Move nullability declaration to type parameter

Author: scordio

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/Converter.java

@@ -37,7 +37,7 @@
  * @see TypedConverter
  */
 @API(status = EXPERIMENTAL, since = "6.0")
-public interface Converter<S, T> {
+public interface Converter<S, T extends @Nullable Object> {
 
 	/**
 	 * Determine if the supplied conversion context is supported.
@@ -59,7 +59,6 @@ public interface Converter<S, T> {
 	 * type is a reference type
 	 * @throws ConversionException if an error occurs during the conversion
 	 */
-	@Nullable
 	T convert(@Nullable S source, ConversionContext context) throws ConversionException;
 
 }

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/DefaultConverter.java

@@ -44,7 +44,7 @@
  * @since 6.0
  */
 @API(status = INTERNAL, since = "6.0")
-public class DefaultConverter implements Converter<String, Object> {
+public class DefaultConverter implements Converter<String, @Nullable Object> {
 
 	static final DefaultConverter INSTANCE = new DefaultConverter();
 

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/FallbackStringToObjectConverter.java

@@ -52,7 +52,7 @@
  * @since 1.11
  * @see ConversionSupport
  */
-class FallbackStringToObjectConverter extends StringToTargetTypeConverter<Object> {
+class FallbackStringToObjectConverter extends StringToTargetTypeConverter<@Nullable Object> {
 
 	/**
 	 * Implementation of the NULL Object Pattern.

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/StringToTargetTypeConverter.java

@@ -17,7 +17,7 @@
  * Internal API for converting arguments of type {@link String} to a specified
  * target type.
  */
-abstract class StringToTargetTypeConverter<T> implements Converter<String, T> {
+abstract class StringToTargetTypeConverter<T extends @Nullable Object> implements Converter<String, T> {
 
 	@Override
 	public final boolean canConvert(ConversionContext context) {
@@ -31,7 +31,7 @@ public final boolean canConvert(ConversionContext context) {
 	abstract boolean canConvert(Class<?> targetType);
 
 	@Override
-	public final @Nullable T convert(@Nullable String source, ConversionContext context) {
+	public final T convert(@Nullable String source, ConversionContext context) {
 		Preconditions.notNull(source, "source cannot be null");
 		return convert(source, context.targetType().getType());
 	}
@@ -42,6 +42,6 @@ public final boolean canConvert(ConversionContext context) {
 	 * <p>This method will only be invoked if {@link #canConvert(Class)}
 	 * returned {@code true} for the same target type.
 	 */
-	abstract @Nullable T convert(String source, Class<?> targetType);
+	abstract T convert(String source, Class<?> targetType);
 
 }

junit-platform-commons/src/main/java/org/junit/platform/commons/support/conversion/TypedConverter.java

@@ -26,7 +26,7 @@
  * @since 6.0
  */
 @API(status = EXPERIMENTAL, since = "6.0")
-public abstract class TypedConverter<S, T> implements Converter<S, T> {
+public abstract class TypedConverter<S, T extends @Nullable Object> implements Converter<S, T> {
 
 	private final Class<S> sourceType;
 	private final Class<T> targetType;
@@ -45,12 +45,13 @@ protected TypedConverter(Class<S> sourceType, Class<T> targetType) {
 
 	@Override
 	public final boolean canConvert(ConversionContext context) {
+		// FIXME TypeDescriptor.NONE handling?
 		// FIXME add test cases with subtypes
 		return this.sourceType == context.sourceType().getType() && this.targetType == context.targetType().getType();
 	}
 
 	@Override
-	public final @Nullable T convert(@Nullable S source, ConversionContext context) {
+	public final T convert(@Nullable S source, ConversionContext context) {
 		return convert(source);
 	}
 
@@ -63,6 +64,6 @@ public final boolean canConvert(ConversionContext context) {
 	 * type is a reference type
 	 * @throws ConversionException if an error occurs during the conversion
 	 */
-	protected abstract @Nullable T convert(@Nullable S source) throws ConversionException;
+	protected abstract T convert(@Nullable S source) throws ConversionException;
 
 }