn source(&self) -> Span {
         Span(self.0.source_callsite())
     }
 
     /// Get the starting line/column in the source file for this span.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn start(&self) -> LineColumn {
         let loc = __internal::lookup_char_pos(self.0.lo());
         LineColumn {
@@ -324,7 +324,7 @@ impl Span {
     }
 
     /// Get the ending line/column in the source file for this span.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn end(&self) -> LineColumn {
         let loc = __internal::lookup_char_pos(self.0.hi());
         LineColumn {
@@ -336,7 +336,7 @@ impl Span {
     /// Create a new span encompassing `self` and `other`.
     ///
     /// Returns `None` if `self` and `other` are from different files.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn join(&self, other: Span) -> Option<Span> {
         let self_loc = __internal::lookup_char_pos(self.0.lo());
         let other_loc = __internal::lookup_char_pos(other.0.lo());
@@ -348,20 +348,20 @@ impl Span {
 
     /// Creates a new span with the same line/column information as `self` but
     /// that resolves symbols as though it were at `other`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn resolved_at(&self, other: Span) -> Span {
         Span(self.0.with_ctxt(other.0.ctxt()))
     }
 
     /// Creates a new span with the same name resolution behavior as `self` but
     /// with the line/column information of `other`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn located_at(&self, other: Span) -> Span {
         other.resolved_at(*self)
     }
 
     /// Compares to spans to see if they're equal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn eq(&self, other: &Span) -> bool {
         self.0 == other.0
     }
@@ -373,7 +373,7 @@ impl Span {
 }
 
 /// Prints a span in a form convenient for debugging.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Debug for Span {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?} bytes({}..{})",
@@ -384,33 +384,33 @@ impl fmt::Debug for Span {
 }
 
 /// A line-column pair representing the start or end of a `Span`.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct LineColumn {
     /// The 1-indexed line in the source file on which the span starts or ends (inclusive).
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub line: usize,
     /// The 0-indexed column (in UTF-8 characters) in the source file on which
     /// the span starts or ends (inclusive).
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub column: usize
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl !Send for LineColumn {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl !Sync for LineColumn {}
 
 /// The source file of a given `Span`.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 #[derive(Clone)]
 pub struct SourceFile {
     filemap: Lrc<FileMap>,
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl !Send for SourceFile {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl !Sync for SourceFile {}
 
 impl SourceFile {
@@ -424,14 +424,14 @@ impl SourceFile {
     /// the command line, the path as given may not actually be valid.
     ///
     /// [`is_real`]: #method.is_real
-    # [unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn path(&self) -> &FileName {
         &self.filemap.name
     }
 
     /// Returns `true` if this source file is a real source file, and not generated by an external
     /// macro's expansion.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_span", issue = "38356")]
     pub fn is_real(&self) -> bool {
         // This is a hack until intercrate spans are implemented and we can have real source files
         // for spans generated in external macros.
@@ -440,14 +440,14 @@ impl SourceFile {
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl AsRef<FileName> for SourceFile {
     fn as_ref(&self) -> &FileName {
         self.path()
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl fmt::Debug for SourceFile {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.debug_struct("SourceFile")
@@ -457,17 +457,17 @@ impl fmt::Debug for SourceFile {
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl PartialEq for SourceFile {
     fn eq(&self, other: &Self) -> bool {
         Lrc::ptr_eq(&self.filemap, &other.filemap)
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl Eq for SourceFile {}
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[unstable(feature = "proc_macro_span", issue = "38356")]
 impl PartialEq<FileName> for SourceFile {
     fn eq(&self, other: &FileName) -> bool {
         self.as_ref() == other
@@ -475,28 +475,44 @@ impl PartialEq<FileName> for SourceFile {
 }
 
