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Mark more things as literals #20604

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57ae6c6
Mark more things as literals
A5rocks Jan 17, 2026
2a869b0
Move `NAMES` to a constant
A5rocks Jan 23, 2026
b98c82a
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Jan 23, 2026
f3b23b1
Expand `is_named_instance`
A5rocks Jan 23, 2026
d836ead
...
A5rocks Jan 23, 2026
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4 changes: 0 additions & 4 deletions mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6543,10 +6543,6 @@ def comparison_type_narrowing_helper(self, node: ComparisonExpr) -> tuple[TypeMa

if (
literal(expr) == LITERAL_TYPE
and not is_literal_none(expr)
and not is_literal_not_implemented(expr)
and not is_false_literal(expr)
and not is_true_literal(expr)
and not self.is_literal_enum(expr)
and not (
isinstance(p_expr := get_proper_type(expr_type), CallableType)
Expand Down
23 changes: 20 additions & 3 deletions mypy/literals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
OpExpr,
ParamSpecExpr,
PromoteExpr,
RefExpr,
RevealExpr,
SetComprehension,
SetExpr,
Expand All @@ -44,6 +45,7 @@
SuperExpr,
TempNode,
TupleExpr,
TypeAlias,
TypeAliasExpr,
TypeApplication,
TypedDictExpr,
Expand All @@ -55,6 +57,7 @@
YieldExpr,
YieldFromExpr,
)
from mypy.types import is_named_instance
from mypy.visitor import ExpressionVisitor

# [Note Literals and literal_hash]
Expand Down Expand Up @@ -135,10 +138,24 @@ def literal(e: Expression) -> int:
else:
return LITERAL_NO

elif isinstance(e, NameExpr):
if isinstance(e.node, Var) and e.node.is_final and e.node.final_value is not None:
elif isinstance(e, RefExpr):
if (
isinstance(e, NameExpr)
and isinstance(e.node, Var)
and e.node.is_final
and e.node.final_value is not None
):
return LITERAL_YES

NAMES = ("builtins.True", "builtins.False", "builtins.None", "builtins.NotImplemented")
if e.fullname in NAMES:
return LITERAL_YES
return LITERAL_TYPE
elif isinstance(e.node, TypeAlias) and not e.node.python_3_12_type_alias:
if is_named_instance(e.node.target, NAMES):
return LITERAL_YES

if isinstance(e, NameExpr):
return LITERAL_TYPE

if isinstance(e, (IntExpr, FloatExpr, ComplexExpr, StrExpr, BytesExpr)):
return LITERAL_YES
Expand Down