diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..8216174
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "d29a20e44207f915f42e6d1668d2864b0152e5a8"
+  }
+}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..a9d37c5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+target
+Cargo.lock
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..c8253df
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,19 @@
+// This file is generated by cargo2android.py.
+
+rust_proc_macro {
+    name: "libproc_macro_hack",
+    crate_name: "proc_macro_hack",
+    srcs: ["src/lib.rs"],
+    edition: "2018",
+    rlibs: [
+        "libproc_macro2",
+        "libquote",
+        "libsyn",
+    ],
+}
+
+// dependent_library ["feature_list"]
+//   proc-macro2-1.0.9 "default,proc-macro"
+//   quote-1.0.3 "default,proc-macro"
+//   syn-1.0.16 "clone-impls,default,derive,parsing,printing,proc-macro,quote"
+//   unicode-xid-0.2.0 "default"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..0096538
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,40 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+edition = "2018"
+name = "proc-macro-hack"
+version = "0.5.12"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+description = "Procedural macros in expression position"
+readme = "README.md"
+categories = ["development-tools::procedural-macro-helpers"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/proc-macro-hack"
+
+[lib]
+proc-macro = true
+[dependencies.proc-macro2]
+version = "1.0"
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "1.0.5"
+[dev-dependencies.demo-hack]
+version = "0.0.5"
+
+[dev-dependencies.demo-hack-impl]
+version = "0.0.5"
+[badges.travis-ci]
+repository = "dtolnay/proc-macro-hack"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..ddc7286
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,28 @@
+[package]
+name = "proc-macro-hack"
+version = "0.5.12"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+edition = "2018"
+license = "MIT OR Apache-2.0"
+description = "Procedural macros in expression position"
+repository = "https://github.com/dtolnay/proc-macro-hack"
+categories = ["development-tools::procedural-macro-helpers"]
+readme = "README.md"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = "1.0.5"
+
+[dev-dependencies]
+demo-hack = { version = "0.0.5", path = "demo-hack" }
+demo-hack-impl = { version = "0.0.5", path = "demo-hack-impl" }
+
+[badges]
+travis-ci = { repository = "dtolnay/proc-macro-hack" }
+
+[workspace]
+members = ["demo-hack", "demo-hack-impl", "example", "nested"]
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
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+   "License" shall mean the terms and conditions for use, reproduction,
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+   "Work" shall mean the work of authorship, whether in Source or
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+   form, that is based on (or derived from) the Work and for which the
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+   of this License, Derivative Works shall not include works that remain
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+   "Contribution" shall mean any work of authorship, including
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+4. Redistribution. You may reproduce and distribute copies of the
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+   (a) You must give any other recipients of the Work or
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+       of the NOTICE file are for informational purposes only and
+       do not modify the License. You may add Your own attribution
+       notices within Derivative Works that You distribute, alongside
+       or as an addendum to the NOTICE text from the Work, provided
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+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
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+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
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+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
+   risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
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+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
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+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
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+Copyright [yyyy] [name of copyright owner]
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+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..f2675cd
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2018 David Tolnay
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..f5a6faa
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,17 @@
+name: "proc-macro-hack"
+description:
+    "Procedural macros in expression position"
+
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/proc-macro-hack"
+  }
+  url {
+    type: GIT
+    value: "https://github.com/dtolnay/proc-macro-hack"
+  }
+  version: "0.5.12"
+  last_upgrade_date { year: 2020 month: 3 day: 19 }
+  license_type: NOTICE
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/NOTICE b/NOTICE
new file mode 120000
index 0000000..7a694c9
--- /dev/null
+++ b/NOTICE
@@ -0,0 +1 @@
+LICENSE
\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7984e6d
--- /dev/null
+++ b/README.md
@@ -0,0 +1,142 @@
+Procedural macros in expression position
+========================================
+
+[![Build Status](https://api.travis-ci.org/dtolnay/proc-macro-hack.svg?branch=master)](https://travis-ci.org/dtolnay/proc-macro-hack)
+[![Latest Version](https://img.shields.io/crates/v/proc-macro-hack.svg)](https://crates.io/crates/proc-macro-hack)
+
+As of Rust 1.30, the language supports user-defined function-like procedural
+macros. However these can only be invoked in item position, not in
+statements or expressions.
