#1338 Using an adder with non generic source collection should work

processor/src/main/java/org/mapstruct/ap/internal/model/assignment/AdderWrapper.java

@@ -19,6 +19,7 @@
 package org.mapstruct.ap.internal.model.assignment;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -27,6 +28,8 @@ import org.mapstruct.ap.internal.model.common.Assignment;
 import org.mapstruct.ap.internal.model.common.Type;
 import org.mapstruct.ap.internal.util.Nouns;
 
+import static org.mapstruct.ap.internal.util.Collections.first;
+
 /**
  * Wraps the assignment in a target setter.
  *
@@ -35,6 +38,7 @@ import org.mapstruct.ap.internal.util.Nouns;
 public class AdderWrapper extends AssignmentWrapper {
 
     private final List<Type> thrownTypesToExclude;
+    private final Type adderType;
 
     public AdderWrapper( Assignment rhs,
                          List<Type> thrownTypesToExclude,
@@ -44,6 +48,7 @@ public class AdderWrapper extends AssignmentWrapper {
         this.thrownTypesToExclude = thrownTypesToExclude;
         String desiredName = Nouns.singularize( targetPropertyName );
         rhs.setSourceLocalVarName( rhs.createLocalVarName( desiredName ) );
+        adderType = first( getSourceType().determineTypeArguments( Collection.class ) );
     }
 
     @Override
@@ -60,11 +65,15 @@ public class AdderWrapper extends AssignmentWrapper {
         return result;
     }
 
+    public Type getAdderType() {
+        return adderType;
+    }
+
     @Override
     public Set<Type> getImportTypes() {
         Set<Type> imported = new HashSet<Type>();
         imported.addAll( super.getImportTypes() );
-        imported.add( getSourceType().getTypeParameters().get( 0 ).getTypeBound() );
+        imported.add( adderType.getTypeBound() );
         return imported;
     }
 

processor/src/main/java/org/mapstruct/ap/internal/model/common/SourceRHS.java

@@ -18,12 +18,15 @@
  */
 package org.mapstruct.ap.internal.model.common;
 
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
 import org.mapstruct.ap.internal.util.Strings;
 
+import static org.mapstruct.ap.internal.util.Collections.first;
+
 /**
  * SourceRHS Assignment. Right Hand Side (RHS), source part of the assignment.
  *
@@ -135,7 +138,7 @@ public class SourceRHS extends ModelElement implements Assignment {
      */
     public Type getSourceTypeForMatching() {
         return useElementAsSourceTypeForMatching && sourceType.isCollectionType() ?
-            sourceType.getTypeParameters().get( 0 ) : sourceType;
+            first( sourceType.determineTypeArguments( Collection.class ) ) : sourceType;
     }
 
     /**

processor/src/main/resources/org/mapstruct/ap/internal/model/assignment/AdderWrapper.ftl

@@ -22,7 +22,7 @@
 <#import "../macro/CommonMacros.ftl" as lib>
 <@lib.handleExceptions>
   if ( ${sourceReference} != null ) {
-      for ( <@includeModel object=sourceType.typeParameters[0].typeBound/> ${sourceLocalVarName} : ${sourceReference} ) {
+      for ( <@includeModel object=adderType.typeBound/> ${sourceLocalVarName} : ${sourceReference} ) {
           ${ext.targetBeanName}.${ext.targetWriteAccessorName}<@lib.handleWrite><@lib.handleAssignment/></@lib.handleWrite>;
       }
   }

processor/src/test/java/org/mapstruct/ap/test/bugs/_1338/Issue1338Mapper.java

@@ -31,4 +31,6 @@ public interface Issue1338Mapper {
     Issue1338Mapper INSTANCE = Mappers.getMapper( Issue1338Mapper.class );
 
     Target map(Source source);
+
+    Source map(Target target);
 }

processor/src/test/java/org/mapstruct/ap/test/bugs/_1338/Issue1338Test.java

@@ -43,11 +43,17 @@ public class Issue1338Test {
 
     @Test
     public void shouldCorrectlyUseAdder() {
-        Target target = Issue1338Mapper.INSTANCE.map( new Source( Arrays.asList( "first", "second" ) ) );
+        Source source = new Source();
+        source.setProperties( Arrays.asList( "first", "second" ) );
+        Target target = Issue1338Mapper.INSTANCE.map( source );
 
         assertThat( target )
             .extracting( "properties" )
             .contains( Arrays.asList( "first", "second" ), atIndex( 0 ) );
 
+        Source mapped = Issue1338Mapper.INSTANCE.map( target );
+
+        assertThat( mapped.getProperties() )
+            .containsExactly( "first", "second" );
     }
 }

processor/src/test/java/org/mapstruct/ap/test/bugs/_1338/Source.java

@@ -18,6 +18,7 @@
  */
 package org.mapstruct.ap.test.bugs._1338;
 
+import java.util.ArrayList;
 import java.util.List;
 
 /**
@@ -25,13 +26,20 @@ import java.util.List;
  */
 public class Source {
 
-    private final List<String> properties;
+    private List<String> properties;
 
-    public Source(List<String> properties) {
+    public void addProperty(String property) {
-        this.properties = properties;
+        if ( properties == null ) {
+            properties = new ArrayList<String>();
+        }
+        properties.add( property );
     }
 
     public List<String> getProperties() {
         return properties;
     }
+
+    public void setProperties(List<String> properties) {
+        this.properties = properties;
+    }
 }

processor/src/test/java/org/mapstruct/ap/test/bugs/_1338/Target.java

@@ -35,6 +35,10 @@ public class Target {
         throw new IllegalStateException( "Setter is there just as a marker it should not be used" );
     }
 
+    public StringList getProperties() {
+        return properties;
+    }
+
     public static class StringList extends ArrayList<String> {
 
         private StringList() {