[filter_map_bool_then]: peel as many refs as needed

tests/ui/filter_map_bool_then.fixed

@@ -59,4 +59,12 @@ fn issue11309<'a>(iter: impl Iterator<Item = (&'a str, &'a str)>) -> Vec<&'a str
 fn issue11503() {
     let bools: &[bool] = &[true, false, false, true];
     let _: Vec<usize> = bools.iter().enumerate().filter(|&(i, b)| *b).map(|(i, b)| i).collect();
+
+    // Need to insert multiple derefs if there is more than one layer of references
+    let bools: &[&&bool] = &[&&true, &&false, &&false, &&true];
+    let _: Vec<usize> = bools.iter().enumerate().filter(|&(i, b)| ***b).map(|(i, b)| i).collect();
+
+    // Should also suggest derefs when going through a mutable reference
+    let bools: &[&mut bool] = &[&mut true];
+    let _: Vec<usize> = bools.iter().enumerate().filter(|&(i, b)| **b).map(|(i, b)| i).collect();
 }

tests/ui/filter_map_bool_then.rs

@@ -59,4 +59,12 @@ fn issue11309<'a>(iter: impl Iterator<Item = (&'a str, &'a str)>) -> Vec<&'a str
 fn issue11503() {
     let bools: &[bool] = &[true, false, false, true];
     let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
+
+    // Need to insert multiple derefs if there is more than one layer of references
+    let bools: &[&&bool] = &[&&true, &&false, &&false, &&true];
+    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
+
+    // Should also suggest derefs when going through a mutable reference
+    let bools: &[&mut bool] = &[&mut true];
+    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
 }

tests/ui/filter_map_bool_then.stderr

@@ -43,5 +43,17 @@ error: usage of `bool::then` in `filter_map`
 LL |     let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
    |                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `filter` then `map` instead: `filter(|&(i, b)| *b).map(|(i, b)| i)`
 
-error: aborting due to 7 previous errors
+error: usage of `bool::then` in `filter_map`
+  --> $DIR/filter_map_bool_then.rs:65:50
+   |
+LL |     let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
+   |                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `filter` then `map` instead: `filter(|&(i, b)| ***b).map(|(i, b)| i)`
+
+error: usage of `bool::then` in `filter_map`
+  --> $DIR/filter_map_bool_then.rs:69:50
+   |
+LL |     let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
+   |                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `filter` then `map` instead: `filter(|&(i, b)| **b).map(|(i, b)| i)`
+
+error: aborting due to 9 previous errors