#981 Refactoring, move SourceRHS init to start of property build.

processor/src/main/java/org/mapstruct/ap/internal/model/IterableMappingMethod.java

@@ -105,12 +105,11 @@ public class IterableMappingMethod extends MappingMethod {
 
             Assignment assignment = ctx.getMappingResolver().getTargetAssignment(
                 method,
-                "collection element",
                 targetElementType,
                 null, // there is no targetPropertyName
                 formattingParameters,
                 selectionParameters,
-                new SourceRHS( loopVariableName, sourceElementType, new HashSet<String>() ),
+                new SourceRHS( loopVariableName, sourceElementType, new HashSet<String>(), "collection element" ),
                 false
             );
 

processor/src/main/java/org/mapstruct/ap/internal/model/MapMappingMethod.java

@@ -108,12 +108,11 @@ public class MapMappingMethod extends MappingMethod {
 
             Assignment keyAssignment = ctx.getMappingResolver().getTargetAssignment(
                 method,
-                "map key",
                 keyTargetType,
                 null, // there is no targetPropertyName
                 keyFormattingParameters,
                 keySelectionParameters,
-                new SourceRHS( "entry.getKey()", keySourceType, new HashSet<String>() ),
+                new SourceRHS( "entry.getKey()", keySourceType, new HashSet<String>(), "map key" ),
                 false
             );
 
@@ -134,12 +133,11 @@ public class MapMappingMethod extends MappingMethod {
 
             Assignment valueAssignment = ctx.getMappingResolver().getTargetAssignment(
                 method,
-                "map value",
                 valueTargetType,
                 null, // there is no targetPropertyName
                 valueFormattingParameters,
                 valueSelectionParameters,
-                new SourceRHS( "entry.getValue()", valueSourceType, new HashSet<String>() ),
+                new SourceRHS( "entry.getValue()", valueSourceType, new HashSet<String>(), "map value" ),
                 false
             );
 

processor/src/main/java/org/mapstruct/ap/internal/model/MappingBuilderContext.java

@@ -75,7 +75,6 @@ public class MappingBuilderContext {
          * returns a parameter assignment
          *
          * @param mappingMethod target mapping method
-         * @param mappedElement used for error messages
          * @param targetType return type to match
          * @param targetPropertyName name of the target property
          * @param formattingParameters used for formatting dates and numbers
@@ -91,9 +90,8 @@ public class MappingBuilderContext {
          * <li>null, no assignment found</li>
          * </ol>
          */
-        @SuppressWarnings("checkstyle:parameternumber")
+        Assignment getTargetAssignment(Method mappingMethod, Type targetType, String targetPropertyName,
-        Assignment getTargetAssignment(Method mappingMethod, String mappedElement, Type targetType,
+                                       FormattingParameters formattingParameters,
-                                       String targetPropertyName, FormattingParameters formattingParameters,
                                        SelectionParameters selectionParameters, SourceRHS sourceRHS,
                                        boolean preferUpdateMethods);
 

processor/src/main/java/org/mapstruct/ap/internal/model/MethodReference.java

@@ -127,6 +127,11 @@ public class MethodReference extends MappingMethod implements Assignment {
         return assignment.getSourceReference();
     }
 
+    @Override
+    public String getSourcePresenceCheckerReference() {
+        return assignment.getSourcePresenceCheckerReference();
+    }
+
     @Override
     public Type getSourceType() {
         return assignment.getSourceType();

processor/src/main/java/org/mapstruct/ap/internal/model/PropertyMapping.java

@@ -203,6 +203,7 @@ public class PropertyMapping extends ModelElement {
         // initial properties
         private String defaultValue;
         private SourceReference sourceReference;
+        private SourceRHS rightHandSide;
         private FormattingParameters formattingParameters;
         private SelectionParameters selectionParameters;
 
@@ -228,14 +229,10 @@ public class PropertyMapping extends ModelElement {
 
         public PropertyMapping build() {
             // handle source
-            String sourceElement = getSourceElement();
+            this.rightHandSide = getSourceRHS( sourceReference );
-            Type sourceType = getSourceType();
+            rightHandSide.setUseElementAsSourceTypeForMatching(
-            SourceRHS sourceRHS = getSourceRHS();
+                targetWriteAccessorType == TargetWriteAccessorType.ADDER );
-            if ( targetWriteAccessorType == TargetWriteAccessorType.ADDER && sourceType.isCollectionType() ) {
+            Type sourceType = rightHandSide.getSourceType();
-                // handle adder, if source is collection then use iterator element type as source type.
-                sourceType = sourceType.getTypeParameters().get( 0 );
-                sourceRHS = new SourceRHS( sourceRHS.getSourceReference(), sourceType, existingVariableNames );
-            }
 
             // all the tricky cases will be excluded for the time being.
             boolean preferUpdateMethods;
@@ -248,22 +245,21 @@ public class PropertyMapping extends ModelElement {
 
