ControlFlowUtil#isVariableAssignedInLoop: evaluate constant conditions

Fixes IDEA-186306 good code red: variable might be assigned in loop

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting/AssignToFinal.java

@@ -111,4 +111,23 @@ class T3a {
     <error descr="Variable 'b' might already have been assigned to">b</error> = true; // red
     System.out.println(b);
   }
+}
+class T29 {
+  // IDEA-186306
+  private final int j;
+  T29 (int b) {
+    do {
+      j = 34; // guaranteed to only be executed once
+      if (true) break;
+    } while (b == 1);
+  }
+}
+class T29a {
+  private final int j;
+  T29a (int b) {
+    do {
+      <error descr="Variable 'j' might be assigned in loop">j</error> = 34; // not guaranteed by JLS to only be executed once
+      if (j > 0) break;
+    } while (b == 1);
+  }
 }