[refurb] Mark the FURB161 fix unsafe except for integers and booleans (#17240)

The PR fixes #16457 .

Specifically, `FURB161` is marked safe, but the rule generates safe
fixes only in specific cases. Therefore, we attempt to mark the fix as
unsafe when we are not in one of these cases.

For instances, the fix is marked as aunsafe just in case of strings (as
pointed out in the issue). Let me know if I should change something.

---------

Co-authored-by: Brent Westbrook <brentrwestbrook@gmail.com>

crates/ruff_linter/resources/test/fixtures/refurb/FURB161.py

@@ -12,6 +12,7 @@ count = bin(0x10 + 0x1000).count("1")  # FURB161
 count = bin(ten()).count("1")  # FURB161
 count = bin((10)).count("1")  # FURB161
 count = bin("10" "15").count("1")  # FURB161
+count = bin("123").count("1") # FURB161
 
 count = x.bit_count()  # OK
 count = (10).bit_count()  # OK

crates/ruff_linter/src/rules/refurb/rules/bit_count.rs

@@ -1,7 +1,8 @@
-use ruff_diagnostics::{AlwaysFixableViolation, Diagnostic, Edit, Fix};
+use ruff_diagnostics::{AlwaysFixableViolation, Applicability, Diagnostic, Edit, Fix};
 use ruff_macros::{derive_message_formats, ViolationMetadata};
 use ruff_python_ast::PythonVersion;
 use ruff_python_ast::{self as ast, Expr, ExprAttribute, ExprCall};
+use ruff_python_semantic::analyze::type_inference::{NumberLike, PythonType, ResolvedPythonType};
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
@@ -27,6 +28,11 @@ use crate::fix::snippet::SourceCodeSnippet;
 /// y = 0b1111011.bit_count()
 /// ```
 ///
+/// ## Fix safety
+/// This rule's fix is marked as unsafe unless the argument to `bin` can be inferred as
+/// an instance of a type that implements the `__index__` and `bit_count` methods because this can
+/// change the exception raised at runtime for an invalid argument.
+///
 /// ## Options
 /// - `target-version`
 ///
@@ -163,6 +169,14 @@ pub(crate) fn bit_count(checker: &Checker, call: &ExprCall) {
         | Expr::Subscript(_) => false,
     };
 
+    // check if the fix is safe or not
+    let applicability: Applicability = match ResolvedPythonType::from(arg) {
+        ResolvedPythonType::Atom(PythonType::Number(NumberLike::Integer | NumberLike::Bool)) => {
+            Applicability::Safe
+        }
+        _ => Applicability::Unsafe,
+    };
+
     let replacement = if parenthesize {
         format!("({literal_text}).bit_count()")
     } else {
@@ -176,11 +190,10 @@ pub(crate) fn bit_count(checker: &Checker, call: &ExprCall) {
         },
         call.range(),
     );
-
-    diagnostic.set_fix(Fix::safe_edit(Edit::range_replacement(
-        replacement,
-        call.range(),
-    )));
+    diagnostic.set_fix(Fix::applicable_edit(
+        Edit::range_replacement(replacement, call.range()),
+        applicability,
+    ));
 
     checker.report_diagnostic(diagnostic);
 }

crates/ruff_linter/src/rules/refurb/snapshots/ruff_linter__rules__refurb__tests__FURB161_FURB161.py.snap

@@ -12,7 +12,7 @@ FURB161.py:6:9: FURB161 [*] Use of `bin(x).count('1')`
   |
   = help: Replace with `(x).bit_count()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 3 3 | def ten() -> int:
 4 4 |     return 10
 5 5 | 
@@ -137,7 +137,7 @@ FURB161.py:12:9: FURB161 [*] Use of `bin(ten()).count('1')`
    |
    = help: Replace with `ten().bit_count()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 9  9  | count = bin(0xA).count("1")  # FURB161
 10 10 | count = bin(0o12).count("1")  # FURB161
 11 11 | count = bin(0x10 + 0x1000).count("1")  # FURB161
@@ -145,7 +145,7 @@ FURB161.py:12:9: FURB161 [*] Use of `bin(ten()).count('1')`
    12 |+count = ten().bit_count()  # FURB161
 13 13 | count = bin((10)).count("1")  # FURB161
 14 14 | count = bin("10" "15").count("1")  # FURB161
-15 15 | 
+15 15 | count = bin("123").count("1") # FURB161
 
 FURB161.py:13:9: FURB161 [*] Use of `bin(10).count('1')`
    |
@@ -154,6 +154,7 @@ FURB161.py:13:9: FURB161 [*] Use of `bin(10).count('1')`
 13 | count = bin((10)).count("1")  # FURB161
    |         ^^^^^^^^^^^^^^^^^^^^ FURB161
 14 | count = bin("10" "15").count("1")  # FURB161
+15 | count = bin("123").count("1") # FURB161
    |
    = help: Replace with `(10).bit_count()`
 
@@ -164,8 +165,8 @@ FURB161.py:13:9: FURB161 [*] Use of `bin(10).count('1')`
 13    |-count = bin((10)).count("1")  # FURB161
    13 |+count = (10).bit_count()  # FURB161
 14 14 | count = bin("10" "15").count("1")  # FURB161
-15 15 | 
-16 16 | count = x.bit_count()  # OK
+15 15 | count = bin("123").count("1") # FURB161
+16 16 | 
 
 FURB161.py:14:9: FURB161 [*] Use of `bin("10" "15").count('1')`
    |
@@ -173,17 +174,37 @@ FURB161.py:14:9: FURB161 [*] Use of `bin("10" "15").count('1')`
 13 | count = bin((10)).count("1")  # FURB161
 14 | count = bin("10" "15").count("1")  # FURB161
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^ FURB161
-15 |
-16 | count = x.bit_count()  # OK
+15 | count = bin("123").count("1") # FURB161
    |
    = help: Replace with `("10" "15").bit_count()`
 
-ℹ Safe fix
+ℹ Unsafe fix
 11 11 | count = bin(0x10 + 0x1000).count("1")  # FURB161
 12 12 | count = bin(ten()).count("1")  # FURB161
 13 13 | count = bin((10)).count("1")  # FURB161
 14    |-count = bin("10" "15").count("1")  # FURB161
    14 |+count = ("10" "15").bit_count()  # FURB161
-15 15 | 
-16 16 | count = x.bit_count()  # OK
-17 17 | count = (10).bit_count()  # OK
+15 15 | count = bin("123").count("1") # FURB161
+16 16 | 
+17 17 | count = x.bit_count()  # OK
+
+FURB161.py:15:9: FURB161 [*] Use of `bin("123").count('1')`
+   |
+13 | count = bin((10)).count("1")  # FURB161
+14 | count = bin("10" "15").count("1")  # FURB161
+15 | count = bin("123").count("1") # FURB161
+   |         ^^^^^^^^^^^^^^^^^^^^^ FURB161
+16 |
+17 | count = x.bit_count()  # OK
+   |
+   = help: Replace with `"123".bit_count()`
+
+ℹ Unsafe fix
+12 12 | count = bin(ten()).count("1")  # FURB161
+13 13 | count = bin((10)).count("1")  # FURB161
+14 14 | count = bin("10" "15").count("1")  # FURB161
+15    |-count = bin("123").count("1") # FURB161
+   15 |+count = "123".bit_count() # FURB161
+16 16 | 
+17 17 | count = x.bit_count()  # OK
+18 18 | count = (10).bit_count()  # OK