Remove unnecessary code from DefaultConverter

This also fixes the corresponding test. Since the NullConverter now
handles both null src and dest, the null logic was unnecessary.
Additionally, the casting logic was unnecessary due to the
CastingConverter. The array and number logic is still necessary, since
there's no converters for List to arrays and the number converters only
handle widening conversions.

Author: awalter17

src/main/java/org/scijava/convert/DefaultConverter.java

@@ -80,16 +80,9 @@ public Object convert(final Object src, final Type dest) {
 
 	@Override
 	public <T> T convert(final Object src, final Class<T> dest) {
-		if (dest == null) return null;
-		if (src == null) return ConversionUtils.getNullValue(dest);
-
 		// ensure type is well-behaved, rather than a primitive type
 		final Class<T> saneDest = ConversionUtils.getNonprimitiveType(dest);
 
-		// cast the existing object, if possible
-		if (ConversionUtils.canCast(src, saneDest)) return ConversionUtils.cast(
-			src, saneDest);
-
 		// Handle array types
 		if (isArray(dest)) {
 			@SuppressWarnings("unchecked")
@@ -302,15 +295,9 @@ public boolean canConvert(final Class<?> src, final Type dest) {
 	@Override
 	@Deprecated
 	public boolean canConvert(final Class<?> src, final Class<?> dest) {
-
-		if (src == null || dest == null) return true;
-
 		// ensure type is well-behaved, rather than a primitive type
 		final Class<?> saneDest = ConversionUtils.getNonprimitiveType(dest);
-		
-		// OK if the existing object can be casted
-		if (ConversionUtils.canCast(src, saneDest)) return true;
-		
+
 		// OK for numerical conversions
 		if (ConversionUtils.canCast(ConversionUtils.getNonprimitiveType(src),
 			Number.class) &&

src/test/java/org/scijava/convert/ConverterTest.java

@@ -94,11 +94,11 @@ public void testCanConvert() {
 
 	@Test
 	public void testCanConvertToGenericCollection() {
-		final DefaultConverter dc = new DefaultConverter();
+		final CastingConverter cc = new CastingConverter();
 
 		final Field destField = ClassUtils.getField(getClass(), "collection");
 		final Type destType = GenericUtils.getFieldType(destField, getClass());
-		assertTrue(dc.canConvert(ArrayList.class, destType));
+		assertTrue(cc.canConvert(ArrayList.class, destType));
 	}
 
 	private static class NumberConverter extends AbstractConverter<Number, Number> {