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## Summary This PR adds scope and definition for comprehension nodes. This includes the following nodes: * List comprehension * Dictionary comprehension * Set comprehension * Generator expression ### Scope Each expression here adds it's own scope with one caveat - the `iter` expression of the first generator is part of the parent scope. For example, in the following code snippet the `iter1` variable is evaluated in the outer scope. ```py [x for x in iter1] ``` > The iterable expression in the leftmost for clause is evaluated directly in the enclosing scope and then passed as an argument to the implicitly nested scope. > > Reference: https://docs.python.org/3/reference/expressions.html#displays-for-lists-sets-and-dictionaries There's another special case for assignment expressions: > There is one special case: an assignment expression occurring in a list, set or dict comprehension or in a generator expression (below collectively referred to as “comprehensions”) binds the target in the containing scope, honoring a nonlocal or global declaration for the target in that scope, if one exists. > > Reference: https://peps.python.org/pep-0572/#scope-of-the-target For example, in the following code snippet, the variables `a` and `b` are available after the comprehension while `x` isn't: ```py [a := 1 for x in range(2) if (b := 2)] ``` ### Definition Each comprehension node adds a single definition, the "target" variable (`[_ for target in iter]`). This has been accounted for and a new variant has been added to `DefinitionKind`. ### Type Inference Currently, type inference is limited to a single scope. It doesn't _enter_ in another scope to infer the types of the remaining expressions of a node. To accommodate this, the type inference for a **scope** requires new methods which _doesn't_ infer the type of the `iter` expression of the leftmost outer generator (that's defined in the enclosing scope). The type inference for the scope region is split into two parts: * `infer_generator_expression` (similarly for comprehensions) infers the type of the `iter` expression of the leftmost outer generator * `infer_generator_expression_scope` (similarly for comprehension) infers the type of the remaining expressions except for the one mentioned in the previous point The type inference for the **definition** also needs to account for this special case of leftmost generator. This is done by defining a `first` boolean parameter which indicates whether this comprehension definition occurs first in the enclosing expression. ## Test Plan New test cases were added to validate multiple scenarios. Refer to the documentation for each test case which explains what is being tested.
Red Knot
Semantic analysis for the red-knot project.
Vendored types for the stdlib
This crate vendors typeshed's stubs for the standard library. The vendored stubs can be found in crates/red_knot_python_semantic/vendor/typeshed. The file crates/red_knot_python_semantic/vendor/typeshed/source_commit.txt tells you the typeshed commit that our vendored stdlib stubs currently correspond to.
The typeshed stubs are updated every two weeks via an automated PR using the sync_typeshed.yaml workflow in the .github/workflows directory. This workflow can also be triggered at any time via workflow dispatch.