E0106 — Missing Lifetime Specifier

このエラーの原因

Rust requires explicit lifetime annotations when there are multiple input lifetimes and the compiler cannot determine the correct output lifetime. Struct fields that are references also need lifetime annotations.

修正方法

Add lifetime parameters to the function signature or struct. Use 'a or other lifetime names. If the function has one input reference, the compiler can usually infer the lifetime. Consider using owned types instead of references.

struct Foo {
  bar: &str, // missing lifetime
}