+
+This crate implements an alternative type of procedural macro that can be
+invoked in statement or expression position.
+
+This approach works with any stable or nightly Rust version 1.31+.
+
+## Defining procedural macros
+
+Two crates are required to define a procedural macro.
+
+### The implementation crate
+
+This crate must contain nothing but procedural macros. Private helper
+functions and private modules are fine but nothing can be public.
+
+[> example of an implementation crate][demo-hack-impl]
+
+Just like you would use a #\[proc_macro\] attribute to define a natively
+supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
+attribute to define a procedural macro that works in expression position.
+The function signature is the same as for ordinary function-like procedural
+macros.
+
+```rust
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro_hack::proc_macro_hack;
+use quote::quote;
+use syn::{parse_macro_input, Expr};
+
+#[proc_macro_hack]
+pub fn add_one(input: TokenStream) -> TokenStream {
+    let expr = parse_macro_input!(input as Expr);
+    TokenStream::from(quote! {
+        1 + (#expr)
+    })
+}
+```
+
+### The declaration crate
+
+This crate is allowed to contain other public things if you need, for
+example traits or functions or ordinary macros.
+
+[> example of a declaration crate][demo-hack]
+
+Within the declaration crate there needs to be a re-export of your
+procedural macro from the implementation crate. The re-export also carries a
+\#\[proc_macro_hack\] attribute.
+
+```rust
+use proc_macro_hack::proc_macro_hack;
+
+/// Add one to an expression.
+///
+/// (Documentation goes here on the re-export, not in the other crate.)
+#[proc_macro_hack]
+pub use demo_hack_impl::add_one;
+```
+
+Both crates depend on `proc-macro-hack`:
+
+```toml
+[dependencies]
+proc-macro-hack = "0.5"
+```
+
+Additionally, your implementation crate (but not your declaration crate) is
+a proc macro crate:
+
+```toml
+[lib]
+proc-macro = true
+```
+
+## Using procedural macros
+
+Users of your crate depend on your declaration crate (not your
+implementation crate), then use your procedural macros as usual.
+
+[> example of a downstream crate][example]
+
+```rust
+use demo_hack::add_one;
+
+fn main() {
+    let two = 2;
+    let nine = add_one!(two) + add_one!(2 + 3);
+    println!("nine = {}", nine);
+}
+```
+
+[demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
+[demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
+[example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
+
+## Limitations
+
+- Only proc macros in expression position are supported. Proc macros in pattern
+  position ([#20]) are not supported.
+
+- By default, nested invocations are not supported i.e. the code emitted by a
+  proc-macro-hack macro invocation cannot contain recursive calls to the same
+  proc-macro-hack macro nor calls to any other proc-macro-hack macros. Use
+  [`proc-macro-nested`] if you require support for nested invocations.
+
+- By default, hygiene is structured such that the expanded code can't refer to
+  local variables other than those passed by name somewhere in the macro input.
+  If your macro must refer to *local* variables that don't get named in the
+  macro input, use `#[proc_macro_hack(fake_call_site)]` on the re-export in your
+  declaration crate. *Most macros won't need this.*
+
+[#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
+[#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
+[`proc-macro-nested`]: https://docs.rs/proc-macro-nested
+
+<br>
+
+#### License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this hack by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+</sub>
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..e9b80e6
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,657 @@
+//! As of Rust 1.30, the language supports user-defined function-like procedural
+//! macros. However these can only be invoked in item position, not in
+//! statements or expressions.
+//!
+//! This crate implements an alternative type of procedural macro that can be
+//! invoked in statement or expression position.
