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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. |
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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.