metalua/compiler/parser/stat.lua

-------------------------------------------------------------------------------
-- 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
--
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
--
-- Summary: metalua parser, statement/block parser. This is part of the
-- definition of module [mlp].
--
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
--
-- Exports API:
-- * [mlp.stat()]
-- * [mlp.block()]
-- * [mlp.for_header()]
--
-------------------------------------------------------------------------------

local mlp      = require 'metalua.compiler.parser.common'
local mlp_misc = require 'metalua.compiler.parser.misc'
local mlp_meta = require 'metalua.compiler.parser.meta'
local annot    = require 'metalua.compiler.parser.annot'
local gg       = require 'metalua.grammar.generator'
local M        = { }

--------------------------------------------------------------------------------
-- eta-expansions to break circular dependency
--------------------------------------------------------------------------------
local expr      = function (lx) return mlp.expr     (lx) end
local func_val  = function (lx) return mlp.func_val (lx) end
local expr_list = function (lx) return mlp.expr_list(lx) end

--------------------------------------------------------------------------------
-- List of all keywords that indicate the end of a statement block. Users are
-- likely to extend this list when designing extensions.
--------------------------------------------------------------------------------


M.block_terminators = { "else", "elseif", "end", "until", ")", "}", "]" }

-- FIXME: this must be handled from within GG!!!
function M.block_terminators :add(x)
   if type (x) == "table" then for _, y in ipairs(x) do self :add (y) end
   else table.insert (self, x) end
end

--------------------------------------------------------------------------------
-- list of statements, possibly followed by semicolons
--------------------------------------------------------------------------------
M.block = gg.list {
   name        = "statements block",
   terminators = M.block_terminators,
   primary     = function (lx)
      -- FIXME use gg.optkeyword()
      local x = mlp.stat (lx)
      if lx:is_keyword (lx:peek(), ";") then lx:next() end
      return x
   end }

--------------------------------------------------------------------------------
-- Helper function for "return <expr_list>" parsing.
-- Called when parsing return statements.
-- The specific test for initial ";" is because it's not a block terminator,
-- so without it gg.list would choke on "return ;" statements.
-- We don't make a modified copy of block_terminators because this list
-- is sometimes modified at runtime, and the return parser would get out of
-- sync if it was relying on a copy.
--------------------------------------------------------------------------------
local return_expr_list_parser = gg.multisequence{
   { ";" , builder = function() return { } end },
   default = gg.list {
      expr, separators = ",", terminators = M.block_terminators } }


local for_vars_list = gg.list{
    name        = "for variables list",
    primary     = mlp_misc.id,
    separators  = ",",
    terminators = "in" }

--------------------------------------------------------------------------------
-- for header, between [for] and [do] (exclusive).
-- Return the `Forxxx{...} AST, without the body element (the last one).
--------------------------------------------------------------------------------
function M.for_header (lx)
    local vars = mlp.id_list(lx)
    if lx :is_keyword (lx:peek(), "=") then
        if #vars ~= 1 then
            gg.parse_error (lx, "numeric for only accepts one variable")
        end
        lx:next() -- skip "="
        local exprs = mlp.expr_list (lx)
        if #exprs < 2 or #exprs > 3 then
            gg.parse_error (lx, "numeric for requires 2 or 3 boundaries")
        end
        return { tag="Fornum", vars[1], unpack (exprs) }
    else
        if not lx :is_keyword (lx :next(), "in") then
            gg.parse_error (lx, '"=" or "in" expected in for loop')
        end
        local exprs = mlp.expr_list (lx)
        return { tag="Forin", vars, exprs }
    end
end

--------------------------------------------------------------------------------
-- Function def parser helper: id ( . id ) *
--------------------------------------------------------------------------------
local function fn_builder (list)
   local r = list[1]
   for i = 2, #list do r = { tag="Index", r, mlp.id2string(list[i]) } end
   return r
end
local func_name = gg.list{ mlp_misc.id, separators = ".", builder = fn_builder }

--------------------------------------------------------------------------------
-- Function def parser helper: ( : id )?
--------------------------------------------------------------------------------
local method_name = gg.onkeyword{ name = "method invocation", ":", mlp_misc.id,
   transformers = { function(x) return x and x.tag=='Id' and mlp_misc.id2string(x) end } }

--------------------------------------------------------------------------------
-- Function def builder
--------------------------------------------------------------------------------
local function funcdef_builder(x)

   local name, method, func = unpack(x)

   if method then
      name = { tag="Index", name, method, lineinfo = {
         first = name.lineinfo.first,
         last  = method.lineinfo.last } }
      table.insert (func[1], 1, {tag="Id", "self"})
   end
   local r = { tag="Set", {name}, {func} }
   r[1].lineinfo = name.lineinfo
   r[2].lineinfo = func.lineinfo
   return r
end


