Avoid spurious clone emission for (void)-discarded function pointer casts in refcount model

[Copilot]

(void)-discarded expressions involving casted function pointers were translated with an unnecessary .clone() in refcount output (e.g. (void)(static_cast<int (*)()>(&f))). This change removes that extra clone while preserving discard semantics.

• Refcount converter: void-cast emission

  • Updated ConverterRefCount::VisitExplicitCastExpr to keep existing clone behavior for non-copyable discarded expressions, but skip clone when the discarded subexpression type is a function pointer.
  • This is scoped to (void) cast handling only.

• Golden output update (unit regression coverage)

  • Updated tests/unit/out/refcount/void_cast.rs expected output to remove clone emission for discarded function-pointer expressions and discarded casted function-pointer expressions.

• Before/after behavior

  // before
  ((FnPtr::<fn() -> i32>::new(bump_and_return_4)).cast::<fn() -> i32>(None)).clone();
  
  // after
  ((FnPtr::<fn() -> i32>::new(bump_and_return_4)).cast::<fn() -> i32>(None));

• Fixes Spurious clone for cast'ed fn ptrs #245

[Copilot]

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

[Copilot]

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

[Copilot]

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

[Copilot]

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

[Copilot]

Copilot was unable to review this pull request because there is no eligible user to bill. To allow Copilot reviews on bot-authored pull requests, enable direct organization billing in your organization's Copilot settings.

[lucic71]

I think this entire check is focusing only on DeclRefExpr, while missing other AST shapes

The correct solution is probably to do computed_expr_type_ = ComputedExprType::FreshPointer in ConvertFunctionToFunctionPointer

Then the check in VisitExplicitCastExpr becomes: !TypeIsCopyable(sub->getType()) && !isFresh()