Import 'uniffi_checksum_derive' crateupstream

Request Document: go/android-rust-importing-crates
For CL Reviewers: go/android3p#cl-review
For Build Team: go/ab-third-party-imports
Bug: http://b/330712489
Test: m libuniffi_checksum_derive

Change-Id: Ia327cf897d4d7362c65859624a302764187c0860

10 files changed, 710 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..4e493dd
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "d5332be35ef497255f7ce49debfd917f6a1009c7"
+  },
+  "path_in_vcs": "uniffi_checksum_derive"
+}
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..735e222
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,46 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.79"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e835ff2298f5721608eb1a980ecaee1aef2c132bf95ecc026a11b7bf3c01c02e"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.53"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7383cd0e49fff4b6b90ca5670bfd3e9d6a733b3f90c686605aa7eec8c4996032"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
+
+[[package]]
+name = "uniffi_checksum_derive"
+version = "0.26.1"
+dependencies = [
+ "quote",
+ "syn",
+]
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..6de6dad
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,43 @@
+# 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 are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+name = "uniffi_checksum_derive"
+version = "0.26.1"
+authors = ["Firefox Sync Team <sync-team@mozilla.com>"]
+description = "a multi-language bindings generator for rust (checksum custom derive)"
+homepage = "https://mozilla.github.io/uniffi-rs"
+documentation = "https://mozilla.github.io/uniffi-rs"
+readme = "README.md"
+keywords = [
+    "ffi",
+    "bindgen",
+]
+license = "MPL-2.0"
+repository = "https://github.com/mozilla/uniffi-rs"
+
+[lib]
+proc-macro = true
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "2.0"
+features = [
+    "derive",
+    "parsing",
+]
+
+[features]
+default = []
+nightly = []
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..a612ad9
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,373 @@
+Mozilla Public License Version 2.0
+==================================
+
+1. Definitions
+--------------
+
+1.1. "Contributor"
+    means each individual or legal entity that creates, contributes to
+    the creation of, or owns Covered Software.
+
+1.2. "Contributor Version"
+    means the combination of the Contributions of others (if any) used
+    by a Contributor and that particular Contributor's Contribution.
+
+1.3. "Contribution"
+    means Covered Software of a particular Contributor.
+
+1.4. "Covered Software"
+    means Source Code Form to which the initial Contributor has attached
+    the notice in Exhibit A, the Executable Form of such Source Code
+    Form, and Modifications of such Source Code Form, in each case
+    including portions thereof.
+
+1.5. "Incompatible With Secondary Licenses"
+    means
+
+    (a) that the initial Contributor has attached the notice described
+        in Exhibit B to the Covered Software; or
+
+    (b) that the Covered Software was made available under the terms of
+        version 1.1 or earlier of the License, but not also under the
+        terms of a Secondary License.
+
+1.6. "Executable Form"
+    means any form of the work other than Source Code Form.
+
+1.7. "Larger Work"
+    means a work that combines Covered Software with other material, in
+    a separate file or files, that is not Covered Software.
+
+1.8. "License"
+    means this document.
+
+1.9. "Licensable"
+    means having the right to grant, to the maximum extent possible,
+    whether at the time of the initial grant or subsequently, any and
+    all of the rights conveyed by this License.
+
+1.10. "Modifications"
+    means any of the following:
+
+    (a) any file in Source Code Form that results from an addition to,
+        deletion from, or modification of the contents of Covered
+        Software; or
+
+    (b) any new file in Source Code Form that contains any Covered
+        Software.
+
+1.11. "Patent Claims" of a Contributor
+    means any patent claim(s), including without limitation, method,
+    process, and apparatus claims, in any patent Licensable by such
+    Contributor that would be infringed, but for the grant of the
+    License, by the making, using, selling, offering for sale, having
+    made, import, or transfer of either its Contributions or its
+    Contributor Version.
+
+1.12. "Secondary License"
+    means either the GNU General Public License, Version 2.0, the GNU
+    Lesser General Public License, Version 2.1, the GNU Affero General
+    Public License, Version 3.0, or any later versions of those
+    licenses.
+
+1.13. "Source Code Form"
+    means the form of the work preferred for making modifications.
