Make the Control Flow Graph of a class never traverse inside the clas…

…s and instead create a directed edge with the code below it.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=158529934

src/com/google/javascript/jscomp/ControlFlowAnalysis.java

@@ -77,7 +77,7 @@ public int compare(
   private int astPositionCounter;
   private int priorityCounter;
 
-  private final boolean shouldTraverseFunctionsAndClasses;
+  private final boolean shouldTraverseFunctions;
   private final boolean edgeAnnotations;
 
   // We need to store where we started, in case we aren't doing a flow analysis
@@ -130,10 +130,10 @@ public int compare(
    * @param shouldTraverseFunctions Whether functions should be traversed
    * @param edgeAnnotations Whether to allow edge annotations.
    */
-  ControlFlowAnalysis(AbstractCompiler compiler,
-      boolean shouldTraverseFunctionsAndClasses, boolean edgeAnnotations) {
+  ControlFlowAnalysis(
+      AbstractCompiler compiler, boolean shouldTraverseFunctions, boolean edgeAnnotations) {
     this.compiler = compiler;
-    this.shouldTraverseFunctionsAndClasses = shouldTraverseFunctionsAndClasses;
+    this.shouldTraverseFunctions = shouldTraverseFunctions;
     this.edgeAnnotations = edgeAnnotations;
   }
 
@@ -159,7 +159,7 @@ public void process(Node externs, Node root) {
     DiGraphNode<Node, Branch> entry = cfg.getEntry();
     prioritizeFromEntryNode(entry);
 
-    if (shouldTraverseFunctionsAndClasses) {
+    if (shouldTraverseFunctions) {
       // If we're traversing inner functions, we need to rank the
       // priority of them too.
       for (DiGraphNode<Node, Branch> candidate : cfg.getDirectedGraphNodes()) {
@@ -213,9 +213,10 @@ public boolean shouldTraverse(
 
     switch (n.getToken()) {
       case CLASS:
-        return shouldTraverseFunctionsAndClasses;
+        createEdge(n, Branch.UNCOND, n.getNext());
+        return false;
       case FUNCTION:
-        if (shouldTraverseFunctionsAndClasses || n == cfg.getEntry().getValue()) {
+        if (shouldTraverseFunctions || n == cfg.getEntry().getValue()) {
           exceptionHandler.push(n);
           return true;
         }

test/com/google/javascript/jscomp/CheckUnreachableCodeTest.java

@@ -311,9 +311,14 @@ public void testClass() {
     assertUnreachable("var C = class{func(){if (true){return;} x = 1;}}");
   }
 
-  // TODO(tbreisacher): This should not produce a warning.
-  public void testClass_incorrect() {
-    assertUnreachable("class C {} alert(1);");
+  public void testUnderClass() {
+    testSame("class C {} alert(1);");
+    testSame("class D {} class C extends D {} alert(1)");
+    testSame("class D{} alert(1); class C extends D {}");
+  }
+
+  public void testFunction() {
+    testSame("function f() {} alert(1);");
   }
 
   public void testSubclass() {

test/com/google/javascript/jscomp/ControlFlowAnalysisTest.java

@@ -827,6 +827,36 @@ public void testSimpleFunction() {
     testCfg(src, expected);
   }
 
+  public void testSimpleClass() {
+    String src = "class C{} f();";
+    String expected =
+        "digraph AST {\n"
+            + "  node [color=lightblue2, style=filled];\n"
+            + "  node0 [label=\"SCRIPT\"];\n"
+            + "  node1 [label=\"CLASS\"];\n"
+            + "  node0 -> node1 [weight=1];\n"
+            + "  node2 [label=\"NAME\"];\n"
+            + "  node1 -> node2 [weight=1];\n"
+            + "  node3 [label=\"EMPTY\"];\n"
+            + "  node1 -> node3 [weight=1];\n"
+            + "  node4 [label=\"CLASS_MEMBERS\"];\n"
+            + "  node1 -> node4 [weight=1];\n"
+            + "  node5 [label=\"EXPR_RESULT\"];\n"
+            + "  node1 -> node5 "
+            + "[label=\"UNCOND\", fontcolor=\"red\", weight=0.01, color=\"red\"];\n"
+            + "  node0 -> node5 [weight=1];\n"
+            + "  node6 [label=\"CALL\"];\n"
+            + "  node5 -> node6 [weight=1];\n"
+            + "  node7 [label=\"NAME\"];\n"
+            + "  node6 -> node7 [weight=1];\n"
+            + "  node5 -> RETURN "
+            + "[label=\"UNCOND\", fontcolor=\"red\", weight=0.01, color=\"red\"];\n"
+            + "  node0 -> node1 "
+            + "[label=\"UNCOND\", fontcolor=\"red\", weight=0.01, color=\"red\"];\n"
+            + "}\n";
+    testCfg(src, expected);
+  }
+
   public void testSimpleCatch() {
     String src = "try{ throw x; x(); x['stuff']; x.x; x} catch (e) { e() }";
     String expected = "digraph AST {\n"