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[ty] typecheck dict methods for TypedDict (#19874)

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## Summary

Typecheck `get()`, `setdefault()`, `pop()` for `TypedDict`

```py
from typing import TypedDict
from typing_extensions import NotRequired

class Employee(TypedDict):
    name: str
    department: NotRequired[str]

emp = Employee(name="Alice", department="Engineering")

emp.get("name")
emp.get("departmen", "Unknown")
emp.pop("department")
emp.pop("name")
```

<img width="838" height="529" alt="Screenshot 2025-08-12 at 11 42 12"
src="https://github.com/user-attachments/assets/77ce150a-223c-4931-b914-551095d8a3a6"
/>


part of https://github.com/astral-sh/ty/issues/154

## Test Plan

Updated Markdown tests

---------

Co-authored-by: David Peter <mail@david-peter.de>
This commit is contained in:
Eric Jolibois
2025-08-29 16:25:03 +02:00
committed by GitHub
parent c2d7c673ca
commit 5a608f7366
6 changed files with 312 additions and 60 deletions
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38
crates/ty_python_semantic/resources/mdtest/typed_dict.md
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@@ -450,19 +450,51 @@ class Person(TypedDict, total=False):
```py
from typing import TypedDict
from typing_extensions import NotRequired
class Person(TypedDict):
name: str
age: int | None
extra: NotRequired[str]
def _(p: Person) -> None:
reveal_type(p.keys()) # revealed: dict_keys[str, object]
reveal_type(p.values()) # revealed: dict_values[str, object]
reveal_type(p.setdefault("name", "Alice")) # revealed: @Todo(Support for `TypedDict`)
# `get()` returns the field type for required keys (no None union)
reveal_type(p.get("name")) # revealed: str
reveal_type(p.get("age")) # revealed: int | None
reveal_type(p.get("name")) # revealed: @Todo(Support for `TypedDict`)
reveal_type(p.get("name", "Unknown")) # revealed: @Todo(Support for `TypedDict`)
# It doesn't matter if a default is specified:
reveal_type(p.get("name", "default")) # revealed: str
reveal_type(p.get("age", 999)) # revealed: int | None
# `get()` can return `None` for non-required keys
reveal_type(p.get("extra")) # revealed: str | None
reveal_type(p.get("extra", "default")) # revealed: str
# The type of the default parameter can be anything:
reveal_type(p.get("extra", 0)) # revealed: str | Literal[0]
# We allow access to unknown keys (they could be set for a subtype of Person)
reveal_type(p.get("unknown")) # revealed: Unknown | None
reveal_type(p.get("unknown", "default")) # revealed: Unknown | Literal["default"]
# `pop()` only works on non-required fields
reveal_type(p.pop("extra")) # revealed: str
reveal_type(p.pop("extra", "fallback")) # revealed: str
# error: [invalid-argument-type] "Cannot pop required field 'name' from TypedDict `Person`"
reveal_type(p.pop("name")) # revealed: Unknown
# Similar to above, the default parameter can be of any type:
reveal_type(p.pop("extra", 0)) # revealed: str | Literal[0]
# `setdefault()` always returns the field type
reveal_type(p.setdefault("name", "Alice")) # revealed: str
reveal_type(p.setdefault("extra", "default")) # revealed: str
# error: [invalid-key] "Invalid key access on TypedDict `Person`: Unknown key "extraz" - did you mean "extra"?"
reveal_type(p.setdefault("extraz", "value")) # revealed: Unknown
```
## Unlike normal classes