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Prevent quadratic runtime for overlap check at large overload counts #15865

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Prevent quadratic runtime for overlap check at large overload counts #15865

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b5a4d7d
Skip overlapping overload check at large overload counts
hauntsaninja Aug 13, 2023
ba15d7d
Merge remote-tracking branch 'upstream/master' into overload-limit
hauntsaninja Dec 15, 2025
f47a455
restrict
hauntsaninja Dec 15, 2025
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9 changes: 9 additions & 0 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -892,6 +892,11 @@ def check_overlapping_overloads(self, defn: OverloadedFuncDef) -> None:
# useful for stubs!
return

max_overload_count = 50
if len(defn.items) >= max_overload_count:
# Since the following is quadratic, we limit the size of the inner loop
self.fail(message_registry.TOO_MANY_OVERLOADS, defn)

# Compute some info about the implementation (if it exists) for use below
impl_type: CallableType | None = None
if defn.impl:
Expand All @@ -914,6 +919,10 @@ def check_overlapping_overloads(self, defn: OverloadedFuncDef) -> None:
continue

for j, item2 in enumerate(defn.items[i + 1 :]):
if j >= max_overload_count:
# Avoid quadratic blowup for large numbers of overloads.
break

assert isinstance(item2, Decorator)
sig2 = self.extract_callable_type(item2.var.type, item2)
if sig2 is None:
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3 changes: 3 additions & 0 deletions mypy/message_registry.py
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Expand Up @@ -106,6 +106,9 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
"Overloaded method has both abstract and non-abstract variants"
)
MULTIPLE_OVERLOADS_REQUIRED: Final = ErrorMessage("Single overload definition, multiple required")
TOO_MANY_OVERLOADS: Final = ErrorMessage(
"Not all overload combinations were checked for overlap because there were too many"
)
READ_ONLY_PROPERTY_OVERRIDES_READ_WRITE: Final = ErrorMessage(
"Read-only property cannot override read-write property"
)
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