             Assignment assignment = ctx.getMappingResolver().getTargetAssignment(
                 method,
-                sourceElement,
                 targetType,
                 targetPropertyName,
                 formattingParameters,
                 selectionParameters,
-                sourceRHS,
+                rightHandSide,
                 preferUpdateMethods
             );
 
             // No mapping found. Try to forge a mapping
             if ( assignment == null ) {
                 if ( (sourceType.isCollectionType() || sourceType.isArrayType()) && targetType.isIterableType() ) {
-                    assignment = forgeIterableMapping( sourceType, targetType, sourceRHS, method.getExecutable() );
+                    assignment = forgeIterableMapping( sourceType, targetType, rightHandSide, method.getExecutable() );
                 }
                 else if ( sourceType.isMapType() && targetType.isMapType() ) {
-                    assignment = forgeMapMapping( sourceType, targetType, sourceRHS, method.getExecutable() );
+                    assignment = forgeMapMapping( sourceType, targetType, rightHandSide, method.getExecutable() );
                 }
             }
 
@@ -282,30 +278,30 @@ public class PropertyMapping extends ModelElement {
                 ctx.getMessager().printMessage(
                     method.getExecutable(),
                     Message.PROPERTYMAPPING_MAPPING_NOT_FOUND,
-                    sourceElement,
+                    rightHandSide.getSourceErrorMessagePart(),
                     targetType,
                     targetPropertyName,
                     targetType,
-                    getSourceType() /* original source type */
+                    rightHandSide.getSourceType() /* original source type */
                 );
             }
 
             return new PropertyMapping(
                 targetPropertyName,
-                sourceReference.getParameter().getName(),
+                rightHandSide.getSourceParameterName(),
                 targetWriteAccessor.getSimpleName().toString(),
                 ValueProvider.of( targetReadAccessor ),
                 targetType,
                 localTargetVarName,
                 assignment,
                 dependsOn,
-                getDefaultValueAssignment()
+                getDefaultValueAssignment( assignment )
             );
         }
 
-        private Assignment getDefaultValueAssignment() {
+        private Assignment getDefaultValueAssignment( Assignment rhs ) {
             if ( defaultValue != null
-                &&  ( !getSourceType().isPrimitive()  || getSourcePresenceCheckerRef() != null) ) {
+                &&  ( !rhs.getSourceType().isPrimitive() || rhs.getSourcePresenceCheckerReference() != null) ) {
                 // cannot check on null source if source is primitive unless it has a presenche checker
                 PropertyMapping build = new ConstantMappingBuilder()
                         .constantExpression( '"' + defaultValue + '"' )
@@ -340,23 +336,23 @@ public class PropertyMapping extends ModelElement {
 
         }
 
-        private Assignment assignToPlainViaSetter(Type sourceType, Type targetType, Assignment rightHandSide) {
+        private Assignment assignToPlainViaSetter(Type sourceType, Type targetType, Assignment rhs) {
 
             Assignment result;
 
-            if ( rightHandSide.isUpdateMethod() ) {
+            if ( rhs.isUpdateMethod() ) {
                 if ( targetReadAccessor == null ) {
                     ctx.getMessager().printMessage( method.getExecutable(),
                         Message.PROPERTYMAPPING_NO_READ_ACCESSOR_FOR_TARGET_TYPE,
                         targetPropertyName );
                 }
                 Assignment factoryMethod = ctx.getMappingResolver().getFactoryMethod( method, targetType, null );
-                result = new UpdateWrapper( rightHandSide, method.getThrownTypes(), factoryMethod,
+                result = new UpdateWrapper( rhs, method.getThrownTypes(), factoryMethod,
                     targetType, isFieldAssignment()
                 );
             }
             else {
-                result = new SetterWrapper( rightHandSide, method.getThrownTypes(), isFieldAssignment() );
+                result = new SetterWrapper( rhs, method.getThrownTypes(), isFieldAssignment() );
             }
 
             // if the sourceReference is the bean mapping method parameter itself, no null check is required
@@ -367,20 +363,20 @@ public class PropertyMapping extends ModelElement {
 
             // add a null / presence checked when required
             if ( sourceType.isPrimitive() ) {
-                if ( getSourcePresenceCheckerRef() != null ) {
+                if ( rhs.getSourcePresenceCheckerReference() != null ) {
-                    result = new NullCheckWrapper( result, getSourcePresenceCheckerRef() );
+                    result = new NullCheckWrapper( result );
                 }
             }
             else {
 
