Module `opshin.rewrite.rewrite_forbidden_overwrites`

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from ast import *

from ..util import CompilingNodeTransformer

"""
Make sure that certain variable names may never be overwritten
"""

FORBIDDEN_NAMES = {
    # type check
    "isinstance",
    # Type annotations
    "List",
    "Dict",
    "Union",
    # decorator and class name
    "dataclass",
    "PlutusData",
    # special decorator marking wrapped builtins
    "wraps_builtin",
}


class ForbiddenOverwriteError(ValueError):
    pass


class RewriteForbiddenOverwrites(CompilingNodeTransformer):
    step = "Checking for forbidden name overwrites"

    def visit_Name(self, node: Name) -> Name:
        if isinstance(node.ctx, Store) and node.id in FORBIDDEN_NAMES:
            raise ForbiddenOverwriteError(
                f"It is not allowed to overwrite name {node.id}"
            )
        return node

Classes

class ForbiddenOverwriteError (*args, **kwargs)

Inappropriate argument value (of correct type).

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class ForbiddenOverwriteError(ValueError):
    pass

Ancestors

builtins.ValueError
builtins.Exception
builtins.BaseException

class RewriteForbiddenOverwrites

A :class:NodeVisitor subclass that walks the abstract syntax tree and allows modification of nodes.

The NodeTransformer will walk the AST and use the return value of the visitor methods to replace or remove the old node. If the return value of the visitor method is None, the node will be removed from its location, otherwise it is replaced with the return value. The return value may be the original node in which case no replacement takes place.

Here is an example transformer that rewrites all occurrences of name lookups (foo) to data['foo']::

class RewriteName(NodeTransformer):

   def visit_Name(self, node):
       return Subscript(
           value=Name(id='data', ctx=Load()),
           slice=Constant(value=node.id),
           ctx=node.ctx
       )

Keep in mind that if the node you're operating on has child nodes you must either transform the child nodes yourself or call the :meth:generic_visit method for the node first.

For nodes that were part of a collection of statements (that applies to all statement nodes), the visitor may also return a list of nodes rather than just a single node.

Usually you use the transformer like this::

node = YourTransformer().visit(node)

Expand source code

class RewriteForbiddenOverwrites(CompilingNodeTransformer):
    step = "Checking for forbidden name overwrites"

    def visit_Name(self, node: Name) -> Name:
        if isinstance(node.ctx, Store) and node.id in FORBIDDEN_NAMES:
            raise ForbiddenOverwriteError(
                f"It is not allowed to overwrite name {node.id}"
            )
        return node

Ancestors

CompilingNodeTransformer
TypedNodeTransformer
ast.NodeTransformer
ast.NodeVisitor

Class variables

var step

Methods

def visit(self, node)

Inherited from: CompilingNodeTransformer.visit

Visit a node.

def visit_Name(self, node: ast.Name) ‑> ast.Name

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def visit_Name(self, node: Name) -> Name:
    if isinstance(node.ctx, Store) and node.id in FORBIDDEN_NAMES:
        raise ForbiddenOverwriteError(
            f"It is not allowed to overwrite name {node.id}"
        )
    return node