fix: add typename and this-> for dependent names in Iterator.hh

[oharboe]

GCC 15 and clang 20 enforce -Wtemplate-body, requiring typename before dependent type names and this-> for member accesses whose type depends on template parameters. Without these qualifiers, two-phase name lookup fails to resolve itr_ in VectorIterator, MapIterator and SetIterator.

[oharboe]

@hzeller FYI

[parallaxsw]

I compiled with clang 22 and do not see an issue.

GCC and Clang template body enforcement

Exported on 4/10/2026 at 09:54:42 PDT from Cursor (3.0.13)

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User

is this true?
GCC 15 and clang 20 enforce -Wtemplate-body, requiring typename before dependent type names and this-> for member accesses whose type depends on template parameters. Without these qualifiers, two-phase name lookup fails to resolve itr_ in VectorIterator, MapIterator and SetIterator.

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Cursor

Let me look at the relevant iterator classes in the codebase and research the compiler warning.

The claim is not true for this code, for two separate reasons. Let me break down what's accurate and what's wrong.

1. -Wtemplate-body is real, but only in GCC

GCC 15 did introduce -Wtemplate-body — it extends template body checking to catch errors in uninstantiated templates (e.g., this->nonexistent_member()). However, Clang 20 does not have a -Wtemplate-body flag. Clang has always been stricter about two-phase lookup, but it uses different diagnostics.

2. typename is NOT required here — you're compiling C++20

The project uses C++20:

target_compile_features(OpenSTA PUBLIC cxx_std_20)

C++20 (via P0634R3 "Down with typename!") relaxed the typename requirement in contexts where only a type is valid. A member variable declaration is exactly such a context. So these lines are perfectly valid C++20:

  VECTOR_TYPE::const_iterator itr_;

  MAP_TYPE::const_iterator itr_;

  SET_TYPE::const_iterator itr_;

Both GCC 9+ and Clang 16+ implement P0634R3, so GCC 15 and Clang 20 both accept this without typename.

3. this-> is NOT needed for itr_ — it's a direct member, not inherited

The claim that two-phase lookup "fails to resolve itr_" is incorrect. The this-> requirement applies only to members inherited from a dependent base class. Here, itr_ is declared directly in each class template itself (in the protected: section), not in the base Iterator<OBJ_TYPE>. For example:

template <typename VECTOR_TYPE, typename OBJ_TYPE>
class VectorIterator : public Iterator<OBJ_TYPE>
{
  // ...
protected:
  const VECTOR_TYPE *seq_;
  VECTOR_TYPE::const_iterator itr_;   // declared RIGHT HERE in VectorIterator
};

When itr_ is used in the constructor or hasNext()/next(), it's found by ordinary unqualified lookup within the class scope — no dependent base traversal is involved. The base class Iterator<OBJ_TYPE> only declares the pure virtual hasNext() and next(); it has no itr_ member at all.

Summary

Claim	Verdict
GCC 15 enforces -Wtemplate-body	True — but it catches this-> calls to non-existent members, not the issues described
Clang 20 enforces -Wtemplate-body	False — Clang doesn't have this flag
typename is required before VECTOR_TYPE::const_iterator	False in C++20 — P0634R3 makes it optional in member declarations
this-> is needed for itr_	False — itr_ is a direct member, not inherited from a dependent base

If you were compiling this as C++17 or earlier, the missing typename on lines 64, 92, and 116 would indeed be an error. But since you're targeting C++20, the code as written is correct.

[oharboe]

👍