Fix "not callable" issue for @dataclass(frozen=True) with Final attr (#18572)

Closes #18567 

We should allow inferenced `a: Final = 1`

Author: sobolevn

mypy/plugins/dataclasses.py

@@ -768,6 +768,8 @@ def _freeze(self, attributes: list[DataclassAttribute]) -> None:
             if sym_node is not None:
                 var = sym_node.node
                 if isinstance(var, Var):
+                    if var.is_final:
+                        continue  # do not turn `Final` attrs to `@property`
                     var.is_property = True
             else:
                 var = attr.to_var(info)

test-data/unit/check-dataclasses.test

@@ -2553,3 +2553,26 @@ class X(metaclass=DCMeta):
 class Y(X):
     a: int  # E: Covariant override of a mutable attribute (base class "X" defined the type as "Optional[int]", expression has type "int")
 [builtins fixtures/tuple.pyi]
+
+
+[case testFrozenWithFinal]
+from dataclasses import dataclass
+from typing import Final
+
+@dataclass(frozen=True)
+class My:
+    a: Final = 1
+    b: Final[int] = 2
+
+reveal_type(My.a)  # N: Revealed type is "Literal[1]?"
+reveal_type(My.b)  # N: Revealed type is "builtins.int"
+My.a = 1  # E: Cannot assign to final attribute "a"
+My.b = 2  # E: Cannot assign to final attribute "b"
+
+m = My()
+reveal_type(m.a)  # N: Revealed type is "Literal[1]?"
+reveal_type(m.b)  # N: Revealed type is "builtins.int"
+
+m.a = 1  # E: Cannot assign to final attribute "a"
+m.b = 2  # E: Cannot assign to final attribute "b"
+[builtins fixtures/tuple.pyi]