Fix crash on dataclass field / property collision

mypy/plugins/dataclasses.py

@@ -23,6 +23,7 @@
     ClassDef,
     Context,
     DataclassTransformSpec,
+    Decorator,
     Expression,
     FuncDef,
     FuncItem,
@@ -575,6 +576,10 @@ def collect_attributes(self) -> list[DataclassAttribute] | None:
                 # but the only alternative would be to modify the SymbolTable,
                 # and it's a little hairy to do that in a plugin.
                 continue
+            if isinstance(node, Decorator):
+                # This might be a property / field name clash.
+                # We will issue an error later.
+                continue
 
             assert isinstance(node, Var)
 

test-data/unit/check-dataclasses.test

@@ -2519,3 +2519,15 @@ a: MyDataclass
 b = [a, a]  # trigger joining the types
 
 [builtins fixtures/dataclasses.pyi]
+
+[case testPropertyAndFieldRedefinitionNoCrash]
+from dataclasses import dataclass
+
+@dataclass
+class Foo:
+    @property
+    def c(self) -> int:
+        return 0
+
+    c: int  # E: Name "c" already defined on line 5
+[builtins fixtures/dataclasses.pyi]