#306 IllegalArgumentException due to void type parameter

processor/src/main/java/org/mapstruct/ap/model/common/Type.java

@@ -32,6 +32,7 @@ import javax.lang.model.element.Modifier;
 import javax.lang.model.element.Name;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
+import javax.lang.model.type.TypeKind;
 import javax.lang.model.type.TypeMirror;
 import javax.lang.model.util.Elements;
 import javax.lang.model.util.Types;
@@ -72,6 +73,8 @@ public class Type extends ModelElement implements Comparable<Type> {
     private final boolean isCollectionType;
     private final boolean isMapType;
     private final boolean isImported;
+    private final boolean isVoid;
+
     private final List<String> enumConstants;
 
     private List<ExecutableElement> getters = null;
@@ -103,6 +106,7 @@ public class Type extends ModelElement implements Comparable<Type> {
         this.isCollectionType = isCollectionType;
         this.isMapType = isMapType;
         this.isImported = isImported;
+        this.isVoid = typeMirror.getKind().equals(  TypeKind.VOID );
 
         if ( isEnumType ) {
             enumConstants = new ArrayList<String>();
@@ -154,6 +158,10 @@ public class Type extends ModelElement implements Comparable<Type> {
         return isEnumType;
     }
 
+    public boolean isVoid() {
+        return isVoid;
+    }
+
     /**
      * Returns this type's enum constants in case it is an enum, an empty list otherwise.
      */

processor/src/main/java/org/mapstruct/ap/model/common/TypeFactory.java

@@ -193,7 +193,10 @@ public class TypeFactory {
      */
     public Type classTypeOf(Type type) {
         TypeMirror typeToUse;
-        if ( type.isPrimitive() ) {
+        if ( type.isVoid() ) {
+            return null;
+        }
+        else if ( type.isPrimitive() ) {
             typeToUse = typeUtils.boxedClass( (PrimitiveType) type.getTypeMirror() ).asType();
         }
         else {

processor/src/test/java/org/mapstruct/ap/test/collection/forged/CollectionMapper.java

@@ -18,14 +18,27 @@
  */
 package org.mapstruct.ap.test.collection.forged;
 
+import java.util.Set;
 import org.mapstruct.Mapper;
+import org.mapstruct.TargetType;
 import org.mapstruct.factory.Mappers;
 
 @Mapper
-public interface CollectionMapper {
+public abstract class CollectionMapper {
 
-    CollectionMapper INSTANCE = Mappers.getMapper( CollectionMapper.class );
+    public static final CollectionMapper INSTANCE = Mappers.getMapper( CollectionMapper.class );
 
-    Target sourceToTarget(Source source);
+    public abstract Target sourceToTarget(Source source);
-    Source targetToSource(Target target);
+    public abstract Source targetToSource(Target target);
+
+
+    // this method is added to reproduce issue 306
+    protected void dummy1( Set<String> arg ) {
+        throw new RuntimeException();
+    }
+
+    // this method is added to reproduce issue 306
+    protected Set<Long> dummy2( Object object,  @TargetType Class clazz ) {
+        throw new RuntimeException();
+    }
 }

processor/src/test/java/org/mapstruct/ap/test/collection/forged/CollectionMappingTest.java

@@ -34,7 +34,7 @@ import org.mapstruct.ap.util.Collections;
  *
  * @author Sjaak Derksen
  */
-@IssueKey("4")
+@IssueKey("4, 306")
 @RunWith(AnnotationProcessorTestRunner.class)
 public class CollectionMappingTest {