+
+1.14. "You" (or "Your")
+    means an individual or a legal entity exercising rights under this
+    License. For legal entities, "You" includes any entity that
+    controls, is controlled by, or is under common control with You. For
+    purposes of this definition, "control" means (a) the power, direct
+    or indirect, to cause the direction or management of such entity,
+    whether by contract or otherwise, or (b) ownership of more than
+    fifty percent (50%) of the outstanding shares or beneficial
+    ownership of such entity.
+
+2. License Grants and Conditions
+--------------------------------
+
+2.1. Grants
+
+Each Contributor hereby grants You a world-wide, royalty-free,
+non-exclusive license:
+
+(a) under intellectual property rights (other than patent or trademark)
+    Licensable by such Contributor to use, reproduce, make available,
+    modify, display, perform, distribute, and otherwise exploit its
+    Contributions, either on an unmodified basis, with Modifications, or
+    as part of a Larger Work; and
+
+(b) under Patent Claims of such Contributor to make, use, sell, offer
+    for sale, have made, import, and otherwise transfer either its
+    Contributions or its Contributor Version.
+
+2.2. Effective Date
+
+The licenses granted in Section 2.1 with respect to any Contribution
+become effective for each Contribution on the date the Contributor first
+distributes such Contribution.
+
+2.3. Limitations on Grant Scope
+
+The licenses granted in this Section 2 are the only rights granted under
+this License. No additional rights or licenses will be implied from the
+distribution or licensing of Covered Software under this License.
+Notwithstanding Section 2.1(b) above, no patent license is granted by a
+Contributor:
+
+(a) for any code that a Contributor has removed from Covered Software;
+    or
+
+(b) for infringements caused by: (i) Your and any other third party's
+    modifications of Covered Software, or (ii) the combination of its
+    Contributions with other software (except as part of its Contributor
+    Version); or
+
+(c) under Patent Claims infringed by Covered Software in the absence of
+    its Contributions.
+
+This License does not grant any rights in the trademarks, service marks,
+or logos of any Contributor (except as may be necessary to comply with
+the notice requirements in Section 3.4).
+
+2.4. Subsequent Licenses
+
+No Contributor makes additional grants as a result of Your choice to
+distribute the Covered Software under a subsequent version of this
+License (see Section 10.2) or under the terms of a Secondary License (if
+permitted under the terms of Section 3.3).
+
+2.5. Representation
+
+Each Contributor represents that the Contributor believes its
+Contributions are its original creation(s) or it has sufficient rights
+to grant the rights to its Contributions conveyed by this License.
+
+2.6. Fair Use
+
+This License is not intended to limit any rights You have under
+applicable copyright doctrines of fair use, fair dealing, or other
+equivalents.
+
+2.7. Conditions
+
+Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
+in Section 2.1.
+
+3. Responsibilities
+-------------------
+
+3.1. Distribution of Source Form
+
+All distribution of Covered Software in Source Code Form, including any
+Modifications that You create or to which You contribute, must be under
+the terms of this License. You must inform recipients that the Source
+Code Form of the Covered Software is governed by the terms of this
+License, and how they can obtain a copy of this License. You may not
+attempt to alter or restrict the recipients' rights in the Source Code
+Form.
+
+3.2. Distribution of Executable Form
+
+If You distribute Covered Software in Executable Form then:
+
+(a) such Covered Software must also be made available in Source Code
+    Form, as described in Section 3.1, and You must inform recipients of
+    the Executable Form how they can obtain a copy of such Source Code
+    Form by reasonable means in a timely manner, at a charge no more
+    than the cost of distribution to the recipient; and
+
+(b) You may distribute such Executable Form under the terms of this
+    License, or sublicense it under different terms, provided that the
+    license for the Executable Form does not attempt to limit or alter
+    the recipients' rights in the Source Code Form under this License.
+
+3.3. Distribution of a Larger Work
+
+You may create and distribute a Larger Work under terms of Your choice,
+provided that You also comply with the requirements of this License for
+the Covered Software. If the Larger Work is a combination of Covered
+Software with a work governed by one or more Secondary Licenses, and the
+Covered Software is not Incompatible With Secondary Licenses, this
+License permits You to additionally distribute such Covered Software
+under the terms of such Secondary License(s), so that the recipient of
+the Larger Work may, at their option, further distribute the Covered
+Software under the terms of either this License or such Secondary
+License(s).
