1 -------------------------------------------------------------------------------
2 -- Copyright (c) 2006-2013 Fabien Fleutot and others.
4 -- All rights reserved.
6 -- This program and the accompanying materials are made available
7 -- under the terms of the Eclipse Public License v1.0 which
8 -- accompanies this distribution, and is available at
9 -- http://www.eclipse.org/legal/epl-v10.html
11 -- This program and the accompanying materials are also made available
12 -- under the terms of the MIT public license which accompanies this
13 -- distribution, and is available at http://www.lua.org/license.html
16 -- Fabien Fleutot - API and implementation
18 -------------------------------------------------------------------------------
20 -- Low level AST traversal library.
21 -- This library is a helper for the higher-level treequery library.
22 -- It walks through every node of an AST, depth-first, and executes
23 -- some callbacks contained in its cfg config table:
25 -- * cfg.down(...) is called when it walks down a node, and receive as
26 -- parameters the node just entered, followed by its parent, grand-parent
27 -- etc. until the root node.
29 -- * cfg.up(...) is called when it walks back up a node, and receive as
30 -- parameters the node just entered, followed by its parent, grand-parent
31 -- etc. until the root node.
33 -- * cfg.occurrence(binder, id_node, ...) is called when it visits an `Id{ }
34 -- node which isn't a local variable creator. binder is a reference to its
35 -- binder with its context. The binder is the `Id{ } node which created
36 -- this local variable. By "binder and its context", we mean a list starting
37 -- with the `Id{ }, and followed by every ancestor of the binder node, up until
38 -- the common root node.
39 -- binder is nil if the variable is global.
40 -- id_node is followed by its ancestor, up until the root node.
42 -- cfg.scope is maintained during the traversal, associating a
43 -- variable name to the binder which creates it in the context of the
44 -- node currently visited.
46 -- walk.traverse.xxx functions are in charge of the recursive descent into
47 -- children nodes. They're private helpers.
49 -- corresponding walk.xxx functions also take care of calling cfg callbacks.
51 -{ extension ("match", ...) }
53 local pp = require 'metalua.pprint'
55 local M = { traverse = { }; tags = { }; debug = false }
57 local function table_transpose(t)
58 local tt = { }; for a, b in pairs(t) do tt[b]=a end; return tt
61 --------------------------------------------------------------------------------
62 -- Standard tags: can be used to guess the type of an AST, or to check
63 -- that the type of an AST is respected.
64 --------------------------------------------------------------------------------
65 M.tags.stat = table_transpose{
66 'Do', 'Set', 'While', 'Repeat', 'Local', 'Localrec', 'Return',
67 'Fornum', 'Forin', 'If', 'Break', 'Goto', 'Label',
69 M.tags.expr = table_transpose{
70 'Paren', 'Call', 'Invoke', 'Index', 'Op', 'Function', 'Stat',
71 'Table', 'Nil', 'Dots', 'True', 'False', 'Number', 'String', 'Id' }
73 --------------------------------------------------------------------------------
74 -- These [M.traverse.xxx()] functions are in charge of actually going through
75 -- ASTs. At each node, they make sure to call the appropriate walker.
76 --------------------------------------------------------------------------------
77 function M.traverse.stat (cfg, x, ...)
78 if M.debug then pp.printf("traverse stat %s", x) end
79 local ancestors = {...}
80 local B = |y| M.block (cfg, y, x, unpack(ancestors)) -- Block
81 local S = |y| M.stat (cfg, y, x, unpack(ancestors)) -- Statement
82 local E = |y| M.expr (cfg, y, x, unpack(ancestors)) -- Expression
83 local EL = |y| M.expr_list (cfg, y, x, unpack(ancestors)) -- Expression List
84 local IL = |y| M.binder_list (cfg, y, x, unpack(ancestors)) -- Id binders List
85 local OS = || cfg.scope :save() -- Open scope
86 local CS = || cfg.scope :restore() -- Close scope
89 | {...} if x.tag == nil -> for _, y in ipairs(x) do M.stat(cfg, y, ...) end
90 -- no tag --> node not inserted in the history ancestors
91 | `Do{...} -> OS(x); for _, y in ipairs(x) do S(y) end; CS(x)
92 | `Set{ lhs, rhs } -> EL(lhs); EL(rhs)
93 | `While{ cond, body } -> E(cond); OS(); B(body); CS()
94 | `Repeat{ body, cond } -> OS(body); B(body); E(cond); CS(body)
95 | `Local{ lhs } -> IL(lhs)
96 | `Local{ lhs, rhs } -> EL(rhs); IL(lhs)
97 | `Localrec{ lhs, rhs } -> IL(lhs); EL(rhs)
98 | `Fornum{ i, a, b, body } -> E(a); E(b); OS(); IL{i}; B(body); CS()
99 | `Fornum{ i, a, b, c, body } -> E(a); E(b); E(c); OS(); IL{i}; B(body); CS()
100 | `Forin{ i, rhs, body } -> EL(rhs); OS(); IL(i); B(body); CS()
103 E(x[i]); OS(); B(x[i+1]); CS()
108 | `Call{...}|`Invoke{...}|`Return{...} -> EL(x)
109 | `Break | `Goto{ _ } | `Label{ _ } -> -- nothing
110 | { tag=tag, ...} if M.tags.stat[tag]->
111 M.malformed (cfg, x, unpack (ancestors))
113 M.unknown (cfg, x, unpack (ancestors))
117 function M.traverse.expr (cfg, x, ...)
