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Type Checker Rule Comparison Table

scenario basedpyright ty/ruff1 pyrefly
property type mismatch reportPropertyTypeMismatch issue issue
invalid member access on functions reportFunctionMemberAccess unresolved-attribute missing-attribute
module import not found reportMissingImports unresolved-import missing-import
import attribute from module not found reportAttributeAccessIssue unresolved-import missing-module-attribute
wrong argument type in function call reportArgumentType invalid-argument-type bad-argument-type
wrong default value type in function call reportArgumentType invalid-parameter-default bad-function-definition
assert_type failure reportAssertTypeFailure type-assertion-failure, assert-type-unspellable-subtype assert-type
bad assignment type reportAssignmentType invalid-assignment, invalid-declaration bad-assignment
unpack to wrong number of variables reportAssignmentType invalid-assignment bad-unpacking
bad attribute access reportAttributeAccessIssue,reportOptionalMemberAccess unresolved-attribute missing-attribute, no-access
instantiate abstract class reportAbstractUsage issue bad-instantiation
abstract @classmethod call reportAbstractUsage call-abstract-method abstract-method-call
@deprecated usage reportDeprecated deprecated deprecated
incompatible method override reportIncompatibleMethodOverride invalid-method-override bad-override, bad-override-param-name
conflicting members in multiple inheritance reportIncompatibleMethodOverride invalid-method-override inconsistent-inheritance
incompatible attribute override reportIncompatibleVariableOverride invalid-attribute-override3, invalid-typed-dict-field bad-override-mutable-attribute
inconsistent overload reportInconsistentOverload invalid-overload inconsistent-overload
overlapping overload reportOverlappingOverload issue issue
no overload implementation reportNoOverloadImplementation invalid-overload invalid-overload
only one overload reportInconsistentOverload invalid-overload invalid-overload
not subscriptable reportIndexIssue, reportOptionalSubscript not-subscriptable unsupported-operation
index out of range reportGeneralTypeIssues index-out-of-bounds bad-index
invalid type argument usage reportInvalidTypeArguments invalid-type-arguments bad-specialization
invalid type form reportInvalidTypeForm invalid-type-form invalid-annotation, invalid-literal, invalid-type-alias,not-a-type
typevar only used once in signature reportInvalidTypeVarUse issue issue
typevar may go unsolved reportInvalidTypeVarUse issue issue
stub exists but no source reportMissingModuleSource issue missing-source, missing-source-for-stubs
no type annotation on parameter reportMissingParameterType, reportUnknownParameterType ANN001 implicit-any-parameter
source exists but no stubs reportMissingTypeStubs issue untyped-import
invalid usage of operator reportOperatorIssue, reportOptionalOperand unsupported-operator unsupported-operation
undefined variable reportUndefinedVariable, reportUnknownVariableType unresolved-reference unknown-name
variable used after being del'd reportUnboundVariable unresolved-reference unbound-name
conditionally bound variable reportPossiblyUnboundVariable possibly-unresolved-reference unbound-name
private member usage reportAttributeAccessIssue unresolved-attribute missing-attribute
protected member usage reportPrivateUsage SLF001 issue
incorrect return type reportReturnType invalid-return-type bad-return
incorrect yield type reportReturnType invalid-yield invalid-yield
yield outside function no code invalid-syntax invalid-yield
yield from non-Iterable reportGeneralTypeIssues not-iterable invalid-yield
uninitialized instance variable reportUninitializedInstanceVariable issue implicitly-defined-attribute4
argument has an unknown type reportUnknownArgumentType issue issue
member has an unknown type reportUnknownMemberType issue implicit-any-attribute15
useless cast reportUnnecessaryCast redundant-cast redundant-cast
unawaited coroutine reportUnusedCoroutine unused-awaitable unused-coroutine
circular imports reportImportCycles issue issue
unused import reportUnusedImport F401 hint5
unused class reportUnusedClass issue 5
unused function reportUnusedFunction issue 5
unused variable reportUnusedVariable issue 5
duplicate import reportDuplicateImport F811 5
wildcard import reportWildcardImportFromLibrary F403 5
missing mandatory argument to callable reportCallIssue missing-argument missing-argument
too many positional arguments to callable reportCallIssue too-many-positional-arguments bad-argument-count, unexpected-positional-argument
positional argument passed as keyword arg reportCallIssue positional-only-parameter-as-kwarg unexpected-keyword
