Do not emit code for @extends tags in JS.

When transpiling JavaScript, TS3.1+ emits `@extends` tags as code. E.g.

    /** @extends {SuperClass} */
    class SubClass {}

Causes an ES5 emit that references SuperClass:

    /**
    * @extends {SomeBase}
    */
    var SubClass = /** @Class */ (function (_super) {
        __extends(SubClass, _super);
        function SubClass() {
            return _super !== null && _super.apply(this, arguments) || this;
        }
        return SubClass;
    }(SomeBase));

Note the literal references to `SomeBase`.

This appears to be an accidental effect of 0f55566. It refactored
`getEffectiveBaseTypeNode` for type checking, but missed an instance
where it is also used for emit logic. This change fixes the problem by
specifically getting the heritage clauses directly off the AST.

Change-Id: I97bf5728a10598c3076fa7125a49dc0c07d4301c

Author: mprobst

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/project/jsFileCompilationExtendsTag/amd/jsFileCompilationExtendsTag.errors.txt

@@ -0,0 +1,22 @@
+ExtendsTag/tsconfig.json(4,5): error TS5053: Option 'allowJs' cannot be specified with option 'declaration'.
+
+
+==== ExtendsTag/tsconfig.json (1 errors) ====
+    {
+      "compilerOptions": {
+        "out": "test.js",
+        "allowJs": true
+        ~~~~~~~~~
+!!! error TS5053: Option 'allowJs' cannot be specified with option 'declaration'.
+      },
+      "files": [ "extends.js" ]
+    }
+    
+==== ExtendsTag/extends.js (0 errors) ====
+    /**
+     * @extends {SomeBase}
+     */
+    class MyClass {
+    
+    }
+    

tests/baselines/reference/project/jsFileCompilationExtendsTag/amd/jsFileCompilationExtendsTag.json

@@ -0,0 +1,14 @@
+{
+    "scenario": "Check that @extends clauses do not cause code emit in JavaScript compilation",
+    "projectRoot": "tests/cases/projects/jsFileCompilation",
+    "baselineCheck": true,
+    "declaration": false,
+    "project": "ExtendsTag",
+    "resolvedInputFiles": [
+        "lib.es5.d.ts",
+        "ExtendsTag/extends.js"
+    ],
+    "emittedFiles": [
+        "test.js"
+    ]
+}

tests/baselines/reference/project/jsFileCompilationExtendsTag/amd/test.d.ts

@@ -0,0 +1,8 @@
+/**
+ * @extends {SomeBase}
+ */
+var MyClass = /** @class */ (function () {
+    function MyClass() {
+    }
+    return MyClass;
+}());

tests/baselines/reference/project/jsFileCompilationExtendsTag/amd/test.js

@@ -0,0 +1,22 @@
+ExtendsTag/tsconfig.json(3,5): error TS6082: Only 'amd' and 'system' modules are supported alongside --out.
+
+
+==== ExtendsTag/tsconfig.json (1 errors) ====
+    {
+      "compilerOptions": {
+        "out": "test.js",
+        ~~~~~
+!!! error TS6082: Only 'amd' and 'system' modules are supported alongside --out.
+        "allowJs": true
+      },
+      "files": [ "extends.js" ]
+    }
+    
+==== ExtendsTag/extends.js (0 errors) ====
+    /**
+     * @extends {SomeBase}
+     */
+    class MyClass {
+    
+    }
+    

tests/baselines/reference/project/jsFileCompilationExtendsTag/node/jsFileCompilationExtendsTag.errors.txt

@@ -0,0 +1,14 @@
+{
+    "scenario": "Check that @extends clauses do not cause code emit in JavaScript compilation",
+    "projectRoot": "tests/cases/projects/jsFileCompilation",
+    "baselineCheck": true,
+    "declaration": false,
+    "project": "ExtendsTag",
+    "resolvedInputFiles": [
+        "lib.es5.d.ts",
+        "ExtendsTag/extends.js"
+    ],
+    "emittedFiles": [
+        "test.js"
+    ]
+}

tests/baselines/reference/project/jsFileCompilationExtendsTag/node/jsFileCompilationExtendsTag.json

@@ -0,0 +1,8 @@
+/**
+ * @extends {SomeBase}
+ */
+var MyClass = /** @class */ (function () {
+    function MyClass() {
+    }
+    return MyClass;
+}());

tests/baselines/reference/project/jsFileCompilationExtendsTag/node/test.d.ts

@@ -0,0 +1,7 @@
+{
+  "scenario": "Check that @extends clauses do not cause code emit in JavaScript compilation",
+  "projectRoot": "tests/cases/projects/jsFileCompilation",
+  "baselineCheck": true,
+  "declaration": false,
+  "project": "ExtendsTag"
+}

tests/baselines/reference/project/jsFileCompilationExtendsTag/node/test.js

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "out": "test.js",
+    "allowJs": true
+  },
+  "files": [ "extends.js" ]
+}