Don't copy static-inherited members that are assigned after the $jsco…

…mp.inherits call.

Because the type checker is not yet aware of static inheritance, this ensures that we get concrete type errors whenever the naive $jscomp.inherits implementation used by IE10 and below will cause problems.

Related to #2708

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175623237

src/com/google/javascript/jscomp/Es6ToEs3ClassSideInheritance.java

@@ -27,10 +27,12 @@
 import com.google.javascript.rhino.Node;
 import com.google.javascript.rhino.Token;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 /**
@@ -132,18 +134,18 @@ public void process(Node externs, Node root) {
     FindStaticMembers findStaticMembers = new FindStaticMembers();
     TranspilationPasses.processTranspile(compiler, externs, findStaticMembers);
     TranspilationPasses.processTranspile(compiler, root, findStaticMembers);
-    processInherits(findStaticMembers.inheritsCalls);
+    processInherits(findStaticMembers);
   }
 
   @Override
   public void hotSwapScript(Node scriptRoot, Node originalRoot) {
     FindStaticMembers findStaticMembers = new FindStaticMembers();
     TranspilationPasses.processTranspile(compiler, scriptRoot, findStaticMembers);
-    processInherits(findStaticMembers.inheritsCalls);
+    processInherits(findStaticMembers);
   }
 
-  private void processInherits(List<Node> inheritsCalls) {
-    for (Node inheritsCall : inheritsCalls) {
+  private void processInherits(FindStaticMembers findStaticMembers) {
+    for (Node inheritsCall : findStaticMembers.inheritsCalls) {
       Node superclassNameNode = inheritsCall.getLastChild();
       String superclassQname = superclassNameNode.getQualifiedName();
       Node subclassNameNode = superclassNameNode.getPrevious();
@@ -157,7 +159,7 @@ private void processInherits(List<Node> inheritsCalls) {
       if (superClass == null || subClass == null) {
         continue;
       }
-      copyStaticMembers(superClass, subClass, inheritsCall);
+      copyStaticMembers(superClass, subClass, inheritsCall, findStaticMembers);
       copyDeclarations(superClass, subClass, inheritsCall);
     }
   }
@@ -205,7 +207,8 @@ private void copyDeclarations(
   }
 
   private void copyStaticMembers(
-      JavascriptClass superClass, JavascriptClass subClass, Node inheritsCall) {
+      JavascriptClass superClass, JavascriptClass subClass, Node inheritsCall,
+      FindStaticMembers findStaticMembers) {
     for (Node staticMember : superClass.staticMembers) {
       checkState(staticMember.isAssign(), staticMember);
       String memberName = staticMember.getFirstChild().getLastChild().getString();
@@ -215,6 +218,13 @@ private void copyStaticMembers(
       if (isOverriden(subClass, memberName)) {
         continue;
       }
+      if (findStaticMembers.isBefore(inheritsCall, staticMember)) {
+        // Don't copy members that are defined after the $jscomp.inherits call,
+        // since they will not work correctly in IE<11, where static inheritance
+        // is done by copying, rather than prototype manipulation.
+        continue;
+      }
+
       JSDocInfoBuilder info = JSDocInfoBuilder.maybeCopyFrom(staticMember.getJSDocInfo());
       Node function = staticMember.getLastChild();
       Node sourceInfoNode = function;
@@ -279,14 +289,18 @@ private boolean isReferenceToClass(NodeTraversal t, Node n) {
   }
 
   private class FindStaticMembers extends AbstractPostOrderCallback {
-    private final List<Node> inheritsCalls = new ArrayList<>();
+    final List<Node> inheritsCalls = new ArrayList<>();
+    // Store the order we find class definitions and static fields.  Copied statics must occur
+    // after both the namespace and the copied property are defined.
+    final Map<Node, Integer> nodeOrder = new HashMap<>();
 
     @Override
     public void visit(NodeTraversal t, Node n, Node parent) {
       switch (n.getToken()) {
         case CALL:
           if (n.getFirstChild().matchesQualifiedName(Es6RewriteClass.INHERITS)) {
             inheritsCalls.add(n);
+            nodeOrder.put(n, nodeOrder.size());
           }
           if (NodeUtil.isObjectDefinePropertiesDefinition(n)) {
             visitDefinedPropertiesCall(t, n);
@@ -359,6 +373,7 @@ private void visitAssign(NodeTraversal t, Node n) {
         Node classNode = getProp.getFirstChild();
         if (isReferenceToClass(t, classNode)) {
           classByAlias.get(classNode.getQualifiedName()).staticMembers.add(n);
+          nodeOrder.put(n, nodeOrder.size());
         }
       }
     }
@@ -376,5 +391,11 @@ private void visitVar(Node n) {
         }
       }
     }
+
+    boolean isBefore(Node earlier, Node later) {
+      Integer earlierPosition = nodeOrder.get(earlier);
+      Integer laterPosition = nodeOrder.get(later);
+      return earlierPosition != null && laterPosition != null && earlierPosition < laterPosition;
+    }
   }
 }

test/com/google/javascript/jscomp/Es6ToEs3ClassSideInheritanceTest.java

@@ -44,6 +44,7 @@ protected int getNumRepetitions() {
   public void testSimple() {
     test(
         lines(
+            // Note: let statement is necessary so that input language is ES6; else pass is skipped.
             "let x = 1;",
             "/** @constructor */",
             "function Example() {}",
@@ -95,6 +96,43 @@ public void testTyped() {
             "Subclass.staticMethod = Example.staticMethod;"));
   }
 
+
+  public void testNestedSubclass() {
+    test(
+        lines(
+            "let x = 1;",
+            "/** @constructor */",
+            "function A() {}",
+            "A.a = 19;",
+            "/** @constructor */",
+            "A.B = function() {};",
+            "/** @constructor @extends {A} */",
+            "A.C = function() {};",
+            "$jscomp.inherits(A.C, A);",
+            "/** @constructor */",
+            "A.D = function() {};",
+            "A.e = 42;"),
+        lines(
+            "let x = 1;",
+            "/** @constructor */",
+            "function A() {}",
+            "A.a = 19;",
+            "/** @constructor */",
+            "A.B = function() {}",
+            "/** @constructor @extends {A} */",
+            "A.C = function() {};",
+            "$jscomp.inherits(A.C, A);",
+            "/** @constructor @extends {A} @suppress {visibility} */",
+            "A.C.C = A.C;",
+            "/** @constructor @suppress {visibility} */",
+            "A.C.B = A.B;",
+            "/** @suppress {visibility} */",
+            "A.C.a = A.a;",
+            "/** @constructor */",
+            "A.D = function() {};",
+            "A.e = 42;"));
+  }
+
   public void testOverride() {
     testSame(
         lines(