Add tests, address review

crates/ty_python_semantic/resources/mdtest/dataclasses/dataclasses.md

@@ -521,6 +521,36 @@ frozen = MyFrozenChildClass()
 del frozen.x  # TODO this should emit an [invalid-assignment]
 ```
 
+A diagnostic is emitted if a non-frozen dataclass inherits from a frozen dataclass:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(frozen=True)
+class FrozenBase:
+    x: int
+
+@dataclass 
+class Child(FrozenBase): # error: [non-frozen-subclass-of-frozen-dataclass] "A non-frozen class `Child` cannot inherit from a class `FrozenBase` that is frozen"
+
+    y: int
+```
+
+A diagnostic is emitted if a frozen dataclass inherits from a non-frozen dataclass:
+
+```py
+from dataclasses import dataclass
+
+@dataclass
+class Base:
+    x: int
+
+@dataclass(frozen=True)
+class FrozenChild(Base): # error: [frozen-subclass-of-non-frozen-dataclass] "A frozen class `FrozenChild` cannot inherit from a class `Base` that is not frozen"
+
+    y: int
+```
+
 ### `match_args`
 
 If `match_args` is set to `True` (the default), the `__match_args__` attribute is a tuple created

crates/ty_python_semantic/src/types/diagnostic.rs

@@ -2227,8 +2227,8 @@ declare_lint! {
     /// Checks for frozen dataclasses that inherit from non-frozen dataclasses.
     ///
     /// ## Why is this bad?
-    /// A frozen dataclass promises immutability. Inheriting from a non-frozen
+    /// Python raises a `TypeError` at runtime when a frozen dataclass
-    /// dataclass breaks that guarantee because the base class allows mutation.
+    /// inherits from a non-frozen dataclass.
     ///
     /// ## Example
     ///
@@ -2255,8 +2255,8 @@ declare_lint! {
     /// Checks for non-frozen dataclasses that inherit from frozen dataclasses.
     ///
     /// ## Why is this bad?
-    /// A frozen dataclass enforces immutability. Allowing a non-frozen subclass
+    /// Python raises a `TypeError` at runtime when a non-frozen dataclass
-    /// would reintroduce mutability and violate the base class contract.
+    /// inherits from a frozen dataclass.
     ///
     /// ## Example
     ///
@@ -2278,8 +2278,6 @@ declare_lint! {
     }
 }
 
-
-
 /// A collection of type check diagnostics.
 #[derive(Default, Eq, PartialEq, get_size2::GetSize)]
 pub struct TypeCheckDiagnostics {

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

@@ -55,7 +55,35 @@ use crate::types::call::{Binding, Bindings, CallArguments, CallError, CallErrorK
 use crate::types::class::{CodeGeneratorKind, FieldKind, MetaclassErrorKind, MethodDecorator};
 use crate::types::context::{InNoTypeCheck, InferContext};
 use crate::types::cyclic::CycleDetector;
-use crate::types::diagnostic::{self, CALL_NON_CALLABLE, CONFLICTING_DECLARATIONS, CONFLICTING_METACLASS, CYCLIC_CLASS_DEFINITION, CYCLIC_TYPE_ALIAS_DEFINITION, DIVISION_BY_ZERO, DUPLICATE_KW_ONLY, INCONSISTENT_MRO, INVALID_ARGUMENT_TYPE, INVALID_ASSIGNMENT, INVALID_ATTRIBUTE_ACCESS, INVALID_BASE, INVALID_DECLARATION, INVALID_GENERIC_CLASS, INVALID_KEY, INVALID_LEGACY_TYPE_VARIABLE, INVALID_METACLASS, INVALID_NAMED_TUPLE, INVALID_NEWTYPE, INVALID_OVERLOAD, INVALID_PARAMETER_DEFAULT, INVALID_PARAMSPEC, INVALID_PROTOCOL, INVALID_TYPE_ARGUMENTS, INVALID_TYPE_FORM, INVALID_TYPE_GUARD_CALL, INVALID_TYPE_VARIABLE_CONSTRAINTS, IncompatibleBases, NON_SUBSCRIPTABLE, POSSIBLY_MISSING_ATTRIBUTE, POSSIBLY_MISSING_IMPLICIT_CALL, POSSIBLY_MISSING_IMPORT, SUBCLASS_OF_FINAL_CLASS, UNDEFINED_REVEAL, UNRESOLVED_ATTRIBUTE, UNRESOLVED_GLOBAL, UNRESOLVED_IMPORT, UNRESOLVED_REFERENCE, UNSUPPORTED_OPERATOR, USELESS_OVERLOAD_BODY, hint_if_stdlib_attribute_exists_on_other_versions, hint_if_stdlib_submodule_exists_on_other_versions, report_attempted_protocol_instantiation, report_bad_dunder_set_call, report_cannot_pop_required_field_on_typed_dict, report_duplicate_bases, report_implicit_return_type, report_index_out_of_bounds, report_instance_layout_conflict, report_invalid_arguments_to_annotated, report_invalid_assignment, report_invalid_attribute_assignment, report_invalid_exception_caught, report_invalid_exception_cause, report_invalid_exception_raised, report_invalid_exception_tuple_caught, report_invalid_generator_function_return_type, report_invalid_key_on_typed_dict, report_invalid_or_unsupported_base, report_invalid_return_type, report_invalid_type_checking_constant, report_named_tuple_field_with_leading_underscore, report_namedtuple_field_without_default_after_field_with_default, report_non_subscriptable, report_possibly_missing_attribute, report_possibly_unresolved_reference, report_rebound_typevar, report_slice_step_size_zero, report_unsupported_augmented_assignment, report_unsupported_binary_operation, report_unsupported_comparison, FROZEN_SUBCLASS_OF_NON_FROZEN_DATACLASS, NON_FROZEN_SUBCLASS_OF_FROZEN_DATACLASS};
+use crate::types::diagnostic::{
+    self, CALL_NON_CALLABLE, CONFLICTING_DECLARATIONS, CONFLICTING_METACLASS,
+    CYCLIC_CLASS_DEFINITION, CYCLIC_TYPE_ALIAS_DEFINITION, DIVISION_BY_ZERO, DUPLICATE_KW_ONLY,
+    FROZEN_SUBCLASS_OF_NON_FROZEN_DATACLASS, INCONSISTENT_MRO, INVALID_ARGUMENT_TYPE,
+    INVALID_ASSIGNMENT, INVALID_ATTRIBUTE_ACCESS, INVALID_BASE, INVALID_DECLARATION,
+    INVALID_GENERIC_CLASS, INVALID_KEY, INVALID_LEGACY_TYPE_VARIABLE, INVALID_METACLASS,
+    INVALID_NAMED_TUPLE, INVALID_NEWTYPE, INVALID_OVERLOAD, INVALID_PARAMETER_DEFAULT,
+    INVALID_PARAMSPEC, INVALID_PROTOCOL, INVALID_TYPE_ARGUMENTS, INVALID_TYPE_FORM,
+    INVALID_TYPE_GUARD_CALL, INVALID_TYPE_VARIABLE_CONSTRAINTS, IncompatibleBases,
+    NON_FROZEN_SUBCLASS_OF_FROZEN_DATACLASS, NON_SUBSCRIPTABLE, POSSIBLY_MISSING_ATTRIBUTE,
+    POSSIBLY_MISSING_IMPLICIT_CALL, POSSIBLY_MISSING_IMPORT, SUBCLASS_OF_FINAL_CLASS,
+    UNDEFINED_REVEAL, UNRESOLVED_ATTRIBUTE, UNRESOLVED_GLOBAL, UNRESOLVED_IMPORT,
+    UNRESOLVED_REFERENCE, UNSUPPORTED_OPERATOR, USELESS_OVERLOAD_BODY,
+    hint_if_stdlib_attribute_exists_on_other_versions,
+    hint_if_stdlib_submodule_exists_on_other_versions, report_attempted_protocol_instantiation,
+    report_bad_dunder_set_call, report_cannot_pop_required_field_on_typed_dict,
+    report_duplicate_bases, report_implicit_return_type, report_index_out_of_bounds,
+    report_instance_layout_conflict, report_invalid_arguments_to_annotated,
+    report_invalid_assignment, report_invalid_attribute_assignment,
+    report_invalid_exception_caught, report_invalid_exception_cause,
+    report_invalid_exception_raised, report_invalid_exception_tuple_caught,
+    report_invalid_generator_function_return_type, report_invalid_key_on_typed_dict,
