[clang-diff] Fix matching for unnamed NamedDecs

[johannes]

Summary

This makes Node::getIdentifier return a valid value for special
NamedDecl nodes that do not have a name, such as ctors, dtors
and unnamed classes / namespaces.

[johannes]

update

lib/Tooling/ASTDiff/ASTDiff.cpp

 }
 
 llvm::Optional<std::string> Node::getQualifiedIdentifier() const {
   if (isMacro())
     return llvm::None;
   if (auto *ND = ASTNode.get<NamedDecl>()) {
     if (ND->getDeclName().isIdentifier())
       return ND->getQualifiedNameAsString();
+    else
+      return std::string();
   }
   return llvm::None;
 }
 
 llvm::Optional<StringRef> Node::getIdentifier() const {
   if (isMacro())
     return llvm::None;
   if (auto *ND = ASTNode.get<NamedDecl>()) {
     if (ND->getDeclName().isIdentifier())
       return ND->getName();
+    else
+      return StringRef();
   }
   return llvm::None;
 }
 
 NodeRefIterator Node::begin() const {
   return {&Tree, isLeaf() ? nullptr : &Children[0]};
 }
 NodeRefIterator Node::end() const {

test/Tooling/clang-diff-heuristics.cpp

 // RUN: %clang_cc1 -E %s > %t.src.cpp
 // RUN: %clang_cc1 -E %s > %t.dst.cpp -DDEST
 // RUN: clang-diff -dump-matches -s=0 %t.src.cpp %t.dst.cpp -- | FileCheck %s
 //
 // Test the heuristics, with maxsize set to 0, so that the optimal matching will never be applied.
 
 #ifndef DEST
 
 void f1() {;}
 
 void f2(int) {;}
 
+class C3 { C3(); };
+
 #else
 
 // same parents, same value
 // CHECK: Match FunctionDecl(1) to FunctionDecl(1)
 // CHECK: Match CompoundStmt
 void f1() {}
 
 // same parents, same identifier
 // CHECK: Match FunctionDecl(4) to FunctionDecl(3)
 // CHECK: Match CompoundStmt
 void f2() {}
 
+// same parents, same identifier
+// CHECK: Match CXXConstructorDecl(9) to CXXConstructorDecl(6)
+class C3 { C3(int); };
+
 #endif