 /// A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Clone)]
 pub enum TokenTree {
     /// A token stream surrounded by bracket delimiters.
-    Group(Group),
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+    Group(
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+        Group
+    ),
     /// An identifier.
-    Ident(Ident),
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+    Ident(
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+        Ident
+    ),
     /// A single punctuation character (`+`, `,`, `$`, etc.).
-    Punct(Punct),
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+    Punct(
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+        Punct
+    ),
     /// A literal character (`'a'`), string (`"hello"`), number (`2.3`), etc.
-    Literal(Literal),
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+    Literal(
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
+        Literal
+    ),
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for TokenTree {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for TokenTree {}
 
 impl TokenTree {
     /// Returns the span of this tree, delegating to the `span` method of
     /// the contained token or a delimited stream.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn span(&self) -> Span {
         match *self {
             TokenTree::Group(ref t) => t.span(),
@@ -511,7 +527,7 @@ impl TokenTree {
     /// Note that if this token is a `Group` then this method will not configure
     /// the span of each of the internal tokens, this will simply delegate to
     /// the `set_span` method of each variant.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn set_span(&mut self, span: Span) {
         match *self {
             TokenTree::Group(ref mut t) => t.set_span(span),
@@ -523,7 +539,7 @@ impl TokenTree {
 }
 
 /// Prints token treee in a form convenient for debugging.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Debug for TokenTree {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // Each of these has the name in the struct type in the derived debug,
@@ -537,28 +553,28 @@ impl fmt::Debug for TokenTree {
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl From<Group> for TokenTree {
     fn from(g: Group) -> TokenTree {
         TokenTree::Group(g)
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl From<Ident> for TokenTree {
     fn from(g: Ident) -> TokenTree {
         TokenTree::Ident(g)
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl From<Punct> for TokenTree {
     fn from(g: Punct) -> TokenTree {
         TokenTree::Punct(g)
     }
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl From<Literal> for TokenTree {
     fn from(g: Literal) -> TokenTree {
         TokenTree::Literal(g)
@@ -568,7 +584,7 @@ impl From<Literal> for TokenTree {
 /// Prints the token tree as a string that is supposed to be losslessly convertible back
 /// into the same token tree (modulo spans), except for possibly `TokenTree::Group`s
 /// with `Delimiter::None` delimiters and negative numeric literals.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Display for TokenTree {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
@@ -584,33 +600,37 @@ impl fmt::Display for TokenTree {
 ///
 /// A `Group` internally contains a `TokenStream` which is surrounded by `Delimiter`s.
 #[derive(Clone, Debug)]
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub struct Group {
     delimiter: Delimiter,
     stream: TokenStream,
     span: Span,
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for Group {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for Group {}
 
 /// Describes how a sequence of token trees is delimited.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub enum Delimiter {
     /// `( ... )`
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Parenthesis,
     /// `{ ... }`
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Brace,
     /// `[ ... ]`
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Bracket,
     /// `Ø ... Ø`
     /// An implicit delimiter, that may, for example, appear around tokens coming from a
     /// "macro variable" `$var`. It is important to preserve operator priorities in cases like
     /// `$var * 3` where `$var` is `1 + 2`.
     /// Implicit delimiters may not survive roundtrip of a token stream through a string.
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     None,
 }
 
@@ -620,7 +640,7 @@ impl Group {
     /// This constructor will set the span for this group to
     /// `Span::call_site()`. To change the span you can use the `set_span`
     /// method below.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn new(delimiter: Delimiter, stream: TokenStream) -> Group {
         Group {
             delimiter: delimiter,
@@ -630,7 +650,7 @@ impl Group {
     }
 
     /// Returns the delimiter of this `Group`
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn delimiter(&self) -> Delimiter {
         self.delimiter
     }
@@ -639,14 +659,14 @@ impl Group {
     ///
     /// Note that the returned token stream does not include the delimiter
     /// returned above.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn stream(&self) -> TokenStream {
         self.stream.clone()
     }
 
