test: notes on issue 18

Author: robjtede

README.md

@@ -127,20 +127,12 @@ All the attributes (requires, ensures, invariant) have `debug_*` and `test_*` ve
 
 To install the latest version, add `contracts` to the dependency section of the `Cargo.toml` file.
 
-```
-[dependencies]
-contracts = "0.6.3"
+```shell
+$ cargo add contracts
 ```
 
 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.

RELEASE_CHECKLIST.md

@@ -52,6 +52,7 @@ test-msrv: downgrade-for-msrv
     @just toolchain={{ msrv_rustup }} test-no-coverage
 
     # Test workspace and generate Codecov coverage file
+
 test-coverage-codecov:
     cargo {{ toolchain }} llvm-cov --workspace --all-features --codecov --output-path codecov.json
 

justfile

@@ -0,0 +1,41 @@
+#[test]
+fn gl_issue_18() {
+    use std::ops::{Div, Mul, Rem, Sub};
+
+    // use contracts::ensures; // <- unused warning
+    use contracts::requires;
+
+    trait Zero {
+        fn zero() -> Self;
+    }
+
+    impl Zero for u32 {
+        fn zero() -> Self {
+            0
+        }
+    }
+
+    #[requires( n != T::zero() || d != T::zero() )]
+    #[ensures( ret != T::zero() && n % ret == T::zero() && d % ret == T::zero() )]
+    fn euclidean<T>(n: T, d: T) -> T
+    where
+        T: Sub<Output = T>
+            + Mul<Output = T>
+            + Div<Output = T>
+            + Rem<Output = T>
+            + Ord
+            + Zero
+            + Copy,
+    {
+        let (mut a, mut b) = (n.max(d), n.min(d));
+        while b != T::zero() {
+            let q: T = a / b;
+            let r: T = a - q * b;
+            a = b;
+            b = r;
+        }
+        a
+    }
+
+    assert_eq!(1, euclidean(3, 4));
+}