+//!
+//! # Defining procedural macros
+//!
+//! Two crates are required to define a procedural macro.
+//!
+//! ## The implementation crate
+//!
+//! This crate must contain nothing but procedural macros. Private helper
+//! functions and private modules are fine but nothing can be public.
+//!
+//! [> example of an implementation crate][demo-hack-impl]
+//!
+//! Just like you would use a #\[proc_macro\] attribute to define a natively
+//! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
+//! attribute to define a procedural macro that works in expression position.
+//! The function signature is the same as for ordinary function-like procedural
+//! macros.
+//!
+//! ```
+//! extern crate proc_macro;
+//!
+//! use proc_macro::TokenStream;
+//! use proc_macro_hack::proc_macro_hack;
+//! use quote::quote;
+//! use syn::{parse_macro_input, Expr};
+//!
+//! # const IGNORE: &str = stringify! {
+//! #[proc_macro_hack]
+//! # };
+//! pub fn add_one(input: TokenStream) -> TokenStream {
+//!     let expr = parse_macro_input!(input as Expr);
+//!     TokenStream::from(quote! {
+//!         1 + (#expr)
+//!     })
+//! }
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! ## The declaration crate
+//!
+//! This crate is allowed to contain other public things if you need, for
+//! example traits or functions or ordinary macros.
+//!
+//! [> example of a declaration crate][demo-hack]
+//!
+//! Within the declaration crate there needs to be a re-export of your
+//! procedural macro from the implementation crate. The re-export also carries a
+//! \#\[proc_macro_hack\] attribute.
+//!
+//! ```
+//! use proc_macro_hack::proc_macro_hack;
+//!
+//! /// Add one to an expression.
+//! ///
+//! /// (Documentation goes here on the re-export, not in the other crate.)
+//! #[proc_macro_hack]
+//! pub use demo_hack_impl::add_one;
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! Both crates depend on `proc-macro-hack`:
+//!
+//! ```toml
+//! [dependencies]
+//! proc-macro-hack = "0.5"
+//! ```
+//!
+//! Additionally, your implementation crate (but not your declaration crate) is
+//! a proc macro crate:
+//!
+//! ```toml
+//! [lib]
+//! proc-macro = true
+//! ```
+//!
+//! # Using procedural macros
+//!
+//! Users of your crate depend on your declaration crate (not your
+//! implementation crate), then use your procedural macros as usual.
+//!
+//! [> example of a downstream crate][example]
+//!
+//! ```
+//! use demo_hack::add_one;
+//!
+//! fn main() {
+//!     let two = 2;
+//!     let nine = add_one!(two) + add_one!(2 + 3);
+//!     println!("nine = {}", nine);
+//! }
+//! ```
+//!
+//! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
+//! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
+//! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
+//!
+//! # Limitations
+//!
+//! - Only proc macros in expression position are supported. Proc macros in
+//!   pattern position ([#20]) are not supported.
+//!
+//! - By default, nested invocations are not supported i.e. the code emitted by
+//!   a proc-macro-hack macro invocation cannot contain recursive calls to the
+//!   same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
+//!   Use [`proc-macro-nested`] if you require support for nested invocations.
+//!
+//! - By default, hygiene is structured such that the expanded code can't refer
+//!   to local variables other than those passed by name somewhere in the macro
+//!   input. If your macro must refer to *local* variables that don't get named
+//!   in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
+//!   re-export in your declaration crate. *Most macros won't need this.*
+//!