                 if ( result.isUpdateMethod() ) {
-                    result = new UpdateNullCheckWrapper( result, getSourcePresenceCheckerRef(), isFieldAssignment() );
+                    result = new UpdateNullCheckWrapper( result, isFieldAssignment() );
                 }
-                else if ( getSourcePresenceCheckerRef() != null ) {
+                else if ( rhs.getSourcePresenceCheckerReference() != null ) {
-                    result = new NullCheckWrapper( result, getSourcePresenceCheckerRef() );
+                    result = new NullCheckWrapper( result );
                 }
                 else if ( ALWAYS.equals( method.getMapperConfiguration().getNullValueCheckStrategy() ) ) {
-                    result = new NullCheckWrapper( result, getSourcePresenceCheckerRef() );
+                    result = new NullCheckWrapper( result );
                     useLocalVarWhenNested( result );
                 }
                 else if ( result.getType() == TYPE_CONVERTED
@@ -389,7 +385,7 @@ public class PropertyMapping extends ModelElement {
                     || (result.getType() == DIRECT && targetType.isPrimitive() ) ) {
                     // for primitive types null check is not possible at all, but a conversion needs
                     // a null check.
-                    result = new NullCheckWrapper( result, getSourcePresenceCheckerRef() );
+                    result = new NullCheckWrapper( result );
                     useLocalVarWhenNested( result );
                 }
             }
@@ -410,13 +406,13 @@ public class PropertyMapping extends ModelElement {
 
             Assignment result = rightHandSide;
 
-            if ( getSourceType().isCollectionType() ) {
+            if ( result.getSourceType().isCollectionType() ) {
                 result = new AdderWrapper( result, method.getThrownTypes(), isFieldAssignment() );
             }
             else {
                 // Possibly adding null to a target collection. So should be surrounded by an null check.
                 result = new SetterWrapper( result, method.getThrownTypes(), isFieldAssignment() );
-                result = new NullCheckWrapper( result, getSourcePresenceCheckerRef() );
+                result = new NullCheckWrapper( result );
             }
             return result;
         }
@@ -450,7 +446,6 @@ public class PropertyMapping extends ModelElement {
                     result = new SetterWrapperForCollectionsAndMaps(
                         result,
                         method.getThrownTypes(),
-                        getSourcePresenceCheckerRef(),
                         existingVariableNames,
                         targetType,
                         ALWAYS == method.getMapperConfiguration().getNullValueCheckStrategy(),
@@ -463,7 +458,6 @@ public class PropertyMapping extends ModelElement {
                 // target accessor is getter, so wrap the setter in getter map/ collection handling
                 result = new GetterWrapperForCollectionsAndMaps( result,
                                                                  method.getThrownTypes(),
-                                                                 getSourcePresenceCheckerRef(),
                                                                  existingVariableNames,
                                                                  targetType,
                                                                  isFieldAssignment()
@@ -484,19 +478,34 @@ public class PropertyMapping extends ModelElement {
                 existingVariableNames,
                 isFieldAssignment()
             );
-            return new NullCheckWrapper( assignment, getSourcePresenceCheckerRef() );
+            return new NullCheckWrapper( assignment );
         }
 
-        private Type getSourceType() {
+        private SourceRHS getSourceRHS( SourceReference sourceReference ) {
-
             Parameter sourceParam = sourceReference.getParameter();
             List<PropertyEntry> propertyEntries = sourceReference.getPropertyEntries();
+
+            // parameter reference
             if ( propertyEntries.isEmpty() ) {
-                return sourceParam.getType();
+                return new SourceRHS( sourceParam.getName(),
+                                      sourceParam.getType(),
+                                      existingVariableNames,
+                                      sourceReference.toString()
+                );
             }
+            // simple property
             else if ( propertyEntries.size() == 1 ) {
-                return last( propertyEntries ).getType();
+                PropertyEntry propertyEntry = propertyEntries.get( 0 );
+                String sourceRef = sourceParam.getName() + "." + ValueProvider.of( propertyEntry.getReadAccessor() );
+                return new SourceRHS( sourceParam.getName(),
+                                      sourceRef,
+                                      getSourcePresenceCheckerRef( sourceReference ),
+                                      propertyEntry.getType(),
+                                      existingVariableNames,
+                                      sourceReference.toString()
+                );
             }
+            // nested property given as dot path
             else {
                 Type sourceType = last( propertyEntries ).getType();
                 if ( sourceType.isPrimitive() && !targetType.isPrimitive() ) {
@@ -505,39 +514,18 @@ public class PropertyMapping extends ModelElement {
                     // type. The source type becomes the wrapped type in that case.
                     sourceType = ctx.getTypeFactory().getWrappedType( sourceType );
                 }
-                return sourceType;
-            }
-        }
 
-        private SourceRHS getSourceRHS() {
-            Parameter sourceParam = sourceReference.getParameter();
-            List<PropertyEntry> propertyEntries = sourceReference.getPropertyEntries();
-
-            // parameter reference
-            if ( propertyEntries.isEmpty() ) {
-                return new SourceRHS( sourceParam.getName(), getSourceType(), existingVariableNames );
-            }
-            // simple property
-            else if ( propertyEntries.size() == 1 ) {
-                PropertyEntry propertyEntry = propertyEntries.get( 0 );
-                String sourceRef = sourceParam.getName() + "." + ValueProvider.of( propertyEntry.getReadAccessor() );
-                return new SourceRHS( sourceRef, propertyEntry.getType(), existingVariableNames );
-            }
-            // nested property given as dot path
-            else {
                 // copy mapper configuration from the source method, its the same mapper
                 MapperConfiguration config = method.getMapperConfiguration();
 