     /// Returns the span for the delimiters of this token stream, spanning the
     /// entire `Group`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn span(&self) -> Span {
         self.span
     }
@@ -657,7 +677,7 @@ impl Group {
     /// This method will **not** set the span of all the internal tokens spanned
     /// by this group, but rather it will only set the span of the delimiter
     /// tokens at the level of the `Group`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn set_span(&mut self, span: Span) {
         self.span = span;
     }
@@ -666,7 +686,7 @@ impl Group {
 /// Prints the group as a string that should be losslessly convertible back
 /// into the same group (modulo spans), except for possibly `TokenTree::Group`s
 /// with `Delimiter::None` delimiters.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Display for Group {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         TokenStream::from(TokenTree::from(self.clone())).fmt(f)
@@ -677,7 +697,7 @@ impl fmt::Display for Group {
 ///
 /// Multicharacter operators like `+=` are represented as two instances of `Punct` with different
 /// forms of `Spacing` returned.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 #[derive(Clone, Debug)]
 pub struct Punct {
     ch: char,
@@ -685,20 +705,22 @@ pub struct Punct {
     span: Span,
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for Punct {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for Punct {}
 
 /// Whether an `Punct` is followed immediately by another `Punct` or
 /// followed by another token or whitespace.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub enum Spacing {
     /// E.g. `+` is `Alone` in `+ =`, `+ident` or `+()`.
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Alone,
     /// E.g. `+` is `Joint` in `+=` or `'#`.
     /// Additionally, single quote `'` can join with identifiers to form lifetimes `'ident`.
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     Joint,
 }
 
@@ -709,7 +731,7 @@ impl Punct {
     ///
     /// The returned `Punct` will have the default span of `Span::call_site()`
     /// which can be further configured with the `set_span` method below.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn new(ch: char, spacing: Spacing) -> Punct {
         const LEGAL_CHARS: &[char] = &['=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^',
                                        '&', '|', '@', '.', ',', ';', ':', '#', '$', '?', '\''];
@@ -724,7 +746,7 @@ impl Punct {
     }
 
     /// Returns the value of this punctuation character as `char`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn as_char(&self) -> char {
         self.ch
     }
@@ -733,19 +755,19 @@ impl Punct {
     /// followed by another `Punct` in the token stream, so they can potentially be combined into
     /// a multicharacter operator (`Joint`), or it's followed by some other token or whitespace
     /// (`Alone`) so the operator has certainly ended.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn spacing(&self) -> Spacing {
         self.spacing
     }
 
     /// Returns the span for this punctuation character.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn span(&self) -> Span {
         self.span
     }
 
     /// Configure the span for this punctuation character.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn set_span(&mut self, span: Span) {
         self.span = span;
     }
@@ -753,7 +775,7 @@ impl Punct {
 
 /// Prints the punctuation character as a string that should be losslessly convertible
 /// back into the same character.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Display for Punct {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         TokenStream::from(TokenTree::from(self.clone())).fmt(f)
@@ -762,16 +784,16 @@ impl fmt::Display for Punct {
 
 /// An identifier (`ident`).
 #[derive(Clone, Debug)]
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub struct Ident {
     sym: Symbol,
     span: Span,
     is_raw: bool,
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for Ident {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for Ident {}
 
 impl Ident {
@@ -794,7 +816,7 @@ impl Ident {
     ///
     /// Due to the current importance of hygiene this constructor, unlike other
     /// tokens, requires a `Span` to be specified at construction.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn new(string: &str, span: Span) -> Ident {
         if !lexer::is_valid_ident(string) {
             panic!("`{:?}` is not a valid identifier", string)
@@ -807,7 +829,7 @@ impl Ident {
     }
 
     /// Same as `Ident::new`, but creates a raw identifier (`r#ident`).
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[unstable(feature = "proc_macro_raw_ident", issue = "38356")]
     pub fn new_raw(string: &str, span: Span) -> Ident {
         let mut ident = Ident::new(string, span);
         if ident.sym == keywords::Underscore.name() ||
@@ -820,13 +842,13 @@ impl Ident {
 
     /// Returns the span of this `Ident`, encompassing the entire string returned
     /// by `as_str`.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn span(&self) -> Span {
         self.span
     }
 
     /// Configures the span of this `Ident`, possibly changing its hygiene context.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn set_span(&mut self, span: Span) {
         self.span = span;
     }
@@ -834,7 +856,7 @@ impl Ident {
 
