relax "!null" contract checking to accept exceptions thrown (IDEA-133488)

java/java-tests/testData/inspection/dataFlow/contractCheck/ExceptionWhenDeclaredNotNull.java

@@ -0,0 +1,17 @@
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+class Foo {
+
+  @Contract(value = "_, true -> !null")
+  public @Nullable String noNotAllowed(@NotNull String bar, boolean reallyNotAllowed) {
+    if (bar.equals("no")) {
+      if (reallyNotAllowed) {
+        throw new IllegalArgumentException("heck no");
+      }
+      return null;
+    }
+    return bar;
+  }
+}