[ty] Support `typing.TypeAliasType` by sharkdp · Pull Request #18156 · astral-sh/ruff

sharkdp · 2025-05-17T20:12:05Z

Summary

Support direct uses of typing.TypeAliasType, as in:

from typing import TypeAliasType

IntOrStr = TypeAliasType("IntOrStr", int | str)

def f(x: IntOrStr) -> None:
    reveal_type(x)  # revealed: int | str

closes astral-sh/ty#392

Ecosystem

The new false positive here:

+ error[invalid-type-form] altair/utils/core.py:49:53: The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`

comes from the fact that we infer the second argument as a type expression now. We silence false positives for PEP695 ParamSpecs, but not for P = ParamSpec("P") inside Callable[P, ...].

Test Plan

New Markdown tests

github-actions · 2025-05-17T20:14:56Z

`mypy_primer` results

Changes were detected when running on open source projects

altair (https://github.com/vega/altair)
+ error[invalid-type-form] altair/utils/core.py:49:53: The first argument to `Callable` must be either a list of types, ParamSpec, Concatenate, or `...`
- error[invalid-argument-type] altair/utils/core.py:48:58: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar]`
- error[invalid-argument-type] altair/utils/core.py:49:60: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[ParamSpec, typing.TypeVar]`
- error[invalid-argument-type] altair/utils/core.py:53:56: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar, typing.TypeVar]`
- error[invalid-argument-type] altair/utils/core.py:56:54: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar, ParamSpec, typing.TypeVar]`
- error[invalid-argument-type] altair/utils/plugin_registry.py:25:52: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar]`
- error[invalid-argument-type] altair/utils/schemapi.py:903:56: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar]`
- error[invalid-argument-type] altair/vegalite/v5/schema/_typing.py:105:61: Argument to bound method `__init__` is incorrect: Expected `tuple[TypeVar | ParamSpec | TypeVarTuple, ...]`, found `tuple[typing.TypeVar]`
- error[invalid-context-manager] tests/vegalite/v5/test_api.py:1409:10: Object of type `Unknown | PluginEnabler[@Todo(unknown type subscript), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
+ error[invalid-context-manager] tests/vegalite/v5/test_api.py:1409:10: Object of type `Unknown | PluginEnabler[@Todo(Generic PEP-695 type alias), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
- error[invalid-context-manager] tests/vegalite/v5/test_api.py:1414:10: Object of type `Unknown | PluginEnabler[@Todo(unknown type subscript), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
+ error[invalid-context-manager] tests/vegalite/v5/test_api.py:1414:10: Object of type `Unknown | PluginEnabler[@Todo(Generic PEP-695 type alias), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
- error[invalid-context-manager] tests/vegalite/v5/test_api.py:1420:10: Object of type `Unknown | PluginEnabler[@Todo(unknown type subscript), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
+ error[invalid-context-manager] tests/vegalite/v5/test_api.py:1420:10: Object of type `Unknown | PluginEnabler[@Todo(Generic PEP-695 type alias), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
- error[invalid-context-manager] tests/vegalite/v5/test_theme.py:48:14: Object of type `Unknown | PluginEnabler[@Todo(unknown type subscript), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
+ error[invalid-context-manager] tests/vegalite/v5/test_theme.py:48:14: Object of type `Unknown | PluginEnabler[@Todo(Generic PEP-695 type alias), ThemeConfig]` cannot be used with `with` because it does not correctly implement `__exit__`
- Found 1349 diagnostics
+ Found 1343 diagnostics

sharkdp · 2025-05-17T20:16:55Z

crates/ty_python_semantic/src/types.rs

+    pub(crate) fn definition(&self, db: &'db dyn Db) -> Option<Definition<'db>> {
+        match self {
+            TypeAliasType::PEP695(type_alias) => Some(type_alias.definition(db)),
+            TypeAliasType::Bare(_) => None,


This is used for go-to-type-definition. It seems more involved to provide the original definition here, as we would need to keep track of it through various Type operations and the calling machinery.

sharkdp · 2025-05-17T20:39:35Z

crates/ty_project/tests/check.rs

+const KNOWN_FAILURES: &[(&str, bool, bool)] = &[
+    // Fails with too-many-cycle-iterations due to a self-referential
+    // type alias, see https://github.com/astral-sh/ty/issues/256
+    ("crates/ruff_linter/resources/test/fixtures/pyflakes/F401_34.py", true, true),


This is unfortunate, but that file could just as easily have been written using PEP 695 type aliases …

crates/ty_python_semantic/src/types.rs

dcreager · 2025-05-18T14:07:49Z

crates/ty_python_semantic/src/types/call/bind.rs

+                        Some(KnownClass::TypeAliasType) => {
+                            if let [Some(name), Some(value), ..] = overload.parameter_types() {
+                                // TODO: emit a diagnostic if the name is not a string literal
+                                if let Some(name) = name.into_string_literal() {
+                                    overload.set_return_type(Type::KnownInstance(
+                                        KnownInstanceType::TypeAliasType(TypeAliasType::Bare(
+                                            BareTypeAliasType::new(db, name.value(db), value),
+                                        )),
+                                    ));
+                                }
+                            }
+                        }