+
+3.4. Notices
+
+You may not remove or alter the substance of any license notices
+(including copyright notices, patent notices, disclaimers of warranty,
+or limitations of liability) contained within the Source Code Form of
+the Covered Software, except that You may alter any license notices to
+the extent required to remedy known factual inaccuracies.
+
+3.5. Application of Additional Terms
+
+You may choose to offer, and to charge a fee for, warranty, support,
+indemnity or liability obligations to one or more recipients of Covered
+Software. However, You may do so only on Your own behalf, and not on
+behalf of any Contributor. You must make it absolutely clear that any
+such warranty, support, indemnity, or liability obligation is offered by
+You alone, and You hereby agree to indemnify every Contributor for any
+liability incurred by such Contributor as a result of warranty, support,
+indemnity or liability terms You offer. You may include additional
+disclaimers of warranty and limitations of liability specific to any
+jurisdiction.
+
+4. Inability to Comply Due to Statute or Regulation
+---------------------------------------------------
+
+If it is impossible for You to comply with any of the terms of this
+License with respect to some or all of the Covered Software due to
+statute, judicial order, or regulation then You must: (a) comply with
+the terms of this License to the maximum extent possible; and (b)
+describe the limitations and the code they affect. Such description must
+be placed in a text file included with all distributions of the Covered
+Software under this License. Except to the extent prohibited by statute
+or regulation, such description must be sufficiently detailed for a
+recipient of ordinary skill to be able to understand it.
+
+5. Termination
+--------------
+
+5.1. The rights granted under this License will terminate automatically
+if You fail to comply with any of its terms. However, if You become
+compliant, then the rights granted under this License from a particular
+Contributor are reinstated (a) provisionally, unless and until such
+Contributor explicitly and finally terminates Your grants, and (b) on an
+ongoing basis, if such Contributor fails to notify You of the
+non-compliance by some reasonable means prior to 60 days after You have
+come back into compliance. Moreover, Your grants from a particular
+Contributor are reinstated on an ongoing basis if such Contributor
+notifies You of the non-compliance by some reasonable means, this is the
+first time You have received notice of non-compliance with this License
+from such Contributor, and You become compliant prior to 30 days after
+Your receipt of the notice.
+
+5.2. If You initiate litigation against any entity by asserting a patent
+infringement claim (excluding declaratory judgment actions,
+counter-claims, and cross-claims) alleging that a Contributor Version
+directly or indirectly infringes any patent, then the rights granted to
+You by any and all Contributors for the Covered Software under Section
+2.1 of this License shall terminate.
+
+5.3. In the event of termination under Sections 5.1 or 5.2 above, all
+end user license agreements (excluding distributors and resellers) which
+have been validly granted by You or Your distributors under this License
+prior to termination shall survive termination.
+
+************************************************************************
+*                                                                      *
+*  6. Disclaimer of Warranty                                           *
+*  -------------------------                                           *
+*                                                                      *
+*  Covered Software is provided under this License on an "as is"       *
+*  basis, without warranty of any kind, either expressed, implied, or  *
+*  statutory, including, without limitation, warranties that the       *
+*  Covered Software is free of defects, merchantable, fit for a        *
+*  particular purpose or non-infringing. The entire risk as to the     *
+*  quality and performance of the Covered Software is with You.        *
+*  Should any Covered Software prove defective in any respect, You     *
+*  (not any Contributor) assume the cost of any necessary servicing,   *
+*  repair, or correction. This disclaimer of warranty constitutes an   *
+*  essential part of this License. No use of any Covered Software is   *
+*  authorized under this License except under this disclaimer.         *
+*                                                                      *
+************************************************************************
+
+************************************************************************
+*                                                                      *
+*  7. Limitation of Liability                                          *
+*  --------------------------                                          *
+*                                                                      *
+*  Under no circumstances and under no legal theory, whether tort      *
+*  (including negligence), contract, or otherwise, shall any           *
+*  Contributor, or anyone who distributes Covered Software as          *
+*  permitted above, be liable to You for any direct, indirect,         *
+*  special, incidental, or consequential damages of any character      *
+*  including, without limitation, damages for lost profits, loss of    *
+*  goodwill, work stoppage, computer failure or malfunction, or any    *
+*  and all other commercial damages or losses, even if such party      *
+*  shall have been informed of the possibility of such damages. This   *
+*  limitation of liability shall not apply to liability for death or   *
+*  personal injury resulting from such party's negligence to the       *
+*  extent applicable law prohibits such limitation. Some               *
+*  jurisdictions do not allow the exclusion or limitation of           *
+*  incidental or consequential damages, so this exclusion and          *
+*  limitation may not apply to You.                                    *
+*                                                                      *
+************************************************************************
+
+8. Litigation
+-------------
+
+Any litigation relating to this License may be brought only in the
+courts of a jurisdiction where the defendant maintains its principal
+place of business and such litigation shall be governed by laws of that
+jurisdiction, without reference to its conflict-of-law provisions.
