feat: added a closure exercise to demonstrate using irrefutable patterns in closure signatures

exercises/closures/closures7.rs

@@ -0,0 +1,26 @@
+// closure7.rs
+// You can use patterns in closure (and function) parameters.
+// However there is one big difference between the patterns
+// you can use in these sorts of places (like let statements)
+// and conditional places (like match). It's called Irrefutability.
+// Make me compile!
+
+// Execute `rustlings hint closures7` for hints!
+
+// I AM NOT DONE
+
+fn main() {
+
+    let clo = |(definitely, _)| {
+        println!("maybe {:?}", definitely);
+    };
+
+    clo(("oh yes", "oh no"));
+
+    let maybe = Some("yes");
+    let list = vec![maybe];
+
+    list.iter().inspect(|&Some(value)| {
+        println!("maybe {:?}", value);
+    });
+}

exercises/closures/mod.rs

@@ -4,3 +4,4 @@ mod closures3;
 mod closures4;
 mod closures5;
 mod closures6;
+mod closures7;

info.toml

@@ -194,6 +194,14 @@ hint = """
 There are two ways to solve this, neither is difficult and both involve just removing
 the offending part. If you're thinking hard, you've missed the point."""
 
+[[exercises]]
+name = "closures7"
+path = "exercises/closures/closures7.rs"
+mode = "compile"
+hint = """
+This is where the info is https://doc.rust-lang.org/book/ch18-02-refutability.html
+So there isn't a satisfying solution, just an acceptance of the facts."""
+
 # IF
 
 [[exercises]]