Class VariableRenameVisitor

mypy/renaming.py:40–424

Rename variables to allow redefinition of variables. For example, consider this code: x = 0 f(x) x = "a" g(x) It will be transformed like this: x' = 0 f(x') x = "a" g(x) There will be two independent variables (x' and x) that will ha

class VariableRenameVisitor(TraverserVisitor):
    """Rename variables to allow redefinition of variables.

    For example, consider this code:

      x = 0
      f(x)

      x = "a"
      g(x)

    It will be transformed like this:

      x' = 0
      f(x')

      x = "a"
      g(x)

    There will be two independent variables (x' and x) that will have separate
    inferred types. The publicly exposed variant will get the non-suffixed name.
    This is the last definition at module top level and the first definition
    (argument) within a function.

    Renaming only happens for assignments within the same block. Renaming is
    performed before semantic analysis, immediately after parsing.

    The implementation performs a rudimentary static analysis. The analysis is
    overly conservative to keep things simple.
    """

    def __init__(self) -> None:
        # Counter for labeling new blocks
        self.block_id = 0
        # Number of surrounding try statements that disallow variable redefinition
        self.disallow_redef_depth = 0
        # Number of surrounding loop statements
        self.loop_depth = 0
        # Map block id to loop depth.
        self.block_loop_depth: dict[int, int] = {}
        # Stack of block ids being processed.
        self.blocks: list[int] = []
        # List of scopes; each scope maps short (unqualified) name to block id.
        self.var_blocks: list[dict[str, int]] = []

        # References to variables that we may need to rename. List of
        # scopes; each scope is a mapping from name to list of collections
        # of names that refer to the same logical variable.
        self.refs: list[dict[str, list[list[NameExpr]]]] = []
        # Number of reads of the most recent definition of a variable (per scope)
        self.num_reads: list[dict[str, int]] = []
        # Kinds of nested scopes (FILE, FUNCTION or CLASS)
        self.scope_kinds: list[int] = []

    def visit_mypy_file(self, file_node: MypyFile) -> None:
        """Rename variables within a file.

        This is the main entry point to this class.