Add instances creation

src/main/fr/celticinfo/lox/LoxClass.kt

@@ -1,5 +1,12 @@
 package fr.celticinfo.lox
 
-class LoxClass(val name: String) {
+class LoxClass(private val name: String) : LoxCallable {
+    override fun call(interpreter: Interpreter, arguments: List<Any?>): Any? {
+        val instance = LoxInstance(this)
+        return instance
+    }
+
+    override fun arity() = 0
+
     override fun toString() = name
 }

src/main/fr/celticinfo/lox/LoxInstance.kt

@@ -0,0 +1,5 @@
+package fr.celticinfo.lox
+
+class LoxInstance(private val klass: LoxClass) {
+    override fun toString() = "$klass instance"
+}

src/test/fr/celticinfo/lox/InterpreterTest.kt

@@ -805,4 +805,36 @@ var a = "global";
             System.setOut(standardOut)
         }
     }
+
+    @Test
+    fun `valid code with class declaration and instantiation`() {
+        val standardOut = System.out
+        val outputStreamCaptor = ByteArrayOutputStream()
+
+        System.setOut(PrintStream(outputStreamCaptor))
+
+        try {
+            val code = """
+                class DevonshireCream {}                       
+                var cream = DevonshireCream();
+                print cream;
+            """.trimIndent()
+            val scanner = Scanner(code)
+            val tokens = scanner.scanTokens()
+            val parser = Parser(tokens)
+            val statements = parser.parse()
+            assertEquals(3, statements.size)
+
+            val interpreter = Interpreter()
+
+            val resolver = Resolver(interpreter)
+            resolver.resolve(statements)
+
+            interpreter.interpret(statements)
+            val output = outputStreamCaptor.toString().trim()
+            assertEquals("DevonshireCream instance", output)
+        } finally {
+            System.setOut(standardOut)
+        }
+    }
 }

src/test/fr/celticinfo/lox/ParserTest.kt

@@ -254,4 +254,20 @@ class ParserTest {
         val stmt = statements[0]
         assertTrue(stmt is ClassStmt)
     }
+
+    @Test
+    fun `valid code with class instantiation`() {
+        val code = """
+            class DevonshireCream {}                       
+            var cream = DevonshireCream();
+            print cream;
+        """.trimIndent()
+        val scanner = Scanner(code)
+        val tokens = scanner.scanTokens()
+        val parser = Parser(tokens)
+        val statements = parser.parse()
+        assertEquals(3,statements.size)
+        val stmt = statements[1]
+        assertTrue(stmt is Var)
+    }
 }