Fix stack overflow in ANN401 on quoted annotations with escape sequences (#23912)

Author: VedantMadane

crates/ruff_linter/resources/test/fixtures/flake8_annotations/annotation_presence.py

@@ -164,3 +164,9 @@ def __init__(self: "Foo", foo: int):
 class Class:
     def __init__(self):
         print(f"{self.attr=}")
+
+
+# Regression test for: https://github.com/astral-sh/ruff/issues/14695
+# A quoted annotation containing a nested string with an escape sequence
+# should not cause a stack overflow.
+def quoted_escape(x: "'in\x74'"): pass

crates/ruff_linter/src/rules/flake8_annotations/snapshots/ruff_linter__rules__flake8_annotations__tests__defaults.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_annotations/mod.rs
+assertion_line: 36
 ---
 ANN201 [*] Missing return type annotation for public function `foo`
  --> annotation_presence.py:5:5
@@ -319,4 +320,31 @@ help: Add return type annotation: `None`
     -     def __init__(self):
 165 +     def __init__(self) -> None:
 166 |         print(f"{self.attr=}")
+167 | 
+168 | 
 note: This is an unsafe fix and may change runtime behavior
+
+ANN201 [*] Missing return type annotation for public function `quoted_escape`
+   --> annotation_presence.py:172:5
+    |
+170 | # A quoted annotation containing a nested string with an escape sequence
+171 | # should not cause a stack overflow.
+172 | def quoted_escape(x: "'in\x74'"): pass
+    |     ^^^^^^^^^^^^^
+    |
+help: Add return type annotation: `None`
+169 | # Regression test for: https://github.com/astral-sh/ruff/issues/14695
+170 | # A quoted annotation containing a nested string with an escape sequence
+171 | # should not cause a stack overflow.
+    - def quoted_escape(x: "'in\x74'"): pass
+172 + def quoted_escape(x: "'in\x74'") -> None: pass
+note: This is an unsafe fix and may change runtime behavior
+
+ANN401 Dynamically typed expressions (typing.Any) are disallowed in `x`
+   --> annotation_presence.py:172:22
+    |
+170 | # A quoted annotation containing a nested string with an escape sequence
+171 | # should not cause a stack overflow.
+172 | def quoted_escape(x: "'in\x74'"): pass
+    |                      ^^^^^^^^^^
+    |

crates/ruff_linter/src/rules/ruff/typing.rs

@@ -114,8 +114,17 @@ impl<'a> TypingTarget<'a> {
             Expr::StringLiteral(string_expr) => checker
                 .parse_type_annotation(string_expr)
                 .ok()
-                .map(|parsed_annotation| {
-                    TypingTarget::ForwardReference(parsed_annotation.expression())
+                .and_then(|parsed_annotation| {
+                    let inner = parsed_annotation.expression();
+                    if inner.is_string_literal_expr() {
+                        // A forward reference that resolves to another string literal
+                        // (e.g. `"'int'"`) is not a valid type annotation. Avoid
+                        // recursing, which would loop forever when `relocate_expr`
+                        // gives the inner literal the same text range as the outer.
+                        None
+                    } else {
+                        Some(TypingTarget::ForwardReference(inner))
+                    }
                 }),
             _ => semantic.resolve_qualified_name(expr).map_or(
                 // If we can't resolve the call path, it must be defined in the