From 0af4b23d9f5f6b77046a0fd1311d2e65b747dfaf Mon Sep 17 00:00:00 2001
From: Dylan <53534755+dylwil3@users.noreply.github.com>
Date: Sun, 9 Feb 2025 10:16:28 -0600
Subject: [PATCH] [`ruff`] Skip type definitions for `missing-f-string-syntax`
 (`RUF027`) (#16054)

As an f-string is never correct in a type definition context, we skip
[missing-f-string-syntax
(RUF027)](https://docs.astral.sh/ruff/rules/missing-f-string-syntax/#missing-f-string-syntax-ruf027)
in this case.

Closes #16037
---
 .../ruff_linter/resources/test/fixtures/ruff/RUF027_0.py   | 7 +++++++
 .../src/rules/ruff/rules/missing_fstring_syntax.rs         | 5 +++++
 ...uff_linter__rules__ruff__tests__RUF027_RUF027_0.py.snap | 5 +++++
 3 files changed, 17 insertions(+)

diff --git a/crates/ruff_linter/resources/test/fixtures/ruff/RUF027_0.py b/crates/ruff_linter/resources/test/fixtures/ruff/RUF027_0.py
index 4780348c12..e5bef3033f 100644
--- a/crates/ruff_linter/resources/test/fixtures/ruff/RUF027_0.py
+++ b/crates/ruff_linter/resources/test/fixtures/ruff/RUF027_0.py
@@ -72,3 +72,10 @@ def method_calls():
 def format_specifiers():
     a = 4
     b = "{a:b} {a:^5}"
+
+# fstrings are never correct as type definitions
+# so we should always skip those
+def in_type_def():
+    from typing import cast
+    a = 'int'
+    cast('f"{a}"','11')
diff --git a/crates/ruff_linter/src/rules/ruff/rules/missing_fstring_syntax.rs b/crates/ruff_linter/src/rules/ruff/rules/missing_fstring_syntax.rs
index 05c7cb54f4..73c77ccdba 100644
--- a/crates/ruff_linter/src/rules/ruff/rules/missing_fstring_syntax.rs
+++ b/crates/ruff_linter/src/rules/ruff/rules/missing_fstring_syntax.rs
@@ -73,6 +73,11 @@ impl AlwaysFixableViolation for MissingFStringSyntax {
 pub(crate) fn missing_fstring_syntax(checker: &Checker, literal: &ast::StringLiteral) {
     let semantic = checker.semantic();
 
+    // fstrings are never correct as type definitions
+    if semantic.in_type_definition() {
+        return;
+    }
+
     // we want to avoid statement expressions that are just a string literal.
     // there's no reason to have standalone f-strings and this lets us avoid docstrings too
     if let ast::Stmt::Expr(ast::StmtExpr { value, .. }) = semantic.current_statement() {
diff --git a/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF027_RUF027_0.py.snap b/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF027_RUF027_0.py.snap
index 2973ba2930..590ff57921 100644
--- a/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF027_RUF027_0.py.snap
+++ b/crates/ruff_linter/src/rules/ruff/snapshots/ruff_linter__rules__ruff__tests__RUF027_RUF027_0.py.snap
@@ -306,6 +306,8 @@ RUF027_0.py:74:9: RUF027 [*] Possible f-string without an `f` prefix
 73 |     a = 4
 74 |     b = "{a:b} {a:^5}"
    |         ^^^^^^^^^^^^^^ RUF027
+75 |
+76 | # fstrings are never correct as type definitions
    |
    = help: Add `f` prefix
 
@@ -315,3 +317,6 @@ RUF027_0.py:74:9: RUF027 [*] Possible f-string without an `f` prefix
 73 73 |     a = 4
 74    |-    b = "{a:b} {a:^5}"
    74 |+    b = f"{a:b} {a:^5}"
+75 75 | 
+76 76 | # fstrings are never correct as type definitions
+77 77 | # so we should always skip those