error[E0308]: mismatched types

Workarounds

1. 92% success Use .into(), .as_ref(), .to_string(), or .as_str() for standard conversions

   let s: String = my_str.into();

   Sources: https://doc.rust-lang.org/error_codes/E0308.html

2. 88% success Handle Option/Result with unwrap_or, map, or pattern matching

   // Pattern matching:
   match get_value() {
       Some(v) => println!("Got: {v}"),
       None => println!("No value"),
   }
   // unwrap_or for defaults:
   let val = opt.unwrap_or(0);
   // map to transform inner value:
   let len: Option<usize> = name.map(|s| s.len());

   Sources: https://doc.rust-lang.org/book/ch06-02-match.html

3. 90% success Check return type annotation matches the actual returned value

   // Wrong: function says it returns String but returns &str
   fn name() -> String {
       "hello"  // error: expected String, found &str
   }
   // Fix: convert with .to_string() or .into():
   fn name() -> String {
       "hello".to_string()
   }

   Sources: https://doc.rust-lang.org/error_codes/E0308.html