small adjustments and test case

Author: dibyendumajumdar

types/src/main/java/com/compilerprogramming/ezlang/types/EZType.java

@@ -52,13 +52,18 @@ public String toString() {
     }
     public String name() { return name; }
 
+    /**
+     * Can we assign a value of other type to a var of this type?
+     */
     public boolean isAssignable(EZType other) {
         if (other == null || other instanceof EZTypeVoid || other instanceof EZTypeUnknown)
             return false;
         if (this == other || equals(other)) return true;
         if (this instanceof EZTypeNullable nullable) {
+            // if this is Nullable and other is null then okay
             if (other instanceof EZTypeNull)
                 return true;
+            // if this is Nullable and other is compatible with base type then okay
             return nullable.baseType.isAssignable(other);
         }
         else if (other instanceof EZTypeNullable nullable) {

types/src/main/java/com/compilerprogramming/ezlang/types/TypeDictionary.java

@@ -2,7 +2,7 @@
 
 import com.compilerprogramming.ezlang.exceptions.CompilerException;
 
-public class TypeDictionary extends Scope {
+public final class TypeDictionary extends Scope {
     public final EZType.EZTypeUnknown UNKNOWN;
     public final EZType.EZTypeInteger INT;
     public final EZType.EZTypeNull NULL;

types/src/test/java/com/compilerprogramming/ezlang/types/TestTypes.java

@@ -1,5 +1,8 @@
 package com.compilerprogramming.ezlang.types;
 
+import org.junit.Assert;
+import org.junit.Test;
+
 public class TestTypes {
 
     EZType buildStruct1(TypeDictionary typeDictionary) {
@@ -18,4 +21,34 @@ EZType buildStruct2(TypeDictionary typeDictionary) {
         return typeDictionary.intern(s);
     }
 
+    @Test
+    public void testTypes() {
+        var typeDict = new TypeDictionary();
+
+        var tint = typeDict.INT;
+        Assert.assertTrue(tint.isPrimitive());
+
+        var s1 = buildStruct1(typeDict);
+        var s2 = buildStruct2(typeDict);
+
+        var s1Type = typeDict.localLookup("S1").type;
+        var s2Type = typeDict.localLookup("S2").type;
+
+        Assert.assertTrue(s1.isAssignable(s1Type));
+        Assert.assertFalse(tint.isAssignable(s1Type));
+        Assert.assertFalse(s1.isAssignable(s2Type));
+
+        Assert.assertTrue(s2.isAssignable(s2Type));
+        Assert.assertFalse(s2.isAssignable(s1Type));
+
+        var s1TypeDup = buildStruct1(typeDict);
+        Assert.assertSame(s1Type, s1TypeDup);
+
+        var nullType = typeDict.NULL;
+        var nullableS1Type = typeDict.merge(s1Type,nullType);
+        Assert.assertTrue(nullableS1Type.isAssignable(nullType));
+        Assert.assertTrue(nullableS1Type.isAssignable(s1Type));
+        Assert.assertFalse(nullableS1Type.isAssignable(s2Type));
+    }
+
 }