Improve map key's evaluator

app/src/main/kotlin/io/smnp/evaluation/evaluator/MapEvaluator.kt

@@ -1,22 +1,39 @@
 package io.smnp.evaluation.evaluator
 
+import io.smnp.dsl.ast.model.node.IdentifierNode
 import io.smnp.dsl.ast.model.node.MapEntryNode
 import io.smnp.dsl.ast.model.node.MapNode
 import io.smnp.dsl.ast.model.node.Node
 import io.smnp.environment.Environment
+import io.smnp.error.EvaluationException
 import io.smnp.evaluation.model.entity.EvaluatorOutput
+import io.smnp.type.enumeration.DataType.*
 import io.smnp.type.model.Value
 
 class MapEvaluator : Evaluator() {
+    private val evaluator = ExpressionEvaluator()
+
     override fun supportedNodes() = listOf(MapNode::class)
 
     override fun tryToEvaluate(node: Node, environment: Environment): EvaluatorOutput {
-        val atomEvaluator = ExpressionEvaluator()
         val value = (node as MapNode).items
             .map { it as MapEntryNode }
-            .map { atomEvaluator.evaluate(it.key, environment).value!! to atomEvaluator.evaluate(it.value, environment).value!! }
+            .map { getKey(it.key, environment) to evaluator.evaluate(it.value, environment).value!! }
             .toMap()
 
         return EvaluatorOutput.value(Value.map(value))
     }
+
+    private fun getKey(keyNode: Node, environment: Environment): Value {
+        val key = when(keyNode) {
+            is IdentifierNode -> Value.string(keyNode.token.rawValue)
+            else -> evaluator.evaluate(keyNode, environment).value!!
+        }
+
+        if(key.type !in listOf(BOOL, INT, NOTE, STRING)) {
+            throw EvaluationException("Invalid map key's type ${key.type.name.toLowerCase()}", keyNode.position)
+        }
+
+        return key
+    }
 }