diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..0b126fe
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "69743a4ceab6c8da1ddb473f54a6a01840de90d9"
+  }
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..1365dbb
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,41 @@
+# 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-error-attr"
+version = "1.0.2"
+authors = ["CreepySkeleton <creepy-skeleton@yandex.ru>"]
+build = "build.rs"
+description = "Attribute macro for proc-macro-error crate"
+license = "MIT OR Apache-2.0"
+repository = "https://gitlab.com/CreepySkeleton/proc-macro-error"
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[lib]
+proc-macro = true
+[dependencies.proc-macro2]
+version = "1"
+
+[dependencies.quote]
+version = "1"
+
+[dependencies.syn]
+version = "1"
+features = ["derive", "parsing", "proc-macro", "printing"]
+default-features = false
+
+[dependencies.syn-mid]
+version = "0.5"
+[build-dependencies.version_check]
+version = "0.9"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..7414642
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,26 @@
+[package]
+name = "proc-macro-error-attr"
+version = "1.0.2"
+authors = ["CreepySkeleton <creepy-skeleton@yandex.ru>"]
+edition = "2018"
+description = "Attribute macro for proc-macro-error crate"
+license = "MIT OR Apache-2.0"
+repository = "https://gitlab.com/CreepySkeleton/proc-macro-error"
+
+build = "build.rs"
+
+[lib]
+proc-macro = true
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+quote = "1"
+proc-macro2 = "1"
+syn-mid = "0.5"
+# "derive" is for `Attribute`, "parsing" is for `Parse`
+syn = { version = "1", default-features = false, features = ["derive", "parsing", "proc-macro", "printing"] }
+
+[build-dependencies]
+version_check = "0.9"
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..658240a
--- /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.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
+   control with that entity. For the purposes of this definition,
+   "control" means (i) the power, direct or indirect, to cause the
+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
+   and conversions to other media types.
+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
+   (an example is provided in the Appendix below).
+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
+   submitted to Licensor for inclusion in the Work by the copyright owner
+   or by an individual or Legal Entity authorized to submit on behalf of
+   the copyright owner. For the purposes of this definition, "submitted"
+   means any form of electronic, verbal, or written communication sent
+   to the Licensor or its representatives, including but not limited to
+   communication on electronic mailing lists, source code control systems,
+   and issue tracking systems that are managed by, or on behalf of, the
+   Licensor for the purpose of discussing and improving the Work, but
+   excluding communication that is conspicuously marked or otherwise
+   designated in writing by the copyright owner as "Not a Contribution."
+
+   "Contributor" shall mean Licensor and any individual or Legal Entity
+   on behalf of whom a Contribution has been received by Licensor and
+   subsequently incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   copyright license to reproduce, prepare Derivative Works of,
+   publicly display, publicly perform, sublicense, and distribute the
+   Work and such Derivative Works in Source or Object form.
+
+3. Grant of Patent License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   (except as stated in this section) patent license to make, have made,
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+   where such license applies only to those patent claims licensable
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+   Contribution(s) alone or by combination of their Contribution(s)
+   with the Work to which such Contribution(s) was submitted. If You
+   institute patent litigation against any entity (including a
+   cross-claim or counterclaim in a lawsuit) alleging that the Work
+   or a Contribution incorporated within the Work constitutes direct
+   or contributory patent infringement, then any patent licenses
+   granted to You under this License for that Work shall terminate
+   as of the date such litigation is filed.
+
+4. Redistribution. You may reproduce and distribute copies of the
+   Work or Derivative Works thereof in any medium, with or without
+   modifications, and in Source or Object form, provided that You
+   meet the following conditions:
+
+   (a) You must give any other recipients of the Work or
+       Derivative Works a copy of this License; and
+
+   (b) You must cause any modified files to carry prominent notices
+       stating that You changed the files; and
+
+   (c) You must retain, in the Source form of any Derivative Works
+       that You distribute, all copyright, patent, trademark, and
+       attribution notices from the Source form of the Work,
+       excluding those notices that do not pertain to any part of
+       the Derivative Works; and
+
+   (d) If the Work includes a "NOTICE" text file as part of its
+       distribution, then any Derivative Works that You distribute must
+       include a readable copy of the attribution notices contained
+       within such NOTICE file, excluding those notices that do not
+       pertain to any part of the Derivative Works, in at least one
+       of the following places: within a NOTICE text file distributed
+       as part of the Derivative Works; within the Source form or
+       documentation, if provided along with the Derivative Works; or,
+       within a display generated by the Derivative Works, if and
+       wherever such third-party notices normally appear. The contents
+       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
+       that such additional attribution notices cannot be construed
+       as modifying the License.
+
+   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,
+   except as required for reasonable and customary use in describing the
+   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
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   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
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
+   or other liability obligations and/or rights consistent with this
+   License. However, in accepting such obligations, You may act only
+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+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
+   the brackets!)  The text should be enclosed in the appropriate
+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
+   identification within third-party archives.