unknown keyword arg to callable reportCallIssue unknown-argument unexpected-keyword
keyword arg already assigned as positional arg reportCallIssue parameter-already-assigned bad-keyword-argument
keyword arg already assigned as keyword arg reportCallIssue invalid-syntax parse-error
possible unpack of already be assigned keyword arg reportCallIssue parameter-already-assigned potential-bad-keyword-argument
no matching overload reportCallIssue no-matching-overload no-matching-overload, incompatible-overload-residual
call non-callable reportCallIssue, reportOptionalCall call-non-callable not-callable
iterate non-iterable reportGeneralTypeIssues, reportOptionalIterable not-iterable not-iterable
with on non-context manager reportGeneralTypeIssues, reportOptionalContextManager invalid-context-manager bad-context-manager
redeclaration with same type reportRedeclaration issue redefinition
redeclaration with different types reportRedeclaration conflicting-declarations redefinition
NotRequired access in TypedDict reportTypedDictNotRequiredAccess issue not-required-key-access
untyped decorator reportUntypedFunctionDecorator, reportUntypedClassDecorator issue untyped-class-decorator, untyped-function-decorator14
untyped base class reportUntypedBaseClass unsupported-base issue
untyped namedtuple reportUntypedNamedTuple PYI024 5
type comment usage reportTypeCommentUsage PYI033 5
implicit re-export reportPrivateImportUsage, reportPrivateLocalImportUsage issue implicit-reexport
all-caps constant re-assignment reportConstantRedefinition issue issue
Final re-assignment reportGeneralTypeIssues invalid-assignment bad-assignment
Final without initial value reportGeneralTypeIssues final-without-value invalid-annotation
inconsistent constructor reportInconsistentConstructor issue issue
missing super call reportMissingSuperCall issue missing-super-call
invalid super call reportGeneralTypeIssues unavailable-implicit-super-arguments invalid-super-call
invalid super call with explicit arguments reportArgumentType invalid-super-argument invalid-super-call, invalid-argument
invalid string escape reportInvalidStringEscapeSequence W605 5
unknown lambda type reportUnknownLambdaType issue implicit-any-lambda
missing type argument reportMissingTypeArgument missing-type-argument implicit-any-type-argument
mutable default value for arguemnt reportCallInDefaultInitializer B006 5
unnecessary conditions reportUnnecessaryIsInstance issue redundant-condition9
unnecessary comparison reportUnnecessaryComparison issue incompatible-comparison, unnecessary-comparison9
unnecessary in reportUnnecessaryContains unsupported-operator issue
wrong name for first method parameter reportSelfClsParameterName N804, N805 5
self must be supertype of its class reportGeneralTypeIssues issue invalid-annotation
implicit string concatenation reportImplicitStringConcatenation ISC001 5
unhashable reportUnhashable issue issue
source code in stub file reportInvalidStubStatement PYI010, PYI015 5
incomplete stub reportIncompleteStub issue 5
invalid name in __all__ reportUnsupportedDunderAll F822 bad-dunder-all
unresolvable __all__ reportUnsupportedDunderAll PLE0605 unresolvable-dunder-all
unused call result reportUnusedCallResult issue unused-call-result
unused coroutine reportUnusedCoroutine issue unused-coroutine
unreachable except statement reportUnusedExcept issue issue
unused expression reportUnusedExpression B018 5
unused ignore comment reportUnnecessaryTypeIgnoreComment unused-ignore-comment, ignore-comment-unknown-rule unused-ignore
ignore comment without code reportIgnoreCommentWithoutRule issue issue
invalid ignore comment reportTypeCommentUsage7 invalid-ignore-comment issue
non-exhaustive match statement reportMatchNotExhaustive issue non-exhaustive-match
too many positional patterns in match reportGeneralTypeIssues invalid-match-pattern bad-match
unreachable code reportUnreachable issue unreachable6, unreachable-match-case
implicit override reportImplicitOverride missing-override-decorator missing-override-decorator
implicit Any expression reportAny issue issue
implicit Any attribute declaration reportUnannotatedClassAttribute issue implicit-any-attribute
explicit Any reportExplicitAny TID2512 explicit-any
implicit relative import reportImplicitRelativeImport unresolved-import missing-import
non-overlapping cast reportInvalidCast issue issue
unsafe multiple inheritance reportUnsafeMultipleInheritance issue issue
unused parameter reportUnusedParameter ARG001 hint5
implicitly abstract class reportImplicitAbstractClass issue implicit-abstract-class
abstract class with no abstract methods reportEmptyAbstractUsage issue bad-instantiation
