Modernize DeclTest

Summary:
This patch removes a call to the old ASTUnit::findFileRegionDecls and
replaces it with ast matchers.

Reviewers: gribozavr, gribozavr2

Reviewed By: gribozavr2

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76121

clang/unittests/AST/DeclTest.cpp

@@ -13,6 +13,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Mangle.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Tooling/Tooling.h"
@@ -77,14 +78,9 @@ TEST(Decl, AsmLabelAttr) {
   assert(Ctx.getTargetInfo().getDataLayout().getGlobalPrefix() &&
          "Expected target to have a global prefix");
   DiagnosticsEngine &Diags = AST->getDiagnostics();
-  SourceManager &SM = AST->getSourceManager();
-  FileID MainFileID = SM.getMainFileID();
 
-  // Find the method decls within the AST.
-  SmallVector<Decl *, 1> Decls;
-  AST->findFileRegionDecls(MainFileID, Code.find('{'), 0, Decls);
-  ASSERT_TRUE(Decls.size() == 1);
-  CXXRecordDecl *DeclS = cast<CXXRecordDecl>(Decls[0]);
+  auto *DeclS =
+      selectFirst<CXXRecordDecl>("d", match(cxxRecordDecl().bind("d"), Ctx));
   NamedDecl *DeclF = *DeclS->method_begin();
   NamedDecl *DeclG = *(++DeclS->method_begin());