Tighten _is_simple_expr to only allow names and literals

As dosisod correctly pointed out, member access (@Property),
unary operators (__neg__), and binary operators (__add__) can
all have side effects via dunder methods. Only bare names and
literals are truly safe for eager evaluation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: worksbyfriday

refurb/checks/logical/use_in.py

@@ -2,18 +2,14 @@
 
 from mypy.nodes import (
     BytesExpr,
-    CallExpr,
     ComparisonExpr,
     ComplexExpr,
     Expression,
     FloatExpr,
-    IndexExpr,
     IntExpr,
-    MemberExpr,
     NameExpr,
     OpExpr,
     StrExpr,
-    UnaryExpr,
 )
 
 from refurb.checks.common import (
@@ -57,26 +53,14 @@ class ErrorInfo(Error):
 def _is_simple_expr(node: Expression) -> bool:
     """Check if an expression is simple enough to be safely eagerly evaluated.
 
-    Simple expressions are those that cannot raise exceptions or have side
-    effects when evaluated, making them safe for use in `in` tuple checks
-    where short-circuit evaluation is lost.
+    Only names and literals are considered safe. Member access, unary
+    operators, and binary operators are excluded because @property and
+    dunder methods (__neg__, __add__, etc.) can have side effects.
     """
     match node:
         case NameExpr() | IntExpr() | StrExpr() | BytesExpr() | FloatExpr() | ComplexExpr():
             return True
 
-        case MemberExpr(expr=expr):
-            return _is_simple_expr(expr)
-
-        case UnaryExpr(expr=expr):
-            return _is_simple_expr(expr)
-
-        case OpExpr(left=left, right=right):
-            return _is_simple_expr(left) and _is_simple_expr(right)
-
-        case IndexExpr() | CallExpr():
-            return False
-
     return False
 
 

test/data/err_108.py

@@ -34,3 +34,9 @@ class C:
 d = {"a": 1}
 _ = x == "abc" or x == d["a"]
 _ = x == len(x) or x == "abc"
+
+# member access, unary, and binary ops as non-common operands should not match
+# because @property and dunder methods can have side effects
+_ = x == c.y or x == "abc"
+_ = x == -y or x == 1
+_ = x == (y + x) or x == 2