Add check for missing interface methods, fixes #423

resources/bytecode/javFiles/Bug423.jav

@@ -0,0 +1,5 @@
+import java.lang.Integer;
+
+interface Bug423I { Integer f(); }
+
+public class Bug423 implements Bug423I { }

resources/bytecode/javFiles/Interfaces.jav

@@ -15,6 +15,7 @@ interface C {
 }
 
 class ClassX implements A {
+    void method1() {}
 }
 
 record ClassY(Integer myInt) implements C {}

src/main/java/de/dhbwstuttgart/bytecode/Codegen.java

@@ -1846,6 +1846,35 @@ public class Codegen {
         clazz.constructors().forEach(this::generateConstructor);
         clazz.methods().forEach(this::generateMethod);
 
+        // Check if non abstract class implements all interface methods
+        if ((access & ACC_ABSTRACT) == 0) {
+            for (var intf : clazz.implementingInterfaces()) {
+                var intfClass = compiler.getClass(new JavaClassName(intf.name()));
+                for (var method : intfClass.getMethods()) {
+                    if ((method.modifier & ACC_ABSTRACT) != 0) {
+                        // Check if the method is implemented in the current class
+                        // TODO This is duplicate code, we should probably refactor instances of this pattern
+                        var foundMethods = clazz.methods().stream().filter(m -> {
+                            if (!m.name().equals(method.name)) return false;
+                            if (m.signature().parameters().size() != method.getParameterList().getFormalparalist().size())
+                                return false;
+                            for (var i = 0; i < m.signature().parameters().size(); i++) {
+                                var param1 = m.signature().parameters().get(i).pattern().type();
+                                var param2 = converter.convert(
+                                    method.getParameterList().getParameterAt(i).getType(),
+                                    ASTToTargetAST.Generics.nullGenerics(compiler).javaGenerics());
+                                if (!param1.equals(param2)) return false;
+                            }
+                            return true;
+                        }).toList();
+                        if (foundMethods.size() != 1) {
+                            throw new CodeGenException("Class " + clazz.qualifiedName() + " does not implement method " + method.name + " from interface " + intfClass.getClassName());
+                        }
+                    }
+                }
+            }
+        }
+
         if (clazz.staticConstructor() != null)
             generateStaticConstructor(clazz.staticConstructor());
 

src/test/java/TestComplete.java

@@ -1704,4 +1704,14 @@ public class TestComplete {
         var clazz = classFiles.get("Bug406");
         clazz.getDeclaredMethod("main", List.class).invoke(null, List.of());
     }
+
+    @Test
+    public void testBug423() throws Exception {
+        try {
+            var classFiles = generateClassFiles(createClassLoader(), "Bug423.jav");
+            fail("No exception thrown!");
+        } catch (CodeGenException e) {
+            assertEquals("Class Bug423 does not implement method f from interface Bug423I", e.getMessage());
+        }
+    }
 }