Fail closed on ambiguous simple-name type compatibility

Reject cross-package class matching and enum parameter compatibility when
types share an ambiguous simple name but differ by package-qualified FQN.

Co-authored-by: Cursor <cursoragent@cursor.com>

state_machine_exporter/src/main/java/click/kamil/springstatemachineexporter/analysis/service/CallGraphPathFinder.java

@@ -361,10 +361,7 @@ public class CallGraphPathFinder {
             
             if (classNeighbor.equals(classTarget)) return true;
             
-            String simpleClassNeighbor = classNeighbor.contains(".") ? classNeighbor.substring(classNeighbor.lastIndexOf('.') + 1) : classNeighbor;
-            String simpleClassTarget = classTarget.contains(".") ? classTarget.substring(classTarget.lastIndexOf('.') + 1) : classTarget;
-            
-            if (simpleClassNeighbor.equals(simpleClassTarget)) return true;
+            if (context.areSameTypeOrUnambiguousSimpleMatch(classNeighbor, classTarget)) return true;
             
             if (context.areClassesPolymorphicallyCompatible(classNeighbor, classTarget)) {
                 return true;

state_machine_exporter/src/main/java/click/kamil/springstatemachineexporter/analysis/service/TypeResolver.java

@@ -245,6 +245,17 @@ public class TypeResolver {
         }
         
         if (actualType.equals(expectedType)) return true;
+
+        String expectedSimple = expectedType.contains(".")
+                ? expectedType.substring(expectedType.lastIndexOf('.') + 1)
+                : expectedType;
+        String actualSimple = actualType.contains(".")
+                ? actualType.substring(actualType.lastIndexOf('.') + 1)
+                : actualType;
+        if (expectedSimple.equals(actualSimple) && context.isAmbiguousSimpleName(expectedSimple)) {
+            return false;
+        }
+
         if (actualType.endsWith("." + expectedType) || expectedType.endsWith("." + actualType)) return true;
 
         AbstractTypeDeclaration td = context.getAbstractTypeDeclaration(actualType);

state_machine_exporter/src/main/java/click/kamil/springstatemachineexporter/ast/common/CodebaseContext.java

@@ -538,6 +538,25 @@ public class CodebaseContext {
         return ambiguousSimpleNames.contains(name);
     }
 
+    /**
+     * True when two type references denote the same type, or share an unambiguous simple name.
+     * Fails closed when the shared simple name exists in multiple packages.
+     */
+    public boolean areSameTypeOrUnambiguousSimpleMatch(String leftFqn, String rightFqn) {
+        if (leftFqn == null || rightFqn == null) {
+            return false;
+        }
+        if (leftFqn.equals(rightFqn)) {
+            return true;
+        }
+        String leftSimple = simpleTypeName(leftFqn);
+        String rightSimple = simpleTypeName(rightFqn);
+        if (!leftSimple.equals(rightSimple)) {
+            return false;
+        }
+        return !isAmbiguousSimpleName(leftSimple);
+    }
+
     public List<String> getEnumValues(String fqnOrSimpleName) {
         if (fqnOrSimpleName == null) return null;
         
@@ -826,9 +845,7 @@ public class CodebaseContext {
         if (classNeighbor.equals(classTarget)) {
             return true;
         }
-        String simpleClassNeighbor = simpleTypeName(classNeighbor);
-        String simpleClassTarget = simpleTypeName(classTarget);
-        if (simpleClassNeighbor.equals(simpleClassTarget)) {
+        if (areSameTypeOrUnambiguousSimpleMatch(classNeighbor, classTarget)) {
             return true;
         }
         return classCompatibilityCache.areClassesCompatible(

state_machine_exporter/src/test/java/click/kamil/springstatemachineexporter/analysis/service/TypeResolverTest.java

@@ -30,4 +30,22 @@ class TypeResolverTest {
         assertThat(resolver.getParameterIndex("com.example.StateMachine.sendEvent", "e")).isEqualTo(-1);
         assertThat(resolver.getParameterIndex("com.example.StateMachine.sendEvent", "payload")).isEqualTo(-1);
     }
+
+    @Test
+    void shouldFailClosedOnAmbiguousSimpleTypeCompatibility(@TempDir Path tempDir) throws Exception {
+        Files.createDirectories(tempDir.resolve("a"));
+        Files.createDirectories(tempDir.resolve("b"));
+        Files.writeString(tempDir.resolve("a/OrderEvent.java"),
+                "package a; public enum OrderEvent { PAY }");
+        Files.writeString(tempDir.resolve("b/OrderEvent.java"),
+                "package b; public enum OrderEvent { SHIP }");
+
+        CodebaseContext context = new CodebaseContext();
+        context.scan(tempDir);
+        TypeResolver resolver = new TypeResolver(context);
+
+        assertThat(resolver.isTypeCompatible("a.OrderEvent", "OrderEvent")).isFalse();
+        assertThat(resolver.isTypeCompatible("a.OrderEvent", "b.OrderEvent")).isFalse();
+        assertThat(resolver.isTypeCompatible("a.OrderEvent", "a.OrderEvent")).isTrue();
+    }
 }

state_machine_exporter/src/test/java/click/kamil/springstatemachineexporter/ast/common/CodebaseContextTest.java

@@ -275,6 +275,22 @@ class CodebaseContextTest {
         assertThat(context.getImplementations("b.Service")).containsExactly("b.BServiceImpl");
     }
 
+    @Test
+    void areSameTypeOrUnambiguousSimpleMatchShouldFailClosedForAmbiguousTypes() throws IOException {
+        Files.createDirectories(tempDir.resolve("a"));
+        Files.createDirectories(tempDir.resolve("b"));
+        Files.writeString(tempDir.resolve("a/Dispatcher.java"),
+                "package a; public class Dispatcher { public void dispatch() {} }");
+        Files.writeString(tempDir.resolve("b/Dispatcher.java"),
+                "package b; public class Dispatcher { public void dispatch() {} }");
+
+        CodebaseContext context = new CodebaseContext();
+        context.scan(tempDir);
+
+        assertThat(context.areSameTypeOrUnambiguousSimpleMatch("a.Dispatcher", "b.Dispatcher")).isFalse();
+        assertThat(context.areClassesPolymorphicallyCompatible("a.Dispatcher", "b.Dispatcher")).isFalse();
+    }
+
     @Test
     void shouldFindClassWithFullyQualifiedAnnotation() throws IOException {
         String source = """