Module `opshin.rewrite.rewrite_forbidden_return`

Expand source code

from ast import *

from ..util import CompilingNodeTransformer

"""
Make sure that returns are not allowed in the outermost scope
"""


class RewriteForbiddenReturn(CompilingNodeTransformer):
    step = "Checking for forbidden return statements"

    def visit_Return(self, node):
        raise SyntaxError(f"Forbidden return statement outside function")

    def visit_FunctionDef(self, node: Name) -> Name:
        # skip the content of the function definition
        return node

Classes

class RewriteForbiddenReturn

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 RewriteForbiddenReturn(CompilingNodeTransformer):
    step = "Checking for forbidden return statements"

    def visit_Return(self, node):
        raise SyntaxError(f"Forbidden return statement outside function")

    def visit_FunctionDef(self, node: Name) -> Name:
        # skip the content of the function definition
        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_FunctionDef(self, node: ast.Name) ‑> ast.Name

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def visit_FunctionDef(self, node: Name) -> Name:
    # skip the content of the function definition
    return node

def visit_Return(self, node)

Expand source code

def visit_Return(self, node):
    raise SyntaxError(f"Forbidden return statement outside function")