From 0e8e7f4fedf45eb6f0e3bb29a5697137b9bfb9ea Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Thu, 22 Feb 2018 06:15:13 -0800
Subject: [PATCH 1/2] Add a feature for linking to `proc-macro`

This commit adds a feature to this crate which enables linking to the
upstream `proc_macro` crate. This should help this compile on targets
which don't have `proc_macro` and allow it to also be suitable for
embedding in Rust binaries.

This feature is turned on by default for backwards compatibility right
now.
---
 .travis.yml   |  1 +
 Cargo.toml    |  3 +++
 src/lib.rs    |  5 ++++-
 src/stable.rs | 11 ++++++-----
 4 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index a524c016..78942c40 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,6 +12,7 @@ matrix:
       script:
         - cargo test
         - cargo build --features nightly
+        - cargo build --no-default-features
         - RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo test
         - RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo build --features nightly
         - RUSTFLAGS='--cfg procmacro2_semver_exempt' cargo doc --no-deps
diff --git a/Cargo.toml b/Cargo.toml
index 4630c184..8c242eba 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,3 +27,6 @@ unicode-xid = "0.1"
 # When disabled: emulate the same API as the nightly compiler's proc_macro crate
 # but in a way that works on all stable compilers >=1.15.0.
 nightly = []
+
+proc-macro = []
+default = ["proc-macro"]
diff --git a/src/lib.rs b/src/lib.rs
index d08988c0..31ba7654 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -28,6 +28,7 @@
 
 #![cfg_attr(feature = "nightly", feature(proc_macro))]
 
+#[cfg(feature = "proc-macro")]
 extern crate proc_macro;
 
 #[cfg(not(feature = "nightly"))]
@@ -67,12 +68,14 @@ impl FromStr for TokenStream {
     }
 }
 
+#[cfg(feature = "proc-macro")]
 impl From<proc_macro::TokenStream> for TokenStream {
     fn from(inner: proc_macro::TokenStream) -> TokenStream {
         TokenStream(inner.into())
     }
 }
 
+#[cfg(feature = "proc-macro")]
 impl From<TokenStream> for proc_macro::TokenStream {
     fn from(inner: TokenStream) -> proc_macro::TokenStream {
         inner.0.into()
@@ -175,7 +178,7 @@ impl Span {
     }
 
     /// This method is only available when the `"nightly"` feature is enabled.
-    #[cfg(feature = "nightly")]
+    #[cfg(all(feature = "nightly", feature = "proc-macro"))]
     pub fn unstable(self) -> proc_macro::Span {
         self.0.unstable()
     }
diff --git a/src/stable.rs b/src/stable.rs
index 41a7c4b3..54210600 100644
--- a/src/stable.rs
+++ b/src/stable.rs
@@ -11,7 +11,6 @@ use std::rc::Rc;
 use std::str::FromStr;
 use std::vec;
 
-use proc_macro;
 use unicode_xid::UnicodeXID;
 use strnom::{Cursor, PResult, skip_whitespace, block_comment, whitespace, word_break};
 
@@ -120,14 +119,16 @@ impl fmt::Display for TokenStream {
     }
 }
 
-impl From<proc_macro::TokenStream> for TokenStream {
-    fn from(inner: proc_macro::TokenStream) -> TokenStream {
+#[cfg(feature = "proc-macro")]
+impl From<::proc_macro::TokenStream> for TokenStream {
+    fn from(inner: ::proc_macro::TokenStream) -> TokenStream {
         inner.to_string().parse().expect("compiler token stream parse failed")
     }
 }
 
-impl From<TokenStream> for proc_macro::TokenStream {
-    fn from(inner: TokenStream) -> proc_macro::TokenStream {
+#[cfg(feature = "proc-macro")]
+impl From<TokenStream> for ::proc_macro::TokenStream {
+    fn from(inner: TokenStream) -> ::proc_macro::TokenStream {
         inner.to_string().parse().expect("failed to parse to compiler tokens")
     }
 }

From 724687bc7b956c966f0eb5168b3943ec04ecb2e1 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Thu, 22 Feb 2018 10:17:48 -0800
Subject: [PATCH 2/2] Fix default-features = false, features = ["nightly"]

---
 Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Cargo.toml b/Cargo.toml
index 8c242eba..5ede4780 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,7 +26,7 @@ unicode-xid = "0.1"
 #
 # When disabled: emulate the same API as the nightly compiler's proc_macro crate
 # but in a way that works on all stable compilers >=1.15.0.
-nightly = []
+nightly = ["proc-macro"]
 
 proc-macro = []
 default = ["proc-macro"]