incompatible unannotated override reportIncompatibleUnannotatedOverride, reportUnannotatedClassAttribute issue bad-override-mutable-attribute
abstract method on non-abstract class reportInvalidAbstractMethod issue invalid-abstract-method
self or cls with default value reportSelfClsDefault issue bad-function-definition
abstract method in @final class reportGeneralTypeIssues abstract-method-in-final-class bad-class-definition
override @final method reportIncompatibleMethodOverride override-of-final-method bad-override
subtype @final class reportGeneralTypeIssues subclass-of-final-class invalid-inheritance
override Final attribute reportGeneralTypeIssues override-of-final-variable bad-override
unannotated protocol attribute reportUnannotatedClassAttribute10 ambiguous-protocol-member unannotated-protocol-member
object used in condition when __bool__ = None reportOperatorIssue unsupported-bool-conversion, unsupported-operator invalid-argument, not-callable, invalid-argument
conflicting metaclass reportGeneralTypeIssues conflicting-metaclass invalid-inheritance
cyclic class definition in .pyi file reportGeneralTypeIssues cyclic-class-definition invalid-inheritance
cyclic type alias reportGeneralTypeIssues cyclic-type-alias-definition invalid-type-alias
dataclass default field order reportGeneralTypeIssues dataclass-field-order bad-class-definition
duplicate base class reportGeneralTypeIssues duplicate-base invalid-inheritance
syntax error in quoted type no code invalid-syntax-in-forward-annotation, escape-character-in-forward-annotation not-a-type
@final on non-method reportGeneralTypeIssues final-on-non-method invalid-decorator
implicit string concatenation in quoted type reportGeneralTypeIssues,reportImplicitStringConcatenation implicit-concatenated-string-type-annotation not-a-type
inconsistent MRO reportGeneralTypeIssues inconsistent-mro invalid-inheritance
not awaitable reportGeneralTypeIssues invalid-await not-async
assign to ClassVar from instance reportAttributeAccessIssue invalid-attribute-access read-only
ClassVar and Final reportInvalidTypeForm, reportAssignmentType redundant-final-classvar invalid-annotation
assign to readonly @property reportAttributeAccessIssue invalid-assignment read-only
invalid base class reportGeneralTypeIssues invalid-base invalid-inheritance
type annotation on enum member reportGeneralTypeIssues invalid-enum-member-annotation invalid-annotation
invalid except type reportGeneralTypeIssues invalid-exception-caught not-a-type
invalid raise/from type reportGeneralTypeIssues invalid-raise bad-raise
@override without overriding anything reportGeneralTypeIssues invalid-explicit-override bad-override
frozen/non-frozen dataclass inheritance reportGeneralTypeIssues invalid-frozen-dataclass-subclass invalid-inheritance
class with both old & new generic syntax reportGeneralTypeIssues invalid-generic-class invalid-type-var
TypeVar with default before one without reportGeneralTypeIssues invalid-generic-class invalid-type-var
invalid key in TypedDict index access reportGeneralTypeIssues invalid-key bad-typed-dict-key
invalid key when instantiating TypedDict reportAssignmentType, reportCallIssue invalid-key bad-typed-dict-key, unexpected-keyword
missing key when instantiating TypedDict reportAssignmentType, reportCallIssue missing-typed-dict-key bad-typed-dict-key,no-matching-overload
legacy positional arg after normal arg reportGeneralTypeIssues invalid-legacy-positional-parameter bad-function-definition
invalid match pattern reportGeneralTypeIssues invalid-match-pattern invalid-pattern
NamedTuple multiple inheritance reportGeneralTypeIssues invalid-named-tuple invalid-inheritance
NamedTuple attribute starting with _ reportGeneralTypeIssues invalid-named-tuple bad-class-definition
override NamedTuple attribute reportIncompatibleVariableOverride invalid-named-tuple-override bad-override
NewType first arg must be LiteralString reportArgumentType invalid-newtype invalid-argument
NewType invalid base reportGeneralTypeIssues invalid-newtype invalid-argument
NewType wrong name reportGeneralTypeIssues mismatched-type-name invalid-argument
invalid legacy ParamSpec reportGeneralTypeIssues, reportCallIssue invalid-paramspec invalid-param-spec
legacy ParamSpec wrong name reportGeneralTypeIssues mismatched-type-name invalid-param-spec
Protocol inheriting from non-Protocol reportGeneralTypeIssues invalid-protocol invalid-inheritance
invalid @total_ordering reportGeneralTypeIssues invalid-total-ordering missing-attribute
invalid TypeAliasType reportGeneralTypeIssues invalid-type-alias-type invalid-type-alias
invalid TypeGuard/TypeIs definition reportGeneralTypeIssues invalid-type-guard-definition bad-function-definition
