core: Fail fast when values of an incorrect type are set

Helps with #210

Author: zml2008

core/src/main/java/org/spongepowered/configurate/ScopedConfigurationNode.java

@@ -16,6 +16,7 @@
  */
 package org.spongepowered.configurate;
 
+import io.leangen.geantyref.GenericTypeReflector;
 import io.leangen.geantyref.TypeToken;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.spongepowered.configurate.serialize.SerializationException;
@@ -104,14 +105,19 @@ default N set(Type type, @Nullable Object value) throws SerializationException {
         if (value == null) {
             return set(null);
         }
+        final Class<?> erasedType = GenericTypeReflector.erase(type);
+        if (!erasedType.isInstance(value)) {
+            throw new SerializationException(this, type, "Got a value of unexpected type "
+                + value.getClass().getName() + ", when the value should be an instance of " + erasedType.getSimpleName());
+        }
 
         final @Nullable TypeSerializer<?> serial = options().serializers().get(type);
         if (serial != null) {
             ((TypeSerializer) serial).serialize(type, value, self());
         } else if (options().acceptsType(value.getClass())) {
             raw(value); // Just write if no applicable serializer exists?
         } else {
-            throw new SerializationException("No serializer available for type " + type);
+            throw new SerializationException(this, type, "No serializer available for type " + type);
         }
         return self();
     }

core/src/test/java/org/spongepowered/configurate/AbstractConfigurationNodeTest.java

@@ -487,4 +487,13 @@ void testMergeToVirtualNode() throws SerializationException {
         assertFalse(target.virtual());
     }
 
+    @Test
+    void testSetValueOfInvalidType() {
+        final BasicConfigurationNode root = BasicConfigurationNode.root(ConfigurationOptions.defaults()
+            .nativeTypes(UnmodifiableCollections.toSet(String.class)));
+
+        assertTrue(assertThrows(SerializationException.class, () -> root.set(Integer.class, "hello"))
+            .getMessage().contains("Got a value of unexpected type"));
+    }
+
 }