require_relative "error" module Lox class Resolver def initialize(interpreter) @interpreter = interpreter @scopes = [] end def resolve(*resolvees) resolvees.each do |resolvee| resolvee.accept(self) end nil end def visit_block(stmt) with_scope do resolve(*stmt.stmts) end nil end def visit_expr(stmt) = resolve(stmt.expr) def visit_function(stmt) declare(stmt.name) define(stmt.name) resolve_function(stmt) nil end def visit_if(stmt) resolve(stmt.cond, stmt.then) resolve(stmt.else) if stmt.else end def visit_print(stmt) = resolve(stmt.expr) def visit_return(stmt) resolve(stmt.value) if stmt.value end def visit_var(stmt) declare(stmt.name) resolve(stmt.initializer) if stmt.initializer define(stmt.name) nil end def visit_while(stmt) = resolve(stmt.cond, stmt.body) def visit_variable(expr) if !@scopes.empty? && @scopes.last[expr.name.lexeme] == false raise ResolverError.new(expr.name, "Can't read local variable in its own initializer.") end resolve_local(expr, expr.name) nil end def visit_assign(expr) resolve(expr.value) resolve_local(expr, expr.name) nil end def visit_binary(expr) = resolve(expr.left, expr.right) def visit_call(expr) = resolve(expr.callee, *expr.args) def visit_grouping(expr) = resolve(expr.expr) def visit_literal(expr) = nil def visit_logical(expr) = resolve(expr.left, expr.right) def visit_unary(expr) = resolve(expr.right) private def with_scope @scopes.push({}) yield @scopes.pop end def declare(name) scope = @scopes.last return if scope.nil? raise ResolverError.new(name, "Already a variable with this name in this scope") if scope.has_key?(name.lexeme) scope[name.lexeme] = false end def define(name) scope = @scopes.last return if scope.nil? scope[name.lexeme] = true end def resolve_local(expr, name) scope_and_depth = @scopes.reverse.each.with_index.find {|scope, depth| scope.has_key?(name.lexeme) } return unless scope_and_depth scope, depth = scope_and_depth @interpreter.resolve(expr, depth) end def resolve_function(fn) with_scope do fn.params.each do |param| declare(param) define(param) end resolve(*fn.body) end end end end