[lldb][NFC] Add a CompilerDecl->clang::Decl conversion function to ClangUtil

This automatically does the type checking for the cast.

Author: Teemperor

lldb/include/lldb/Symbol/ClangUtil.h

@@ -24,6 +24,10 @@ namespace lldb_private {
 struct ClangUtil {
   static bool IsClangType(const CompilerType &ct);
 
+  /// Returns the clang::Decl of the given CompilerDecl.
+  /// CompilerDecl has to be valid and represent a clang::Decl.
+  static clang::Decl *GetDecl(const CompilerDecl &decl);
+
   static clang::QualType GetQualType(const CompilerType &ct);
 
   static clang::QualType GetCanonicalQualType(const CompilerType &ct);

lldb/source/Plugins/ExpressionParser/Clang/ClangDeclVendor.cpp

@@ -8,6 +8,7 @@
 
 #include "Plugins/ExpressionParser/Clang/ClangDeclVendor.h"
 
+#include "lldb/Symbol/ClangUtil.h"
 #include "lldb/Symbol/TypeSystemClang.h"
 #include "lldb/Utility/ConstString.h"
 
@@ -22,7 +23,7 @@ uint32_t ClangDeclVendor::FindDecls(ConstString name, bool append,
   std::vector<CompilerDecl> compiler_decls;
   uint32_t ret = FindDecls(name, /*append*/ false, max_matches, compiler_decls);
   for (CompilerDecl compiler_decl : compiler_decls) {
-    clang::Decl *d = static_cast<clang::Decl *>(compiler_decl.GetOpaqueDecl());
+    clang::Decl *d = ClangUtil::GetDecl(compiler_decl);
     clang::NamedDecl *nd = llvm::cast<clang::NamedDecl>(d);
     decls.push_back(nd);
   }

lldb/source/Plugins/SymbolFile/NativePDB/PdbAstBuilder.cpp

@@ -1347,7 +1347,7 @@ PdbAstBuilder::ToCompilerDeclContext(clang::DeclContext &context) {
 }
 
 clang::Decl * PdbAstBuilder::FromCompilerDecl(CompilerDecl decl) {
-  return static_cast<clang::Decl *>(decl.GetOpaqueDecl());
+  return ClangUtil::GetDecl(decl);
 }
 
 clang::DeclContext *

lldb/source/Symbol/ClangUtil.cpp

@@ -28,6 +28,11 @@ bool ClangUtil::IsClangType(const CompilerType &ct) {
   return true;
 }
 
+clang::Decl *ClangUtil::GetDecl(const CompilerDecl &decl) {
+  assert(llvm::isa<TypeSystemClang>(decl.GetTypeSystem()));
+  return static_cast<clang::Decl *>(decl.GetOpaqueDecl());
+}
+
 QualType ClangUtil::GetQualType(const CompilerType &ct) {
   // Make sure we have a clang type before making a clang::QualType
   if (!IsClangType(ct))