+//! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
+//! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
+//! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested
+
+#![recursion_limit = "512"]
+#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
+#![cfg_attr(feature = "cargo-clippy", allow(needless_pass_by_value))]
+
+extern crate proc_macro;
+
+use proc_macro2::{Span, TokenStream, TokenTree};
+use quote::{format_ident, quote, ToTokens};
+use std::fmt::Write;
+use syn::ext::IdentExt;
+use syn::parse::{Parse, ParseStream, Result};
+use syn::{braced, bracketed, parenthesized, parse_macro_input, token, Ident, LitInt, Token};
+
+type Visibility = Option<Token![pub]>;
+
+enum Input {
+    Export(Export),
+    Define(Define),
+}
+
+// pub use demo_hack_impl::{m1, m2 as qrst};
+struct Export {
+    attrs: TokenStream,
+    vis: Visibility,
+    from: Ident,
+    macros: Vec<Macro>,
+}
+
+// pub fn m1(input: TokenStream) -> TokenStream { ... }
+struct Define {
+    attrs: TokenStream,
+    name: Ident,
+    body: TokenStream,
+}
+
+struct Macro {
+    name: Ident,
+    export_as: Ident,
+}
+
+impl Parse for Input {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let ahead = input.fork();
+        parse_attributes(&ahead)?;
+        ahead.parse::<Visibility>()?;
+
+        if ahead.peek(Token![use]) {
+            input.parse().map(Input::Export)
+        } else if ahead.peek(Token![fn]) {
+            input.parse().map(Input::Define)
+        } else {
+            Err(input.error("unexpected input to #[proc_macro_hack]"))
+        }
+    }
+}
+
+impl Parse for Export {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let attrs = input.call(parse_attributes)?;
+        let vis: Visibility = input.parse()?;
+        input.parse::<Token![use]>()?;
+        input.parse::<Option<Token![::]>>()?;
+        let from: Ident = input.parse()?;
+        input.parse::<Token![::]>()?;
+
+        let mut macros = Vec::new();
+        if input.peek(token::Brace) {
+            let content;
+            braced!(content in input);
+            loop {
+                macros.push(content.parse()?);
+                if content.is_empty() {
+                    break;
+                }
+                content.parse::<Token![,]>()?;
+                if content.is_empty() {
+                    break;
+                }
+            }
+        } else {
+            macros.push(input.parse()?);
+        }
+
+        input.parse::<Token![;]>()?;
+        Ok(Export {
+            attrs,
+            vis,
+            from,
+            macros,
+        })
+    }
+}
+
+impl Parse for Define {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let attrs = input.call(parse_attributes)?;
+        let vis: Visibility = input.parse()?;
+        if vis.is_none() {
+            return Err(input.error("functions tagged with `#[proc_macro_hack]` must be `pub`"));
+        }
+
+        input.parse::<Token![fn]>()?;
+        let name: Ident = input.parse()?;
+        let body: TokenStream = input.parse()?;
+        Ok(Define { attrs, name, body })
+    }
+}
+
+impl Parse for Macro {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let name: Ident = input.parse()?;
+        let renamed: Option<Token![as]> = input.parse()?;
+        let export_as = if renamed.is_some() {
+            input.parse()?
+        } else {
+            name.clone()
+        };
+        Ok(Macro { name, export_as })
+    }
+}
+
+fn parse_attributes(input: ParseStream) -> Result<TokenStream> {
+    let mut attrs = TokenStream::new();
+    while input.peek(Token![#]) {
+        let pound: Token![#] = input.parse()?;
+        pound.to_tokens(&mut attrs);
+        let content;
+        let bracket_token = bracketed!(content in input);
+        let content: TokenStream = content.parse()?;
+        bracket_token.surround(&mut attrs, |tokens| content.to_tokens(tokens));
+    }
+    Ok(attrs)
+}
+
+#[proc_macro_attribute]
+pub fn proc_macro_hack(
+    args: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    proc_macro::TokenStream::from(match parse_macro_input!(input) {
+        Input::Export(export) => {
