diff --git a/tests/baselines/reference/classDoesNotDependOnBaseTypes.js b/tests/baselines/reference/classDoesNotDependOnBaseTypes.js
new file mode 100644
index 00000000000..a62d5b1532b
--- /dev/null
+++ b/tests/baselines/reference/classDoesNotDependOnBaseTypes.js
@@ -0,0 +1,38 @@
+//// [classDoesNotDependOnBaseTypes.ts]
+var x: StringTree;
+if (typeof x !== "string") {
+    x[0] = "";
+    x[0] = new StringTreeCollection;
+}
+
+type StringTree = string | StringTreeCollection;
+class StringTreeCollectionBase {
+    [n: number]: StringTree;
+}
+
+class StringTreeCollection extends StringTreeCollectionBase { }
+
+//// [classDoesNotDependOnBaseTypes.js]
+var __extends = this.__extends || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    __.prototype = b.prototype;
+    d.prototype = new __();
+};
+var x;
+if (typeof x !== "string") {
+    x[0] = "";
+    x[0] = new StringTreeCollection;
+}
+var StringTreeCollectionBase = (function () {
+    function StringTreeCollectionBase() {
+    }
+    return StringTreeCollectionBase;
+})();
+var StringTreeCollection = (function (_super) {
+    __extends(StringTreeCollection, _super);
+    function StringTreeCollection() {
+        _super.apply(this, arguments);
+    }
+    return StringTreeCollection;
+})(StringTreeCollectionBase);
diff --git a/tests/baselines/reference/classDoesNotDependOnBaseTypes.types b/tests/baselines/reference/classDoesNotDependOnBaseTypes.types
new file mode 100644
index 00000000000..c342f0ea002
--- /dev/null
+++ b/tests/baselines/reference/classDoesNotDependOnBaseTypes.types
@@ -0,0 +1,43 @@
+=== tests/cases/conformance/types/typeAliases/classDoesNotDependOnBaseTypes.ts ===
+var x: StringTree;
+>x : string | StringTreeCollection
+>StringTree : string | StringTreeCollection
+
+if (typeof x !== "string") {
+>typeof x !== "string" : boolean
+>typeof x : string
+>x : string | StringTreeCollection
+>"string" : string
+
+    x[0] = "";
+>x[0] = "" : string
+>x[0] : string | StringTreeCollection
+>x : StringTreeCollection
+>0 : number
+>"" : string
+
+    x[0] = new StringTreeCollection;
+>x[0] = new StringTreeCollection : StringTreeCollection
+>x[0] : string | StringTreeCollection
+>x : StringTreeCollection
+>0 : number
+>new StringTreeCollection : StringTreeCollection
+>StringTreeCollection : typeof StringTreeCollection
+}
+
+type StringTree = string | StringTreeCollection;
+>StringTree : string | StringTreeCollection
+>StringTreeCollection : StringTreeCollection
+
+class StringTreeCollectionBase {
+>StringTreeCollectionBase : StringTreeCollectionBase
+
+    [n: number]: StringTree;
+>n : number
+>StringTree : string | StringTreeCollection
+}
+
+class StringTreeCollection extends StringTreeCollectionBase { }
+>StringTreeCollection : StringTreeCollection
+>StringTreeCollectionBase : StringTreeCollectionBase
+
diff --git a/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.js b/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.js
new file mode 100644
index 00000000000..4d8a23ddd25
--- /dev/null
+++ b/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.js
@@ -0,0 +1,16 @@
+//// [interfaceDoesNotDependOnBaseTypes.ts]
+var x: StringTree;
+if (typeof x !== "string") {
+    x.push("");
+    x.push([""]);
+}
+
+type StringTree = string | StringTreeArray;
+interface StringTreeArray extends Array<StringTree> { }
+
+//// [interfaceDoesNotDependOnBaseTypes.js]
+var x;
+if (typeof x !== "string") {
+    x.push("");
+    x.push([""]);
+}
diff --git a/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.types b/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.types
new file mode 100644
index 00000000000..7b5d60a5261
--- /dev/null
+++ b/tests/baselines/reference/interfaceDoesNotDependOnBaseTypes.types
@@ -0,0 +1,36 @@
+=== tests/cases/conformance/types/typeAliases/interfaceDoesNotDependOnBaseTypes.ts ===
+var x: StringTree;
+>x : string | StringTreeArray
+>StringTree : string | StringTreeArray
+
+if (typeof x !== "string") {
+>typeof x !== "string" : boolean
+>typeof x : string
+>x : string | StringTreeArray
+>"string" : string
+
+    x.push("");
+>x.push("") : number
+>x.push : (...items: (string | StringTreeArray)[]) => number
+>x : StringTreeArray
+>push : (...items: (string | StringTreeArray)[]) => number
+>"" : string
+
+    x.push([""]);
+>x.push([""]) : number
+>x.push : (...items: (string | StringTreeArray)[]) => number
+>x : StringTreeArray
+>push : (...items: (string | StringTreeArray)[]) => number
+>[""] : string[]
+>"" : string
+}
+
+type StringTree = string | StringTreeArray;
+>StringTree : string | StringTreeArray
+>StringTreeArray : StringTreeArray
+
+interface StringTreeArray extends Array<StringTree> { }
+>StringTreeArray : StringTreeArray
+>Array : T[]
+>StringTree : string | StringTreeArray
+
diff --git a/tests/cases/conformance/types/typeAliases/classDoesNotDependOnBaseTypes.ts b/tests/cases/conformance/types/typeAliases/classDoesNotDependOnBaseTypes.ts
new file mode 100644
index 00000000000..98f94718f30
--- /dev/null
+++ b/tests/cases/conformance/types/typeAliases/classDoesNotDependOnBaseTypes.ts
@@ -0,0 +1,12 @@
+var x: StringTree;
+if (typeof x !== "string") {
+    x[0] = "";
+    x[0] = new StringTreeCollection;
+}
+
+type StringTree = string | StringTreeCollection;
+class StringTreeCollectionBase {
+    [n: number]: StringTree;
+}
+
+class StringTreeCollection extends StringTreeCollectionBase { }
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeAliases/interfaceDoesNotDependOnBaseTypes.ts b/tests/cases/conformance/types/typeAliases/interfaceDoesNotDependOnBaseTypes.ts
new file mode 100644
index 00000000000..4e380e96b37
--- /dev/null
+++ b/tests/cases/conformance/types/typeAliases/interfaceDoesNotDependOnBaseTypes.ts
@@ -0,0 +1,8 @@
+var x: StringTree;
+if (typeof x !== "string") {
+    x.push("");
+    x.push([""]);
+}
+
+type StringTree = string | StringTreeArray;
+interface StringTreeArray extends Array<StringTree> { }
\ No newline at end of file