lib/metalua/walk/bindings.mlua

-------------------------------------------------------------------------------
-- Copyright (c) 2006-2013 Fabien Fleutot and others.
--
-- All rights reserved.
--
-- This program and the accompanying materials are made available
-- under the terms of the Eclipse Public License v1.0 which
-- accompanies this distribution, and is available at
-- http://www.eclipse.org/legal/epl-v10.html
--
-- This program and the accompanying materials are also made available
-- under the terms of the MIT public license which accompanies this
-- distribution, and is available at http://www.lua.org/license.html
--
-- Contributors:
--     Fabien Fleutot - API and implementation
--
-------------------------------------------------------------------------------

require 'metalua.walk'
require 'metalua.walk.scope'

function bindings(ast)
   -- binders :: ast  => name => occurences
   -- unbound :: name => occurences
   -- scope   :: name => ast

   local binders, unbound, cfg, scope = { }, { }, { scope={ } }, scope:new()

   -- * id: identifier entering in scope
   -- * ast: statement or expr carrying this id, on of:
   --        Local, Localrec, Forin, Fornum, Function.
   function cfg.binder (id, ast)
      if id.tag ~= 'Id' then return end
      local id_name = id[1]
      -- Reference in scope, so that the binding statement can be retrieved:
      scope.current[id_name] = ast
      -- Init the occurences list for this identifier:
      if binders[ast] then binders[ast][id_name] = { }
      else binders[ast] = { [id_name] = { } } end
   end
   
   -- identifier occurence, not as a binder: reference this occurence
   function cfg.Id (id)
      local id_name = id[1]
      -- ast which binds this id, might be nil:
      local binder_ast = scope.current [id_name] 
      -- dict id_name => occurences, might be the list of unbound occurences:
      local occur_dict = binder_ast and binders[binder_ast] or unbound
      -- add an occurence of `id' in the occurences list:
      local occurences = occur_dict [id_name]
      if occurences then table.insert (occurences, id) 
      else occur_dict [id_name] = { id } end
   end

   --Do not choke on partial ASTs which contain `Error{} nodes
   function cfg.error(x) end

   function cfg.scope.down() scope:push() end
   function cfg.scope.up()   scope:pop()  end

   walk.guess (cfg, ast)
   return binders, unbound
end