Stop right there! Too many Rust crimes going on there!

resultteststest/src/lib.rs

@@ -1,11 +1,49 @@
-fn not_zero(num: usize) -> Result<(), ()> {
+use std::{ops::Deref, path::{Path, PathBuf}};
+
+fn not_zero(num: usize) -> Result<(), String> {
     if num == 0 {
-        Err(())
+        Err("It's zero!".into())
     } else {
         Ok(())
     }
 }
 
+trait BoolExt {
+    fn ok(&self, fail: String) -> Result<(), String>;
+}
+
+impl BoolExt for bool {
+    fn ok(&self, fail: String) -> Result<(), String> {
+        if *self {
+            Ok(())
+        } else {
+            Err(fail)
+        }
+    }
+}
+
+struct TestDir(PathBuf);
+impl TestDir {
+    pub fn new(name: &str) -> Self {
+        let wd = std::env::temp_dir().join(name);
+        std::fs::create_dir_all(&wd).unwrap();
+
+        Self(wd)
+    }
+}
+impl Deref for TestDir {
+    type Target = Path;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl Drop for TestDir {
+    fn drop(&mut self) {
+        std::fs::remove_dir_all(&self.0).unwrap();
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -21,19 +59,19 @@ mod tests {
     }
 
     #[test]
-    fn nested() -> Result<(), ()> {
+    fn nested() -> Result<(), String> {
         not_zero(1)?;
         Ok(())
     }
 
     #[test]
-    fn nested2() -> Result<(), ()> {
+    fn nested2() -> Result<(), String> {
         not_zero(0)?;
         Ok(())
     }
 
     #[test]
-    fn nested3() -> Result<(), ()> {
+    fn nested3() -> Result<(), String> {
         let result = (|| {
             not_zero(2)?;
             Ok(())
@@ -43,4 +81,41 @@ mod tests {
 
         result
     }
+
+    #[test]
+    fn comparison() -> Result<(), String> {
+        let result = (|| {
+            not_zero(2)?;
+            // Ok, this is weird:
+            // bool.then_some() will convert true to Some(x) and false to None;
+            // Option.ok_or() will convert the Option to Result
+            // Result.map() will convert the Ok to some other value
+            (1 == 1)
+                .then_some(0)
+                .ok_or("1 is not 1!".into())
+                .map(|_| ())
+        })();
+
+        result
+    }
+
+    #[test]
+    fn magic() -> Result<(), String> {
+        let result = (|| {
+            not_zero(2)?;
+            (1 == 1).ok("1 is not 1".into())
+        })();
+
+        result
+    }
+
+    #[test]
+    fn magic_dir() -> Result<(), String> {
+        let wd = TestDir::new("magic-dir");
+        let file1 = wd.join("file");
+        std::fs::write(&file1, "this is file").map_err(|_| "No file!")?;
+        assert!(1 == 1);
+        assert!(!file1.is_file());
+        Ok(())
+    }
 }