[index] Fix forward declarations interfering with USR generation of external source symbols

Patch by Nathan Hawes.
https://reviews.llvm.org/D33346

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@303484 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index f6f8169261..81cd1cc426 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -407,6 +407,27 @@ bool Decl::isExported() const {
   return false;
 }
 
+ExternalSourceSymbolAttr *Decl::getExternalSourceSymbolAttr() const {
+  const Decl *Definition = nullptr;
+  if (auto ID = dyn_cast<ObjCInterfaceDecl>(this)) {
+    Definition = ID->getDefinition();
+  } else if (auto PD = dyn_cast<ObjCProtocolDecl>(this)) {
+    Definition = PD->getDefinition();
+  } else if (auto TD = dyn_cast<TagDecl>(this)) {
+    Definition = TD->getDefinition();
+  }
+  if (!Definition)
+    Definition = this;
+
+  if (auto *attr = Definition->getAttr<ExternalSourceSymbolAttr>())
+    return attr;
+  if (auto *dcd = dyn_cast<Decl>(getDeclContext())) {
+    return dcd->getAttr<ExternalSourceSymbolAttr>();
+  }
+
+  return nullptr;
+}
+
 bool Decl::hasDefiningAttr() const {
   return hasAttr<AliasAttr>() || hasAttr<IFuncAttr>();
 }