118 if M.debug then pp.printf("traverse expr %s", x) end
119 local ancestors = {...}
120 local B = |y| M.block (cfg, y, x, unpack(ancestors)) -- Block
121 local S = |y| M.stat (cfg, y, x, unpack(ancestors)) -- Statement
122 local E = |y| M.expr (cfg, y, x, unpack(ancestors)) -- Expression
123 local EL = |y| M.expr_list (cfg, y, x, unpack(ancestors)) -- Expression List
124 local IL = |y| M.binder_list (cfg, y, x, unpack(ancestors)) -- Id binders list
125 local OS = || cfg.scope :save() -- Open scope
126 local CS = || cfg.scope :restore() -- Close scope
129 | `Paren{ e } -> E(e)
130 | `Call{...} | `Invoke{...} -> EL(x)
131 | `Index{ a, b } -> E(a); E(b)
132 | `Op{ opid, ... } -> E(x[2]); if #x==3 then E(x[3]) end
133 | `Function{ params, body } -> OS(body); IL(params); B(body); CS(body)
134 | `Stat{ b, e } -> OS(b); B(b); E(e); CS(b)
135 | `Id{ name } -> M.occurrence(cfg, x, unpack(ancestors))
137 for i = 1, #x do match x[i] with
138 | `Pair{ k, v } -> E(k); E(v)
141 | `Nil|`Dots|`True|`False|`Number{_}|`String{_} -> -- terminal node
142 | { tag=tag, ...} if M.tags.expr[tag]-> M.malformed (cfg, x, unpack (ancestors))
143 | _ -> M.unknown (cfg, x, unpack (ancestors))
147 function M.traverse.block (cfg, x, ...)
148 assert(type(x)=='table', "traverse.block() expects a table")
149 if x.tag then M.malformed(cfg, x, ...)
150 else for _, y in ipairs(x) do M.stat(cfg, y, x, ...) end
154 function M.traverse.expr_list (cfg, x, ...)
155 assert(type(x)=='table', "traverse.expr_list() expects a table")
156 -- x doesn't appear in the ancestors
157 for _, y in ipairs(x) do M.expr(cfg, y, ...) end
160 function M.malformed(cfg, x, ...)
161 local f = cfg.malformed or cfg.error
162 if f then f(x, ...) else
163 error ("Malformed node of tag "..(x.tag or '(nil)'))
167 function M.unknown(cfg, x, ...)
168 local f = cfg.unknown or cfg.error
169 if f then f(x, ...) else
170 error ("Unknown node tag "..(x.tag or '(nil)'))
174 function M.occurrence(cfg, x, ...)
175 if cfg.occurrence then cfg.occurrence(cfg.scope :get(x[1]), x, ...) end
178 -- TODO: Is it useful to call each error handling function?
179 function M.binder_list (cfg, id_list, ...)
181 local ferror = cfg.error or cfg.malformed or cfg.unknown
182 for i, id_node in ipairs(id_list) do
183 if id_node.tag == 'Id' then
184 cfg.scope :set (id_node[1], { id_node, ... })
185 if f then f(id_node, ...) end
186 elseif i==#id_list and id_node.tag=='Dots' then
187 -- Do nothing, those are valid `Dots
189 -- Traverse error handling function
192 error("Invalid binders list")
197 ----------------------------------------------------------------------
198 -- Generic walker generator.
199 -- * if `cfg' has an entry matching the tree name, use this entry
200 -- * if not, try to use the entry whose name matched the ast kind
201 -- * if an entry is a table, look for 'up' and 'down' entries
202 -- * if it is a function, consider it as a `down' traverser.
203 ----------------------------------------------------------------------
204 local walker_builder = function(traverse)
206 return function (cfg, ...)
207 if not cfg.scope then cfg.scope = M.newscope() end
208 local down, up = cfg.down, cfg.up
209 local broken = down and down(...)
210 if broken ~= 'break' then M.traverse[traverse] (cfg, ...) end
211 if up then up(...) end
215 ----------------------------------------------------------------------
216 -- Declare [M.stat], [M.expr], [M.block] and [M.expr_list]
217 ----------------------------------------------------------------------
218 for _, w in ipairs{ "stat", "expr", "block" } do --, "malformed", "unknown" } do
219 M[w] = walker_builder (w, M.traverse[w])
222 -- Don't call up/down callbacks on expr lists
223 M.expr_list = M.traverse.expr_list
226 ----------------------------------------------------------------------
227 -- Try to guess the type of the AST then choose the right walkker.
228 ----------------------------------------------------------------------
229 function M.guess (cfg, x, ...)
230 assert(type(x)=='table', "arg #2 in a walker must be an AST")
231 if M.tags.expr[x.tag] then return M.expr(cfg, x, ...) end
232 if M.tags.stat[x.tag] then return M.stat(cfg, x, ...) end
233 if not x.tag then return M.block(cfg, x, ...) end
234 error ("Can't guess the AST type from tag "..(x.tag or '<none>'))
237 local S = { }; S.__index = S
239 function M.newscope()
240 local instance = { current = { } }
241 instance.stack = { instance.current }
242 setmetatable (instance, S)
246 function S :save(...)
247 local current_copy = { }
248 for a, b in pairs(self.current) do current_copy[a]=b end
249 table.insert (self.stack, current_copy)
250 if ... then return self :add(...) end
253 function S :restore() self.current = table.remove (self.stack) end
254 function S :get (var_name) return self.current[var_name] end
255 function S :set (key, val) self.current[key] = val end