Add use-isinstance-bool check

docs/checks.md

@@ -2414,4 +2414,25 @@ def normalize_phone_number(phone_number: str) -> int:
     digits = filter(str.isdigit, phone_number)
 
     return int("".join(digits))
+```
+
+## FURB191: `use-isinstance-bool`
+
+Categories: `readability`
+
+Don't check if a value is `True` or `False` using `in`, use an
+`isinstance()` call.
+
+Bad:
+
+```python
+if value in {True, False}:
+    pass
+```
+
+Good:
+
+```python
+if isinstance(value, bool):
+    pass
 ```

refurb/checks/readability/use_isinstance_bool.py

@@ -0,0 +1,69 @@
+from dataclasses import dataclass
+
+from mypy.nodes import ComparisonExpr, Expression, ListExpr, NameExpr, SetExpr, TupleExpr
+
+from refurb.checks.common import stringify
+from refurb.error import Error
+
+
+@dataclass
+class ErrorInfo(Error):
+    """
+    Don't check if a value is `True` or `False` using `in`, use an
+    `isinstance()` call.
+
+    Bad:
+
+    ```
+    if value in {True, False}:
+        pass
+    ```
+
+    Good:
+
+    ```
+    if isinstance(value, bool):
+        pass
+    ```
+    """
+
+    name = "use-isinstance-bool"
+    code = 191
+    categories = ("readability",)
+
+
+# TODO: move to common
+def is_true(expr: Expression) -> bool:
+    match expr:
+        case NameExpr(fullname="builtins.True"):
+            return True
+
+    return False
+
+
+def is_false(expr: Expression) -> bool:
+    match expr:
+        case NameExpr(fullname="builtins.False"):
+            return True
+
+    return False
+
+
+def check(node: ComparisonExpr, errors: list[Error]) -> None:
+    match node:
+        case ComparisonExpr(
+            operators=["in" | "not in" as op],
+            operands=[
+                lhs,
+                SetExpr(items=[t, f]) | TupleExpr(items=[t, f]) | ListExpr(items=[t, f]),
+            ],
+        ) if (is_true(t) and is_false(f)) or (is_false(t) and is_true(f)):
+            old = stringify(node)
+            new = f"isinstance({stringify(lhs)}, bool)"
+
+            if op == "not in":
+                new = f"not {new}"
+
+            msg = f"Replace `{old}` with `{new}`"
+
+            errors.append(ErrorInfo.from_node(node, msg))

test/data/err_191.py

@@ -0,0 +1,54 @@
+b = True
+
+# these should match
+
+if b in {True, False}: pass
+if b in {False, True}: pass
+if b in [True, False]: pass  # noqa: FURB109
+if b in [False, True]: pass  # noqa: FURB109
+if b in (True, False): pass
+if b in (False, True): pass
+
+_ = [x for x in [] if b in (True, False)]  # noqa: FURB109
+_ = {x for x in [] if b in (True, False)}  # noqa: FURB109
+_ = (x for x in [] if b in (True, False))  # noqa: FURB109
+_ = {k: v for k, v in {}.items() if b in (True, False)}
+
+_ = 1 if b in (True, False) else 2
+
+match b:
+    case _ if b in (True, False):
+        pass
+
+while b in {True, False}:
+    pass
+
+assert b in {True, False}
+
+if b not in {True, False}: pass
+
+
+# these should not
+if b in {True}: pass  # noqa: FURB171
+if b in [True]: pass  # noqa: FURB109, FURB171
+if b in (True,): pass  # noqa: FURB171
+
+if b in {True, True}: pass
+
+for x in [True, False]: pass  # noqa: FURB109
+
+_ = [x for x in [True, False]]  # noqa: FURB109
+_ = {x for x in [True, False]}  # noqa: FURB109
+_ = (x for x in [True, False])  # noqa: FURB109
+
+# TODO: suggest `isinstance(x, bool) or y`
+if b in {True, False, 123}: pass
+if b in {False, True, 123}: pass
+if b in [True, False, 123]: pass  # noqa: FURB109
+if b in [False, True, 123]: pass  # noqa: FURB109
+if b in (True, False, 123): pass
+if b in (False, True, 123): pass
+
+if b == {True, False}: pass
+if b == {False, True}: pass
+if b == [True, False]: pass

test/data/err_191.txt

@@ -0,0 +1,15 @@
+test/data/err_191.py:5:4 [FURB191]: Replace `b in {True, False}` with `isinstance(b, bool)`
+test/data/err_191.py:6:4 [FURB191]: Replace `b in {False, True}` with `isinstance(b, bool)`
+test/data/err_191.py:7:4 [FURB191]: Replace `b in [True, False]` with `isinstance(b, bool)`
+test/data/err_191.py:8:4 [FURB191]: Replace `b in [False, True]` with `isinstance(b, bool)`
+test/data/err_191.py:9:4 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:10:4 [FURB191]: Replace `b in (False, True)` with `isinstance(b, bool)`
+test/data/err_191.py:12:23 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:13:23 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:14:23 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:15:37 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:17:10 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:20:15 [FURB191]: Replace `b in (True, False)` with `isinstance(b, bool)`
+test/data/err_191.py:23:7 [FURB191]: Replace `b in {True, False}` with `isinstance(b, bool)`
+test/data/err_191.py:26:8 [FURB191]: Replace `b in {True, False}` with `isinstance(b, bool)`
+test/data/err_191.py:28:4 [FURB191]: Replace `b not in {True, False}` with `not isinstance(b, bool)`