-
                 // forge a method from the parameter type to the last entry type.
                 String forgedName = Strings.joinAndCamelize( sourceReference.getElementNames() );
                 forgedName = Strings.getSaveVariableName( forgedName, ctx.getNamesOfMappingsToGenerate() );
-                ForgedMethod methodRef = new ForgedMethod(
+                ForgedMethod methodRef = new ForgedMethod( forgedName,
-                    forgedName,
+                                                           sourceReference.getParameter().getType(),
-                    sourceReference.getParameter().getType(),
+                                                           sourceType,
-                    getSourceType(),
+                                                           config,
-                    config,
+                                                           method.getExecutable()
-                    method.getExecutable()
                 );
                 NestedPropertyMappingMethod.Builder builder = new NestedPropertyMappingMethod.Builder();
                 NestedPropertyMappingMethod nestedPropertyMapping = builder
@@ -553,36 +541,24 @@ public class PropertyMapping extends ModelElement {
                     forgedName = ctx.getExistingMappingMethod( nestedPropertyMapping ).getName();
                 }
                 String sourceRef = forgedName + "( " + sourceParam.getName() + " )";
-                return new SourceRHS( sourceRef, getSourceType(), existingVariableNames );
+                SourceRHS sourceRhs = new SourceRHS( sourceParam.getName(),
-
+                                                     sourceRef,
-            }
+                                                     getSourcePresenceCheckerRef( sourceReference ),
-        }
+                                                     sourceType,
-
+                                                     existingVariableNames,
-        private String getSourceElement() {
+                                                     sourceReference.toString()
-
-            Parameter sourceParam = sourceReference.getParameter();
-            List<PropertyEntry> propertyEntries = sourceReference.getPropertyEntries();
-            if ( propertyEntries.isEmpty() ) {
-                return String.format( "parameter \"%s %s\"", sourceParam.getType(), sourceParam.getName() );
-            }
-            else if ( propertyEntries.size() == 1 ) {
-                PropertyEntry propertyEntry = propertyEntries.get( 0 );
-                return String.format( "property \"%s %s\"", propertyEntry.getType(), propertyEntry.getName() );
-            }
-            else {
-                PropertyEntry lastPropertyEntry = propertyEntries.get( propertyEntries.size() - 1 );
-                return String.format(
-                    "property \"%s %s\"",
-                    lastPropertyEntry.getType(),
-                    Strings.join( sourceReference.getElementNames(), "." )
                 );
+                return sourceRhs;
+
             }
         }
 
-        private String getSourcePresenceCheckerRef() {
+        private String getSourcePresenceCheckerRef( SourceReference sourceReference ) {
             String sourcePresenceChecker = null;
             if ( !sourceReference.getPropertyEntries().isEmpty() ) {
                 Parameter sourceParam = sourceReference.getParameter();
+                // TODO is first correct here?? shouldn't it be last since the remainer is checked
+                // in the forged method?
                 PropertyEntry propertyEntry = first( sourceReference.getPropertyEntries() );
                 if ( propertyEntry.getPresenceChecker() != null ) {
                     sourcePresenceChecker = sourceParam.getName()
@@ -699,19 +675,18 @@ public class PropertyMapping extends ModelElement {
 
         public PropertyMapping build() {
             // source
-            String mappedElement = "constant '" + constantExpression + "'";
+            String sourceErrorMessagePart = "constant '" + constantExpression + "'";
             Type sourceType = ctx.getTypeFactory().getType( String.class );
 
             Assignment assignment = null;
             if ( !targetType.isEnumType() ) {
                 assignment = ctx.getMappingResolver().getTargetAssignment(
                     method,
-                    mappedElement,
                     targetType,
                     targetPropertyName,
                     formattingParameters,
                     selectionParameters,
-                    new SourceRHS( constantExpression, sourceType, existingVariableNames ),
+                    new SourceRHS( constantExpression, sourceType, existingVariableNames, sourceErrorMessagePart ),
                     method.getMappingTargetParameter() != null
                 );
             }
@@ -780,7 +755,8 @@ public class PropertyMapping extends ModelElement {
             // String String quotation marks.
             String enumExpression = constantExpression.substring( 1, constantExpression.length() - 1 );
             if ( targetType.getEnumConstants().contains( enumExpression ) ) {
-                assignment = new SourceRHS( enumExpression, targetType, existingVariableNames );
+                String sourceErrorMessagePart = "constant '" + constantExpression + "'";
+                assignment = new SourceRHS( enumExpression, targetType, existingVariableNames, sourceErrorMessagePart );
                 assignment = new EnumConstantWrapper( assignment, targetType );
             }
             else {
@@ -806,7 +782,7 @@ public class PropertyMapping extends ModelElement {
         }
 
         public PropertyMapping build() {
-            Assignment assignment = new SourceRHS( javaExpression, null, existingVariableNames );
+            Assignment assignment = new SourceRHS( javaExpression, null, existingVariableNames, "" );
 
             if ( Executables.isSetterMethod( targetWriteAccessor ) ||
                 Executables.isFieldAccessor( targetWriteAccessor ) ) {

