Do not emit code for @extends tags in JS.

src/compiler/transformers/es2015.ts

@@ -780,7 +780,7 @@ namespace ts {
                 enableSubstitutionsForBlockScopedBindings();
             }
 
-            const extendsClauseElement = getEffectiveBaseTypeNode(node);
+            const extendsClauseElement = getClassExtendsHeritageElement(node);
             const classFunction = createFunctionExpression(
                 /*modifiers*/ undefined,
                 /*asteriskToken*/ undefined,

tests/baselines/reference/extendsJavaScript.js

@@ -0,0 +1,18 @@
+//// [extendsJavaScript.js]
+/**
+ * @extends {SomeBase}
+ */
+class MyClass {
+
+}
+
+
+//// [extendsJavaScript.js]
+/**
+ * @extends {SomeBase}
+ */
+var MyClass = /** @class */ (function () {
+    function MyClass() {
+    }
+    return MyClass;
+}());

tests/baselines/reference/extendsJavaScript.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/extendsJavaScript.js ===
+/**
+ * @extends {SomeBase}
+ */
+class MyClass {
+>MyClass : Symbol(MyClass, Decl(extendsJavaScript.js, 0, 0))
+
+}
+

tests/baselines/reference/extendsJavaScript.types

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/extendsJavaScript.js ===
+/**
+ * @extends {SomeBase}
+ */
+class MyClass {
+>MyClass : MyClass
+
+}
+

tests/cases/compiler/extendsJavaScript.ts

@@ -0,0 +1,11 @@
+// @allowJs: true
+// @checkJs: false
+// @outDir: ./out
+// @filename: extendsJavaScript.js
+
+/**
+ * @extends {SomeBase}
+ */
+class MyClass {
+
+}