1 | """Statically classify symbols by scope, for code generation.
|
2 |
|
3 | Great article about CPython's symbol tables, which are slightly different:
|
4 |
|
5 | https://eli.thegreenplace.net/2010/09/20/python-internals-symbol-tables-part-2
|
6 |
|
7 | In particular, see footnote 6: Why does CPython's algorithm have 2 passes,
|
8 | while there is only one pass here?
|
9 | """
|
10 | from __future__ import print_function
|
11 |
|
12 | from . import ast
|
13 | from . import misc
|
14 | from .consts import SC_LOCAL, SC_GLOBAL_IMPLICIT, SC_GLOBAL_EXPLICIT, \
|
15 | SC_FREE, SC_CELL, SC_UNKNOWN
|
16 | from .visitor import ASTVisitor
|
17 |
|
18 | import itertools
|
19 | import types
|
20 |
|
21 |
|
22 | class Scope(object):
|
23 | # XXX how much information do I need about each name?
|
24 | def __init__(self, name, module, klass=None):
|
25 | self.name = name
|
26 | self.module = module
|
27 |
|
28 | self.defs = set()
|
29 | self.uses = set()
|
30 | self.globals = set()
|
31 | self.params = set()
|
32 | self.frees = set()
|
33 | self.cells = set()
|
34 |
|
35 | self.children = []
|
36 | # nested is true if the class could contain free variables,
|
37 | # i.e. if it is nested within another function.
|
38 | self.nested = None
|
39 | self.generator = None
|
40 | self.klass = None
|
41 | if klass is not None:
|
42 | # Strip leading _. I guess this is for name mangling; you don't
|
43 | # want more than one _.
|
44 | self.klass = klass.lstrip('_')
|
45 |
|
46 | def __repr__(self):
|
47 | n = '(nested)' if self.nested else ''
|
48 | return "<%s: %s> %s" % (self.__class__.__name__, self.name, n)
|
49 |
|
50 | def PrettyPrint(self):
|
51 | def p(s):
|
52 | return ' '.join(sorted(s))
|
53 | print(repr(self))
|
54 | print("\tglobals: ", p(self.globals))
|
55 | print("\tcells: ", p(self.cells))
|
56 | print("\tdefs: ", p(self.defs))
|
57 | print("\tuses: ", p(self.uses))
|
58 | print("\tfrees:", p(self.frees))
|
59 |
|
60 | def mangle(self, name):
|
61 | return misc.mangle(name, self.klass)
|
62 |
|
63 | def add_def(self, name):
|
64 | self.defs.add(self.mangle(name))
|
65 |
|
66 | def add_use(self, name):
|
67 | self.uses.add(self.mangle(name))
|
68 |
|
69 | def add_global(self, name):
|
70 | name = self.mangle(name)
|
71 | if name in self.uses or name in self.defs:
|
72 | pass # XXX warn about global following def/use
|
73 | if name in self.params:
|
74 | raise SyntaxError, "%s in %s is global and parameter" % \
|
75 | (name, self.name)
|
76 | self.globals.add(name)
|
77 | self.module.add_def(name)
|
78 |
|
79 | def add_param(self, name):
|
80 | name = self.mangle(name)
|
81 | self.defs.add(name)
|
82 | self.params.add(name)
|
83 |
|
84 | def get_names(self):
|
85 | return list(self.defs | self.uses | self.globals) # union
|
86 |
|
87 | def add_child(self, child):
|
88 | self.children.append(child)
|
89 |
|
90 | def get_children(self):
|
91 | return self.children
|
92 |
|
93 | def check_name(self, name):
|
94 | """Return scope of name.
|
95 |
|
96 | The scope of a name could be LOCAL, GLOBAL, FREE, or CELL.
|
97 | """
|
98 | if name in self.globals:
|
99 | return SC_GLOBAL_EXPLICIT
|
100 | if name in self.cells:
|
101 | return SC_CELL
|
102 | if name in self.defs:
|
103 | return SC_LOCAL
|
104 | if self.nested and (name in self.frees or name in self.uses):
|
105 | return SC_FREE
|
106 | if self.nested:
|
107 | return SC_UNKNOWN
|
108 | else:
|
109 | return SC_GLOBAL_IMPLICIT
|
110 |
|
111 | def get_free_vars(self):
|
112 | """Variables not defined in this scope, and that are not globals either.
