mapstruct · filiphr · Nov 8, 2020 · Nov 2, 2020
diff --git a/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java b/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java
@@ -1159,7 +1159,12 @@ public Type visitTypeVariable(TypeVariable t, Type parameterized) {
         @Override
         public Type visitDeclared(DeclaredType t, Type parameterized) {
             if ( types.isAssignable( types.erasure( t ), types.erasure( parameterized.getTypeMirror() ) ) ) {
-                // if same type, we can cast en assume number of type args are also the same
+                // We can't assume that the type args are the same
+                // e.g. List<T> is assignable to Object
+                if ( t.getTypeArguments().size() != parameterized.getTypeParameters().size() ) {
+                    return super.visitDeclared( t, parameterized );
+                }
+
                 for ( int i = 0; i < t.getTypeArguments().size(); i++ ) {
                     Type result = visit( t.getTypeArguments().get( i ), parameterized.getTypeParameters().get( i ) );
                     if ( result != null ) {

diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Erroneous2263Mapper.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Erroneous2263Mapper.java
@@ -0,0 +1,17 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2263;
+
+import org.mapstruct.Mapper;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface Erroneous2263Mapper {
+
+    Target map(Source source);
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Issue2263Test.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Issue2263Test.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2263;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
+import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
+
+/**
+ * @author Filip Hrisafov
+ */
+@IssueKey("2263")
+@RunWith(AnnotationProcessorTestRunner.class)
+@WithClasses({
+    Erroneous2263Mapper.class,
+    Source.class,
+    Target.class,
+})
+public class Issue2263Test {
+
+    @Test
+    @ExpectedCompilationOutcome(value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = Erroneous2263Mapper.class,
+                kind = javax.tools.Diagnostic.Kind.ERROR,
+                line = 16,
+                message = "Can't map property \"Object value\" to \"String value\". " +
+                    "Consider to declare/implement a mapping method: \"String map(Object value)\".")
+        })
+    public void shouldCorrectlyReportUnmappableTargetObject() {
+
+    }
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Source.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Source.java
@@ -0,0 +1,22 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2263;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class Source {
+
+    private final Object value;
+
+    public Source(Object value) {
+        this.value = value;
+    }
+
+    public Object getValue() {
+        return value;
+    }
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Target.java b/processor/src/test/java/org/mapstruct/ap/test/bugs/_2263/Target.java
@@ -0,0 +1,22 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.bugs._2263;
+
+/**
+ * @author Filip Hrisafov
+ */
+public class Target {
+
+    private final String value;
+
+    public Target(String value) {
+        this.value = value;
+    }
+
+    public String getValue() {
+        return value;
+    }
+}