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Vendor contracts crate

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@ -27,3 +27,9 @@ features = ["gfx"]
[dependencies.enum-as-inner] [dependencies.enum-as-inner]
version = "0.6.0" version = "0.6.0"
[dependencies.contracts]
version = "0.6.3"
[patch.crates-io]
contracts = { path = "vendor/contracts" }

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/target
**/*.rs.bk
Cargo.lock
.idea

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stages:
- fmt-check
- test
fmt-check:
stage: fmt-check
image: rust:latest
before_script:
- rustup component add rustfmt
script:
- cargo fmt --all -- --check
test-stable:
stage: test
image: rust:latest
script:
- cargo test --all
test-nightly:
stage: test
image: rustlang/rust:nightly
script:
- cargo test --all
allow_failure: true
clippy-tests-stable:
stage: test
image: rust:latest
before_script:
- rustup component add clippy
script:
- cargo clippy --tests

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# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## Unreleased
## [0.6.3] - 2022-03-13
### Fixed
- improved hygiene around `self` parameters
- fix contract messages containing `{}` emitting warnings as they are interpreted as format strings
## [0.6.2] - 2021-07-21
### Changed
- better handling of mutable borrows and lifetime relationships for functions
with contracts
## [0.6.1] - 2021-07-13
### Added
- support for `impl Trait` return types
## [0.6.0] - 2020-09-05
### Changed
- `pre` is now `requires`
- `post` is now `ensures`
## [0.5.2] - 2020-09-05
### Fixed
- Unused braces in function body generated code are removed
## [0.5.1] - 2020-08-06
### Changed
- Trait methods now handle attributes better.
## [0.5.0] - 2020-08-06
### Changed
- Implication operator is now `->`.
## [0.4.0] - 2020-05-01
### Added
- Added support for MIRAI assertions
- Added implication operator
## [0.3.0] - 2019-07-20
### Added
- Pseudo-function `old(expr)` which in a post-condition evaluates the expression before function execution.
- Automatic generation of documentation containing all contracts.
## [0.2.2] - 2019-07-17
### Fixed
- Errors inside functions/methods are now properly reported with the correct source location.
### Changed
- internal handling of contracts is now done in a single proc-macro pass instead of one for each contract.
## [0.2.1] - 2019-06-07
### Fixed
- Functions/methods with explicit return statements no longer skip `post` conditions
## [0.2.0] - 2014-04-12
### Added
- `contract_trait` attribute to make all implementors of a trait respect contracts.
## [0.1.1] - 2019-04-08
### Added
- Feature flags to override contract behavior.
- `disable_contracts` ignores all checks
- `override_debug` only checks contracts in debug configurations.
- `override_log` only prints using the `log`-crate interface.
## [0.1.0] - 2019-04-06
### Added
- attributes `pre`/`post`/`invariant` and `debug_` versions of each.

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[package]
name = "contracts"
version = "0.6.3"
authors = ["karroffel <therzog@mail.de>"]
edition = "2018"
repository = "https://gitlab.com/karroffel/contracts"
license = "MPL-2.0"
readme = "README.md"
categories = [
"development-tools",
"development-tools::procedural-macro-helpers",
]
keywords = [
"design-by-contract",
"precondition",
"postcondition",
"invariant",
"verification",
]
documentation = "https://docs.rs/contracts"
description = "Design-by-contract attributes"
[badges]
gitlab = { repository = "karroffel/contracts", branch = "master" }
[lib]
name = "contracts"
path = "src/lib.rs"
proc-macro = true
[features]
disable_contracts = []
override_debug = []
override_log = []
mirai_assertions = []
[dependencies]
syn = { version = "1.0", features = ["extra-traits", "full", "visit", "visit-mut"] }
quote = "1.0"
proc-macro2 = "1.0"

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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.

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# *Design By Contract* for Rust
[![License][license]][LICENSE]
![Build status][build]
![Lines of Code][loc]
[license]: https://img.shields.io/badge/license-MPL%202.0-blue.svg
[build]: https://gitlab.com/karroffel/contracts/badges/master/pipeline.svg
[loc]: https://tokei.rs/b1/gitlab/karroffel/contracts?category=code
Annotate functions and methods with "contracts", using *invariants*,
*pre-conditions* and *post-conditions*.
[Design by contract][dbc] is a popular method to augment code with formal
interface specifications.
These specifications are used to increase the correctness of the code by
checking them as assertions at runtime.
[dbc]: https://en.wikipedia.org/wiki/Design_by_contract
```rust
pub struct Library {
available: HashSet<String>,
lent: HashSet<String>,
}
impl Library {
fn book_exists(&self, book_id: &str) -> bool {
self.available.contains(book_id)
|| self.lent.contains(book_id)
}
#[debug_requires(!self.book_exists(book_id), "Book IDs are unique")]
#[debug_ensures(self.available.contains(book_id), "Book now available")]
#[ensures(self.available.len() == old(self.available.len()) + 1)]
#[ensures(self.lent.len() == old(self.lent.len()), "No lent change")]
pub fn add_book(&mut self, book_id: &str) {
self.available.insert(book_id.to_string());
}
#[debug_requires(self.book_exists(book_id))]
#[ensures(ret -> self.available.len() == old(self.available.len()) - 1)]
#[ensures(ret -> self.lent.len() == old(self.lent.len()) + 1)]
#[debug_ensures(ret -> self.lent.contains(book_id))]
#[debug_ensures(!ret -> self.lent.contains(book_id), "Book already lent")]
pub fn lend(&mut self, book_id: &str) -> bool {
if self.available.contains(book_id) {
self.available.remove(book_id);
self.lent.insert(book_id.to_string());
true
} else {
false
}
}
#[debug_requires(self.lent.contains(book_id), "Can't return a non-lent book")]
#[ensures(self.lent.len() == old(self.lent.len()) - 1)]
#[ensures(self.available.len() == old(self.available.len()) + 1)]
#[debug_ensures(!self.lent.contains(book_id))]
#[debug_ensures(self.available.contains(book_id), "Book available again")]
pub fn return_book(&mut self, book_id: &str) {
self.lent.remove(book_id);
self.available.insert(book_id.to_string());
}
}
```
## Attributes
This crate exposes the `requires`, `ensures` and `invariant` attributes.
- `requires` are checked before a function/method is executed.
- `ensures` are checked after a function/method ran to completion
- `invariant`s are checked both before *and* after a function/method ran.
Additionally, all those attributes have versions with different "modes". See
[the Modes section](#Modes) below.
For `trait`s and trait `impl`s the `contract_trait` attribute can be used.
More specific information can be found in the crate documentation.
## Pseudo-functions and operators
### `old()` function
One unique feature that this crate provides is an `old()` pseudo-function which
allows to perform checks using a value of a parameter before the function call
happened. This is only available in `ensures` attributes.
```rust
#[ensures(*x == old(*x) + 1, "after the call `x` was incremented")]
fn incr(x: &mut usize) {
*x += 1;
}
```
### `->` operator
For more complex functions it can be useful to express behaviour using logical
implication. Because Rust does not feature an operator for implication, this
crate adds this operator for use in attributes.
```rust
#[ensures(person_name.is_some() -> ret.contains(person_name.unwrap()))]
fn geeting(person_name: Option<&str>) -> String {
let mut s = String::from("Hello");
if let Some(name) = person_name {
s.push(' ');
s.push_str(name);
}
s.push('!');
s
}
```
This operator is right-associative.
**Note**: Because of the design of `syn`, it is tricky to add custom operators
to be parsed, so this crate performs a rewrite of the `TokenStream` instead.
The rewrite works by separating the expression into a part that's left of the
`->` operator and the rest on the right side. This means that
`if a -> b { c } else { d }` will not generate the expected code.
Explicit grouping using parenthesis or curly-brackets can be used to avoid this.
## Modes
All the attributes (requires, ensures, invariant) have `debug_*` and `test_*` versions.
- `debug_requires`/`debug_ensures`/`debug_invariant` use `debug_assert!`
internally rather than `assert!`
- `test_requires`/`test_ensures`/`test_invariant` guard the `assert!` with an
`if cfg!(test)`.
This should mostly be used for stating equivalence to "slow but obviously
correct" alternative implementations or checks.
For example, a merge-sort implementation might look like this
```rust
#[test_ensures(is_sorted(input))]
fn merge_sort<T: Ord + Copy>(input: &mut [T]) {
// ...
}
```
## Set-up
To install the latest version, add `contracts` to the dependency section of the
`Cargo.toml` file.
```
[dependencies]
contracts = "0.6.3"
```
To then bring all procedural macros into scope, you can add `use contracts::*;`
in all files you plan to use the contract attributes.
Alternatively use the "old-style" of importing macros to have them available
project-wide.
```rust
#[macro_use]
extern crate contracts;
```
## Configuration
This crate exposes a number of feature flags to configure the assertion behavior.
- `disable_contracts` - disables all checks and assertions.
- `override_debug` - changes all contracts (except `test_` ones) into `debug_*`
versions
- `override_log` - changes all contracts (except `test_` ones) into a
`log::error!()` call if the condition is violated.
No abortion happens.
- `mirai_assertions` - instead of regular assert! style macros, emit macros
used by the [MIRAI] static analyzer. For more documentation of this usage,
head to the [MIRAI] repo.
[MIRAI]: https://github.com/facebookexperimental/MIRAI
## TODOs
- implement more contracts for traits.
- add a static analyzer à la SPARK for whole-projects using the contracts to
make static assertions.