+            let args = parse_macro_input!(args as ExportArgs);
+            expand_export(export, args)
+        }
+        Input::Define(define) => {
+            parse_macro_input!(args as DefineArgs);
+            expand_define(define)
+        }
+    })
+}
+
+mod kw {
+    syn::custom_keyword!(derive);
+    syn::custom_keyword!(fake_call_site);
+    syn::custom_keyword!(internal_macro_calls);
+    syn::custom_keyword!(support_nested);
+}
+
+struct ExportArgs {
+    support_nested: bool,
+    internal_macro_calls: u16,
+    fake_call_site: bool,
+}
+
+impl Parse for ExportArgs {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let mut args = ExportArgs {
+            support_nested: false,
+            internal_macro_calls: 0,
+            fake_call_site: false,
+        };
+
+        while !input.is_empty() {
+            let ahead = input.lookahead1();
+            if ahead.peek(kw::support_nested) {
+                input.parse::<kw::support_nested>()?;
+                args.support_nested = true;
+            } else if ahead.peek(kw::internal_macro_calls) {
+                input.parse::<kw::internal_macro_calls>()?;
+                input.parse::<Token![=]>()?;
+                let calls = input.parse::<LitInt>()?.base10_parse()?;
+                args.internal_macro_calls = calls;
+            } else if ahead.peek(kw::fake_call_site) {
+                input.parse::<kw::fake_call_site>()?;
+                args.fake_call_site = true;
+            } else {
+                return Err(ahead.error());
+            }
+            if input.is_empty() {
+                break;
+            }
+            input.parse::<Token![,]>()?;
+        }
+
+        Ok(args)
+    }
+}
+
+struct DefineArgs;
+
+impl Parse for DefineArgs {
+    fn parse(_input: ParseStream) -> Result<Self> {
+        Ok(DefineArgs)
+    }
+}
+
+struct EnumHack {
+    token_stream: TokenStream,
+}
+
+impl Parse for EnumHack {
+    fn parse(input: ParseStream) -> Result<Self> {
+        input.parse::<Token![enum]>()?;
+        input.parse::<Ident>()?;
+
+        let braces;
+        braced!(braces in input);
+        braces.parse::<Ident>()?;
+        braces.parse::<Token![=]>()?;
+
+        let parens;
+        parenthesized!(parens in braces);
+        parens.parse::<Ident>()?;
+        parens.parse::<Token![!]>()?;
+
+        let inner;
+        braced!(inner in parens);
+        let token_stream: TokenStream = inner.parse()?;
+
+        parens.parse::<Token![,]>()?;
+        parens.parse::<TokenTree>()?;
+        braces.parse::<Token![.]>()?;
+        braces.parse::<TokenTree>()?;
+        braces.parse::<Token![,]>()?;
+
+        Ok(EnumHack { token_stream })
+    }
+}
+
+#[doc(hidden)]
+#[proc_macro_derive(ProcMacroHack)]
+pub fn enum_hack(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let inner = parse_macro_input!(input as EnumHack);
+    proc_macro::TokenStream::from(inner.token_stream)
+}
+
+struct FakeCallSite {
+    derive: Ident,
+    rest: TokenStream,
+}
+
+impl Parse for FakeCallSite {
+    fn parse(input: ParseStream) -> Result<Self> {
+        input.parse::<Token![#]>()?;
+        let attr;
+        bracketed!(attr in input);
+        attr.parse::<kw::derive>()?;
+        let path;
+        parenthesized!(path in attr);
+        Ok(FakeCallSite {
+            derive: path.parse()?,
+            rest: input.parse()?,
+        })
+    }
+}
+
+#[doc(hidden)]
+#[proc_macro_attribute]
+pub fn fake_call_site(
+    args: proc_macro::TokenStream,
+    input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    let args = TokenStream::from(args);
+    let span = match args.into_iter().next() {
+        Some(token) => token.span(),
+        None => return input,
+    };
+
+    let input = parse_macro_input!(input as FakeCallSite);
+    let mut derive = input.derive;
+    derive.set_span(span);
+    let rest = input.rest;
+
+    let expanded = quote! {
+        #[derive(#derive)]
+        #rest
+    };
+
+    proc_macro::TokenStream::from(expanded)
+}
+
+fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
+    let dummy = dummy_name_for_export(&export);
+
+    let attrs = export.attrs;
+    let vis = export.vis;
+    let macro_export = match vis {