If you move this construction logic into infer.rs, like we do for legacy typevars, you'll be able to get the Definition of the assignment statement, at least for the case where a call to the TypeAliasType constructor is being immediately assigned to a variable. That will let you return a non-None result for definition up above for bare type aliases too.

ruff/crates/ty_python_semantic/src/types/infer.rs

Lines 5197 to 5199 in dd04ca7

let assigned_to = (self.index)

.try_expression(call_expression_node)

.and_then(|expr| expr.assigned_to(self.db()));

(Moving the construction logic also made it easier to emit diagnostics for legacy typevar construction, which might help you discharge the TODO comment)

Thank you — I didn't realize we had call-related code in infer.rs, too. That was really helpful. TODO comment is also resolved.

sharkdp · 2025-05-19T07:41:28Z

crates/ty_python_semantic/src/types/diagnostic.rs

+    /// from typing import TypeAliasType
+    ///
+    /// IntOrStr = TypeAliasType("IntOrStr", int | str)  # okay
+    /// NewAlias = TypeAliasType(get_name(), int)        # error: TypeAliasType name must be a string literal


I wasn't sure if we should have the same strict requirements here as for legacy TypeVar constructions. I couldn't find anything in the spec, but pyright also emits diagnostics, if a TypeAliasType is not immediately assigned to a variable, for example.

Works for me!

dcreager · 2025-05-19T14:30:11Z

crates/ty/docs/rules.md

 ### Links
 * [Related issues](https://github.com/astral-sh/ty/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20call-non-callable)
-* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L86)
+* [View source](https://github.com/astral-sh/ruff/blob/main/crates%2Fty_python_semantic%2Fsrc%2Ftypes%2Fdiagnostic.rs#L87)


~~Did you have to update these manually?~~

Whew, you did not! Looks like this was auto-generated from diagnostic.rs

[Not for this PR] We might consider marking this as a generated file in .gitattributes to hide them in PR diffs

dcreager · 2025-05-19T14:34:36Z

crates/ty_python_semantic/src/types/diagnostic.rs

+    /// from typing import TypeAliasType
+    ///
+    /// IntOrStr = TypeAliasType("IntOrStr", int | str)  # okay
+    /// NewAlias = TypeAliasType(get_name(), int)        # error: TypeAliasType name must be a string literal


Works for me!

## Summary See comment here: #18156 (comment)

* main: [ty] Infer function call typevars in both directions (#18155) Add rustfmt.toml file (#18197) [ty] Update mypy primer (#18196) [ty] Mark generated files as such in .gitattributes (#18195) [ty] Support `typing.TypeAliasType` (#18156)

sharkdp added the ty Multi-file analysis & type inference label May 17, 2025

sharkdp commented May 17, 2025

View reviewed changes

sharkdp force-pushed the david/bare-type-alias-type branch 2 times, most recently from a66b2fd to c89a7f2 Compare May 17, 2025 20:31

[ty] Support typing.TypeAliasType

2c0a65d

sharkdp force-pushed the david/bare-type-alias-type branch from c89a7f2 to 2c0a65d Compare May 17, 2025 20:36

sharkdp marked this pull request as ready for review May 17, 2025 20:36

sharkdp requested review from AlexWaygood, MichaReiser, carljm and dcreager as code owners May 17, 2025 20:36

sharkdp commented May 17, 2025

View reviewed changes

AlexWaygood reviewed May 17, 2025

View reviewed changes

crates/ty_python_semantic/src/types.rs Outdated Show resolved Hide resolved

dcreager reviewed May 18, 2025

View reviewed changes

Use ast::name::Name

26d40ec

sharkdp commented May 19, 2025

View reviewed changes

Move to infer.rs, add diagnostic

4852009

sharkdp force-pushed the david/bare-type-alias-type branch from d9729e6 to 4852009 Compare May 19, 2025 07:47

dcreager approved these changes May 19, 2025

View reviewed changes

sharkdp merged commit 4c889d5 into main May 19, 2025
35 checks passed

sharkdp deleted the david/bare-type-alias-type branch May 19, 2025 14:36

sharkdp mentioned this pull request May 19, 2025

[ty] Mark generated files as such in .gitattributes #18195

Merged

sharkdp added a commit that referenced this pull request May 19, 2025

[ty] Mark generated files as such in .gitattributes (#18195)

b913f56

## Summary See comment here: #18156 (comment)

carljm mentioned this pull request May 22, 2025

memory regression between 0.0.1a5 and 0.0.1a6? astral-sh/ty#482

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[ty] Support `typing.TypeAliasType`#18156

[ty] Support `typing.TypeAliasType`#18156
sharkdp merged 3 commits intomainfrom
david/bare-type-alias-type

sharkdp commented May 17, 2025 •

edited

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	let assigned_to = (self.index)
	.try_expression(call_expression_node)
	.and_then(\|expr\| expr.assigned_to(self.db()));

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Summary

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mypy_primer results

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sharkdp commented May 17, 2025 •

edited

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`mypy_primer` results