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