Better diagnostics if an attempt is made to redeclare a type under the same name

as an existing type in that scope. Support for anonymous struct/unions.

Change-Id: I0122cfae4da848419956c7b27bacaca66f8021d5
Bug: 30896059
diff --git a/Scope.cpp b/Scope.cpp
index abad31d..0e21c8e 100644
--- a/Scope.cpp
+++ b/Scope.cpp
@@ -12,6 +12,10 @@
 
 bool Scope::addType(const char *localName, NamedType *type) {
     if (mTypeIndexByName.indexOfKey(localName) >= 0) {
+        fprintf(stderr,
+                "A type named '%s' is already declared in the current scope.\n",
+                localName);
+
         return false;
     }
 
@@ -67,6 +71,18 @@
     return false;
 }
 
+std::string Scope::pickUniqueAnonymousName() const {
+    static size_t sNextID = 0;
+
+    for (;;) {
+        std::string anonName = "_hidl_Anon_" + std::to_string(sNextID++);
+
+        if (mTypeIndexByName.indexOfKey(anonName) < 0) {
+            return anonName;
+        }
+    }
+}
+
 std::string Scope::getJavaType() const {
     CHECK(!"Should not be here");
     return std::string();