fix: Fix bug in ReferenceType equality check

fixes #1383

src/lib/models/types/reference.ts

@@ -92,7 +92,9 @@ export class ReferenceType extends Type {
         return (
             other instanceof ReferenceType &&
             (other.symbolFullyQualifiedName === this.symbolFullyQualifiedName ||
-                other.reflection === this.reflection)
+                (other.reflection === this.reflection &&
+                    other.reflection != null &&
+                    this.reflection != null))
         );
     }
 

src/test/models/types/reference.test.ts

@@ -0,0 +1,44 @@
+import { deepStrictEqual as equal } from "assert";
+import { ReflectionKind } from "../../../lib/models";
+import { DeclarationReflection } from "../../../lib/models/reflections/declaration";
+import { ReferenceType } from "../../../lib/models/types/reference";
+
+describe("Reference Type", () => {
+    describe("equals", () => {
+        it("types with same symbolFullyQualifiedName are equal", () => {
+            const type1 = new ReferenceType("Type", "Type");
+            const type2 = new ReferenceType("Type", "Type");
+
+            equal(type1.equals(type2), true);
+        });
+
+        it("types with different symbolFullyQualifiedName are not equal", () => {
+            const type1 = new ReferenceType("Type1", "Type1");
+            const type2 = new ReferenceType("Type2", "Type2");
+
+            equal(type1.equals(type2), false);
+        });
+
+        it("types with different symbolFullyQualifiedName but same reflection are equal", () => {
+            const reflection = new DeclarationReflection(
+                "declaration",
+                ReflectionKind.Function
+            );
+            const type1 = new ReferenceType("Type1", "Type1", reflection);
+            const type2 = new ReferenceType("Type2", "Type2", reflection);
+
+            equal(type1.equals(type2), true);
+        });
+
+        it("types with different symbolFullyQualifiedName but different reflection (one is undefined) are equal", () => {
+            const reflection = new DeclarationReflection(
+                "declaration",
+                ReflectionKind.Function
+            );
+            const type1 = new ReferenceType("Type1", "Type1", reflection);
+            const type2 = new ReferenceType("Type2", "Type2", undefined);
+
+            equal(type1.equals(type2), false);
+        });
+    });
+});