+    report_invalid_or_unsupported_base, report_invalid_return_type,
+    report_invalid_type_checking_constant, report_named_tuple_field_with_leading_underscore,
+    report_namedtuple_field_without_default_after_field_with_default, report_non_subscriptable,
+    report_possibly_missing_attribute, report_possibly_unresolved_reference,
+    report_rebound_typevar, report_slice_step_size_zero, report_unsupported_augmented_assignment,
+    report_unsupported_binary_operation, report_unsupported_comparison,
+};
 use crate::types::function::{
     FunctionDecorators, FunctionLiteral, FunctionType, KnownFunction, OverloadLiteral,
     is_implicit_classmethod, is_implicit_staticmethod,
@@ -77,14 +105,15 @@ use crate::types::typed_dict::{
 use crate::types::visitor::any_over_type;
 use crate::types::{
     BoundTypeVarInstance, CallDunderError, CallableBinding, CallableType, CallableTypeKind,
-    ClassLiteral, ClassType, DataclassFlags, DataclassParams, DynamicType, InternedType, IntersectionBuilder,
+    ClassLiteral, ClassType, DataclassFlags, DataclassParams, DynamicType, InternedType,
-    IntersectionType, KnownClass, KnownInstanceType, KnownUnion, LintDiagnosticGuard,
+    IntersectionBuilder, IntersectionType, KnownClass, KnownInstanceType, KnownUnion,
-    MemberLookupPolicy, MetaclassCandidate, PEP695TypeAliasType, ParamSpecAttrKind, Parameter,
+    LintDiagnosticGuard, MemberLookupPolicy, MetaclassCandidate, PEP695TypeAliasType,
-    ParameterForm, Parameters, Signature, SpecialFormType, SubclassOfType, TrackedConstraintSet,
+    ParamSpecAttrKind, Parameter, ParameterForm, Parameters, Signature, SpecialFormType,
-    Truthiness, Type, TypeAliasType, TypeAndQualifiers, TypeContext, TypeQualifiers,
+    SubclassOfType, TrackedConstraintSet, Truthiness, Type, TypeAliasType, TypeAndQualifiers,
-    TypeVarBoundOrConstraints, TypeVarBoundOrConstraintsEvaluation, TypeVarDefaultEvaluation,
+    TypeContext, TypeQualifiers, TypeVarBoundOrConstraints, TypeVarBoundOrConstraintsEvaluation,
-    TypeVarIdentity, TypeVarInstance, TypeVarKind, TypeVarVariance, TypedDictType, UnionBuilder,
+    TypeVarDefaultEvaluation, TypeVarIdentity, TypeVarInstance, TypeVarKind, TypeVarVariance,
-    UnionType, UnionTypeInstance, binding_type, infer_scope_types, todo_type,
+    TypedDictType, UnionBuilder, UnionType, UnionTypeInstance, binding_type, infer_scope_types,
+    todo_type,
 };
 use crate::types::{CallableTypes, overrides};
 use crate::types::{ClassBase, add_inferred_python_version_hint_to_diagnostic};
@@ -735,10 +764,12 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                     base_class_literal.dataclass_params(self.db()),
                     class.dataclass_params(self.db()),
                 ) {
-                    let base_is_frozen = base_params.flags(self.db())
+                    let base_is_frozen = base_params
+                        .flags(self.db())
                         .contains(DataclassFlags::FROZEN);
 
-                    let class_is_frozen = class_params.flags(self.db())
+                    let class_is_frozen = class_params
+                        .flags(self.db())
                         .contains(DataclassFlags::FROZEN);
 
                     match (base_is_frozen, class_is_frozen) {