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[ty] Emit diagnostic for functional TypedDict with non-literal name #24331

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charliermarsh merged 2 commits into from
Mar 31, 2026
+41 −25
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[ty] Emit diagnostic for functional TypedDict with non-literal name #24331

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[ty] Raise diagnostic for functional TypedDict with non-literal name
charliermarsh Mar 31, 2026
35b633c
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charliermarsh Mar 31, 2026
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14 changes: 12 additions & 2 deletions crates/ty_python_semantic/resources/mdtest/typed_dict.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2529,12 +2529,22 @@ Movie2 = TypedDict("Movie2", name=str, year=int)
```py
from typing_extensions import TypedDict

# error: [invalid-argument-type] "Invalid argument to parameter `typename` of `TypedDict()`"
# error: [invalid-argument-type] "TypedDict name must match the variable it is assigned to: Expected "Bad1", got variable of type `Literal[123]`"
Bad1 = TypedDict(123, {"name": str})

# error: [invalid-argument-type] "The name of a `TypedDict` (`WrongName`) must match the name of the variable it is assigned to (`BadTypedDict3`)"
# error: [invalid-argument-type] "TypedDict name must match the variable it is assigned to: Expected "BadTypedDict3", got "WrongName""
BadTypedDict3 = TypedDict("WrongName", {"name": str})

def f(x: str) -> None:
# error: [invalid-argument-type] "TypedDict name must match the variable it is assigned to: Expected "Y", got variable of type `str`"
Y = TypedDict(x, {})

def g(x: str) -> None:
TypedDict(x, {}) # fine

name = "GoodTypedDict"
GoodTypedDict = TypedDict(name, {"name": str})

# error: [invalid-argument-type] "Expected a dict literal for parameter `fields` of `TypedDict()`"
Bad2 = TypedDict("Bad2", "not a dict")

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52 changes: 29 additions & 23 deletions crates/ty_python_semantic/src/types/infer/builder/typed_dict.rs
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Expand Up @@ -158,34 +158,40 @@ impl<'db> TypeInferenceBuilder<'db, '_> {
);
}

let name = if let Some(literal) = name_type.as_string_literal() {
let name = literal.value(db);

if let Some(assigned_name) = definition.and_then(|definition| definition.name(db))
&& name != assigned_name
&& let Some(builder) = self.context.report_lint(&INVALID_ARGUMENT_TYPE, name_arg)
{
builder.into_diagnostic(format_args!(
"The name of a `TypedDict` (`{name}`) must match \
the name of the variable it is assigned to (`{assigned_name}`)"
));
}

Name::new(name)
} else {
if !name_type.is_assignable_to(db, KnownClass::Str.to_instance(db))
&& let Some(builder) = self.context.report_lint(&INVALID_ARGUMENT_TYPE, name_arg)
{
let mut diagnostic = builder.into_diagnostic(format_args!(
"Invalid argument to parameter `typename` of `TypedDict()`"
let name = name_type
.as_string_literal()
.map(|literal| Name::new(literal.value(db)));

if let Some(definition) = definition
&& let Some(assigned_name) = definition.name(db)
&& Some(assigned_name.as_str()) != name.as_deref()
&& let Some(builder) = self.context.report_lint(&INVALID_ARGUMENT_TYPE, name_arg)
{
let mut diagnostic =
builder.into_diagnostic("TypedDict name must match the variable it is assigned to");
if let Some(name) = name.as_deref() {
diagnostic.set_primary_message(format_args!(
"Expected \"{assigned_name}\", got \"{name}\""
));
} else {
diagnostic.set_primary_message(format_args!(
"Expected `str`, found `{}`",
"Expected \"{assigned_name}\", got variable of type `{}`",
name_type.display(db)
));
}
Name::new_static("<unknown>")
};
} else if !name_type.is_assignable_to(db, KnownClass::Str.to_instance(db))
&& let Some(builder) = self.context.report_lint(&INVALID_ARGUMENT_TYPE, name_arg)
{
let mut diagnostic = builder.into_diagnostic(format_args!(
"Invalid argument to parameter `typename` of `TypedDict()`"
));
diagnostic.set_primary_message(format_args!(
"Expected `str`, found `{}`",
name_type.display(db)
));
}

let name = name.unwrap_or_else(|| Name::new_static("<unknown>"));

if let Some(definition) = definition {
self.deferred.insert(definition);
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