--------------------------------------------------------------------------------
-- if statement builder
--------------------------------------------------------------------------------
local function if_builder (x)
   local cond_block_pairs, else_block, r = x[1], x[2], {tag="If"}
   local n_pairs = #cond_block_pairs
   for i = 1, n_pairs do
       local cond, block = unpack(cond_block_pairs[i])
       r[2*i-1], r[2*i] = cond, block
   end
   if else_block then table.insert(r, #r+1, else_block) end
   return r
end 

--------------------------------------------------------------------------------
-- produce a list of (expr,block) pairs
--------------------------------------------------------------------------------
local elseifs_parser = gg.list {
   gg.sequence { expr, "then", M.block , name='elseif parser' },
   separators  = "elseif",
   terminators = { "else", "end" }
}

local annot_expr = gg.sequence {
    expr,
    gg.onkeyword{ "#", annot.tf },
    builder = function(x) 
                  local e, a = unpack(x)
                  if a then return { tag='Annot', e, a }
                  else return e end
              end }

local annot_expr_list = gg.list {
    primary = annot.opt(expr, 'tf'), separators = ',' }

--------------------------------------------------------------------------------
-- assignments and calls: statements that don't start with a keyword
--------------------------------------------------------------------------------
local function assign_or_call_stat_parser (lx)
   local e = annot_expr_list (lx)
   local a = lx:is_keyword(lx:peek())
   local op = a and mlp.stat.assignments[a]
   -- TODO: refactor annotations
   if op then
      --FIXME: check that [e] is a LHS
      lx :next()
      local annots
      e, annots = annot.split(e)
      local v = mlp.expr_list (lx)
      if type(op)=="string" then return { tag=op, e, v, annots }
      else return op (e, v) end
   else
      assert (#e > 0)
      if #e > 1 then
         gg.parse_error (lx,
            "comma is not a valid statement separator; statement can be "..
            "separated by semicolons, or not separated at all") end
      if e[1].tag ~= "Call" and e[1].tag ~= "Invoke" then
         local typename
         if e[1].tag == 'Id' then
            typename = '("'..e[1][1]..'") is an identifier'
         elseif e[1].tag == 'Op' then
            typename = "is an arithmetic operation"
         else typename = "is of type '"..(e[1].tag or "<list>").."'" end

         gg.parse_error (lx,
                         "This expression %s; "..
                         "a statement was expected, and only function and method call "..
                         "expressions can be used as statements", typename);
      end
      return e[1]
   end
end

M.local_stat_parser = gg.multisequence{
    -- local function <name> <func_val>
    { "function", mlp_misc.id, func_val, builder =
      function(x)
          local vars = { x[1], lineinfo = x[1].lineinfo }
          local vals = { x[2], lineinfo = x[2].lineinfo }
          return { tag="Localrec", vars, vals }
      end },
    -- local <id_list> ( = <expr_list> )?
    default = gg.sequence{
        gg.list{
            primary = annot.opt(mlp_misc.id, 'tf'),
            separators = ',' },
        gg.onkeyword{ "=", expr_list },
        builder = function(x)
            local annotated_left, right = unpack(x)
            local left, annotations = annot.split(annotated_left)
            return {tag="Local", left, right or { }, annotations }
        end } }

--------------------------------------------------------------------------------
-- statement
--------------------------------------------------------------------------------
M.stat = gg.multisequence {
   name = "statement",
   { "do", M.block, "end", builder =
      function (x) return { tag="Do", unpack (x[1]) } end },
   { "for", M.for_header, "do", M.block, "end", builder =
      function (x) x[1][#x[1]+1] = x[2]; return x[1] end },
   { "function", func_name, method_name, func_val, builder=funcdef_builder },
   { "while", expr, "do", M.block, "end", builder = "While" },
   { "repeat", M.block, "until", expr, builder = "Repeat" },
   { "local", M.local_stat_parser, builder = unpack },
   { "return", return_expr_list_parser, builder =
     function(x) x[1].tag='Return'; return x[1] end },
   { "break", builder = function() return { tag="Break" } end },
   { "-{", mlp_meta.splice_content, "}", builder = unpack },
   { "if", gg.nonempty(elseifs_parser), gg.onkeyword{ "else", M.block }, "end",
     builder = if_builder },
   default = assign_or_call_stat_parser }

M.stat.assignments = {
   ["="] = "Set"
}

function M.stat.assignments:add(k, v) self[k] = v end

return M