[pylint] Also reports case np.nan/case math.nan (PLW0177) (#1…

…6378)

## Summary

Resolves #16374.

`PLW0177` now also reports the pattern of a case branch if it is an
attribute access whose qualified name is that of either `np.nan` or
`math.nan`.

As the rule is in preview, the changes are not preview-gated.

## Test Plan

`cargo nextest run` and `cargo insta test`.

crates/ruff_linter/resources/test/fixtures/pylint/nan_comparison.py

@@ -53,6 +53,18 @@
 if x == builtins.float("nan"):
     pass
 
+# https://github.com/astral-sh/ruff/issues/16374
+match number:
+    # Errors
+    case np.nan: ...
+    case math.nan: ...
+
+    # No errors
+    case np.nan(): ...
+    case math.nan(): ...
+    case float('nan'): ...
+    case npy_nan: ...
+
 # OK
 if math.isnan(x):
     pass

crates/ruff_linter/src/checkers/ast/analyze/statement.rs

@@ -1742,6 +1742,15 @@ pub(crate) fn statement(stmt: &Stmt, checker: &mut Checker) {
                 pylint::rules::useless_exception_statement(checker, expr);
             }
         }
+        Stmt::Match(ast::StmtMatch {
+            subject: _,
+            cases,
+            range: _,
+        }) => {
+            if checker.enabled(Rule::NanComparison) {
+                pylint::rules::nan_comparison_match(checker, cases);
+            }
+        }
         _ => {}
     }
 }

crates/ruff_linter/src/rules/pylint/rules/nan_comparison.rs

@@ -48,7 +48,21 @@ impl Violation for NanComparison {
 
 /// PLW0177
 pub(crate) fn nan_comparison(checker: &Checker, left: &Expr, comparators: &[Expr]) {
-    for expr in std::iter::once(left).chain(comparators) {
+    nan_comparison_impl(checker, std::iter::once(left).chain(comparators));
+}
+
+/// PLW0177
+pub(crate) fn nan_comparison_match(checker: &Checker, cases: &[ast::MatchCase]) {
+    nan_comparison_impl(
+        checker,
+        cases
+            .iter()
+            .filter_map(|case| case.pattern.as_match_value().map(|pattern| &*pattern.value)),
+    );
+}
+
+fn nan_comparison_impl<'a>(checker: &Checker, comparators: impl Iterator<Item = &'a Expr>) {
+    for expr in comparators {
         if let Some(qualified_name) = checker.semantic().resolve_qualified_name(expr) {
             match qualified_name.segments() {
                 ["numpy", "nan" | "NAN" | "NaN"] => {

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW0177_nan_comparison.py.snap

@@ -1,6 +1,5 @@
 ---
 source: crates/ruff_linter/src/rules/pylint/mod.rs
-snapshot_kind: text
 ---
 nan_comparison.py:11:9: PLW0177 Comparing against a NaN value; use `math.isnan` instead
    |
@@ -89,3 +88,22 @@ nan_comparison.py:53:9: PLW0177 Comparing against a NaN value; use `math.isnan`
    |         ^^^^^^^^^^^^^^^^^^^^^ PLW0177
 54 |     pass
    |
+
+nan_comparison.py:59:10: PLW0177 Comparing against a NaN value; use `np.isnan` instead
+   |
+57 | match number:
+58 |     # Errors
+59 |     case np.nan: ...
+   |          ^^^^^^ PLW0177
+60 |     case math.nan: ...
+   |
+
+nan_comparison.py:60:10: PLW0177 Comparing against a NaN value; use `math.isnan` instead
+   |
+58 |     # Errors
+59 |     case np.nan: ...
+60 |     case math.nan: ...
+   |          ^^^^^^^^ PLW0177
+61 |
+62 |     # No errors
+   |