[lldb] Assert when TypeSystemClang::CreateFunctionDeclaration is called on a record

[teemperor]

Summary

As discussed in D85993, using CreateFunctionDeclaration to add a member function to a record will probably
cause Clang to run into several assertions and is most likely not what one wants to do. All functions in a
record are CXXMethodDecls and never plain FunctionDecls. Not sure if there is an obscure Clang extension
that would support free functions inside a record, but I'm sure we don't have this use case when building an AST in LLDB.

[labath]

Sounds like a good idea, after the pdb plugin is fixed...

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

 FunctionDecl *TypeSystemClang::CreateFunctionDeclaration(
     clang::DeclContext *decl_ctx, OptionalClangModuleID owning_module,
     const char *name, const CompilerType &function_clang_type, int storage,
     bool is_inline) {
   FunctionDecl *func_decl = nullptr;
   ASTContext &ast = getASTContext();
   if (!decl_ctx)
     decl_ctx = ast.getTranslationUnitDecl();
+  assert(!decl_ctx->isRecord() &&
+         "Use AddMethodToCXXRecordType to add member functions to a record");
 
   const bool hasWrittenPrototype = true;
   const bool isConstexprSpecified = false;
 
   clang::DeclarationName declarationName =
       GetDeclarationName(name, function_clang_type);
   func_decl = FunctionDecl::CreateDeserialized(ast, 0);
   func_decl->setDeclContext(decl_ctx);