feat: Add move_semantics6.rs exercise

exercises/move_semantics/move_semantics6.rs

@@ -0,0 +1,24 @@
+// move_semantics6.rs
+// Make me compile! `rustlings hint move_semantics6` for hints
+// You can't change anything except adding or removing reference
+
+// I AM NOT DONE
+
+fn main() {
+    let data = "Rust is great!".to_string();
+    println!("{}", get_char(data));
+
+
+    string_uppercase(&data);
+}
+
+// Should not take ownership
+fn get_char(data: String) -> char {
+    data.chars().last().unwrap()
+}
+
+// Should take ownership
+fn string_uppercase(mut data: &String) {
+    data = &data.to_uppercase();
+    println!("{}", data);
+}

info.toml

@@ -221,6 +221,20 @@ in the book's section References and Borrowing':
 https://doc.rust-lang.org/book/ch04-02-references-and-borrowing.html#mutable-references.
 """
 
+[[exercises]]
+name = "move_semantics6"
+path = "exercises/move_semantics/move_semantics6.rs"
+mode = "compile"
+hint = """
+Here if you want to find the answer by yourself, you can read in the book's section References and Borrowing:
+https://doc.rust-lang.org/stable/book/ch04-02-references-and-borrowing.html
+Else the first problem is that `get_char` is taking ownership of the string
+So `data` is moved and can't be used for `string_uppercase`
+- `get_char` should borrow data (use &)
+One it's fix now is `string_uppercase` who's trying to change a borrowed value
+so it's the opposite of `get_char` (remove &)
+"""
+
 # PRIMITIVE TYPES
 
 [[exercises]]