TypedDict with metaclass reportGeneralTypeIssues invalid-typed-dict-header invalid-inheritance
TypedDict with invalid class argument reportGeneralTypeIssues unknown-argument bad-typed-dict
TypedDict with method reportGeneralTypeIssues invalid-typed-dict-statement bad-class-definition
legacy TypedDict wrong name reportGeneralTypeIssues mismatched-type-name name-mismatch
isinstance on TypedDict reportArgumentType, reportGeneralTypeIssues isinstance-against-typed-dict invalid-argument, invalid-pattern
isinstance on non-@runtime_checkable Protocol reportArgumentType isinstance-against-protocol invalid-argument, invalid-pattern
unsafe @runtime_checkable isinstance call reportGeneralTypeIssues issue unsafe-overlap
non-callable __init_subclass__ reportAssignmentType non-callable-init-subclass issue
implicitly imported submodule reportAttributeAccessIssue possibly-missing-submodule implicit-import
type annotation on subscript assignment reportInvalidTypeForm invalid-type-form invalid-syntax
r-string quoted type reportGeneralTypeIssues raw-string-type-annotation invalid-annotation
protocol attribute not defined on the class reportGeneralTypeIssues ambiguous-protocol-member
reveal_type info message no code revealed-type reveal-type
unsupported del reportGeneralTypeIssues invalid-syntax unsupported-delete, parse-error
invalid sentinel reportArgumentType, reportCallIssue issue invalid-sentinel12
type var with type var in bound reportGeneralTypeIssues invalid-type-variable-bound invalid-annotation
type var with type var in constraints reportGeneralTypeIssues invalid-type-variable-constraints invalid-annotation
invalid type var default reportGeneralTypeIssues invalid-type-variable-default invalid-type-var
shadowed type var reportGeneralTypeIssues shadowed-type-variable invalid-type-var
unbound type var reportGeneralTypeIssues unbound-type-variable invalid-type-var
type var tuple must be unpacked reportGeneralTypeIssues issue invalid-type-var-tuple
legacy TypeVar wrong name reportGeneralTypeIssues mismatched-type-name invalid-type-var
legacy TypeVar with one constraint reportGeneralTypeIssues invalid-legacy-type-variable invalid-type-var
legacy TypeVar used with wrong variance reportGeneralTypeIssues issue invalid-variance
legacy TypeVar can be covariant/contravariant reportInvalidTypeVarUse issue variance-mismatch
legacy TypeVar redefinition invalid-legacy-type-variable 13
legacy TypeVar not assigned to variable invalid-legacy-type-variable invalid-type-var
legacy namedtuple wrong name mismatched-type-name name-mismatch
invalid TYPE_CHECKING assignment invalid-type-checking-constant invalid-type-checking-constant
generic Enum invalid-generic-enum invalid-inheritance
invalid use of @dataclass invalid-dataclass bad-class-definition
invalid override on frozen dataclass invalid-dataclass-override bad-class-definition
assign to instance variable from class invalid-attribute-access11 issue
instance layout conflict instance-layout-conflict invalid-inheritance
non-decorator usage of final ineffective-final issue
empty function body empty-body empty-body
call "top" callable type call-top-callable issue
division by zero division-by-zero division-by-zero
duplicate KW_ONLY duplicate-kw-only issue
invalid metaclass invalid-metaclass invalid-inheritance
TypedDict unpacked class arguments invalid-typed-dict-header invalid-inheritance
conditionally defined member possibly-missing-attribute,possibly-missing-implicit-call issue
conditionally defined import issue possibly-missing-import issue
static_assert error static-assert-error issue
subclass dataclass with order=True subclass-of-dataclass-with-order issue
super call in NamedTuple super-call-in-named-tuple-method invalid-super-call
reveal_type used without importing it undefined-reveal unimported-directive
global with no declaration unresolved-global unknown-name
dynamic base class unsupported-dynamic-base issue
useless overload body useless-overload-body useless-overload-body
zero step in slice zero-stepsize-in-slice bad-index
implicit Any from empty container issue implicit-any-empty-container
inconsistent overload default parameter issue inconsistent-overload-default
invalid Self type issue invalid-self-type
dvergent type issue non-convergent-recursion
unpack open TypedDict issue open-unpacking
pytorch lints8 pytorch-efficiency-lint-cuda-call, pytorch-efficiency-lint-item-call, pytorch-efficiency-lint-print-tensor, pytorch-efficiency-lint-redundant-to-call
str as Iterable[str] or Sequence[str] issue string-as-iterable
function without return type annotation issue ANN201 unannotated-return
useless builtin type conversion issue unnecessary-type-conversion