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

@@ -30,6 +30,8 @@ import org.mapstruct.ap.internal.util.Strings;
 /**
  * SourceRHS Assignment. Right Hand Side (RHS), source part of the assignment.
  *
+ * This class contains all information on the source side of an assignment needed for common use in the mapping.
+ *
  * @author Sjaak Derksen
  */
 public class SourceRHS extends ModelElement implements Assignment {
@@ -38,11 +40,24 @@ public class SourceRHS extends ModelElement implements Assignment {
     private final Type sourceType;
     private String sourceLocalVarName;
     private final Set<String> existingVariableNames;
+    private final String sourceErrorMessagePart;
+    private final String sourcePresenceCheckerReference;
+    private boolean useElementAsSourceTypeForMatching = false;
+    private final String sourceParameterName;
 
-    public SourceRHS(String sourceReference, Type sourceType, Set<String> existingVariableNames ) {
+    public SourceRHS(String sourceReference, Type sourceType, Set<String> existingVariableNames,
+        String sourceErrorMessagePart ) {
+        this( null, sourceReference, null, sourceType, existingVariableNames, sourceErrorMessagePart );
+    }
+
+    public SourceRHS(String sourceParameterName, String sourceReference, String sourcePresenceCheckerReference,
+        Type sourceType, Set<String> existingVariableNames,  String sourceErrorMessagePart ) {
         this.sourceReference = sourceReference;
         this.sourceType = sourceType;
         this.existingVariableNames = existingVariableNames;
+        this.sourceErrorMessagePart = sourceErrorMessagePart;
+        this.sourcePresenceCheckerReference = sourcePresenceCheckerReference;
+        this.sourceParameterName = sourceParameterName;
     }
 
     @Override
@@ -50,6 +65,11 @@ public class SourceRHS extends ModelElement implements Assignment {
         return sourceReference;
     }
 
+    @Override
+    public String getSourcePresenceCheckerReference() {
+        return sourcePresenceCheckerReference;
+    }
+
     @Override
     public Type getSourceType() {
         return sourceType;
@@ -99,4 +119,32 @@ public class SourceRHS extends ModelElement implements Assignment {
     public String toString() {
         return sourceReference;
     }
+
+    public String getSourceErrorMessagePart() {
+        return sourceErrorMessagePart;
+    }
+
+    /**
+     * The source type that is to be used when resolving the mapping from source to target.
+     *
+     * @return the source type to be used in the matching process.
+     */
+    public Type getSourceTypeForMatching() {
+        return useElementAsSourceTypeForMatching && sourceType.isCollectionType() ?
+            sourceType.getTypeParameters().get( 0 ) : sourceType;
+    }
+
+    /**
+     * For collection type, use element as source type to find a suitable mapping method.
+     *
+     * @param useElementAsSourceTypeForMatching
+     */
+    public void setUseElementAsSourceTypeForMatching(boolean useElementAsSourceTypeForMatching) {
+        this.useElementAsSourceTypeForMatching = useElementAsSourceTypeForMatching;
+    }
+
+    public String getSourceParameterName() {
+        return sourceParameterName;
+    }
+
 }

processor/src/main/java/org/mapstruct/ap/internal/model/TypeConversion.java

@@ -86,6 +86,11 @@ public class TypeConversion extends ModelElement implements Assignment {
         return assignment.getSourceReference();
     }
 
+    @Override
+    public String getSourcePresenceCheckerReference() {
+        return assignment.getSourcePresenceCheckerReference();
+    }
+
     @Override
     public Type getSourceType() {
         return assignment.getSourceType();

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

@@ -38,8 +38,8 @@ public class AdderWrapper extends AssignmentWrapper {
     public AdderWrapper( Assignment decoratedAssignment, List<Type> thrownTypesToExclude, boolean fieldAssignment ) {
         super( decoratedAssignment, fieldAssignment );
         this.thrownTypesToExclude = thrownTypesToExclude;
-        this.sourceIteratorName =
+        String desiredName = decoratedAssignment.getSourceType().getTypeParameters().get( 0 ).getName();
-            decoratedAssignment.createLocalVarName( decoratedAssignment.getSourceType().getName() );
+        this.sourceIteratorName = decoratedAssignment.createLocalVarName( desiredName );
         decoratedAssignment.setSourceLocalVarName( sourceIteratorName );
     }
 
