static-typing 0.2.7.dev1

AST manipulation

Additionally to the main features, the library contains static_typing.ast_manipulation module which contains low-level tools and building blocks allowing for:

• recursive AST traversal,

• AST validation,

• recursive AST transformations,

• AST transcribing (from typed_ast to built-in ast and vice versa) and

• resolving type hints (described in detail below).

Type hint resolution

In all applicable nodes, type hints are stored in fields type_comment, annotation and returns. The type hint resolver reads those fields – which themseves are either raw strings or ASTs.

It uses provided Python symbol tables to resolve type hints into actual type objects using introspection.

By default, the resolver uses only built-in symbols when called directly or through augment(). However, when called through parse() it uses globals() and locals() of the caller by default.

The resolved type hints are stored directly in the AST. Specifically, each resolved field is stored in a correspondingly named field, which is either resolved_type_comment, resolved_annotation or resolved_returns.

Thus, static type information becomes available in the AST.

Type information combining

For each AST node that might contain any name declarations, an exetended version of a node is provided. Each extended AST node has new fields that store those declared names and type information associated with each name.

These new fields store all type information from all resolved type hints within any local scope, so that a type conflict or lack of type information can be detected. Also, based on this combined information, type inference can be performed.

Specifically, new versions of following AST nodes with new fields are provided: Module, FunctionDef, ClassDef, Assign, AnnAssign, For and With. Those new versions have their names prefixed StaticallyTyped....

A list of entities for which information is gathered in those new fields follows.

For Module:

• defined variables

• defined functions

• defined classes

For FunctionDef:

• parameters and their types

• return types

• kind (i.e. function, instance method, class method, static method, etc.)

• local variables and their types

For ClassDef:

• defined methods (all together and grouped by kind)

• class fields and their types

• instance fields and their types

For Assign and AnnAssign:

• assignment targets and their types

For For:

• index variables and their types

For With:

• context variables and their types

AST rewriting

The AST rewriting means replacing ordinary AST nodes listed above with their extended versions.