Prepare TypedScopeCreator to work with ES6 block scopes.

1. Split the `scope` field in TypedScopeCreator.AbstractScopeBuilder into `currentScope` and `currentHoistScope`.  These currently point to the same object, so no behavior change is expected.
2. Declare qualified names on their owner's scope: this is a slight behavior change that improves type inference.  It's included in this change because with the introduction of block scopes, the question of which scope to declare a qualified name on is becoming more nuanced, so it helps to start by making the behavior more consistent.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=191386776

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

@@ -90,6 +90,7 @@ final class FunctionTypeBuilder {
   // TODO(johnlenz): verify we want both template and class template lists instead of a unified
   // list.
   private ImmutableList<TemplateType> classTemplateTypeNames = ImmutableList.of();
+  private TypedScope declarationScope = null;
 
   static final DiagnosticType EXTENDS_WITHOUT_TYPEDEF = DiagnosticType.warning(
       "JSC_EXTENDS_WITHOUT_TYPEDEF",
@@ -246,6 +247,16 @@ FunctionTypeBuilder setContents(@Nullable FunctionContents contents) {
     return this;
   }
 
+  /**
+   * Sets a declaration scope explicitly. This is important with block scopes because a function
+   * declared in an inner scope with 'var' needs to use the inner scope to resolve names, but needs
+   * to be declared in the outer scope.
+   */
+  FunctionTypeBuilder setDeclarationScope(TypedScope declarationScope) {
+    this.declarationScope = declarationScope;
+    return this;
+  }
+
   /**
    * Infer the parameter and return types of a function from
    * the parameter and return types of the function it is overriding.
@@ -876,6 +887,10 @@ static boolean isFunctionTypeDeclaration(JSDocInfo info) {
    * care of most scope-declaring.
    */
   private TypedScope getScopeDeclaredIn() {
+    if (declarationScope != null) {
+      return declarationScope;
+    }
+
     int dotIndex = fnName.indexOf('.');
     if (dotIndex != -1) {
       String rootVarName = fnName.substring(0, dotIndex);

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

@@ -5133,6 +5133,27 @@ static String getBestLValueName(@Nullable Node lValue) {
     return lValue.getQualifiedName();
   }
 
+  /** Gets the root of a qualified name l-value. */
+  static Node getBestLValueRoot(@Nullable Node lValue) {
+    if (lValue == null) {
+      return null;
+    }
+    switch (lValue.getToken()) {
+      case STRING_KEY:
+        // NOTE: beware of getBestLValue returning null (or be null-permissive?)
+        return getBestLValueRoot(NodeUtil.getBestLValue(lValue.getParent()));
+      case GETPROP:
+      case GETELEM:
+        return getBestLValueRoot(lValue.getFirstChild());
+      case THIS:
+      case SUPER:
+      case NAME:
+        return lValue;
+      default:
+        return null;
+    }
+  }
+
   /**
    * @return true iff the result of the expression is consumed.
    */