@@ -61,7 +61,7 @@ public class AdderWrapper extends AssignmentWrapper {
     public Set<Type> getImportTypes() {
         Set<Type> imported = new HashSet<Type>();
         imported.addAll( super.getImportTypes() );
-        imported.add( getSourceType() );
+        imported.add( getSourceType().getTypeParameters().get( 0 ) );
         return imported;
     }
 

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

@@ -77,6 +77,13 @@ public interface Assignment {
      */
     String getSourceReference();
 
+    /**
+     * the source presence checker reference
+     *
+     * @return source reference
+     */
+    String getSourcePresenceCheckerReference();
+
     /**
      * the source type used in the matching process
      *

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

@@ -63,6 +63,11 @@ public abstract class AssignmentWrapper extends ModelElement implements Assignme
         return decoratedAssignment.getSourceReference();
     }
 
+    @Override
+    public String getSourcePresenceCheckerReference() {
+        return decoratedAssignment.getSourcePresenceCheckerReference();
+    }
+
     @Override
     public Type getSourceType() {
         return decoratedAssignment.getSourceType();

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

@@ -39,17 +39,14 @@ import org.mapstruct.ap.internal.model.common.Type;
 public class GetterWrapperForCollectionsAndMaps extends WrapperForCollectionsAndMaps {
 
     /**
-     * constructor for property mapping
-     *
      * @param decoratedAssignment
      * @param thrownTypesToExclude
-     * @param sourcePresenceChecker
      * @param existingVariableNames
      * @param targetType
+     * @param fieldAssignment
      */
     public GetterWrapperForCollectionsAndMaps(Assignment decoratedAssignment,
                                               List<Type> thrownTypesToExclude,
-                                              String sourcePresenceChecker,
                                               Set<String> existingVariableNames,
                                               Type targetType,
                                               boolean fieldAssignment) {
@@ -57,28 +54,10 @@ public class GetterWrapperForCollectionsAndMaps extends WrapperForCollectionsAnd
         super(
             decoratedAssignment,
             thrownTypesToExclude,
-            sourcePresenceChecker,
             existingVariableNames,
             targetType,
             fieldAssignment
         );
     }
 
-    /**
-     * constructor for e.g. constants and expressions
-     *
-     * @param decoratedAssignment
-     * @param thrownTypesToExclude
-     * @param existingVariableNames
-     * @param targetType
-     */
-    public GetterWrapperForCollectionsAndMaps(Assignment decoratedAssignment,
-                                              List<Type> thrownTypesToExclude,
-                                              Set<String> existingVariableNames,
-                                              Type targetType,
-                                              boolean fieldAssignment) {
-
-        super( decoratedAssignment, thrownTypesToExclude, null, existingVariableNames, targetType, fieldAssignment );
-    }
-
 }

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

@@ -25,14 +25,8 @@ package org.mapstruct.ap.internal.model.assignment;
  */
 public class NullCheckWrapper extends AssignmentWrapper {
 
-    private final String sourcePresenceChecker;
+    public NullCheckWrapper( Assignment decoratedAssignment ) {
-
-    public NullCheckWrapper( Assignment decoratedAssignment, String sourcePresenceChecker ) {
         super( decoratedAssignment, false );
-        this.sourcePresenceChecker = sourcePresenceChecker;
     }
 
-    public String getSourcePresenceChecker() {
-        return sourcePresenceChecker;
-    }
 }

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

@@ -47,7 +47,6 @@ public class SetterWrapperForCollectionsAndMaps extends WrapperForCollectionsAnd
 
     public SetterWrapperForCollectionsAndMaps(Assignment decoratedAssignment,
                                               List<Type> thrownTypesToExclude,
-                                              String sourcePresenceChecker,
                                               Set<String> existingVariableNames,
                                               Type targetType,
                                               boolean allwaysIncludeNullCheck,
@@ -57,7 +56,6 @@ public class SetterWrapperForCollectionsAndMaps extends WrapperForCollectionsAnd
         super(
             decoratedAssignment,
             thrownTypesToExclude,
-            sourcePresenceChecker,
             existingVariableNames,
             targetType,
             fieldAssignment
@@ -97,8 +95,4 @@ public class SetterWrapperForCollectionsAndMaps extends WrapperForCollectionsAnd
         return "java.util.EnumSet".equals( targetType.getFullyQualifiedName() );
     }
 
-    public boolean isFieldAssignment() {
-        return fieldAssignment;
-    }
-
 }

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

@@ -26,16 +26,8 @@ package org.mapstruct.ap.internal.model.assignment;
  */
 public class UpdateNullCheckWrapper extends AssignmentWrapper {
 
-    private final String sourcePresenceChecker;
+    public UpdateNullCheckWrapper(Assignment decoratedAssignment, boolean fieldAssignment) {
-
-    public UpdateNullCheckWrapper(Assignment decoratedAssignment, String sourcePresenceChecker,
-                                  boolean fieldAssignment) {
         super( decoratedAssignment, fieldAssignment );
-        this.sourcePresenceChecker = sourcePresenceChecker;
-    }
-
-    public String getSourcePresenceChecker() {
-        return sourcePresenceChecker;
     }
 
