Jedi was able to go crazy and loop endlessly in certain if/self assignment combinations.

Here we limit type inferance per tree scope. I'm still not sure this is the way
to go, but it looks okay for now and we can still go anther way in the future.
Tests are there.

Fixes #929.

jedi/evaluate/__init__.py

@@ -86,6 +86,29 @@ from jedi.evaluate.context import ContextualizedName, ContextualizedNode
 from jedi import parser_utils
 
 
+def _limit_context_infers(func):
+    """
+    This is for now the way how we limit type inferance going wild. There are
+    other ways to ensure recursion limits as well. This is mostly necessary
+    because of instance (self) access that can be quite tricky to limit.
+
+    I'm still not sure this is the way to go, but it looks okay for now and we
+    can still go anther way in the future. Tests are there. ~ dave
+    """
+    def wrapper(evaluator, context, *args, **kwargs):
+        n = context.tree_node
+        try:
+            evaluator.inferred_element_counts[n] += 1
+            if evaluator.inferred_element_counts[n] > 300:
+                debug.warning('In context %s there were too many inferences.', n)
+                return set()
+        except KeyError:
+            evaluator.inferred_element_counts[n] = 1
+        return func(evaluator, context, *args, **kwargs)
+
+    return wrapper
+
+
 class Evaluator(object):
     def __init__(self, grammar, sys_path=None):
         self.grammar = grammar
@@ -94,6 +117,7 @@ class Evaluator(object):
         # To memorize modules -> equals `sys.modules`.
         self.modules = {}  # like `sys.modules`.
         self.compiled_cache = {}  # see `evaluate.compiled.create()`
+        self.inferred_element_counts = {}
         self.mixed_cache = {}  # see `evaluate.compiled.mixed._create()`
         self.analysis = []
         self.dynamic_params_depth = 0
@@ -134,6 +158,7 @@ class Evaluator(object):
             return f.filter_name(filters)
         return f.find(filters, attribute_lookup=not search_global)
 
+    @_limit_context_infers
     def eval_statement(self, context, stmt, seek_name=None):
         with recursion.execution_allowed(self, stmt) as allowed:
             if allowed or context.get_root_context() == self.BUILTINS:
@@ -273,6 +298,7 @@ class Evaluator(object):
         return self._eval_element_not_cached(context, element)
 
     @debug.increase_indent
+    @_limit_context_infers
     def _eval_element_not_cached(self, context, element):
         debug.dbg('eval_element %s@%s', element, element.start_pos)
         types = set()

test/completion/stdlib.py

@@ -236,3 +236,16 @@ import contextlib
 with contextlib.closing('asd') as string:
     #? str()
     string
+
+# -----------------
+# shlex
+# -----------------
+
+# Github issue #929
+import shlex
+qsplit = shlex.split("foo, ferwerwerw werw werw e")
+for part in qsplit:
+    #? str() None
+    part
+    #? str() None
+    part