Rethrow Error from @PostConstruct method instead of wrapping it in RuntimeException

PostConstructAdapterFactory rethrows a RuntimeException cause as-is but wraps
everything else. An Error thrown by the @PostConstruct method (AssertionError,
OutOfMemoryError, ...) is unchecked like RuntimeException and should propagate
as-is, not be smothered in a RuntimeException. Rethrow Error the same way.
Adds a regression test.

Author: vasiliy-mikhailov

extras/src/main/java/com/google/gson/typeadapters/PostConstructAdapterFactory.java

@@ -65,6 +65,8 @@ public T read(JsonReader in) throws IOException {
         } catch (InvocationTargetException e) {
           if (e.getCause() instanceof RuntimeException) {
             throw (RuntimeException) e.getCause();
+          } else if (e.getCause() instanceof Error) {
+            throw (Error) e.getCause();
           }
           throw new RuntimeException(e.getCause());
         }

extras/src/test/java/com/google/gson/typeadapters/PostConstructAdapterFactoryTest.java

@@ -95,6 +95,27 @@ public boolean equals(Object o) {
     }
   }
 
+  @Test
+  public void testErrorFromPostConstructPropagatesAsError() {
+    Gson gson =
+        new GsonBuilder().registerTypeAdapterFactory(new PostConstructAdapterFactory()).create();
+
+    AssertionError thrown =
+        assertThrows(
+            AssertionError.class, () -> gson.fromJson("{\"value\": 1}", ErrorThrowingClass.class));
+
+    assertThat(thrown).hasMessageThat().contains("error from post-construct");
+  }
+
+  static class ErrorThrowingClass {
+    public int value;
+
+    @PostConstruct
+    private void init() {
+      throw new AssertionError("error from post-construct");
+    }
+  }
+
   @SuppressWarnings({"overrides", "EqualsHashCode"}) // for missing hashCode() override
   static class MultipleSandwiches {
     public List<Sandwich> sandwiches;