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� ZdS )a� A bottom-up tree matching algorithm implementation meant to speed
up 2to3's matching process. After the tree patterns are reduced to
their rarest linear path, a linear Aho-Corasick automaton is
created. The linear automaton traverses the linear paths from the
leaves to the root of the AST and returns a set of nodes for further
matching. This reduces significantly the number of candidate nodes.z+George Boutsioukis <gboutsioukis@gmail.com>� N)� defaultdict� )�pytree)� reduce_treec @ s e Zd ZdZe�� Zdd� ZdS )�BMNodez?Class for a node of the Aho-Corasick automaton used in matchingc C s" i | _ g | _ttj�| _d| _d S )N� )�transition_table�fixers�nextr �count�id�content��self� r �)/usr/lib/python3.8/lib2to3/btm_matcher.py�__init__ s zBMNode.__init__N)�__name__�
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BottomMatcherzgThe main matcher class. After instantiating the patterns should
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isinstance�tupler �extendr r )r �patternr r" Z alternativeZ end_nodes�endZ next_noder r r r 1 s" zBottomMatcher.addc C s� | j }tt�}|D ]�}|}|rd|_|jD ]$}t|tj�r*|jdkr*d|_ qPq*|j dkrb|j}n|j }||j
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}qq|S )au The main interface with the bottom matcher. The tree is
traversed from the bottom using the constructed
automaton. Nodes are only checked once as the tree is
retraversed. When the automaton fails, we give it one more
shot(in case the above tree matches as a whole with the
rejected leaf), then we break for the next leaf. There is the
special case of multiple arguments(see code comments) where we
recheck the nodes
Args:
The leaves of the AST tree to be matched
Returns:
A dictionary of node matches with fixers as the keys
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