+Nothing in this Section shall prevent a party's ability to bring
+cross-claims or counter-claims.
+
+9. Miscellaneous
+----------------
+
+This License represents the complete agreement concerning the subject
+matter hereof. If any provision of this License is held to be
+unenforceable, such provision shall be reformed only to the extent
+necessary to make it enforceable. Any law or regulation which provides
+that the language of a contract shall be construed against the drafter
+shall not be used to construe this License against a Contributor.
+
+10. Versions of the License
+---------------------------
+
+10.1. New Versions
+
+Mozilla Foundation is the license steward. Except as provided in Section
+10.3, no one other than the license steward has the right to modify or
+publish new versions of this License. Each version will be given a
+distinguishing version number.
+
+10.2. Effect of New Versions
+
+You may distribute the Covered Software under the terms of the version
+of the License under which You originally received the Covered Software,
+or under the terms of any subsequent version published by the license
+steward.
+
+10.3. Modified Versions
+
+If you create software not governed by this License, and you want to
+create a new license for such software, you may create and use a
+modified version of this License if you rename the license and remove
+any references to the name of the license steward (except to note that
+such modified license differs from this License).
+
+10.4. Distributing Source Code Form that is Incompatible With Secondary
+Licenses
+
+If You choose to distribute Source Code Form that is Incompatible With
+Secondary Licenses under the terms of this version of the License, the
+notice described in Exhibit B of this License must be attached.
+
+Exhibit A - Source Code Form License Notice
+-------------------------------------------
+
+  This Source Code Form is subject to the terms of the Mozilla Public
+  License, v. 2.0. If a copy of the MPL was not distributed with this
+  file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+If it is not possible or desirable to put the notice in a particular
+file, then You may include the notice in a location (such as a LICENSE
+file in a relevant directory) where a recipient would be likely to look
+for such a notice.
+
+You may add additional accurate notices of copyright ownership.
+
+Exhibit B - "Incompatible With Secondary Licenses" Notice
+---------------------------------------------------------
+
+  This Source Code Form is "Incompatible With Secondary Licenses", as
+  defined by the Mozilla Public License, v. 2.0.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..90475db
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,20 @@
+name: "uniffi_checksum_derive"
+description: "a multi-language bindings generator for rust (checksum custom derive)"
+third_party {
+  identifier {
+    type: "crates.io"
+    value: "uniffi_checksum_derive"
+  }
+  identifier {
+    type: "Archive"
+    value: "https://static.crates.io/crates/uniffi_checksum_derive/uniffi_checksum_derive-0.26.1.crate"
+    primary_source: true
+  }
+  version: "0.26.1"
+  license_type: RECIPROCAL
+  last_upgrade_date {
+    year: 2024
+    month: 3
+    day: 21
+  }
+}
diff --git a/MODULE_LICENSE_MPL b/MODULE_LICENSE_MPL
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_MPL
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..48bea6e
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1,2 @@
+# Bug component: 688011
+include platform/prebuilts/rust:main:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..bb72360
--- /dev/null
+++ b/README.md
@@ -0,0 +1,79 @@
+# UniFFI - a multi-language bindings generator for Rust
+
+UniFFI is a toolkit for building cross-platform software components in Rust.
+
+For the impatient, see [**the UniFFI user guide**](https://mozilla.github.io/uniffi-rs/)
+or [**the UniFFI examples**](https://github.com/mozilla/uniffi-rs/tree/main/examples#example-uniffi-components).
+
+By writing your core business logic in Rust and describing its interface in an "object model",
+you can use UniFFI to help you:
+
+* Compile your Rust code into a shared library for use on different target platforms.