+        Some(_) => quote!(#[macro_export]),
+        None => quote!(),
+    };
+    let crate_prefix = vis.map(|_| quote!($crate::));
+    let enum_variant = if args.support_nested {
+        if args.internal_macro_calls == 0 {
+            quote!(Nested)
+        } else {
+            format_ident!("Nested{}", args.internal_macro_calls).to_token_stream()
+        }
+    } else {
+        quote!(Value)
+    };
+
+    let from = export.from;
+    let rules = export
+        .macros
+        .into_iter()
+        .map(|Macro { name, export_as }| {
+            let actual_name = actual_proc_macro_name(&name);
+            let dispatch = dispatch_macro_name(&name);
+            let call_site = call_site_macro_name(&name);
+
+            let export_dispatch = if args.support_nested {
+                quote! {
+                    #[doc(hidden)]
+                    #vis use proc_macro_nested::dispatch as #dispatch;
+                }
+            } else {
+                quote!()
+            };
+
+            let proc_macro_call = if args.support_nested {
+                let extra_bangs = (0..args.internal_macro_calls).map(|_| quote!(!));
+                quote! {
+                    #crate_prefix #dispatch! { ($($proc_macro)*) #(#extra_bangs)* }
+                }
+            } else {
+                quote! {
+                    proc_macro_call!()
+                }
+            };
+
+            let export_call_site = if args.fake_call_site {
+                quote! {
+                    #[doc(hidden)]
+                    #vis use proc_macro_hack::fake_call_site as #call_site;
+                }
+            } else {
+                quote!()
+            };
+
+            let do_derive = if !args.fake_call_site {
+                quote! {
+                    #[derive(#crate_prefix #actual_name)]
+                }
+            } else if crate_prefix.is_some() {
+                quote! {
+                    use #crate_prefix #actual_name;
+                    #[#crate_prefix #call_site ($($proc_macro)*)]
+                    #[derive(#actual_name)]
+                }
+            } else {
+                quote! {
+                    #[#call_site ($($proc_macro)*)]
+                    #[derive(#actual_name)]
+                }
+            };
+
+            quote! {
+                #[doc(hidden)]
+                #vis use #from::#actual_name;
+
+                #export_dispatch
+                #export_call_site
+
+                #attrs
+                #macro_export
+                macro_rules! #export_as {
+                    ($($proc_macro:tt)*) => {{
+                        #do_derive
+                        enum ProcMacroHack {
+                            #enum_variant = (stringify! { $($proc_macro)* }, 0).1,
+                        }
+                        #proc_macro_call
+                    }};
+                }
+            }
+        })
+        .collect();
+
+    wrap_in_enum_hack(dummy, rules)
+}
+
+fn expand_define(define: Define) -> TokenStream {
+    let attrs = define.attrs;
+    let name = define.name;
+    let dummy = actual_proc_macro_name(&name);
+    let body = define.body;
+
+    quote! {
+        mod #dummy {
+            extern crate proc_macro;
+            pub use self::proc_macro::*;
+        }
+
+        #attrs
+        #[proc_macro_derive(#dummy)]
+        pub fn #dummy(input: #dummy::TokenStream) -> #dummy::TokenStream {
+            use std::iter::FromIterator;
+
+            let mut iter = input.into_iter();
+            iter.next().unwrap(); // `enum`
+            iter.next().unwrap(); // `ProcMacroHack`
+
+            let mut braces = match iter.next().unwrap() {
+                #dummy::TokenTree::Group(group) => group.stream().into_iter(),
+                _ => unimplemented!(),
+            };
+            let variant = braces.next().unwrap(); // `Value` or `Nested`
+            let varname = variant.to_string();
+            let support_nested = varname.starts_with("Nested");
+            braces.next().unwrap(); // `=`
+
+            let mut parens = match braces.next().unwrap() {