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# Things to check/change before pushing a release
1. Run all the tests with `cargo test --all`
2. Run `cargo run --example library` to make sure the examples still run properly
3. Run `cargo fmt`
4. Change version numbers
- inside `README.md` in the "Set-up" section
- inside `Cargo.toml`
5. Write or finish entry in `CHANGELOG.md`
6. Run `cargo doc --open` and check if the documentation looks fine and is up to date
7. Run `cargo package` and check the output for any unwanted or missing files
8. Run `cargo publish` to upload to crates.io

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/* 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/. */
use contracts::*;
use std::collections::HashSet;
pub struct Library {
available: HashSet<String>,
lent: HashSet<String>,
}
impl Library {
fn book_exists(&self, book_id: &str) -> bool {
self.available.contains(book_id) || self.lent.contains(book_id)
}
#[debug_requires(!self.book_exists(book_id), "Book IDs are unique")]
#[debug_ensures(self.available.contains(book_id), "Book now available")]
#[ensures(self.available.len() == old(self.available.len()) + 1)]
#[ensures(self.lent.len() == old(self.lent.len()), "No lent change")]
pub fn add_book(&mut self, book_id: &str) {
self.available.insert(book_id.to_string());
}
#[debug_requires(self.book_exists(book_id))]
#[ensures(ret -> self.available.len() == old(self.available.len()) - 1)]
#[ensures(ret -> self.lent.len() == old(self.lent.len()) + 1)]
#[debug_ensures(ret -> self.lent.contains(book_id))]
#[debug_ensures(!ret -> self.lent.contains(book_id), "Book already lent")]
pub fn lend(&mut self, book_id: &str) -> bool {
if self.available.contains(book_id) {
self.available.remove(book_id);
self.lent.insert(book_id.to_string());
true
} else {
false
}
}
#[debug_requires(self.lent.contains(book_id), "Can't return a non-lent book")]
#[ensures(self.lent.len() == old(self.lent.len()) - 1)]
#[ensures(self.available.len() == old(self.available.len()) + 1)]
#[debug_ensures(!self.lent.contains(book_id))]
#[debug_ensures(self.available.contains(book_id), "Book available again")]
pub fn return_book(&mut self, book_id: &str) {
self.lent.remove(book_id);
self.available.insert(book_id.to_string());
}
}
fn main() {
let mut lib = Library {
available: HashSet::new(),
lent: HashSet::new(),
};
lib.add_book("Das Kapital");
println!("Adding a book.");
let lent_successful = lib.lend("Das Kapital");
assert!(lent_successful);
if lent_successful {
println!("Lent out the book.");
println!("Reading for a bit...");
println!("Giving back the book.");
lib.return_book("Das Kapital");
}
}

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/* 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/. */
use proc_macro2::{Ident, Span, TokenStream};
use quote::ToTokens;
use syn::{
spanned::Spanned, visit_mut as visitor, Attribute, Expr, ExprCall,
ReturnType,
};
use crate::implementation::{
Contract, ContractMode, ContractType, FuncWithContracts,
};
/// Substitution for `old()` expressions.
pub(crate) struct OldExpr {
/// Name of the variable binder.
pub(crate) name: String,
/// Expression to be evaluated.
pub(crate) expr: Expr,
}
/// Extract calls to the pseudo-function `old()` in post-conditions,
/// which evaluates an expression in a context *before* the
/// to-be-checked-function is executed.
pub(crate) fn extract_old_calls(contracts: &mut [Contract]) -> Vec<OldExpr> {
struct OldExtractor {
last_id: usize,
olds: Vec<OldExpr>,
}
// if the call is a call to old() then the argument will be
// returned.
fn get_old_data(call: &ExprCall) -> Option<Expr> {
// must have only one argument
if call.args.len() != 1 {
return None;
}
if let Expr::Path(path) = &*call.func {
if path.path.is_ident("old") {
Some(call.args[0].clone())
} else {
None
}
} else {
None
}
}
impl visitor::VisitMut for OldExtractor {
fn visit_expr_mut(&mut self, expr: &mut Expr) {
if let Expr::Call(call) = expr {
if let Some(mut old_arg) = get_old_data(call) {
// if it's a call to old() then add to list of
// old expressions and continue to check the
// argument.
self.visit_expr_mut(&mut old_arg);
let id = self.last_id;
self.last_id += 1;
let old_var_name = format!("__contract_old_{}", id);
let old_expr = OldExpr {
name: old_var_name.clone(),
expr: old_arg,
};
self.olds.push(old_expr);
// override the original expression with the new variable
// identifier
*expr = {
let span = expr.span();
let ident = syn::Ident::new(&old_var_name, span);
let toks = quote::quote_spanned! { span=> #ident };
syn::parse(toks.into()).unwrap()
};
} else {
// otherwise continue visiting the expression call
visitor::visit_expr_call_mut(self, call);
}
} else {
visitor::visit_expr_mut(self, expr);
}
}
}
let mut extractor = OldExtractor {
last_id: 0,
olds: vec![],
};
for contract in contracts {
if contract.ty != ContractType::Ensures {
continue;
}
for assertion in &mut contract.assertions {
use visitor::VisitMut;
extractor.visit_expr_mut(assertion);
}
}
extractor.olds
}
fn get_assert_macro(
ctype: ContractType, // only Pre/Post allowed.
mode: ContractMode,
span: Span,
) -> Option<Ident> {
if cfg!(feature = "mirai_assertions") {
match (ctype, mode) {
(ContractType::Requires, ContractMode::Always) => {
Some(Ident::new("checked_precondition", span))
}
(ContractType::Requires, ContractMode::Debug) => {
Some(Ident::new("debug_checked_precondition", span))
}
(ContractType::Requires, ContractMode::Test) => {
Some(Ident::new("debug_checked_precondition", span))
}
(ContractType::Requires, ContractMode::Disabled) => {
Some(Ident::new("precondition", span))
}
(ContractType::Requires, ContractMode::LogOnly) => {
Some(Ident::new("precondition", span))
}
(ContractType::Ensures, ContractMode::Always) => {
Some(Ident::new("checked_postcondition", span))
}
(ContractType::Ensures, ContractMode::Debug) => {
Some(Ident::new("debug_checked_postcondition", span))
}
(ContractType::Ensures, ContractMode::Test) => {
Some(Ident::new("debug_checked_postcondition", span))
}
(ContractType::Ensures, ContractMode::Disabled) => {
Some(Ident::new("postcondition", span))
}
(ContractType::Ensures, ContractMode::LogOnly) => {
Some(Ident::new("postcondition", span))
}
(ContractType::Invariant, _) => {
panic!("expected Invariant to be narrowed down to Pre/Post")
}
}
} else {
match mode {
ContractMode::Always => Some(Ident::new("assert", span)),
ContractMode::Debug => Some(Ident::new("debug_assert", span)),
ContractMode::Test => Some(Ident::new("debug_assert", span)),
ContractMode::Disabled => None,
ContractMode::LogOnly => None,
}
}
}
/// Generate the resulting code for this function by inserting assertions.
pub(crate) fn generate(
mut func: FuncWithContracts,
docs: Vec<Attribute>,
olds: Vec<OldExpr>,
) -> TokenStream {
let func_name = func.function.sig.ident.to_string();
// creates an assertion appropriate for the current mode
let make_assertion = |mode: ContractMode,
ctype: ContractType,
display: proc_macro2::TokenStream,
exec_expr: &Expr,
desc: &str| {
let span = display.span();
let mut result = proc_macro2::TokenStream::new();
let format_args = quote::quote_spanned! { span=>
concat!(concat!(#desc, ": "), stringify!(#display))
};
if mode == ContractMode::LogOnly {
result.extend(
quote::quote_spanned! { span=>
if !(#exec_expr) {
log::error!("{}", #format_args);
}
}
.into_iter(),
);
}
if let Some(assert_macro) = get_assert_macro(ctype, mode, span) {
result.extend(
quote::quote_spanned! { span=>
#assert_macro!(#exec_expr, "{}", #format_args);
}
.into_iter(),
);
}
if mode == ContractMode::Test {
quote::quote_spanned! { span=>
#[cfg(test)] {
#result
}
}
} else {
result
}
};
//
// generate assertion code for pre-conditions
//
let pre: proc_macro2::TokenStream = func
.contracts
.iter()
.filter(|c| {
c.ty == ContractType::Requires || c.ty == ContractType::Invariant
})
.flat_map(|c| {
let desc = if let Some(desc) = c.desc.as_ref() {
format!(
"{} of {} violated: {}",
c.ty.message_name(),
func_name,
desc
)
} else {
format!("{} of {} violated", c.ty.message_name(), func_name)
};
c.assertions.iter().zip(c.streams.iter()).map(
move |(expr, display)| {
let mode = c.mode.final_mode();
make_assertion(
mode,
ContractType::Requires,
display.clone(),
expr,
&desc.clone(),
)
},
)
})
.collect();
//
// generate assertion code for post-conditions
//
let post: proc_macro2::TokenStream = func
.contracts
.iter()
.filter(|c| {
c.ty == ContractType::Ensures || c.ty == ContractType::Invariant
})
.flat_map(|c| {
let desc = if let Some(desc) = c.desc.as_ref() {
format!(
"{} of {} violated: {}",
c.ty.message_name(),
func_name,
desc
)
} else {
format!("{} of {} violated", c.ty.message_name(), func_name)
};
c.assertions.iter().zip(c.streams.iter()).map(
move |(expr, display)| {
let mode = c.mode.final_mode();
make_assertion(
mode,
ContractType::Ensures,
display.clone(),
expr,
&desc.clone(),
)
},
)
})
.collect();
//
// bind "old()" expressions
//
let olds = {
let mut toks = proc_macro2::TokenStream::new();
for old in olds {
let span = old.expr.span();
let name = syn::Ident::new(&old.name, span);
let expr = old.expr;
let binding = quote::quote_spanned! { span=>
let #name = #expr;
};
toks.extend(Some(binding));
}
toks
};
//
// wrap the function body in a closure if we have any postconditions
//
let body = if post.is_empty() {
let block = &func.function.block;
quote::quote! { let ret = #block; }
} else {
create_body_closure(&func.function)
};
//
// create a new function body containing all assertions
//
let new_block = quote::quote! {
{
#pre
#olds
#body
#post
ret
}
};
// insert documentation attributes
func.function.attrs.extend(docs);
// replace the old function body with the new one
func.function.block = Box::new(syn::parse_quote!(#new_block));
func.function.into_token_stream()
}
struct SelfReplacer<'a> {
replace_with: &'a syn::Ident,
}
impl syn::visit_mut::VisitMut for SelfReplacer<'_> {
fn visit_ident_mut(&mut self, i: &mut Ident) {
if i == "self" {
*i = self.replace_with.clone();
}
}
}
fn ty_contains_impl_trait(ty: &syn::Type) -> bool {
use syn::visit::Visit;
struct TyContainsImplTrait {
seen_impl_trait: bool,
}
impl syn::visit::Visit<'_> for TyContainsImplTrait {
fn visit_type_impl_trait(&mut self, _: &syn::TypeImplTrait) {
self.seen_impl_trait = true;
}
}
let mut vis = TyContainsImplTrait {
seen_impl_trait: false,
};
vis.visit_type(ty);
vis.seen_impl_trait
}
fn create_body_closure(func: &syn::ItemFn) -> TokenStream {
let is_method = func.sig.receiver().is_some();
// If the function has a receiver (e.g. `self`, `&mut self`, or `self: Box<Self>`) rename it
// to `this` within the closure
let mut block = func.block.clone();
let mut closure_args = vec![];
let mut arg_names = vec![];
if is_method {
// `mixed_site` makes the identifier hygienic so it won't collide with a local variable
// named `this`.
let this_ident = syn::Ident::new("this", Span::mixed_site());
let mut receiver = func.sig.inputs[0].clone();
match receiver {
// self, &self, &mut self
syn::FnArg::Receiver(rcv) => {
// The `Self` type.
let self_ty = Box::new(syn::Type::Path(syn::TypePath {
qself: None,
path: syn::Path::from(syn::Ident::new("Self", rcv.span())),
}));
let ty = if let Some((and_token, ref lifetime)) = rcv.reference
{
Box::new(syn::Type::Reference(syn::TypeReference {
and_token,
lifetime: lifetime.clone(),
mutability: rcv.mutability,
elem: self_ty,
}))
} else {
self_ty
};
let pat_mut = if rcv.reference.is_none() {
rcv.mutability
} else {
None
};
// this: [& [mut]] Self
let new_rcv = syn::PatType {
attrs: rcv.attrs.clone(),
pat: Box::new(syn::Pat::Ident(syn::PatIdent {
attrs: vec![],
by_ref: None,
mutability: pat_mut,
ident: this_ident.clone(),
subpat: None,
})),
colon_token: syn::Token![:](rcv.span()),
ty,
};
receiver = syn::FnArg::Typed(new_rcv);
}
// self: Box<Self>
syn::FnArg::Typed(ref mut pat) => {
if let syn::Pat::Ident(ref mut ident) = *pat.pat {
if ident.ident == "self" {
ident.ident = this_ident.clone();
}
}
}
}
closure_args.push(receiver);
match &func.sig.inputs[0] {
syn::FnArg::Receiver(receiver) => {
arg_names
.push(syn::Ident::new("self", receiver.self_token.span()));
}
syn::FnArg::Typed(pat) => {
if let syn::Pat::Ident(ident) = &*pat.pat {
arg_names.push(ident.ident.clone());
} else {
// Non-trivial receiver pattern => do not capture
closure_args.pop();
}
}
};
// Replace any references to `self` in the function body with references to `this`.
syn::visit_mut::visit_block_mut(
&mut SelfReplacer {
replace_with: &this_ident,
},
&mut block,
);
}
// Any function arguments of the form `ident: ty` become closure arguments and get passed
// explicitly. More complex ones, e.g. pattern matching like `(a, b): (u32, u32)`, are
// captured instead.
let args = func.sig.inputs.iter().skip(if is_method { 1 } else { 0 });
for arg in args {
match arg {
syn::FnArg::Receiver(_) => unreachable!("Multiple receivers?"),
syn::FnArg::Typed(syn::PatType { pat, ty, .. }) => {
if !ty_contains_impl_trait(ty) {
if let syn::Pat::Ident(ident) = &**pat {
let ident_str = ident.ident.to_string();
// Any function argument identifier starting with '_' signals
// that the binding will not be used.
if !ident_str.starts_with('_')
|| ident_str.starts_with("__")
{
arg_names.push(ident.ident.clone());
closure_args.push(arg.clone());
}
}
}
}
}
}
let ret_ty = match &func.sig.output {
ReturnType::Type(_, ty) => {
let span = ty.span();
match ty.as_ref() {
syn::Type::ImplTrait(_) => quote::quote! {},
ty => quote::quote_spanned! { span=>
-> #ty
},
}
}
ReturnType::Default => quote::quote! {},
};
let closure_args = closure_args.iter();
let arg_names = arg_names.iter();
quote::quote! {
#[allow(unused_mut)]
let mut run = |#(#closure_args),*| #ret_ty #block;
let ret = run(#(#arg_names),*);
}
}

