[cfe-dev] DeclContext in matcher results

[Manuel Klimek]

On Sat, Jul 14, 2012 at 3:13 AM, Sam Panzer <panzer at google.com> wrote:
> Hi everyone,
>
> When a tool introduces a new declaration or renames an old one, it will need
> to make sure that the existing semantics are preserved. In particular, it is
> possible for the new declaration to conflict with or shadow an existing one,
> which means the tool needs to be particularly careful.
>
> My first guess would be to check all enclosing and enclosed DeclContexts for
> declarations with the same identifier. Is this a reasonable strategy, and if
> so, would matchers be able to track the DeclContexts of their results? It
> gets even more interesting when the refactoring tool wants to introduce two
> separate declarations that might conflict with each other.

If you have a declaration, you can traverse the decl-contexts from the
ast context. We have some snippets of code that we haven't upstreamed
yet, which do traversal of the decl-contexts, and are probably not
perfect yet. See below.

I'd rather not have the matcher layer try to implement pulling
together additional information. I'd rather try to either get Sema
involved (like you suggested earlier) or add stuff somewhere into the
AST so we can retrieve it later; perhaps make that optional.

Thoughts?
/Manuel

inline bool HasSymbol(
    const clang::ASTContext& ast_context,
    const clang::DeclContext* context,
    const llvm::SmallVectorImpl<llvm::StringRef>& components,
    int component) {
  if (context == NULL) {
    return false;
  }
  if (component == components.size()) {
    // Found the symbol.
    return true;
  }
  clang::IdentifierInfo& identifier =
      ast_context.Idents.get(components[component]);
  clang::DeclContext::lookup_const_result result = context->lookup(&identifier);
  for (clang::NamedDecl* const * it = result.first; it != result.second; ++it) {
    if (HasSymbol(ast_context, clang::NamedDecl::castToDeclContext(*it),
                  components, component+1)) {
      return true;
    }
  }
  return false;
}
inline bool HasGlobalSymbol(
    const clang::ASTContext& ast_context, const string& symbol) {
  llvm::StringRef symbol_ref(symbol.c_str(), symbol.size());
  llvm::SmallVector<llvm::StringRef, 4> components;
  symbol_ref.split(components, "::");
  clang::DeclContext* decl = ast_context.getTranslationUnitDecl();
  return HasSymbol(ast_context, decl, components, 0);
}

>
> Thanks!
>
> -Sam