Put type checking in one place

4 files changed, 21 insertions, 13 deletions

diff --git a/src/main/java/org/zwobble/couscous/interpreter/Environment.java b/src/main/java/org/zwobble/couscous/interpreter/Environment.java
index 0bbc808..d91664d 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/Environment.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/Environment.java
@@ -72,10 +72,7 @@ public class Environment {
 
     private void checkVariableType(int variableId, InterpreterValue value) {
         val variableType = stackFrame.get(variableId).getType();
-        val valueType = value.getType().getName();
-        if (!variableType.equals(valueType)) {
-            throw new UnexpectedValueType(variableType, valueType);
-        }
+        InterpreterTypes.checkIsInstance(variableType, value);
     }
     
     @AllArgsConstructor(staticName="of")
diff --git a/src/main/java/org/zwobble/couscous/interpreter/InterpreterTypes.java b/src/main/java/org/zwobble/couscous/interpreter/InterpreterTypes.java
new file mode 100644
index 0000000..cc66cb6
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/interpreter/InterpreterTypes.java
@@ -0,0 +1,16 @@
+package org.zwobble.couscous.interpreter;
+
+import org.zwobble.couscous.ast.TypeName;
+import org.zwobble.couscous.interpreter.values.InterpreterValue;
+
+public class InterpreterTypes {
+    public static void checkIsInstance(TypeName type, InterpreterValue value) {
+        checkIsSubType(type, value.getType().getName());
+    }
+
+    private static void checkIsSubType(TypeName superType, TypeName subType) {
+        if (!superType.equals(subType)) {
+            throw new UnexpectedValueType(superType, subType);
+        }
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/ConcreteType.java b/src/main/java/org/zwobble/couscous/interpreter/values/ConcreteType.java
index 93dd651..6332b89 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/values/ConcreteType.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/ConcreteType.java
@@ -11,9 +11,9 @@ import org.zwobble.couscous.ast.FormalArgumentNode;
 import org.zwobble.couscous.ast.TypeName;
 import org.zwobble.couscous.interpreter.Environment;
 import org.zwobble.couscous.interpreter.Executor;
+import org.zwobble.couscous.interpreter.InterpreterTypes;
 import org.zwobble.couscous.interpreter.NoSuchMethod;
 import org.zwobble.couscous.interpreter.PositionalArguments;
-import org.zwobble.couscous.interpreter.UnexpectedValueType;
 import org.zwobble.couscous.interpreter.WrongNumberOfArguments;
 import org.zwobble.couscous.util.Casts;
 
@@ -208,10 +208,7 @@ public class ConcreteType {
         
         for (int index = 0; index < arguments.size(); index++) {
             val formalArgumentType = method.getArgumentTypes().get(index);
-            val actualArgumentType = arguments.get(index).getType();
-            if (!formalArgumentType.equals(actualArgumentType.getName())) {
-                throw new UnexpectedValueType(formalArgumentType, actualArgumentType.getName());
-            }
+            InterpreterTypes.checkIsInstance(formalArgumentType, arguments.get(index));
         }
     }
     
diff --git a/src/main/java/org/zwobble/couscous/interpreter/values/ObjectInterpreterValue.java b/src/main/java/org/zwobble/couscous/interpreter/values/ObjectInterpreterValue.java
index f0ecbd1..6e653d2 100644
--- a/src/main/java/org/zwobble/couscous/interpreter/values/ObjectInterpreterValue.java
+++ b/src/main/java/org/zwobble/couscous/interpreter/values/ObjectInterpreterValue.java
@@ -4,8 +4,8 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Optional;
 
+import org.zwobble.couscous.interpreter.InterpreterTypes;
 import org.zwobble.couscous.interpreter.NoSuchField;
-import org.zwobble.couscous.interpreter.UnexpectedValueType;
 import org.zwobble.couscous.values.PrimitiveValue;
 
 import lombok.val;
@@ -40,9 +40,7 @@ public class ObjectInterpreterValue implements InterpreterValue {
 
     public void setField(String fieldName, InterpreterValue value) {
         val field = type.getField(fieldName).orElseThrow(() -> new NoSuchField(fieldName));
-        if (!field.getType().equals(value.getType().getName())) {
-            throw new UnexpectedValueType(field.getType(), value.getType().getName());
-        }
+        InterpreterTypes.checkIsInstance(field.getType(), value);
         fields.put(fieldName, value);   
     }
 }