Add additional test for broken loop in mut_range_bound

Author: dswij

tests/ui/mut_range_bound.rs

@@ -8,6 +8,9 @@ fn main() {
     immut_range_bound();
     mut_borrow_range_bound();
     immut_borrow_range_bound();
+    mut_range_bound_break();
+    mut_range_bound_nested_break();
+    multiple_mut_range_bound_break();
 }
 
 fn mut_range_bound_upper() {
@@ -61,3 +64,36 @@ fn immut_range_bound() {
         continue;
     } // no warning
 }
+
+fn mut_range_bound_break() {
+    let mut m = 4;
+    for i in 0..m {
+        if m == 4 {
+            m = 5;
+            break;
+        }
+    } // no warning because of immediate break
+}
+
+fn mut_range_bound_nested_break() {
+    let mut m = 4;
+    for i in 0..m {
+        if m == 5 {
+            break;
+        }
+
+        m = 4; // warning because it is not immediately followed by break
+    }
+}
+
+fn multiple_mut_range_bound_break() {
+    let mut m = 4;
+    for i in 0..m {
+        m = 5;
+
+        if m == 4 {
+            m = 0;
+            break;
+        }
+    } // warning because the break is not always reachable
+}