|
113 |
|
114 | It must be like this:
|
115 | # def MakeAdder(inc):
|
116 | # def Adder(x):
|
117 | # return x + inc # x is a local, inc is a free var?
|
118 | # return Adder
|
119 | """
|
120 | # TODO: Fix this calculation!
|
121 |
|
122 | if not self.nested:
|
123 | return []
|
124 | free = set()
|
125 | free.update(self.frees)
|
126 | for name in self.uses:
|
127 | if name not in self.defs and name not in self.globals:
|
128 | free.add(name)
|
129 | return list(free)
|
130 |
|
131 | def get_cell_vars(self):
|
132 | return list(self.cells)
|
133 |
|
134 | def handle_children(self):
|
135 | for child in self.children:
|
136 | frees = child.get_free_vars()
|
137 | globals_ = self.add_frees(frees)
|
138 | for name in globals_:
|
139 | child.force_global(name)
|
140 |
|
141 | def force_global(self, name):
|
142 | """Force name to be global in scope.
|
143 |
|
144 | Some child of the current node had a free reference to name.
|
145 | When the child was processed, it was labelled a free
|
146 | variable. Now that all its enclosing scope have been
|
147 | processed, the name is known to be a global or builtin. So
|
148 | walk back down the child chain and set the name to be global
|
149 | rather than free.
|
150 |
|
151 | Be careful to stop if a child does not think the name is
|
152 | free.
|
153 | """
|
154 | self.globals.add(name)
|
155 | if name in self.frees:
|
156 | self.frees.remove(name)
|
157 | for child in self.children:
|
158 | if child.check_name(name) == SC_FREE:
|
159 | child.force_global(name)
|
160 |
|
161 | def add_frees(self, names):
|
162 | """Process list of free vars from nested scope.
|
163 |
|
164 | Returns a list of names that are either 1) declared global in the
|
165 | parent or 2) undefined in a top-level parent. In either case,
|
166 | the nested scope should treat them as globals.
|
167 | """
|
168 | child_globals = []
|
169 | for name in names:
|
170 | sc = self.check_name(name)
|
171 | if self.nested:
|
172 | if sc == SC_UNKNOWN or sc == SC_FREE \
|
173 | or isinstance(self, ClassScope):
|
174 | self.frees.add(name)
|
175 | elif sc == SC_GLOBAL_IMPLICIT:
|
176 | child_globals.append(name)
|
177 | elif isinstance(self, FunctionScope) and sc == SC_LOCAL:
|
178 | self.cells.add(name)
|
179 | elif sc != SC_CELL:
|
180 | child_globals.append(name)
|
181 | else:
|
182 | if sc == SC_LOCAL:
|
183 | self.cells.add(name)
|
184 | elif sc != SC_CELL:
|
185 | child_globals.append(name)
|
186 | return child_globals
|
187 |
|
188 |
|
189 | class ModuleScope(Scope):
|
190 |
|
191 | def __init__(self):
|
192 | Scope.__init__(self, "global", self)
|
193 |
|
194 |
|
195 | class FunctionScope(Scope):
|
196 | pass
|
197 |
|
198 |
|
199 | class GenExprScope(Scope):
|
200 |
|
201 | def __init__(self, name, module, klass=None):
|
202 | Scope.__init__(self, name, module, klass)
|
203 | self.add_param('.0')
|
204 |
|
205 | def get_names(self):
|
206 | keys = Scope.get_names(self)
|
207 | return keys
|
208 |
|
209 |
|
210 | class LambdaScope(FunctionScope):
|
211 | pass
|
212 |
|
213 |
|
214 | class ClassScope(Scope):
|
215 | pass
|
216 |
|
217 |
|
218 |
|
219 | gLambdaCounter = itertools.count()
|
220 | gGenExprCounter = itertools.count()
|
221 |
|
222 |
|
223 | class SymbolVisitor(ASTVisitor):
|
224 | def __init__(self):
|
225 | ASTVisitor.__init__(self)
|
226 | self.scopes = {} # node -> Scope instance, the "return value".