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/* 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/. */
use crate::implementation::{Contract, ContractMode};
use proc_macro2::Span;
use proc_macro2::TokenStream;
use syn::{parse::Parser, Attribute};
pub(crate) fn generate_attributes(contracts: &[Contract]) -> Vec<Attribute> {
let mut attrs = vec![];
fn make_attribute(content: &str) -> Attribute {
let span = Span::call_site();
let content_str = syn::LitStr::new(content, span);
let toks: TokenStream =
quote::quote_spanned!( span=> #[doc = #content_str] );
let parser = Attribute::parse_outer;
let mut attributes = parser.parse2(toks).unwrap();
attributes.remove(0)
}
fn print_stream(stream: &TokenStream) -> String {
stream.to_string()
}
// header
attrs.push(make_attribute("# Contracts"));
for contract in contracts {
let ty = contract.ty;
let mode = match contract.mode {
ContractMode::Always => None,
ContractMode::Disabled => None,
ContractMode::Debug => Some("debug"),
ContractMode::Test => Some("test"),
ContractMode::LogOnly => None,
};
if let Some(desc) = &contract.desc {
// document all assertions under the description
let header_txt = if let Some(name) = mode {
format!("{} - {}: {}", ty.message_name(), name, desc)
} else {
format!("{}: {}", ty.message_name(), desc)
};
attrs.push(make_attribute(&header_txt));
for (_assert, stream) in
contract.assertions.iter().zip(contract.streams.iter())
{
attrs.push(make_attribute(&format!(
" - `{}`",
print_stream(stream)
)));
}
attrs.push(make_attribute(""));
} else {
// document each assertion on its own
for stream in &contract.streams {
let doc_str = if let Some(name) = mode {
format!(
"{} - {}: `{}`",
ty.message_name(),
name,
print_stream(stream)
)
} else {
format!("{}: `{}`", ty.message_name(), print_stream(stream))
};
attrs.push(make_attribute(&doc_str));
attrs.push(make_attribute(""));
}
}
}
attrs
}

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/* 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/. */
use crate::implementation::{ContractMode, ContractType, FuncWithContracts};
use proc_macro2::TokenStream;
pub(crate) fn ensures(
mode: ContractMode,
attr: TokenStream,
toks: TokenStream,
) -> TokenStream {
let ty = ContractType::Ensures;
let func = syn::parse_quote!(#toks);
let f = FuncWithContracts::new_with_initial_contract(func, ty, mode, attr);
f.generate()
}