+* Generate bindings to load and use the library from different target languages.
+
+You can describe your object model in an [interface definition file](https://mozilla.github.io/uniffi-rs/udl_file_spec.html)
+or [by using proc-macros](https://mozilla.github.io/uniffi-rs/proc_macro/index.html).
+
+UniFFI is currently extensively by Mozilla in Firefox mobile and desktop browsers;
+written once in Rust, auto-generated bindings allow that functionality to be called
+from both Kotlin (for Android apps) and Swift (for iOS apps).
+It also has a growing community of users shipping various cool things to many users.
+
+UniFII comes with support for **Kotlin**, **Swift**, **Python** and **Ruby** with 3rd party bindings available for **C#** and **Golang**.
+Additional foreign language bindings can be developed externally and we welcome contributions to list them here.
+See [Third-party foreign language bindings](#third-party-foreign-language-bindings).
+
+## User Guide
+
+You can read more about using the tool in [**the UniFFI user guide**](https://mozilla.github.io/uniffi-rs/).
+
+We consider it ready for production use, but UniFFI is a long way from a 1.0 release with lots of internal work still going on.
+We try hard to avoid breaking simple consumers, but more advanced things might break as you upgrade over time.
+
+### Etymology and Pronunciation
+
+ˈjuːnɪfaɪ. Pronounced to rhyme with "unify".
+
+A portmanteau word that also puns with "unify", to signify the joining of one codebase accessed from many languages.
+
+uni - [Latin ūni-, from ūnus, one]
+FFI - [Abbreviation, Foreign Function Interface]
+
+## Alternative tools
+
+Other tools we know of which try and solve a similarly shaped problem are:
+
+* [Diplomat](https://github.com/rust-diplomat/diplomat/) - see our [writeup of
+  the different approach taken by that tool](docs/diplomat-and-macros.md)
+* [Interoptopus](https://github.com/ralfbiedert/interoptopus/)
+
+(Please open a PR if you think other tools should be listed!)
+
+## Third-party foreign language bindings
+
+* [Kotlin Multiplatform support](https://gitlab.com/trixnity/uniffi-kotlin-multiplatform-bindings). The repository contains Kotlin Multiplatform bindings generation for UniFFI, letting you target both JVM and Native.
+* [Go bindings](https://github.com/NordSecurity/uniffi-bindgen-go)
+* [C# bindings](https://github.com/NordSecurity/uniffi-bindgen-cs)
+* [Dart bindings](https://github.com/NiallBunting/uniffi-rs-dart)
+
+### External resources
+
+There are a few third-party resources that make it easier to work with UniFFI:
+
+* [Plugin support for `.udl` files](https://github.com/Lonami/uniffi-dl) for the IDEA platform ([*uniffi-dl* in the JetBrains marketplace](https://plugins.jetbrains.com/plugin/20527-uniffi-dl)). It provides syntax highlighting, code folding, code completion, reference resolution and navigation (among others features) for the [UniFFI Definition Language (UDL)](https://mozilla.github.io/uniffi-rs/).
+* [cargo swift](https://github.com/antoniusnaumann/cargo-swift), a cargo plugin to build a Swift Package from Rust code. It provides an init command for setting up a UniFFI crate and a package command for building a Swift package from Rust code - without the need for additional configuration or build scripts.
+
+(Please open a PR if you think other resources should be listed!)
+
+## Contributing
+
+If this tool sounds interesting to you, please help us develop it! You can:
+
+* View the [contributor guidelines](./docs/contributing.md).
+* File or work on [issues](https://github.com/mozilla/uniffi-rs/issues) here in GitHub.
+* Join discussions in the [#uniffi:mozilla.org](https://matrix.to/#/#uniffi:mozilla.org)
+  room on Matrix.