|
227 | self.klass = None
|
228 |
|
229 | # Nodes that define new scopes
|
230 |
|
231 | def visitModule(self, node):
|
232 | scope = self.module = self.scopes[node] = ModuleScope()
|
233 | self.visit(node.node, scope)
|
234 |
|
235 | visitExpression = visitModule
|
236 |
|
237 | def visitFunction(self, node, parent):
|
238 | if node.decorators:
|
239 | self.visit(node.decorators, parent)
|
240 | parent.add_def(node.name)
|
241 | for n in node.defaults:
|
242 | self.visit(n, parent)
|
243 | scope = FunctionScope(node.name, self.module, self.klass)
|
244 | if parent.nested or isinstance(parent, FunctionScope):
|
245 | scope.nested = 1
|
246 | self.scopes[node] = scope
|
247 | self._do_args(scope, node.argnames)
|
248 | self.visit(node.code, scope)
|
249 | self.handle_free_vars(scope, parent)
|
250 |
|
251 | def visitGenExpr(self, node, parent):
|
252 | obj_name = "generator expression<%d>" % gGenExprCounter.next()
|
253 |
|
254 | # BUG FIX: These name references happen OUTSIDE the GenExprScope!
|
255 | # NOTE: I can see the difference with 'opyc symbols', but somehow I
|
256 | # can't construct a difference in the executed code (opyc dis).
|
257 |
|
258 | # NOTE: This should probably just be quals[0] like visitGenExpr() in
|
259 | # pycodegen.py: "precomputation of outmost iterable".
|
260 | # TODO: Test it out with gold/genexpr_nested.py.
|
261 | for genfor in node.code.quals:
|
262 | self.visit(genfor.iter, parent)
|
263 |
|
264 | scope = GenExprScope(obj_name, self.module, self.klass)
|
265 |
|
266 | if parent.nested or isinstance(parent, (FunctionScope, GenExprScope)):
|
267 | scope.nested = 1
|
268 |
|
269 | self.scopes[node] = scope
|
270 |
|
271 | self.visit(node.code, scope)
|
272 |
|
273 | self.handle_free_vars(scope, parent)
|
274 |
|
275 | def visitGenExprInner(self, node, scope):
|
276 | for genfor in node.quals:
|
277 | self.visit(genfor, scope)
|
278 |
|
279 | self.visit(node.expr, scope)
|
280 |
|
281 | def visitGenExprFor(self, node, scope):
|
282 | self.visit(node.assign, scope, 1)
|
283 |
|
284 | # BUG FIX: node.iter contains a Name() node for the iterable variable.
|
285 | # But it is not really used -- an ITERABLE to it is passed to the
|
286 | # generator CodeObject instead!
|
287 |
|
288 | # That is, in each of these cases, we are using the GET_ITER bytecode, then
|
289 | # CALL_FUNCTION to pass it in to the generator.
|
290 | # print(x for x in nums)
|
291 | # print(x for x in range(3))
|
292 | # print(x for x in [1,2,3])
|
293 |
|
294 | #self.visit(node.iter, scope)
|
295 |
|
296 | for if_ in node.ifs:
|
297 | self.visit(if_, scope)
|
298 |
|
299 | def visitGenExprIf(self, node, scope):
|
300 | self.visit(node.test, scope)
|
301 |
|
302 | def visitLambda(self, node, parent, assign=0):
|
303 | # Lambda is an expression, so it could appear in an expression
|
304 | # context where assign is passed. The transformer should catch
|
305 | # any code that has a lambda on the left-hand side.
|
306 | assert not assign
|
307 |
|
308 | for n in node.defaults:
|
309 | self.visit(n, parent)
|
310 |
|
311 | obj_name = "lambda.%d" % gLambdaCounter.next()
|
312 |
|
313 | scope = LambdaScope(obj_name, self.module, klass=self.klass)
|
314 |
|
315 | if parent.nested or isinstance(parent, FunctionScope):
|
316 | scope.nested = 1
|
317 | self.scopes[node] = scope
|
318 | self._do_args(scope, node.argnames)
|
319 | self.visit(node.code, scope)
|
320 | self.handle_free_vars(scope, parent)
|
321 |
|
322 | def _do_args(self, scope, args):
|
323 | for name in args:
|
324 | if type(name) == types.TupleType:
|
325 | self._do_args(scope, name)
|
326 | else:
|
327 | scope.add_param(name)
|
328 |
|
329 | def handle_free_vars(self, scope, parent):
|
330 | parent.add_child(scope)
|
331 | scope.handle_children()
|
332 |
|
333 | def visitClass(self, node, parent):
|
334 | parent.add_def(node.name)
|
335 | for n in node.bases:
|
336 | self.visit(n, parent)
|
337 | scope = ClassScope(node.name, self.module)
|
338 | if parent.nested or isinstance(parent, FunctionScope):
|
339 | scope.nested = 1
|
340 | if node.doc is not None:
|
341 | scope.add_def('__doc__')
|
342 | scope.add_def('__module__')
|
343 | self.scopes[node] = scope
|
344 | prev = self.klass
|
345 | self.klass = node.name
|
346 | self.visit(node.code, scope)
|
347 | self.klass = prev
|
348 | self.handle_free_vars(scope, parent)
|
349 |
|
350 | # name can be a def or a use
|
351 |
|
352 | # XXX a few calls and nodes expect a third "assign" arg that is
|
353 | # true if the name is being used as an assignment. only
|
354 | # expressions contained within statements may have the assign arg.