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/* 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/. */
use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::{FnArg, ImplItem, ImplItemMethod, Item, ItemFn, ItemImpl};
use crate::implementation::{ContractMode, ContractType, FuncWithContracts};
pub(crate) fn invariant(
mode: ContractMode,
attr: TokenStream,
toks: TokenStream,
) -> TokenStream {
let item: Item = syn::parse_quote!(#toks);
let name = mode.name().unwrap().to_string() + "invariant";
match item {
Item::Fn(fn_) => invariant_fn(mode, attr, fn_),
Item::Impl(impl_) => invariant_impl(mode, attr, impl_),
_ => unimplemented!(
"The #[{}] attribute only works on functions and impl-blocks.",
name
),
}
}
fn invariant_fn(
mode: ContractMode,
attr: TokenStream,
func: ItemFn,
) -> TokenStream {
let ty = ContractType::Invariant;
let f = FuncWithContracts::new_with_initial_contract(func, ty, mode, attr);
f.generate()
}
/// Generate the token-stream for an `impl` block with a "global" invariant.
fn invariant_impl(
mode: ContractMode,
invariant: TokenStream,
mut impl_def: ItemImpl,
) -> TokenStream {
// all that is done is prefix all the function definitions with
// the invariant attribute.
// The following expansion of the attributes will then implement the
// invariant just like it's done for functions.
// The mode received is "raw", so it can't be "Disabled" or "LogOnly"
// but it can't hurt to deal with it anyway.
let name = match mode.name() {
Some(n) => n.to_string() + "invariant",
None => {
return quote::quote!( #impl_def );
}
};
let invariant_ident =
syn::Ident::new(&name, proc_macro2::Span::call_site());
fn method_uses_self(method: &ImplItemMethod) -> bool {
let inputs = &method.sig.inputs;
if !inputs.is_empty() {
matches!(inputs[0], FnArg::Receiver(_))
} else {
false
}
}
for item in &mut impl_def.items {
if let ImplItem::Method(method) = item {
// only implement invariants for methods that take `self`
if !method_uses_self(method) {
continue;
}
let method_toks = quote::quote! {
#[#invariant_ident(#invariant)]
#method
};
let met: ImplItemMethod = syn::parse_quote!(#method_toks);
*method = met;
}
}
impl_def.into_token_stream()
}

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/* 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/. */
pub(crate) mod codegen;
pub(crate) mod doc;
pub(crate) mod ensures;
pub(crate) mod invariant;
pub(crate) mod parse;
pub(crate) mod requires;
pub(crate) mod traits;
use quote::ToTokens;
use syn::{Expr, ItemFn};
pub(crate) use ensures::ensures;
pub(crate) use invariant::invariant;
use proc_macro2::{Span, TokenStream, TokenTree};
pub(crate) use requires::requires;
pub(crate) use traits::{contract_trait_item_impl, contract_trait_item_trait};
/// Checking-mode of a contract.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub(crate) enum ContractMode {
/// Always check contract
Always,
/// Never check contract
Disabled,
/// Check contract only in debug builds
Debug,
/// Check contract only in `#[cfg(test)]` configurations
Test,
/// Check the contract and print information upon violation, but don't abort
/// the program.
LogOnly,
}
impl ContractMode {
/// Return the prefix of attributes of `self` mode.
pub(crate) fn name(self) -> Option<&'static str> {
match self {
ContractMode::Always => Some(""),
ContractMode::Disabled => None,
ContractMode::Debug => Some("debug_"),
ContractMode::Test => Some("test_"),
ContractMode::LogOnly => None,
}
}
/// Computes the contract type based on feature flags.
pub(crate) fn final_mode(self) -> Self {
// disabled ones can't be "forced", test ones should stay test, no
// matter what.
if self == ContractMode::Disabled || self == ContractMode::Test {
return self;
}
if cfg!(feature = "disable_contracts") {
ContractMode::Disabled
} else if cfg!(feature = "override_debug") {
// log is "weaker" than debug, so keep log
if self == ContractMode::LogOnly {
self
} else {
ContractMode::Debug
}
} else if cfg!(feature = "override_log") {
ContractMode::LogOnly
} else {
self
}
}
}
/// The different contract types.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub(crate) enum ContractType {
Requires,
Ensures,
Invariant,
}
impl ContractType {
/// Get the name that is used as a message-prefix on violation of a
/// contract.
pub(crate) fn message_name(self) -> &'static str {
match self {
ContractType::Requires => "Pre-condition",
ContractType::Ensures => "Post-condition",
ContractType::Invariant => "Invariant",
}
}
/// Determine the type and mode of an identifier.
pub(crate) fn contract_type_and_mode(
ident: &str,
) -> Option<(ContractType, ContractMode)> {
match ident {
"requires" => Some((ContractType::Requires, ContractMode::Always)),
"ensures" => Some((ContractType::Ensures, ContractMode::Always)),
"invariant" => {
Some((ContractType::Invariant, ContractMode::Always))
}
"debug_requires" => {
Some((ContractType::Requires, ContractMode::Debug))
}
"debug_ensures" => {
Some((ContractType::Ensures, ContractMode::Debug))
}
"debug_invariant" => {
Some((ContractType::Invariant, ContractMode::Debug))
}
"test_requires" => {
Some((ContractType::Requires, ContractMode::Test))
}
"test_ensures" => Some((ContractType::Ensures, ContractMode::Test)),
"test_invariant" => {
Some((ContractType::Invariant, ContractMode::Test))
}
_ => None,
}
}
}
/// Representation of a contract
#[derive(Debug)]
pub(crate) struct Contract {
pub(crate) _span: Span,
pub(crate) ty: ContractType,
pub(crate) mode: ContractMode,
pub(crate) assertions: Vec<Expr>,
pub(crate) streams: Vec<TokenStream>,
pub(crate) desc: Option<String>,
}
impl Contract {
pub(crate) fn from_toks(
ty: ContractType,
mode: ContractMode,
toks: TokenStream,
) -> Self {
let (assertions, streams, desc) = parse::parse_attributes(toks);
let span = Span::call_site();
Self {
_span: span,
ty,
mode,
assertions,
streams,
desc,
}
}
}
/// A function that is annotated with contracts
#[derive(Debug)]
pub(crate) struct FuncWithContracts {
pub(crate) contracts: Vec<Contract>,
pub(crate) function: ItemFn,
}
impl FuncWithContracts {
/// Create a `FuncWithContracts` value from the attribute-tokens of the
/// first contract and a parsed version of the function.
///
/// The initial contract is parsed from the tokens, others will be read from
/// parsed function.
pub(crate) fn new_with_initial_contract(
mut func: ItemFn,
cty: ContractType,
cmode: ContractMode,
ctoks: TokenStream,
) -> Self {
// add in the first attribute
let mut contracts: Vec<Contract> = {
let initial_contract = Contract::from_toks(cty, cmode, ctoks);
vec![initial_contract]
};
// find all other attributes
let contract_attrs = func
.attrs
.iter()
.filter_map(|a| {
let name = a.path.segments.last().unwrap().ident.to_string();
let (ty, mode) = ContractType::contract_type_and_mode(&name)?;
Some((ty, mode, a))
})
.map(|(ty, mode, a)| {
// the tts on attributes contains the out parenthesis, so some
// code might be mistakenly parsed as tuples, that's not good!
//
// this is a hack to get to the inner token stream.
let tok_tree = a.tokens.clone().into_iter().next().unwrap();
let toks = match tok_tree {
TokenTree::Group(group) => group.stream(),
TokenTree::Ident(i) => i.into_token_stream(),
TokenTree::Punct(p) => p.into_token_stream(),
TokenTree::Literal(l) => l.into_token_stream(),
};
Contract::from_toks(ty, mode, toks)
});
contracts.extend(contract_attrs);
// remove contract attributes
{
let attrs = std::mem::take(&mut func.attrs);
let other_attrs = attrs
.into_iter()
.filter(|attr| {
ContractType::contract_type_and_mode(
&attr.path.segments.last().unwrap().ident.to_string(),
)
.is_none()
})
.collect();
func.attrs = other_attrs;
}
Self {
function: func,
contracts,
}
}
/// Generates the resulting tokens including all contract-checks
pub(crate) fn generate(mut self) -> TokenStream {
let doc_attrs = doc::generate_attributes(&self.contracts);
let olds = codegen::extract_old_calls(&mut self.contracts);
codegen::generate(self, doc_attrs, olds)
}
}

