Class: Collie::Linter::Rules::UnusedNonterminal

Inherits:
Base
  • Object
show all
Defined in:
lib/collie/linter/rules/unused_nonterminal.rb

Overview

Detects nonterminals that are defined but never referenced

Constant Summary

Constants inherited from Base

Base::VALID_SEVERITIES

Instance Method Summary collapse

Methods inherited from Base

#autocorrectable?, #initialize

Constructor Details

This class inherits a constructor from Collie::Linter::Base

Instance Method Details

#check(ast, _context = {}) ⇒ Object 



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# File 'lib/collie/linter/rules/unused_nonterminal.rb', line 17

def check(ast, _context = {})
  symbol_table = Analyzer::SymbolTable.new

  # Register all nonterminals
  ast.rules.each do |rule|
    symbol_table.add_nonterminal(rule.name, location: rule.location)
  end

  ast.declarations.each do |decl|
    case decl
    when AST::TokenDeclaration
      decl.names.each do |name|
        symbol_table.add_token(name, type_tag: decl.type_tag, location: decl.location)
      rescue Error
        # Ignore duplicates while building the resolver table.
      end
    when AST::PrecedenceDeclaration
      decl.tokens.each do |name|
        symbol_table.add_token(name, location: decl.location)
      rescue Error
        # Ignore duplicates while building the resolver table.
      end
    when AST::ParameterizedRule
      symbol_table.add_nonterminal(decl.name, location: decl.location)
    when AST::InlineRule
      symbol_table.add_nonterminal(decl.rule, location: decl.location)
    end
  end

  Analyzer::SymbolResolver.resolve(ast, symbol_table)

  # Find start symbol
  start_symbol = find_start_symbol(ast)

  # Track nonterminal usage in normal rules
  ast.rules.each do |rule|
    rule.alternatives.each do |alt|
      alt.symbols.each do |symbol|
        if symbol.nonterminal?
          symbol_table.use_nonterminal(symbol.name)
          # Also consider parameterized rule call arguments: list(expr)
          if symbol.arguments
            symbol.arguments.each do |arg|
              symbol_table.use_nonterminal(arg.name) if arg.nonterminal?
            end
          end
        end
      end
    end
  end

  # Track nonterminal usage in parameterized rules (%rule)
  ast.declarations.each do |decl|
    next unless decl.is_a?(AST::ParameterizedRule) || decl.is_a?(AST::InlineRule)

    decl.alternatives.each do |alt|
      alt.symbols.each do |symbol|
        if symbol.nonterminal?
          symbol_table.use_nonterminal(symbol.name)
          if symbol.arguments
            symbol.arguments.each do |arg|
              symbol_table.use_nonterminal(arg.name) if arg.nonterminal?
            end
          end
        end
      end
    end
  end

  # Mark start symbol as used
  symbol_table.use_nonterminal(start_symbol) if start_symbol
  unreachable_rules = unreachable_rules(ast, start_symbol)

  # Find unused nonterminals
  symbol_table.unused_nonterminals.each do |nonterminal_name|
    # Skip start symbol
    next if nonterminal_name == start_symbol
    next if unreachable_rules.include?(nonterminal_name)

    rule = ast.rules.find { |r| r.name == nonterminal_name }
    next unless rule

    add_offense(rule,
                message: "Nonterminal '#{nonterminal_name}' is defined but never used")
  end

  @offenses
end