|
355 |
|
356 | def visitName(self, node, scope, assign=0):
|
357 | if assign:
|
358 | scope.add_def(node.name)
|
359 | else:
|
360 | scope.add_use(node.name)
|
361 |
|
362 | # operations that bind new names
|
363 |
|
364 | def visitFor(self, node, scope):
|
365 | self.visit(node.assign, scope, 1)
|
366 | self.visit(node.list, scope)
|
367 | self.visit(node.body, scope)
|
368 | if node.else_:
|
369 | self.visit(node.else_, scope)
|
370 |
|
371 | def visitFrom(self, node, scope):
|
372 | for name, asname in node.names:
|
373 | if name == "*":
|
374 | continue
|
375 | scope.add_def(asname or name)
|
376 |
|
377 | def visitImport(self, node, scope):
|
378 | for name, asname in node.names:
|
379 | i = name.find(".")
|
380 | if i > -1:
|
381 | name = name[:i]
|
382 | scope.add_def(asname or name)
|
383 |
|
384 | def visitGlobal(self, node, scope):
|
385 | for name in node.names:
|
386 | scope.add_global(name)
|
387 |
|
388 | def visitAssign(self, node, scope):
|
389 | """Propagate assignment flag down to child nodes.
|
390 |
|
391 | The Assign node doesn't itself contains the variables being
|
392 | assigned to. Instead, the children in node.nodes are visited
|
393 | with the assign flag set to true. When the names occur in
|
394 | those nodes, they are marked as defs.
|
395 |
|
396 | Some names that occur in an assignment target are not bound by
|
397 | the assignment, e.g. a name occurring inside a slice. The
|
398 | visitor handles these nodes specially; they do not propagate
|
399 | the assign flag to their children.
|
400 | """
|
401 | for n in node.nodes:
|
402 | self.visit(n, scope, 1)
|
403 | self.visit(node.expr, scope)
|
404 |
|
405 | def visitAssName(self, node, scope, assign=1):
|
406 | scope.add_def(node.name)
|
407 |
|
408 | def visitAssAttr(self, node, scope, assign=0):
|
409 | self.visit(node.expr, scope, 0)
|
410 |
|
411 | def visitSubscript(self, node, scope, assign=0):
|
412 | self.visit(node.expr, scope, 0)
|
413 | for n in node.subs:
|
414 | self.visit(n, scope, 0)
|
415 |
|
416 | def visitSlice(self, node, scope, assign=0):
|
417 | self.visit(node.expr, scope, 0)
|
418 | if node.lower:
|
419 | self.visit(node.lower, scope, 0)
|
420 | if node.upper:
|
421 | self.visit(node.upper, scope, 0)
|
422 |
|
423 | def visitAugAssign(self, node, scope):
|
424 | # If the LHS is a name, then this counts as assignment.
|
425 | # Otherwise, it's just use.
|
426 | self.visit(node.node, scope)
|
427 | if isinstance(node.node, ast.Name):
|
428 | self.visit(node.node, scope, 1) # XXX worry about this
|
429 | self.visit(node.expr, scope)
|
430 |
|
431 | # prune if statements if tests are false
|
432 |
|
433 | _CONST_TYPES = (types.StringType, types.IntType, types.FloatType)
|
434 |
|
435 | def visitIf(self, node, scope):
|
436 | for test, body in node.tests:
|
437 | if isinstance(test, ast.Const):
|
438 | if isinstance(test.value, self._CONST_TYPES):
|
439 | if not test.value:
|
440 | continue
|
441 | self.visit(test, scope)
|
442 | self.visit(body, scope)
|
443 | if node.else_:
|
444 | self.visit(node.else_, scope)
|
445 |
|
446 | # a yield statement signals a generator
|
447 |
|
448 | def visitYield(self, node, scope):
|
449 | scope.generator = 1
|
450 | self.visit(node.value, scope)
|