  1. Some checks are not present in ty, but are covered by ruff. It's safe to assume that astral won't duplicate functionality they already have in their linter, so we combine the two tools in this table. to avoid ambiguity, we reference the cryptic code when referring to ruff rules rather than their human readable name. ↩

  2. Requires config to explicitly ban Any ↩

  3. This rule barely works, see https://github.com/astral-sh/ty/issues/2158 ↩

  4. This rule is half broken, see https://github.com/facebook/pyrefly/issues/3660 ↩

  5. Lint rule covered by ruff, not in scope for a type checker ↩↩↩↩↩↩↩↩↩↩↩↩↩↩↩↩

  6. This rule is mostly broken, see https://github.com/facebook/pyrefly/issues/3689 ↩

  7. Does not detect invalid # pyright: comments, only # type: ones ↩

  8. These are lint rules specific to a 3rd party library which are out of scope for a type checker, so i'm not going to bother with these ↩

  9. Doesn't catch everything, see https://github.com/facebook/pyrefly/issues/3690 ↩↩

  10. Not the intended use case for this rule, it reports all unannotated class attributes not just Protocols ↩

  11. see https://github.com/astral-sh/ty/issues/3992 ↩

  12. doesn't currently report mismatched sentinel name, see https://github.com/facebook/pyrefly/issues/4142#issuecomment-5087594256 ↩

  13. see https://github.com/facebook/pyrefly/issues/3754#issuecomment-4678649318 ↩

  14. doesn't catch most cases, see https://github.com/facebook/pyrefly/issues/3661#issuecomment-5099332062 ↩

  15. see https://github.com/facebook/pyrefly/issues/3661#issuecomment-5098798075 ↩