+
+Copyright 2019-2020 CreepySkeleton <creepy-skeleton@yandex.ru>
+
+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..fc73e59
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2019-2020 CreepySkeleton
+
+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/build.rs b/build.rs
new file mode 100644
index 0000000..f2ac6a7
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,5 @@
+fn main() {
+    if version_check::is_max_version("1.36.0").unwrap_or(false) {
+        println!("cargo:rustc-cfg=always_assert_unwind");
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..75953fe
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,152 @@
+//! This is `#[proc_macro_error]` attribute to be used with
+//! [`proc-macro-error`](https://docs.rs/proc-macro-error/). There you go.
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro2::Ident;
+use quote::quote;
+use std::iter::FromIterator;
+use syn::{
+    parse::{Parse, ParseStream},
+    parse_macro_input,
+    punctuated::Punctuated,
+    Attribute, Token,
+};
+use syn_mid::{Block, ItemFn};
+
+use self::Setting::*;
+
+#[proc_macro_attribute]
+pub fn proc_macro_error(attr: TokenStream, input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as ItemFn);
+    let mut settings = match syn::parse::<Settings>(attr) {
+        Ok(settings) => settings,
+        Err(err) => {
+            let err = err.to_compile_error();
+            return quote!(#input #err).into();
+        }
+    };
+
+    let is_proc_macro = is_proc_macro(&input.attrs);
+    if is_proc_macro {
+        settings.set(AssertUnwindSafe);
+    }
+
+    if detect_proc_macro_hack(&input.attrs) {
+        settings.set(ProcMacroHack);
+    }
+
+    if settings.is_set(ProcMacroHack) {
+        settings.set(AllowNotMacro);
+    }
+
+    if !(settings.is_set(AllowNotMacro) || is_proc_macro) {
+        return quote!(
+            #input
+            compile_error!(
+                "#[proc_macro_error] attribute can be used only with a proc-macro\n\n  \
+                = hint: if you are really sure that #[proc_macro_error] should be applied \
+                to this exact function use #[proc_macro_error(allow_not_macro)]\n");
+        )
+        .into();
+    }
+
+    let ItemFn {
+        attrs,
+        vis,
+        sig,
+        block,
+    } = input;
+
+    let body = gen_body(*block, settings);
+
+    quote!(
+        #(#attrs)*
+        #vis
+        #sig
+        { #body }
+    )
+    .into()
+}
+
+#[derive(PartialEq)]
+enum Setting {
+    AssertUnwindSafe,
+    AllowNotMacro,
+    ProcMacroHack,
+}
+
+impl Parse for Setting {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident: Ident = input.parse()?;
+        match &*ident.to_string() {
+            "assert_unwind_safe" => Ok(AssertUnwindSafe),
+            "allow_not_macro" => Ok(AllowNotMacro),
+            "proc_macro_hack" => Ok(ProcMacroHack),
+            _ => Err(syn::Error::new(
+                ident.span(),
+                format!(
+                    "unknown setting `{}`, expected one of \
+                     `assert_unwind_safe`, `allow_not_macro`, `proc_macro_hack`",
+                    ident
+                ),
+            )),
+        }
+    }
+}
+
+struct Settings(Vec<Setting>);
+impl Parse for Settings {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let punct = Punctuated::<Setting, Token![,]>::parse_terminated(input)?;
+        Ok(Settings(Vec::from_iter(punct)))
+    }
+}
+
+impl Settings {
+    fn is_set(&self, setting: Setting) -> bool {
+        self.0.iter().any(|s| *s == setting)
+    }
+
+    fn set(&mut self, setting: Setting) {
+        self.0.push(setting)
+    }
+}
+
+#[cfg(not(always_assert_unwind))]
+fn gen_body(block: Block, settings: Settings) -> proc_macro2::TokenStream {
+    let is_proc_macro_hack = settings.is_set(ProcMacroHack);
+    let closure = if settings.is_set(AssertUnwindSafe) {
+        quote!(::std::panic::AssertUnwindSafe(|| #block ))
+    } else {
+        quote!(|| #block)
+    };
+
+    quote!( ::proc_macro_error::entry_point(#closure, #is_proc_macro_hack) )
+}
+
+// FIXME:
+// proc_macro::TokenStream does not implement UnwindSafe until 1.37.0.
+// Considering this is the closure's return type the unwind safety check would fail
+// for virtually every closure possible, the check is meaningless.
+#[cfg(always_assert_unwind)]
+fn gen_body(block: Block, settings: Settings) -> proc_macro2::TokenStream {
+    let is_proc_macro_hack = settings.is_set(ProcMacroHack);
+    let closure = quote!(::std::panic::AssertUnwindSafe(|| #block ));
+    quote!( ::proc_macro_error::entry_point(#closure, #is_proc_macro_hack) )
+}
+
+fn detect_proc_macro_hack(attrs: &[Attribute]) -> bool {
+    attrs
+        .iter()
+        .any(|attr| attr.path.is_ident("proc_macro_hack"))
+}
+
+fn is_proc_macro(attrs: &[Attribute]) -> bool {
+    attrs.iter().any(|attr| {
+        attr.path.is_ident("proc_macro")
+            || attr.path.is_ident("proc_macro_derive")
+            || attr.path.is_ident("proc_macro_attribute")
+    })
+}