 /// Prints the identifier as a string that should be losslessly convertible
 /// back into the same identifier.
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Display for Ident {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         if self.is_raw {
@@ -849,16 +871,16 @@ impl fmt::Display for Ident {
 /// with or without a suffix (`1`, `1u8`, `2.3`, `2.3f32`).
 /// Boolean literals like `true` and `false` do not belong here, they are `Ident`s.
 #[derive(Clone, Debug)]
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 pub struct Literal {
     lit: token::Lit,
     suffix: Option<ast::Name>,
     span: Span,
 }
 
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Send for Literal {}
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl !Sync for Literal {}
 
 macro_rules! suffixed_int_literals {
@@ -874,7 +896,7 @@ macro_rules! suffixed_int_literals {
         /// Literals created through this method have the `Span::call_site()`
         /// span by default, which can be configured with the `set_span` method
         /// below.
-        #[unstable(feature = "proc_macro", issue = "38356")]
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
         pub fn $name(n: $kind) -> Literal {
             Literal {
                 lit: token::Lit::Integer(Symbol::intern(&n.to_string())),
@@ -900,7 +922,7 @@ macro_rules! unsuffixed_int_literals {
         /// Literals created through this method have the `Span::call_site()`
         /// span by default, which can be configured with the `set_span` method
         /// below.
-        #[unstable(feature = "proc_macro", issue = "38356")]
+        #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
         pub fn $name(n: $kind) -> Literal {
             Literal {
                 lit: token::Lit::Integer(Symbol::intern(&n.to_string())),
@@ -954,7 +976,7 @@ impl Literal {
     ///
     /// This function requires that the specified float is finite, for
     /// example if it is infinity or NaN this function will panic.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn f32_unsuffixed(n: f32) -> Literal {
         if !n.is_finite() {
             panic!("Invalid float literal {}", n);
@@ -979,7 +1001,7 @@ impl Literal {
     ///
     /// This function requires that the specified float is finite, for
     /// example if it is infinity or NaN this function will panic.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn f32_suffixed(n: f32) -> Literal {
         if !n.is_finite() {
             panic!("Invalid float literal {}", n);
@@ -1003,7 +1025,7 @@ impl Literal {
     ///
     /// This function requires that the specified float is finite, for
     /// example if it is infinity or NaN this function will panic.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn f64_unsuffixed(n: f64) -> Literal {
         if !n.is_finite() {
             panic!("Invalid float literal {}", n);
@@ -1028,7 +1050,7 @@ impl Literal {
     ///
     /// This function requires that the specified float is finite, for
     /// example if it is infinity or NaN this function will panic.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn f64_suffixed(n: f64) -> Literal {
         if !n.is_finite() {
             panic!("Invalid float literal {}", n);
@@ -1041,7 +1063,7 @@ impl Literal {
     }
 
     /// String literal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn string(string: &str) -> Literal {
         let mut escaped = String::new();
         for ch in string.chars() {
@@ -1055,7 +1077,7 @@ impl Literal {
     }
 
     /// Character literal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn character(ch: char) -> Literal {
         let mut escaped = String::new();
         escaped.extend(ch.escape_unicode());
@@ -1067,7 +1089,7 @@ impl Literal {
     }
 
     /// Byte string literal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn byte_string(bytes: &[u8]) -> Literal {
         let string = bytes.iter().cloned().flat_map(ascii::escape_default)
             .map(Into::<char>::into).collect::<String>();
@@ -1079,13 +1101,13 @@ impl Literal {
     }
 
     /// Returns the span encompassing this literal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn span(&self) -> Span {
         self.span
     }
 
     /// Configures the span associated for this literal.
-    #[unstable(feature = "proc_macro", issue = "38356")]
+    #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
     pub fn set_span(&mut self, span: Span) {
         self.span = span;
     }
@@ -1093,7 +1115,7 @@ impl Literal {
 
 /// Prints the literal as a string that should be losslessly convertible
 /// back into the same literal (except for possible rounding for floating point literals).
-#[unstable(feature = "proc_macro", issue = "38356")]
+#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
 impl fmt::Display for Literal {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         TokenStream::from(TokenTree::from(self.clone())).fmt(f)