+
+## Code of Conduct
+
+This project is governed by Mozilla's [Community Participation Guidelines](./CODE_OF_CONDUCT.md).
diff --git a/cargo_embargo.json b/cargo_embargo.json
new file mode 100644
index 0000000..cb908d7
--- /dev/null
+++ b/cargo_embargo.json
@@ -0,0 +1,3 @@
+{
+  "run_cargo": false
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..e600982
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,138 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Custom derive for uniffi_meta::Checksum
+
+use proc_macro::TokenStream;
+use quote::{format_ident, quote};
+use syn::{
+    parse_macro_input, Attribute, Data, DeriveInput, Expr, ExprLit, Fields, Index, Lit, Meta,
+};
+
+fn has_ignore_attribute(attrs: &[Attribute]) -> bool {
+    attrs.iter().any(|attr| {
+        if attr.path().is_ident("checksum_ignore") {
+            if let Meta::List(_) | Meta::NameValue(_) = &attr.meta {
+                panic!("#[checksum_ignore] doesn't accept extra information");
+            }
+            true
+        } else {
+            false
+        }
+    })
+}
+
+#[proc_macro_derive(Checksum, attributes(checksum_ignore))]
+pub fn checksum_derive(input: TokenStream) -> TokenStream {
+    let input: DeriveInput = parse_macro_input!(input);
+
+    let name = input.ident;
+
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+    let code = match input.data {
+        Data::Enum(enum_)
+            if enum_.variants.len() == 1
+                && enum_
+                    .variants
+                    .iter()
+                    .all(|variant| matches!(variant.fields, Fields::Unit)) =>
+        {
+            quote!()
+        }
+        Data::Enum(enum_) => {
+            let mut next_discriminant = 0u64;
+            let match_inner = enum_.variants.iter().map(|variant| {
+                let ident = &variant.ident;
+                if has_ignore_attribute(&variant.attrs) {
+                    panic!("#[checksum_ignore] is not supported in enums");
+                }
+                match &variant.discriminant {
+                    Some((_, Expr::Lit(ExprLit { lit: Lit::Int(value), .. }))) => {
+                        next_discriminant = value.base10_parse::<u64>().unwrap();
+                    }
+                    Some(_) => {
+                        panic!("#[derive(Checksum)] doesn't support non-numeric explicit discriminants in enums");
+                    }
+                    None => {}
+                }
+                let discriminant = quote! { state.write(&#next_discriminant.to_le_bytes()) };
+                next_discriminant += 1;
+                match &variant.fields {
+                    Fields::Unnamed(fields) => {
+                        let field_idents = fields
+                            .unnamed
+                            .iter()
+                            .enumerate()
+                            .map(|(num, _)| format_ident!("__self_{}", num));
+                        let field_stmts = field_idents
+                            .clone()
+                            .map(|ident| quote! { Checksum::checksum(#ident, state); });
+                        quote! {
+                            Self::#ident(#(#field_idents,)*) => {
+                                #discriminant;
+                                #(#field_stmts)*
+                            }
+                        }
+                    }
+                    Fields::Named(fields) => {
+                        let field_idents = fields
+                            .named
+                            .iter()
+                            .map(|field| field.ident.as_ref().unwrap());
+                        let field_stmts = fields.named.iter()
+                            .filter(|field| !has_ignore_attribute(&field.attrs))
+                            .map(|field| {
+                                    let ident = field.ident.as_ref().unwrap();
+                                    quote! { Checksum::checksum(#ident, state); }
+                            });
+                        quote! {
+                            Self::#ident { #(#field_idents,)* } => {
+                                #discriminant;
+                                #(#field_stmts)*
+                            }
+                        }
+                    }
+                    Fields::Unit => quote! { Self::#ident => #discriminant, },
+                }
+            });
+            quote! {
+                match self {
+                    #(#match_inner)*
+                }
+            }
+        }
+        Data::Struct(struct_) => {
+            let stmts = struct_
+                .fields
+                .iter()
+                .enumerate()
+                .filter_map(|(num, field)| {
+                    (!has_ignore_attribute(&field.attrs)).then(|| match field.ident.as_ref() {
+                        Some(ident) => quote! { Checksum::checksum(&self.#ident, state); },
+                        None => {
+                            let i = Index::from(num);
+                            quote! { Checksum::checksum(&self.#i, state); }
+                        }
+                    })
+                });
+            quote! {
+                #(#stmts)*
+            }
+        }
+        Data::Union(_) => {
+            panic!("#[derive(Checksum)] is not supported for unions");
+        }
+    };
+
+    quote! {
+        #[automatically_derived]
+        impl #impl_generics Checksum for #name #ty_generics #where_clause {
+            fn checksum<__H: ::core::hash::Hasher>(&self, state: &mut __H) {
+                #code
+            }
+        }
+    }
+    .into()
+}