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/* 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/. */
use proc_macro2::{Spacing, TokenStream, TokenTree};
use syn::{Expr, ExprLit, Lit};
/// Parse attributes into a list of expression and an optional description of
/// the assert
pub(crate) fn parse_attributes(
attrs: TokenStream,
) -> (Vec<Expr>, Vec<TokenStream>, Option<String>) {
let segments = segment_input(attrs);
let mut segments_stream: Vec<TokenStream> = segments
.iter()
.map(|x| x.iter().cloned().collect::<TokenStream>())
.collect();
let rewritten_segs: Vec<_> = segments.into_iter().map(rewrite).collect();
let mut conds: Vec<Expr> = vec![];
for seg in rewritten_segs {
let expr = match syn::parse2::<Expr>(seg) {
Ok(val) => val,
Err(err) => Expr::Verbatim(err.to_compile_error()),
};
conds.push(expr);
}
let desc = conds
.last()
.map(|expr| match expr {
Expr::Lit(ExprLit {
lit: Lit::Str(str), ..
}) => Some(str.value()),
_ => None,
})
.unwrap_or(None);
if desc.is_some() {
conds.pop();
segments_stream.pop();
}
(conds, segments_stream, desc)
}
// This function rewrites a list of TokenTrees so that the "pseudooperator" for
// implication `==>` gets transformed into an `if` expression.
//
// This has to happen on a TokenStream/Tree because it's not possible to easily
// add new syntax to the syn parsers without basically re-writing the whole
// expression parsing functions from scratch.
//
// The input gets classified into "before `==>` op" and "after `==>` op". Those
// two groups are then used to create an `if` that has implication semantics.
// However, because the input is only split based on the operator, no precedence
// is respected, including keywords such as `if`. This means the implication
// operator should only be used in grouped expressions.
// This also has the effect that implication is right-associative, which is the
// expected behaviour.
fn rewrite(segments: Vec<TokenTree>) -> proc_macro2::TokenStream {
let mut lhs = vec![];
let mut rhs: Option<_> = None;
let mut span: Option<_> = None;
let mut idx = 0;
'segment: while let Some(tt) = segments.get(idx) {
match tt {
TokenTree::Group(group) => {
let stream: Vec<_> = group.stream().into_iter().collect();
let new_stream: TokenStream =
rewrite(stream).into_iter().collect();
let mut new_group =
proc_macro2::Group::new(group.delimiter(), new_stream);
new_group.set_span(group.span());
lhs.push(TokenTree::Group(new_group));
idx += 1;
}
TokenTree::Ident(_) => {
lhs.push(tt.clone());
idx += 1;
}
TokenTree::Literal(_) => {
lhs.push(tt.clone());
idx += 1;
}
TokenTree::Punct(_) => {
let punct = |idx: usize, c: char, s: Spacing| -> bool {
let tt = if let Some(val) = segments.get(idx) {
val
} else {
return false;
};
if let TokenTree::Punct(p) = tt {
p.as_char() == c && p.spacing() == s
} else {
false
}
};
if punct(idx, '-', Spacing::Joint)
&& punct(idx + 1, '>', Spacing::Alone)
{
// found the implication
let rest = Vec::from(&segments[idx + 2..]);
let rhs_stream = rewrite(rest);
rhs = Some(rhs_stream);
span = Some(segments[idx + 1].span());
break 'segment;
} else {
// consume all so that =========> would not match with
// implication
'op: while let Some(tt) = segments.get(idx) {
match tt {
TokenTree::Punct(p) => {
if p.spacing() == Spacing::Alone {
// read this one but finish afterwards
lhs.push(tt.clone());
idx += 1;
break 'op;
} else {
// this punctuation is a joint-punctuation
// so needs to be read and then continue
lhs.push(tt.clone());
idx += 1;
}
}
_ => {
// not a punktuation, so do not increase idx
break 'op;
}
}
}
}
}
}
}
match (rhs, span) {
(None, None) => lhs.into_iter().collect(),
(None, Some(_)) => {
unreachable!("If there's a span there should be an implication")
}
(Some(_), None) => unreachable!("Invalid spans"),
(Some(rhs), Some(span)) => {
let lhs: TokenStream = lhs.into_iter().collect();
quote::quote_spanned! {
span =>
(!(#lhs) || #rhs)
}
}
}
}
// The tokenstream can contain multiple expressions to be checked, separated by
// a comma. This function "pulls" those expressions apart.
fn segment_input(tts: TokenStream) -> Vec<Vec<TokenTree>> {
let mut groups = vec![];
let mut group = vec![];
for tt in tts {
match tt {
TokenTree::Punct(p)
if p.as_char() == ',' && p.spacing() == Spacing::Alone =>
{
groups.push(group);
group = vec![];
}
t => group.push(t),
}
}
if !group.is_empty() {
groups.push(group);
}
groups
}

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/* 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/. */
use crate::implementation::{ContractMode, ContractType, FuncWithContracts};
use proc_macro2::TokenStream;
use syn::ItemFn;
pub(crate) fn requires(
mode: ContractMode,
attr: TokenStream,
toks: TokenStream,
) -> TokenStream {
let ty = ContractType::Requires;
let func: ItemFn = syn::parse_quote!(#toks);
let f = FuncWithContracts::new_with_initial_contract(func, ty, mode, attr);
f.generate()
}

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/* 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/. */
use crate::implementation::ContractType;
use proc_macro2::TokenStream;
use quote::ToTokens;
use syn::{
FnArg, ImplItem, ItemImpl, ItemTrait, Pat, TraitItem, TraitItemMethod,
};
/// Name used for the "re-routed" method.
fn contract_method_impl_name(name: &str) -> String {
format!("__contracts_impl_{}", name)
}
/// Modifies a trait item in a way that it includes contracts.
pub(crate) fn contract_trait_item_trait(
_attrs: TokenStream,
mut trait_: ItemTrait,
) -> TokenStream {
/// Just rename the method to have an internal, generated name.
fn create_method_rename(method: &TraitItemMethod) -> TraitItemMethod {
let mut m: TraitItemMethod = (*method).clone();
// rename method and modify attributes
{
// remove any contracts attributes and rename
let name = m.sig.ident.to_string();
let new_name = contract_method_impl_name(&name);
let mut new_attrs = vec![];
new_attrs.push(syn::parse_quote!(#[doc(hidden)]));
new_attrs.push(syn::parse_quote!(#[doc = "This is an internal function that is not meant to be used directly!"]));
new_attrs.push(syn::parse_quote!(#[doc = "See the documentation of the `#[contract_trait]` attribute."]));
// add all existing non-contract attributes
new_attrs.extend(
m.attrs
.iter()
.filter(|a| {
let name =
a.path.segments.last().unwrap().ident.to_string();
ContractType::contract_type_and_mode(&name).is_none()
})
.cloned(),
);
m.attrs = new_attrs;
m.sig.ident = syn::Ident::new(&new_name, m.sig.ident.span());
}
m
}
/// Create a wrapper function which has a default implementation and
/// includes contracts.
///
/// This new function forwards the call to the actual implementation.
fn create_method_wrapper(method: &TraitItemMethod) -> TraitItemMethod {
struct ArgInfo {
call_toks: proc_macro2::TokenStream,
}
// Calculate name and pattern tokens
fn arg_pat_info(pat: &Pat) -> ArgInfo {
match pat {
Pat::Ident(ident) => {
let toks = quote::quote! {
#ident
};
ArgInfo { call_toks: toks }
}
Pat::Tuple(tup) => {
let infos = tup.elems.iter().map(arg_pat_info);
let toks = {
let mut toks = proc_macro2::TokenStream::new();
for info in infos {
toks.extend(info.call_toks);
toks.extend(quote::quote!(,));
}
toks
};
ArgInfo {
call_toks: quote::quote!((#toks)),
}
}
Pat::TupleStruct(_tup) => unimplemented!(),
p => panic!("Unsupported pattern type: {:?}", p),
}
}
let mut m: TraitItemMethod = (*method).clone();
let argument_data = m
.sig
.inputs
.clone()
.into_iter()
.map(|t: FnArg| match &t {
FnArg::Receiver(_) => quote::quote!(self),
FnArg::Typed(p) => {
let info = arg_pat_info(&p.pat);
info.call_toks
}
})
.collect::<Vec<_>>();
let arguments = {
let mut toks = proc_macro2::TokenStream::new();
for arg in argument_data {
toks.extend(arg);
toks.extend(quote::quote!(,));
}
toks
};
let body: TokenStream = {
let name = contract_method_impl_name(&m.sig.ident.to_string());
let name = syn::Ident::new(&name, m.sig.ident.span());
quote::quote! {
{
Self::#name(#arguments)
}
}
};
let mut attrs = vec![];
// keep the documentation and contracts of the original method
attrs.extend(
m.attrs
.iter()
.filter(|a| {
let name =
a.path.segments.last().unwrap().ident.to_string();
// is doc?
if name == "doc" {
return true;
}
// is contract?
ContractType::contract_type_and_mode(&name).is_some()
})
.cloned(),
);
// always inline
attrs.push(syn::parse_quote!(#[inline(always)]));
m.attrs = attrs;
{
let block: syn::Block = syn::parse2(body).unwrap();
m.default = Some(block);
m.semi_token = None;
}
m
}
// create method wrappers and renamed items
let funcs = trait_
.items
.iter()
.filter_map(|item| {
if let TraitItem::Method(m) = item {
let rename = create_method_rename(m);
let wrapper = create_method_wrapper(m);
Some(vec![
TraitItem::Method(rename),
TraitItem::Method(wrapper),
])
} else {
None
}
})
.flatten()
.collect::<Vec<_>>();
// remove all previous methods
trait_.items = trait_
.items
.into_iter()
.filter(|item| !matches!(item, TraitItem::Method(_)))
.collect();
// add back new methods
trait_.items.extend(funcs);
trait_.into_token_stream()
}
/// Rename all methods inside an `impl` to use the "internal implementation"
/// name.
pub(crate) fn contract_trait_item_impl(
_attrs: TokenStream,
impl_: ItemImpl,
) -> TokenStream {
let new_impl = {
let mut impl_: ItemImpl = impl_;
impl_.items.iter_mut().for_each(|it| {
if let ImplItem::Method(method) = it {
let new_name =
contract_method_impl_name(&method.sig.ident.to_string());
let new_ident =
syn::Ident::new(&new_name, method.sig.ident.span());
method.sig.ident = new_ident;
}
});
impl_
};
new_impl.to_token_stream()
}
#[cfg(test)]
mod tests {
#[test]
fn attributes_stay_on_trait_def() {
// attributes on functions should apply to the outer "wrapping" function
// only, the "internal" function should be hidden and be inlined.
let code = syn::parse_quote! {
trait Random {
/// Test!
#[aaa]
#[ensures((min..max).contains(ret))]
fn random_number(min: u8, max: u8) -> u8;
}
};
let expected = quote::quote! {
trait Random {
#[doc(hidden)]
#[doc = "This is an internal function that is not meant to be used directly!"]
#[doc = "See the documentation of the `#[contract_trait]` attribute."]
/// Test!
#[aaa]
fn __contracts_impl_random_number(min: u8, max: u8) -> u8;
/// Test!
#[ensures((min..max).contains(ret))]
#[inline(always)]
fn random_number(min: u8, max: u8) -> u8 {
Self::__contracts_impl_random_number(min, max,)
}
}
};
let generated =
super::contract_trait_item_trait(Default::default(), code);
assert_eq!(generated.to_string(), expected.to_string());
}
#[test]
fn attributes_stay_on_trait_impl() {
// attributes on functions should apply to the outer "wrapping" function
// only, the "internal" function should be hidden and be inlined.
let code = syn::parse_quote! {
impl Random for AlwaysMin {
/// docs for this function!
#[no_panic]
fn random_number(min: u8, max: u8) -> u8 {
min
}
}
};
let expected = quote::quote! {
impl Random for AlwaysMin {
/// docs for this function!
#[no_panic]
fn __contracts_impl_random_number(min: u8, max: u8) -> u8 {
min
}
}
};
let generated =
super::contract_trait_item_impl(Default::default(), code);
assert_eq!(generated.to_string(), expected.to_string());
}
}

