Throw exception if getting value of variable out of scope

2 files changed, 16 insertions, 2 deletions

diff --git a/src/main/java/org/zwobble/couscous/interpreter/Environment.java b/src/main/java/org/zwobble/couscous/interpreter/Environment.java
index 5985a94..d748654 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Environment.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Environment.java
@@ -18,8 +18,9 @@ public class Environment {
         this.stackFrame = new HashMap<>(stackFrame);
     }
 
-    public InterpreterValue get(int referentId) {
-        return stackFrame.get(referentId).get();
+    public InterpreterValue get(int variableId) {
+        checkVariable(variableId);
+        return stackFrame.get(variableId).get();
     }
 
     public void put(int variableId, InterpreterValue value) {
diff --git a/src/test/java/org/zwobble/couscous/tests/interpreter/InterpreterTests.java b/src/test/java/org/zwobble/couscous/tests/interpreter/InterpreterTests.java
index 66a1f8b..58a1b6b 100644
--- a/src/test/java/org/zwobble/couscous/tests/interpreter/InterpreterTests.java
+++ b/src/test/java/org/zwobble/couscous/tests/interpreter/InterpreterTests.java
@@ -117,6 +117,19 @@ public class InterpreterTests {
         
         assertEquals(new VariableNotInScope(42), exception);
     }
+    
+    @Test
+    public void errorIfTryingToGetValueOfVariableNotInScope() {
+        val localVariableDeclaration = localVariableDeclaration(
+            42, StringValue.REF, "x", literal(""));
+        val method = staticMethod("hello")
+            .statement(new ReturnNode(reference(localVariableDeclaration)));
+
+        val exception = assertThrows(VariableNotInScope.class,
+            () -> runMethod(method));
+        
+        assertEquals(new VariableNotInScope(42), exception);
+    }
 
     private InterpreterValue runMethod(MethodNode.MethodNodeBuilder methodBuilder, InterpreterValue... arguments) {
         val method = methodBuilder.build();