 }

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

@@ -35,13 +35,11 @@ import org.mapstruct.ap.internal.util.Strings;
 public class WrapperForCollectionsAndMaps extends AssignmentWrapper {
 
     private final List<Type> thrownTypesToExclude;
-    private final String sourcePresenceChecker;
     private final String localVarName;
     private final Type localVarType;
 
     public WrapperForCollectionsAndMaps(Assignment decoratedAssignment,
                                         List<Type> thrownTypesToExclude,
-                                        String sourcePresenceChecker,
                                         Set<String> existingVariableNames,
                                         Type targetType,
                                         boolean fieldAssignment) {
@@ -49,7 +47,6 @@ public class WrapperForCollectionsAndMaps extends AssignmentWrapper {
         super( decoratedAssignment, fieldAssignment );
 
         this.thrownTypesToExclude = thrownTypesToExclude;
-        this.sourcePresenceChecker = sourcePresenceChecker;
         if ( getType() == AssignmentType.DIRECT && getSourceType() != null ) {
             this.localVarType = getSourceType();
         }
@@ -83,10 +80,6 @@ public class WrapperForCollectionsAndMaps extends AssignmentWrapper {
         return imported;
     }
 
-    public String getSourcePresenceChecker() {
-        return sourcePresenceChecker;
-    }
-
     public String getLocalVarName() {
         return localVarName;
     }

processor/src/main/java/org/mapstruct/ap/internal/model/source/SourceReference.java

@@ -296,4 +296,25 @@ public class SourceReference {
 
         return new SourceReference( replacement, propertyEntries, isValid );
     }
+
+    @Override
+    public String toString() {
+
+        if ( propertyEntries.isEmpty() ) {
+            return String.format( "parameter \"%s %s\"", getParameter().getType(), getParameter().getName() );
+        }
+        else if ( propertyEntries.size() == 1 ) {
+            PropertyEntry propertyEntry = propertyEntries.get( 0 );
+            return String.format( "property \"%s %s\"", propertyEntry.getType(), propertyEntry.getName() );
+        }
+        else {
+            PropertyEntry lastPropertyEntry = propertyEntries.get( propertyEntries.size() - 1 );
+            return String.format(
+                "property \"%s %s\"",
+                lastPropertyEntry.getType(),
+                Strings.join( getElementNames(), "." )
+            );
+        }
+    }
+
 }

processor/src/main/java/org/mapstruct/ap/internal/processor/creation/MappingResolverImpl.java

@@ -104,10 +104,9 @@ public class MappingResolverImpl implements MappingResolver {
     }
 
     @Override
-    @SuppressWarnings("checkstyle:parameternumber")
+    public Assignment getTargetAssignment(Method mappingMethod, Type targetType, String targetPropertyName,
-    public Assignment getTargetAssignment(Method mappingMethod, String mappedElement,
+        FormattingParameters formattingParameters, SelectionParameters selectionParameters, SourceRHS sourceRHS,
-        Type targetType, String targetPropertyName, FormattingParameters formattingParameters,
+        boolean preferUpdateMapping) {
-        SelectionParameters selectionParameters, SourceRHS sourceRHS, boolean preferUpdateMapping) {
 
         SelectionCriteria criteria =
             new SelectionCriteria( selectionParameters, targetPropertyName, preferUpdateMapping, false );
@@ -122,14 +121,13 @@ public class MappingResolverImpl implements MappingResolver {
         ResolvingAttempt attempt = new ResolvingAttempt(
             sourceModel,
             mappingMethod,
-            mappedElement,
             dateFormat,
             numberFormat,
             sourceRHS,
             criteria
         );
 
-        return attempt.getTargetAssignment( sourceRHS.getSourceType(), targetType );
+        return attempt.getTargetAssignment( sourceRHS.getSourceTypeForMatching(), targetType );
     }
 
     @Override
@@ -143,7 +141,7 @@ public class MappingResolverImpl implements MappingResolver {
 
         SelectionCriteria criteria = new SelectionCriteria( selectionParameters, null, false, true );
 
-        ResolvingAttempt attempt = new ResolvingAttempt( sourceModel, mappingMethod, null, null, null, null, criteria );
+        ResolvingAttempt attempt = new ResolvingAttempt( sourceModel, mappingMethod, null, null, null, criteria );
 
         List<SourceMethod> matchingSourceMethods = attempt.getMatches( sourceModel, null, targetType );
 
@@ -199,7 +197,6 @@ public class MappingResolverImpl implements MappingResolver {
     private class ResolvingAttempt {
 
         private final Method mappingMethod;
-        private final String mappedElement;
         private final List<SourceMethod> methods;
         private final String dateFormat;
         private final String numberFormat;
@@ -212,12 +209,10 @@ public class MappingResolverImpl implements MappingResolver {
         // so this set must be cleared.
         private final Set<VirtualMappingMethod> virtualMethodCandidates;
 