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/* 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/. */
//! A crate implementing ["Design by Contract"][dbc] via procedural macros.
//!
//! This crate is heavily inspired by the [`libhoare`] compiler plugin.
//!
//! The main use of this crate is to annotate functions and methods using
//! "contracts" in the form of [*pre-conditions* (`requires`)][precond],
//! [*post-conditions* (`ensures`)][postcond] and [*invariants*][invariant].
//!
//! Each "contract" annotation that is violated will cause an assertion failure.
//!
//! The attributes use "function call form" and can contain 1 or more conditions
//! to check.
//! If the last argument to an attribute is a string constant it will be
//! inserted into the assertion message.
//!
//! ## Example
//!
//! ```rust
//! # use contracts::*;
//! #[requires(x > 0, "x must be in the valid input range")]
//! #[ensures(ret.is_some() -> ret.unwrap() * ret.unwrap() == x)]
//! fn integer_sqrt(x: u64) -> Option<u64> {
//! // ...
//! # unimplemented!()
//! }
//! ```
//!
//! ```rust
//! # use std::collections::HashSet;
//! # use contracts::*;
//! pub struct Library {
//! available: HashSet<String>,
//! lent: HashSet<String>,
//! }
//!
//! impl Library {
//! fn book_exists(&self, book_id: &str) -> bool {
//! self.available.contains(book_id)
//! || self.lent.contains(book_id)
//! }
//!
//! #[debug_requires(!self.book_exists(book_id), "Book IDs are unique")]
//! #[debug_ensures(self.available.contains(book_id), "Book now available")]
//! #[ensures(self.available.len() == old(self.available.len()) + 1)]
//! #[ensures(self.lent.len() == old(self.lent.len()), "No lent change")]
//! pub fn add_book(&mut self, book_id: &str) {
//! self.available.insert(book_id.to_string());
//! }
//!
//! #[debug_requires(self.book_exists(book_id))]
//! #[ensures(ret -> self.available.len() == old(self.available.len()) - 1)]
//! #[ensures(ret -> self.lent.len() == old(self.lent.len()) + 1)]
//! #[debug_ensures(ret -> self.lent.contains(book_id))]
//! #[debug_ensures(!ret -> self.lent.contains(book_id), "Book already lent")]
//! pub fn lend(&mut self, book_id: &str) -> bool {
//! if self.available.contains(book_id) {
//! self.available.remove(book_id);
//! self.lent.insert(book_id.to_string());
//! true
//! } else {
//! false
//! }
//! }
//!
//! #[debug_requires(self.lent.contains(book_id), "Can't return a non-lent book")]
//! #[ensures(self.lent.len() == old(self.lent.len()) - 1)]
//! #[ensures(self.available.len() == old(self.available.len()) + 1)]
//! #[debug_ensures(!self.lent.contains(book_id))]
//! #[debug_ensures(self.available.contains(book_id), "Book available again")]
//! pub fn return_book(&mut self, book_id: &str) {
//! self.lent.remove(book_id);
//! self.available.insert(book_id.to_string());
//! }
//! }
//! ```
//!
//! ## Attributes
//!
//! This crate exposes the `requires`, `ensures` and `invariant` attributes.
//!
//! - `requires` are checked before a function/method is executed.
//! - `ensures` are checked after a function/method ran to completion
//! - `invariant`s are checked both before *and* after a function/method ran.
//!
//! Additionally, all those attributes have versions with different "modes". See
//! [the Modes section](#modes) below.
//!
//! For `trait`s and trait `impl`s the `contract_trait` attribute can be used.
//!
//! ## Pseudo-functions and operators
//!
//! ### `old()` function
//!
//! One unique feature that this crate provides is an `old()` pseudo-function which
//! allows to perform checks using a value of a parameter before the function call
//! happened. This is only available in `ensures` attributes.
//!
//! ```rust
//! # use contracts::*;
//! #[ensures(*x == old(*x) + 1, "after the call `x` was incremented")]
//! fn incr(x: &mut usize) {
//! *x += 1;
//! }
//! ```
//!
//! ### `->` operator
//!
//! For more complex functions it can be useful to express behaviour using logical
//! implication. Because Rust does not feature an operator for implication, this
//! crate adds this operator for use in attributes.
//!
//! ```rust
//! # use contracts::*;
//! #[ensures(person_name.is_some() -> ret.contains(person_name.unwrap()))]
//! fn geeting(person_name: Option<&str>) -> String {
//! let mut s = String::from("Hello");
//! if let Some(name) = person_name {
//! s.push(' ');
//! s.push_str(name);
//! }
//! s.push('!');
//! s
//! }
//! ```
//!
//! This operator is right-associative.
//!
//! **Note**: Because of the design of `syn`, it is tricky to add custom operators
//! to be parsed, so this crate performs a rewrite of the `TokenStream` instead.
//! The rewrite works by separating the expression into a part that's left of the
//! `->` operator and the rest on the right side. This means that
//! `if a -> b { c } else { d }` will not generate the expected code.
//! Explicit grouping using parenthesis or curly-brackets can be used to avoid this.
//!
//! ## Modes
//!
//! All the attributes (requires, ensures, invariant) have `debug_*` and `test_*` versions.
//!
//! - `debug_requires`/`debug_ensures`/`debug_invariant` use `debug_assert!`
//! internally rather than `assert!`
//! - `test_requires`/`test_ensures`/`test_invariant` guard the `assert!` with an
//! `if cfg!(test)`.
//! This should mostly be used for stating equivalence to "slow but obviously
//! correct" alternative implementations or checks.
//!
//! For example, a merge-sort implementation might look like this
//! ```rust
//! # use contracts::*;
//! # fn is_sorted<T>(x: T) -> bool { true }
//! #[test_ensures(is_sorted(input))]
//! fn merge_sort<T: Ord + Copy>(input: &mut [T]) {
//! // ...
//! }
//! ```
//!
//! ## Feature flags
//!
//! Following feature flags are available:
//! - `disable_contracts` - disables all checks and assertions.
//! - `override_debug` - changes all contracts (except `test_` ones) into
//! `debug_*` versions
//! - `override_log` - changes all contracts (except `test_` ones) into a
//! `log::error!()` call if the condition is violated.
//! No abortion happens.
//! - `mirai_assertions` - instead of regular assert! style macros, emit macros
//! used by the [MIRAI] static analyzer.
//!
//! [dbc]: https://en.wikipedia.org/wiki/Design_by_contract
//! [`libhoare`]: https://github.com/nrc/libhoare
//! [precond]: attr.requires.html
//! [postcond]: attr.ensures.html
//! [invariant]: attr.invariant.html
//! [MIRAI]: https://github.com/facebookexperimental/MIRAI
extern crate proc_macro;
mod implementation;
use implementation::ContractMode;
use proc_macro::TokenStream;
/// Pre-conditions are checked before the function body is run.
///
/// ## Example
///
/// ```rust
/// # use contracts::*;
/// #[requires(elems.len() >= 1)]
/// fn max<T: Ord + Copy>(elems: &[T]) -> T {
/// // ...
/// # unimplemented!()
/// }
/// ```
#[proc_macro_attribute]
pub fn requires(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::requires(ContractMode::Always, attr, toks).into()
}
/// Same as [`requires`], but uses `debug_assert!`.
///
/// [`requires`]: attr.requires.html
#[proc_macro_attribute]
pub fn debug_requires(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::requires(ContractMode::Debug, attr, toks).into()
}
/// Same as [`requires`], but is only enabled in `#[cfg(test)]` environments.
///
/// [`requires`]: attr.requires.html
#[proc_macro_attribute]
pub fn test_requires(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::requires(ContractMode::Test, attr, toks).into()
}
/// Post-conditions are checked after the function body is run.
///
/// The result of the function call is accessible in conditions using the `ret`
/// identifier.
///
/// A "pseudo-function" named `old` can be used to evaluate expressions in a
/// context *prior* to function execution.
/// This function takes only a single argument and the result of it will be
/// stored in a variable before the function is called. Because of this,
/// handling references might require special care.
///
/// ## Examples
///
/// ```rust
/// # use contracts::*;
/// #[ensures(ret > x)]
/// fn incr(x: usize) -> usize {
/// x + 1
/// }
/// ```
///
/// ```rust
/// # use contracts::*;
/// #[ensures(*x == old(*x) + 1, "x is incremented")]
/// fn incr(x: &mut usize) {
/// *x += 1;
/// }
/// ```
#[proc_macro_attribute]
pub fn ensures(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::ensures(ContractMode::Always, attr, toks).into()
}
/// Same as [`ensures`], but uses `debug_assert!`.
///
/// [`ensures`]: attr.ensures.html
#[proc_macro_attribute]
pub fn debug_ensures(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::ensures(ContractMode::Debug, attr, toks).into()
}
/// Same as [`ensures`], but is only enabled in `#[cfg(test)]` environments.
///
/// [`ensures`]: attr.ensures.html
#[proc_macro_attribute]
pub fn test_ensures(attr: TokenStream, toks: TokenStream) -> TokenStream {
let attr = attr.into();
let toks = toks.into();
implementation::ensures(ContractMode::Test, attr, toks).into()
}
/// Invariants are conditions that have to be maintained at the "interface
/// boundaries".
///
/// Invariants can be supplied to functions (and "methods"), as well as on
/// `impl` blocks.
///
/// When applied to an `impl`-block all methods taking `self` (either by value
/// or reference) will be checked for the invariant.
///
/// ## Example
///
/// On a function:
///
/// ```rust
/// # use contracts::*;
/// /// Update `num` to the next bigger even number.
/// #[invariant(*num % 2 == 0)]
/// fn advance_even(num: &mut usize) {
/// *num += 2;
/// }
/// ```
///
/// On an `impl`-block:
///
/// ```rust
/// # use contracts::*;
/// struct EvenAdder {
/// count: usize,
/// }
///
/// #[invariant(self.count % 2 == 0)]
/// impl EvenAdder {
/// pub fn tell(&self) -> usize {
/// self.count
/// }
///
/// pub fn advance(&mut self) {
/// self.count += 2;
/// }
/// }
/// ```
#[proc_macro_attribute]
pub fn invariant(attr: TokenStream, toks: TokenStream) -> TokenStream {
// Invariant attributes might apply to `impl` blocks as well, where the same
// level is simply replicated on all methods.
// Function expansions will resolve the actual mode themselves, so the
// actual "raw" mode is passed here
//
// TODO: update comment when implemented for traits
let attr = attr.into();
let toks = toks.into();
let mode = ContractMode::Always;
implementation::invariant(mode, attr, toks).into()
}
/// Same as [`invariant`], but uses `debug_assert!`.
///
/// [`invariant`]: attr.invariant.html
#[proc_macro_attribute]
pub fn debug_invariant(attr: TokenStream, toks: TokenStream) -> TokenStream {
let mode = ContractMode::Debug;
let attr = attr.into();
let toks = toks.into();
implementation::invariant(mode, attr, toks).into()
}
/// Same as [`invariant`], but is only enabled in `#[cfg(test)]` environments.
///
/// [`invariant`]: attr.invariant.html
#[proc_macro_attribute]
pub fn test_invariant(attr: TokenStream, toks: TokenStream) -> TokenStream {
let mode = ContractMode::Test;
let attr = attr.into();
let toks = toks.into();
implementation::invariant(mode, attr, toks).into()
}
/// A "contract_trait" is a trait which ensures all implementors respect all
/// provided contracts.
///
/// When this attribute is applied to a `trait` definition, the trait gets
/// modified so that all invocations of methods are checked.
///
/// When this attribute is applied to an `impl Trait for Type` item, the
/// implementation gets modified so it matches the trait definition.
///
/// **When the `#[contract_trait]` is not applied to either the trait or an
/// `impl` it will cause compile errors**.
///
/// ## Example
///
/// ```rust
/// # use contracts::*;
/// #[contract_trait]
/// trait MyRandom {
/// #[requires(min < max)]
/// #[ensures(min <= ret, ret <= max)]
/// fn gen(min: f64, max: f64) -> f64;
/// }
///
/// // Not a very useful random number generator, but a valid one!
/// struct AlwaysMax;
///
/// #[contract_trait]
/// impl MyRandom for AlwaysMax {
/// fn gen(min: f64, max: f64) -> f64 {
/// max
/// }
/// }
/// ```
#[proc_macro_attribute]
pub fn contract_trait(attrs: TokenStream, toks: TokenStream) -> TokenStream {
let attrs: proc_macro2::TokenStream = attrs.into();
let toks: proc_macro2::TokenStream = toks.into();
let item: syn::Item = syn::parse_quote!(#toks);
let tts = match item {
syn::Item::Trait(trait_) => implementation::contract_trait_item_trait(attrs, trait_),
syn::Item::Impl(impl_) => {
assert!(
impl_.trait_.is_some(),
"#[contract_trait] can only be applied to `trait` and `impl ... for` items"
);
implementation::contract_trait_item_impl(attrs, impl_)
}
_ => panic!("#[contract_trait] can only be applied to `trait` and `impl ... for` items"),
};
tts.into()
}

