GSoC syncup: Rewrite Rust lints to operate on frontend's HIR

Rolling agenda.

Proposal

2025-07-07

Progress

• Implementing ReadonlyChecker on HIR
  • draft PR

Questions

• I don't have any question to ask.

2025-06-30

Progress

• Implementing ReadonlyChecker on HIR

Strategy

• Find AssignmentExpr
• Get left operand of it (that is assignee expression)
• Check if it is mutable or not

Example Code

void
ReadonlyChecker::visit (AssignmentExpr &expr)
{
  Expr &lhs = expr.get_lhs ();
  switch (lhs.get_expression_type ())
    {
    case Expr::ExprType::Path:
      {
	// QualifiedPathInExpression or PathInExpression
	// readonly check for local variables and static variables
    
        std::unique_ptr<Path> path = static_cast<Path>(*lhs);
    
        switch (path.get_path_type()) {
            case Path::PathType::QualifiedPathInExpression: {}
            case Path::PathType::PathInExpression: {}
        }
    
    
      }
    case Expr::ExprType::FieldAccess:
      {
	// readonly check for field access
      }

    case Expr::ExprType::ArrayIndex:
      {
	// readonly check for array index access
      }
    case Expr::ExprType::Operator:
      {
	// readonly check for dereferences
      }
    case Expr::ExprType::Tuple:
      {
	// readonly check for tuples of expressions
      }
    default:
      rust_error_at (expr.get_locus (),
		     "cannot assign to expression of type %s",
		     lhs.get_expression_type ());
    }
}

Question

• Both QualifiedPathInExpression and PathInExpression has Expr::ExprType::Path. How can we distinguish between these two types of nodes?

2025-06-23

Progress

• finished implementing default HIR visitor
  • please review it https://github.com/Rust-GCC/gccrs/pull/3854

Questions

• I think the MatchArm node should have a get_outer_attrs method, because it has outer attributes but no way to access them.
• SelfParam::get_lifetime returns a const object, but the accept_vis method for Lifetime is not const qualified.
  • Should I add const qualified version of accept_vis function?
  • https://github.com/Rust-GCC/gccrs/blob/1f1fefef9af07328e990a731fbb9b09989cb74c8/gcc/rust/hir/tree/rust-hir-item.h#L403

2025-06-16

Progress

• continue to implement default HIR visitor class
  • about 60% done!
  • https://github.com/sakupan102/gccrs/pull/1/files
  • As previously scheduled, I have to finish implementing it by the end of this week.

Questions

• Should I visit inner or outer attributes?
  • attributes are belongs to AST, so I don't think this should be visited
• Should I visit StructBase nodes?
  • this type of node doesn't have accept_vis function, but Default AST vistor visits StructBase nodes.

2025-06-09

Progress

• [WIP] Implementing default HIR visitor class
  • https://github.com/sakupan102/gccrs/pull/1/files

Questions

• Do you think it's better to create individual feature branches directly from the master branch, rather than creating a project branch and then creating feature branches from that?
• Some types of nodes have an accept_vis function, but others don't. What is the difference? Do you think all types of nodes need to have an accept_vis function?
  • e.g. PathIdentSegment class does not have accept_vis function https://github.com/Rust-GCC/gccrs/blob/b037a1b1bcd00800612ea3a06017d2ac09a9fe10/gcc/rust/hir/tree/rust-hir-path.h#L32-L57

Links

• DefaultASTVisitor class
• DefaultASTVisitor implementation

These template functions can also be quite helpful for you:

  template <typename T> void visit (T &node) { node.accept_vis (*this); }

  template <typename T> void visit (std::unique_ptr<T> &node)
  {
    node->accept_vis (*this);
  }

Actions:

• Ryutaro to continue DefaultHIRVisitor implementation for next week

2025-06-01

• Introduction

Actions:

• Ryutaro to write down questions if you have any :D
• Arthur to setup a groupchat for PE and Ryutaro