-        private ResolvingAttempt(List<SourceMethod> sourceModel, Method mappingMethod, String mappedElement,
+        private ResolvingAttempt(List<SourceMethod> sourceModel, Method mappingMethod, String dateFormat,
-                String dateFormat, String numberFormat, SourceRHS sourceRHS, SelectionCriteria criteria) {
+                                 String numberFormat, SourceRHS sourceRHS, SelectionCriteria criteria) {
-
 
             this.mappingMethod = mappingMethod;
-            this.mappedElement = mappedElement;
             this.methods = filterPossibleCandidateMethods( sourceModel );
             this.dateFormat = dateFormat;
             this.numberFormat = numberFormat;
@@ -520,10 +515,10 @@ public class MappingResolverImpl implements MappingResolver {
             // into the target type
             if ( candidates.size() > 1 ) {
 
-                if ( mappedElement != null ) {
+                if ( sourceRHS.getSourceErrorMessagePart() != null ) {
                     messager.printMessage( mappingMethod.getExecutable(),
                         Message.GENERAL_AMBIGIOUS_MAPPING_METHOD,
-                        mappedElement,
+                        sourceRHS.getSourceErrorMessagePart(),
                         returnType,
                         Strings.join( candidates, ", " )
                     );

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

@@ -21,7 +21,7 @@
 <#import "../macro/CommonMacros.ftl" as lib>
 <@lib.handleExceptions>
   if ( ${sourceReference} != null ) {
-      for ( <@includeModel object=sourceType/> ${sourceIteratorName} : ${sourceReference} ) {
+      for ( <@includeModel object=sourceType.typeParameters[0]/> ${sourceIteratorName} : ${sourceReference} ) {
           ${ext.targetBeanName}.${ext.targetWriteAccessorName}<@lib.handleWrite><@lib.handleAssignment/></@lib.handleWrite>;
       }
   }

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

@@ -25,7 +25,7 @@ if ( ${sourceLocalVarName} != null ) {
     <@_assignment object=assignment defaultValue=ext.defaultValueAssignment/>
 }
 <#else>
-if ( <#if sourcePresenceChecker?? >${sourcePresenceChecker}<#else>${sourceReference} != null</#if> ) {
+if ( <#if sourcePresenceCheckerReference?? >${sourcePresenceCheckerReference}<#else>${sourceReference} != null</#if> ) {
     <@_assignment object=assignment defaultValue=ext.defaultValueAssignment/>
 }
 </#if>

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

@@ -26,7 +26,7 @@
             ${ext.targetBeanName}.${ext.targetReadAccessorName}.clear();
             ${ext.targetBeanName}.${ext.targetReadAccessorName}.<#if ext.targetType.collectionType>addAll<#else>putAll</#if>( ${localVarName} );
         </@lib.handleNullCheck>
-        <#if !ext.defaultValueAssignment?? && !sourcePresenceChecker?? && !allwaysIncludeNullCheck>else {<#-- the opposite (defaultValueAssignment) case is handeld inside lib.handleNullCheck -->
+        <#if !ext.defaultValueAssignment?? && !sourcePresenceCheckerReference?? && !allwaysIncludeNullCheck>else {<#-- the opposite (defaultValueAssignment) case is handeld inside lib.handleNullCheck -->
           ${ext.targetBeanName}.${ext.targetWriteAccessorName}<@lib.handleWrite>null</@lib.handleWrite>;
         }
         </#if>
@@ -55,4 +55,4 @@
     <#else>
       new <#if ext.targetType.implementationType??><@includeModel object=ext.targetType.implementationType/><#else><@includeModel object=ext.targetType/></#if>( ${localVarName} )
     </#if>
-</@compress></#macro>
+</@compress></#macro>

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

@@ -19,7 +19,7 @@
 
 -->
 <#import '../macro/CommonMacros.ftl' as lib>
-if ( <#if sourcePresenceChecker?? >${sourcePresenceChecker}<#else>${sourceReference} != null</#if> ) {
+if ( <#if sourcePresenceCheckerReference?? >${sourcePresenceCheckerReference}<#else>${sourceReference} != null</#if> ) {
     <@includeModel object=assignment
                 targetBeanName=ext.targetBeanName
                 existingInstanceMapping=ext.existingInstanceMapping

processor/src/main/resources/org/mapstruct/ap/internal/model/macro/CommonMacros.ftl

@@ -28,8 +28,8 @@
            present.
 -->
 <#macro handleNullCheck>
-  <#if sourcePresenceChecker??>
+  <#if sourcePresenceCheckerReference??>
-    if ( ${sourcePresenceChecker} ) {
+    if ( ${sourcePresenceCheckerReference} ) {
       <@includeModel object=localVarType/> ${localVarName} = <@lib.handleAssignment/>;
       <#nested>
     }