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/* 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/. */
//! Testing of simple functions.
use contracts::*;
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[test]
fn test_a_thing() {
#[requires(x > 10, x < 20, "x must be in valid range")]
#[ensures(ret > x, "result will be bigger than input")]
fn a(x: usize) -> usize {
x + 1
}
a(15);
}
#[test]
fn test_sort() {
fn is_sorted(input: &[usize]) -> bool {
if input.len() < 2 {
return true;
}
for i in 1..input.len() {
if input[i - 1] > input[i] {
return false;
}
}
true
}
#[ensures(ret.len() == input.len())]
#[test_ensures(is_sorted(&ret))]
fn sort(input: &[usize]) -> Vec<usize> {
let mut vec = input.to_owned();
vec.sort_unstable();
vec
}
let input = vec![31, 234, 34, 0, 4234, 85];
sort(&input);
}
#[test]
fn test_invariant() {
#[invariant(*val <= 10)]
fn add_to_10(val: &mut usize) {
if *val >= 10 {
return;
}
*val += 1;
}
let mut val = 8;
add_to_10(&mut val);
add_to_10(&mut val);
add_to_10(&mut val);
add_to_10(&mut val);
add_to_10(&mut val);
}
#[test]
#[should_panic(expected = "Post-condition of abs violated")]
fn test_early_return() {
// make sure that post-conditions are executed even if an early return happened.
#[ensures(ret >= 0)]
#[ensures(ret == x || ret == -x)]
#[ensures(ret * ret == x * x)]
fn abs(x: isize) -> isize {
if x < 0 {
// this implementation does not respect the contracts!
return 0;
}
x
}
abs(-4);
}
#[test]
fn test_mut_ref_and_lifetimes() {
#[requires(i < s.len())]
#[ensures(*ret == 0)]
fn insert_zero<'a>(s: &'a mut [u8], i: usize) -> &'a mut u8 {
s[i] = 0;
&mut s[i]
}
insert_zero(&mut [4, 2], 1);
}
#[test]
fn test_pattern_match() {
#[ensures(ret > a && ret > b)]
fn add((a, b): (u8, u8)) -> u8 {
a.saturating_add(b)
}
assert_eq!(add((4, 2)), 6);
}
#[test]
fn test_impl_trait_return() {
// make sure that compiling functions that return existentially
// qualified types works properly.
#[requires(x >= 10)]
#[ensures(Clone::clone(&ret) == ret)]
#[allow(unused_variables)]
fn impl_test(x: isize) -> impl Clone + PartialEq + std::fmt::Debug {
"it worked"
}
let x = impl_test(200);
let y = x.clone();
assert_eq!(
format!("{:?} and {:?}", x, y),
r#""it worked" and "it worked""#
);
}
#[test]
fn test_impl_trait_arg() {
#[requires(Clone::clone(&x) == x)]
#[ensures(Clone::clone(&ret) == ret)]
fn impl_test(x: impl Clone + PartialEq + std::fmt::Debug) -> &'static str {
"it worked"
}
let x = impl_test(200);
let y = Clone::clone(&x);
assert_eq!(
format!("{:?} and {:?}", x, y),
r#""it worked" and "it worked""#
);
}
#[test]
#[deny(clippy::used_underscore_binding)]
fn test_unbound_parameters_clippy() {
#[requires(__y == 3)]
#[ensures(ret)]
fn param_test(_x: i32, __y: i32) -> bool {
true
}
}
#[test]
#[deny(non_fmt_panics)]
fn test_braced_condition_expression_clippy() {
#[requires(if __y == 3 {
__y != 0
} else {
false
})]
fn param_test(_x: i32, __y: i32) {}
}

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/* 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/. */
use contracts::*;
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[test]
fn test_ret_implication() {
#[ensures(do_thing -> ret.is_some(), "do_thing should cause a Some(_)")]
#[ensures(!do_thing -> ret.is_none(), "!do_thing should cause a None")]
fn perform_thing(do_thing: bool) -> Option<usize> {
if do_thing {
Some(12)
} else {
None
}
}
perform_thing(true);
perform_thing(false);
}
#[test]
fn test_ret_implication_old() {
#[ensures(old(*x) % 2 == 0 -> *x % 2 == 0)]
#[ensures(old(*x) % 2 == 1 -> *x % 2 == 1)]
fn incr(x: &mut usize) {
*x += 2;
}
let mut x = 0;
incr(&mut x);
let mut x = 1;
incr(&mut x);
}
#[test]
fn test_requires_implication() {
#[requires(!negative -> value >= 0)]
#[requires(negative -> value < 0)]
fn thing(negative: bool, value: isize) {}
thing(true, -123);
thing(false, 123);
}
#[test]
#[should_panic(expected = "Post")]
fn test_failing_implication() {
#[ensures(t -> ret)]
#[allow(unused_variables)]
fn only_true(t: bool) -> bool {
false // oops
}
only_true(true);
}
#[test]
fn test_nested_implication() {
#[ensures(a -> b -> ret.is_some())]
fn test(a: bool, b: bool) -> Option<usize> {
if a {
if b {
Some(9)
} else {
Some(3)
}
} else {
None
}
}
test(true, false);
test(false, true);
test(true, true);
}

