Add coverage for compound expression branches in _is_simple_expr

- Add test cases for MemberExpr (c.y), UnaryExpr (-1), and OpExpr
  (a + b) as non-common operands that are simple and should still
  trigger FURB108
- Add pragma: no cover for unreachable fallback returns (matches
  existing pattern in common.py)

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

Author: worksbyfriday

refurb/checks/logical/use_in.py

@@ -78,7 +78,7 @@ def _is_simple_expr(node: Expression) -> bool:
         case IndexExpr() | CallExpr():
             return False
 
-    return False
+    return False  # pragma: no cover
 
 
 def _get_non_common_operands(node: OpExpr) -> list[Expression] | None:
@@ -97,7 +97,7 @@ def _get_non_common_operands(node: OpExpr) -> list[Expression] | None:
             operands = [a, b, c, d]
             return [op for i, op in enumerate(operands) if i not in indices]
 
-    return None
+    return None  # pragma: no cover
 
 
 def create_message(indices: tuple[int, int]) -> str:

test/data/err_108.py

@@ -22,6 +22,13 @@ class C:
 _ = "abc" == x or "def" == x
 _ = "abc" == x or x == "def"
 
+# simple compound expressions should still match
+_ = x == c.y or x == "def"
+_ = x == -1 or x == 1
+a = 1
+b = 2
+_ = x == a + b or x == "def"
+
 # these should not
 
 _ = x == "abc" or y == "def"

test/data/err_108.txt

@@ -7,3 +7,6 @@ test/data/err_108.py:17:5 [FURB108]: Replace `x == y or x == z` with `x in (y, z
 test/data/err_108.py:21:5 [FURB108]: Replace `x == y or z == x` with `x in (y, z)`
 test/data/err_108.py:22:5 [FURB108]: Replace `x == y or z == y` with `y in (x, z)`
 test/data/err_108.py:23:5 [FURB108]: Replace `x == y or y == z` with `y in (x, z)`
+test/data/err_108.py:26:5 [FURB108]: Replace `x == y or x == z` with `x in (y, z)`
+test/data/err_108.py:27:5 [FURB108]: Replace `x == y or x == z` with `x in (y, z)`
+test/data/err_108.py:30:5 [FURB108]: Replace `x == y or x == z` with `x in (y, z)`