Fix control flow check for breaking with diverging values

src/test/ui/break-diverging-value.rs

@@ -0,0 +1,13 @@
+fn loop_break_return() -> i32 {
+    let loop_value = loop { break return 0 }; // ok
+}
+
+fn loop_break_loop() -> i32 {
+    let loop_value = loop { break loop {} }; // ok
+}
+
+fn loop_break_break() -> i32 { //~ ERROR mismatched types
+    let loop_value = loop { break break };
+}
+
+fn main() {}

src/test/ui/break-diverging-value.stderr

@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+  --> $DIR/break-diverging-value.rs:9:26
+   |
+LL | fn loop_break_break() -> i32 {
+   |    ----------------      ^^^ expected `i32`, found `()`
+   |    |
+   |    implicitly returns `()` as its body has no tail or `return` expression
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.