[flake8-comprehensions] Skip iterables with named expressions in `u…

…nnecessary-map` (`C417`) (#14827)

This PR modifies [unnecessary-map
(C417)](https://docs.astral.sh/ruff/rules/unnecessary-map/#unnecessary-map-c417)
to skip `map` expressions if the iterable contains a named expression,
since those cannot appear in comprehensions.

Closes #14808

crates/ruff_linter/resources/test/fixtures/flake8_comprehensions/C417.py

@@ -47,3 +47,13 @@ def func(arg1: int, arg2: int = 4):
 map(lambda x: x, y if y else z)
 map(lambda x: x, (y if y else z))
 map(lambda x: x, (x, y, z))
+
+# See https://github.com/astral-sh/ruff/issues/14808
+# The following should be Ok since 
+# named expressions are a syntax error inside comprehensions
+a = [1, 2, 3]
+b = map(lambda x: x, c := a)
+print(c)
+
+# Check nested as well
+map(lambda x:x, [c:=a])

crates/ruff_linter/src/rules/flake8_comprehensions/rules/unnecessary_map.rs

@@ -3,6 +3,7 @@ use std::fmt;
 use ruff_diagnostics::{Diagnostic, Fix};
 use ruff_diagnostics::{FixAvailability, Violation};
 use ruff_macros::{derive_message_formats, ViolationMetadata};
+use ruff_python_ast::helpers::any_over_expr;
 use ruff_python_ast::visitor;
 use ruff_python_ast::visitor::Visitor;
 use ruff_python_ast::{self as ast, Arguments, Expr, ExprContext, Parameters, Stmt};
@@ -99,11 +100,17 @@ pub(crate) fn unnecessary_map(
             // Only flag, e.g., `map(lambda x: x + 1, iterable)`.
             let [Expr::Lambda(ast::ExprLambda {
                 parameters, body, ..
-            }), _] = args
+            }), iterable] = args
             else {
                 return;
             };
 
+            // For example, (x+1 for x in (c:=a)) is invalid syntax
+            // so we can't suggest it.
+            if any_over_expr(iterable, &|expr| expr.is_named_expr()) {
+                return;
+            }
+
             if parameters.as_ref().is_some_and(|parameters| {
                 late_binding(parameters, body)
                     || parameters

crates/ruff_linter/src/rules/flake8_comprehensions/snapshots/ruff_linter__rules__flake8_comprehensions__tests__C417_C417.py.snap

@@ -329,6 +329,7 @@ C417.py:47:1: C417 [*] Unnecessary `map()` usage (rewrite using a generator expr
    47 |+(x for x in (y if y else z))
 48 48 | map(lambda x: x, (y if y else z))
 49 49 | map(lambda x: x, (x, y, z))
+50 50 | 
 
 C417.py:48:1: C417 [*] Unnecessary `map()` usage (rewrite using a generator expression)
    |
@@ -347,13 +348,17 @@ C417.py:48:1: C417 [*] Unnecessary `map()` usage (rewrite using a generator expr
 48    |-map(lambda x: x, (y if y else z))
    48 |+(x for x in (y if y else z))
 49 49 | map(lambda x: x, (x, y, z))
+50 50 | 
+51 51 | # See https://github.com/astral-sh/ruff/issues/14808
 
 C417.py:49:1: C417 [*] Unnecessary `map()` usage (rewrite using a generator expression)
    |
 47 | map(lambda x: x, y if y else z)
 48 | map(lambda x: x, (y if y else z))
 49 | map(lambda x: x, (x, y, z))
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ C417
+50 | 
+51 | # See https://github.com/astral-sh/ruff/issues/14808
    |
    = help: Replace `map()` with a generator expression
 
@@ -363,3 +368,6 @@ C417.py:49:1: C417 [*] Unnecessary `map()` usage (rewrite using a generator expr
 48 48 | map(lambda x: x, (y if y else z))
 49    |-map(lambda x: x, (x, y, z))
    49 |+(x for x in (x, y, z))
+50 50 | 
+51 51 | # See https://github.com/astral-sh/ruff/issues/14808
+52 52 | # The following should be Ok since