+                #dummy::TokenTree::Group(group) => group.stream().into_iter(),
+                _ => unimplemented!(),
+            };
+            parens.next().unwrap(); // `stringify`
+            parens.next().unwrap(); // `!`
+
+            let inner = match parens.next().unwrap() {
+                #dummy::TokenTree::Group(group) => group.stream(),
+                _ => unimplemented!(),
+            };
+
+            let output: #dummy::TokenStream = #name(inner.clone());
+
+            fn count_bangs(input: #dummy::TokenStream) -> usize {
+                let mut count = 0;
+                for token in input {
+                    match token {
+                        #dummy::TokenTree::Punct(punct) => {
+                            if punct.as_char() == '!' {
+                                count += 1;
+                            }
+                        }
+                        #dummy::TokenTree::Group(group) => {
+                            count += count_bangs(group.stream());
+                        }
+                        _ => {}
+                    }
+                }
+                count
+            }
+
+            // macro_rules! proc_macro_call {
+            //     () => { #output }
+            // }
+            #dummy::TokenStream::from_iter(vec![
+                #dummy::TokenTree::Ident(
+                    #dummy::Ident::new("macro_rules", #dummy::Span::call_site()),
+                ),
+                #dummy::TokenTree::Punct(
+                    #dummy::Punct::new('!', #dummy::Spacing::Alone),
+                ),
+                #dummy::TokenTree::Ident(
+                    #dummy::Ident::new(
+                        &if support_nested {
+                            let extra_bangs = if varname == "Nested" {
+                                0
+                            } else {
+                                varname["Nested".len()..].parse().unwrap()
+                            };
+                            format!("proc_macro_call_{}", extra_bangs + count_bangs(inner))
+                        } else {
+                            String::from("proc_macro_call")
+                        },
+                        #dummy::Span::call_site(),
+                    ),
+                ),
+                #dummy::TokenTree::Group(
+                    #dummy::Group::new(#dummy::Delimiter::Brace, #dummy::TokenStream::from_iter(vec![
+                        #dummy::TokenTree::Group(
+                            #dummy::Group::new(#dummy::Delimiter::Parenthesis, #dummy::TokenStream::new()),
+                        ),
+                        #dummy::TokenTree::Punct(
+                            #dummy::Punct::new('=', #dummy::Spacing::Joint),
+                        ),
+                        #dummy::TokenTree::Punct(
+                            #dummy::Punct::new('>', #dummy::Spacing::Alone),
+                        ),
+                        #dummy::TokenTree::Group(
+                            #dummy::Group::new(#dummy::Delimiter::Brace, output),
+                        ),
+                    ])),
+                ),
+            ])
+        }
+
+        fn #name #body
+    }
+}
+
+fn actual_proc_macro_name(conceptual: &Ident) -> Ident {
+    format_ident!("proc_macro_hack_{}", conceptual)
+}
+
+fn dispatch_macro_name(conceptual: &Ident) -> Ident {
+    format_ident!("proc_macro_call_{}", conceptual)
+}
+
+fn call_site_macro_name(conceptual: &Ident) -> Ident {
+    format_ident!("proc_macro_fake_call_site_{}", conceptual)
+}
+
+fn dummy_name_for_export(export: &Export) -> String {
+    let mut dummy = String::new();
+    let from = export.from.unraw().to_string();
+    write!(dummy, "_{}{}", from.len(), from).unwrap();
+    for m in &export.macros {
+        let name = m.name.unraw().to_string();
+        write!(dummy, "_{}{}", name.len(), name).unwrap();
+    }
+    dummy
+}
+
+fn wrap_in_enum_hack(dummy: String, inner: TokenStream) -> TokenStream {
+    let dummy = Ident::new(&dummy, Span::call_site());
+    quote! {
+        #[derive(proc_macro_hack::ProcMacroHack)]
+        enum #dummy {
+            Value = (stringify! { #inner }, 0).1,
+        }
+    }
+}