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/* 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/. */
//! Testing of methods and `impl`-blocks.
use contracts::*;
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[test]
fn methods() {
fn is_even(x: usize) -> bool {
x % 2 == 0
}
struct EvenAdder {
count: usize,
}
impl EvenAdder {
#[invariant(is_even(self.count))]
#[ensures(self.count == old(self.count) + 2)]
fn next_even(&mut self) {
self.count += 2;
}
// Manually express the invariant in terms of `ret` since `self.count` is mutably borrowed.
#[requires(is_even(self.count))]
#[ensures(is_even(*ret))]
#[ensures(*ret == old(self.count) + 2)]
fn next_even_and_get<'a>(&'a mut self) -> &'a mut usize {
self.count += 2;
&mut self.count
}
#[invariant(is_even(self.count))]
#[requires(self.count >= 2)]
#[ensures(self.count == old(self.count) - 2)]
fn prev_even(&mut self) {
self.count -= 2;
}
#[invariant(is_even(self.count))]
fn this_var_collision(&mut self) -> usize {
#[allow(unused_variables)]
let (this, this__) = (42, 42);
self.count
}
}
let mut adder = EvenAdder { count: 0 };
adder.next_even();
adder.next_even();
adder.prev_even();
adder.prev_even();
assert_eq!(*adder.next_even_and_get(), 2);
}
#[test]
fn impl_invariant() {
fn is_even(x: usize) -> bool {
x % 2 == 0
}
struct EvenAdder {
count: usize,
}
#[invariant(is_even(self.count), "Count has to always be even")]
impl EvenAdder {
const fn step() -> usize {
2
}
fn new() -> Self {
EvenAdder { count: 0 }
}
#[ensures(self.count == old(self.count) + 2)]
fn next_even(&mut self) {
self.count += Self::step();
}
#[requires(self.count >= 2)]
#[ensures(self.count == old(self.count) - 2)]
fn prev_even(&mut self) {
self.count -= Self::step();
}
}
let mut adder = EvenAdder::new();
adder.next_even();
adder.next_even();
adder.prev_even();
adder.prev_even();
}
#[test]
fn test_self_macro_hygiene() {
struct S {
value: i32,
}
// Use a macro to generate the function impl
// This requires strict hygiene of the `self` receiver
macro_rules! __impl {
(
$(#[$metas:meta])*
fn $function:ident(&mut $this:ident, $value:ident: $ty:ty)
$body:block
) => {
$(#[$metas])*
fn $function(&mut $this, $value: $ty)
$body
};
}
impl S {
__impl! {
#[ensures(self.value == old(value))]
fn set_value(&mut self, value: i32) {
self.value = value;
}
}
}
let mut s = S { value: 24 };
s.set_value(42);
assert_eq!(s.value, 42);
}

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/* 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/.
*/
#[macro_export]
macro_rules! debug_checked_precondition {
($condition:expr, $($arg:tt)*) => ( debug_assert!($condition, $($arg)*); );
}
#[macro_export]
macro_rules! debug_checked_postcondition {
($condition:expr, $($arg:tt)*) => ( debug_assert!($condition, $($arg)*); );
}
#[macro_export]
macro_rules! checked_precondition {
($condition:expr, $($arg:tt)*) => ( assert!($condition, $($arg)*); );
}
#[macro_export]
macro_rules! checked_postcondition {
($condition:expr, $($arg:tt)*) => ( assert!($condition, $($arg)*); );
}

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/* 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/. */
use contracts::*;
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[test]
fn test_old_simple() {
#[ensures(*x == old(*x) + 1, "x increments")]
fn incr(x: &mut usize) {
*x += 1;
}
let mut val = 0;
incr(&mut val);
}
#[test]
fn test_old_nested() {
#[ensures(*x == old(old(old(*x))) + 1, "x increments")]
fn incr(x: &mut usize) {
*x += 1;
}
let mut val = 0;
incr(&mut val);
}
#[test]
#[should_panic(expected = "Post-condition of incr violated")]
fn test_violation() {
#[ensures(*x == old(*x) + 1, "x increments")]
fn incr(x: &mut usize) {
*x += 0; // oops
}
let mut val = 0;
incr(&mut val);
}

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/* 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/. */
//! Test implementing a `RangedInt` type.
use contracts::*;
use std::ops::{Add, Deref};
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[derive(Copy, Clone, Debug)]
pub struct Range {
min: usize,
max: usize,
}
impl Range {
#[requires(min < max)]
pub fn new(min: usize, max: usize) -> Self {
Range { min, max }
}
#[ensures(ret.min == self.min.min(other.min))]
#[ensures(ret.max == self.max.max(other.max))]
pub fn merge(self, other: Range) -> Range {
let min = self.min.min(other.min);
let max = self.max.max(other.max);
Range::new(min, max)
}
pub fn contains(self, val: usize) -> bool {
self.min <= val && val <= self.max
}
}
#[derive(Copy, Clone, Debug)]
pub struct RangedInt {
range: Range,
value: usize,
}
#[invariant(self.range.contains(self.value))]
impl RangedInt {
#[requires(range.contains(val))]
pub fn new(range: Range, val: usize) -> Self {
RangedInt { range, value: val }
}
pub fn to_usize(self) -> usize {
self.value
}
pub fn range(self) -> Range {
self.range
}
#[ensures(ret.range.contains(ret.value))]
pub fn extend(self, range: Range) -> Self {
let new_range = self.range.merge(range);
RangedInt::new(new_range, self.value)
}
}
impl Add<Self> for RangedInt {
type Output = RangedInt;
#[requires(self.range.merge(rhs.range).contains(self.value + rhs.value))]
#[ensures(ret.range.contains(ret.value))]
#[ensures(ret.value == self.value + rhs.value)]
fn add(self, rhs: Self) -> Self::Output {
let mut new_ranged = self.extend(rhs.range);
new_ranged.value += rhs.value;
new_ranged
}
}
impl Add<usize> for RangedInt {
type Output = RangedInt;
#[requires(self.range.contains(rhs))]
#[ensures(ret.value == self.value + rhs)]
fn add(self, rhs: usize) -> Self::Output {
let mut new = self;
new.value += rhs;
new
}
}
impl Deref for RangedInt {
type Target = usize;
fn deref(&self) -> &Self::Target {
&self.value
}
}
#[test]
fn ranged_int_add() {
let days = RangedInt::new(Range::new(0, 6), 0);
assert_eq!(*days, 0);
assert_eq!(*(days + 1), 1);
assert_eq!(*(days + 5), 5);
assert_eq!(*(days + 6), 6);
}
#[test]
fn ranged_int_add_reassign() {
let mut days = RangedInt::new(Range::new(0, 6), 0);
assert_eq!(*days, 0);
days = days + 3;
assert_eq!(*days, 3);
days = days + 2;
assert_eq!(*days, 5);
}
#[test]
#[should_panic(expected = "Pre-condition of add violated")]
fn ranged_overflow() {
let days = RangedInt::new(Range::new(0, 6), 0);
// cause overflow
let _ = days + 7;
}
#[test]
#[should_panic(expected = "Pre-condition of new violated")]
fn construction_underflow() {
// value below of permitted range
RangedInt::new(Range::new(4, 6), 0);
}
#[test]
#[should_panic(expected = "Pre-condition of new violated")]
fn construction_overflow() {
// value above of permitted range
RangedInt::new(Range::new(0, 6), 8);
}

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/* 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/. */
use contracts::*;
#[cfg(feature = "mirai_assertions")]
mod mirai_assertion_mocks;
#[test]
fn adder_example() {
#[contract_trait]
trait Adder {
fn tell(&self) -> usize;
#[requires((self.tell() + val) < 20)]
fn add(&mut self, val: usize);
}
struct MyAdder(usize);
#[contract_trait]
impl Adder for MyAdder {
fn tell(&self) -> usize {
self.0
}
fn add(&mut self, val: usize) {
self.0 += val;
}
}
let mut add = MyAdder(0);
add.add(3);
add.add(16);
// this would violate the contract
// add.add(2);
}
#[test]
fn interpolate_example() {
#[contract_trait]
trait Interpolate {
#[requires(0.0 <= val, val <= 1.0)]
#[requires(min < max)]
#[ensures(min <= ret, ret <= max)]
fn interpolate(min: f64, max: f64, val: f64) -> f64;
}
struct Linear;
#[contract_trait]
impl Interpolate for Linear {
fn interpolate(min: f64, max: f64, val: f64) -> f64 {
min + (val * (max - min))
}
}
struct Quadratic;
#[contract_trait]
impl Interpolate for Quadratic {
fn interpolate(min: f64, max: f64, val: f64) -> f64 {
let val = val * val;
Linear::interpolate(min, max, val)
}
}
let min = 12.00;
let max = 24.00;
let val = 0.4;
Linear::interpolate(min, max, val);
Quadratic::interpolate(min, max, val);
}