Implement F722

README.md

@@ -124,13 +124,13 @@ ruff's goal is to achieve feature-parity with Flake8 when used (1) without any p
 stylistic checks; limiting to Python 3 obviates the need for certain compatibility checks.)
 
 Under those conditions, Flake8 implements about 60 rules, give or take. At time of writing, ruff
-implements 37 rules. (Note that these 37 rules likely cover a disproportionate share of errors:
+implements 38 rules. (Note that these 38 rules likely cover a disproportionate share of errors:
 unused imports, undefined variables, etc.)
 
-The 23 unimplemented rules are tracked in #170, and include:
+The unimplemented rules are tracked in #170, and include:
 
 - 14 rules related to string `.format` calls.
-- 3 rules related to parsing and syntax errors.
+- 1 rule related to parsing and syntax.
 - 6 logical rules.
 
 Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis Flake8:
@@ -172,6 +172,7 @@ Beyond rule-set parity, ruff suffers from the following limitations vis-à-vis F
 | F704 | YieldOutsideFunction | a `yield` or `yield from` statement outside of a function/method |
 | F706 | ReturnOutsideFunction | a `return` statement outside of a function/method |
 | F707 | DefaultExceptNotLast | an `except:` block as not the last exception handler |
+| F722 | ForwardAnnotationSyntaxError | syntax error in forward annotation '...' |
 | F821 | UndefinedName | Undefined name `...` |
 | F822 | UndefinedExport | Undefined name `...` in `__all__` |
 | F823 | UndefinedLocal | Local variable `...` referenced before assignment |

examples/generate_rules_table.rs

@@ -13,6 +13,7 @@ fn main() {
         CheckKind::DoNotAssignLambda,
         CheckKind::DoNotUseBareExcept,
         CheckKind::DuplicateArgumentName,
+        CheckKind::ForwardAnnotationSyntaxError("...".to_string()),
         CheckKind::FStringMissingPlaceholders,
         CheckKind::FutureFeatureNotDefined("...".to_string()),
         CheckKind::IOError("...".to_string()),

resources/test/fixtures/F722.py

@@ -0,0 +1,10 @@
+class A:
+    pass
+
+
+def f() -> "A":
+    pass
+
+
+def g() -> "///":
+    pass

resources/test/fixtures/pyproject.toml

@@ -31,6 +31,7 @@ select = [
     "F704",
     "F706",
     "F707",
+    "F722",
     "F821",
     "F822",
     "F823",

src/check_ast.rs

@@ -1181,6 +1181,11 @@ impl<'a> Checker<'a> {
             if let Ok(mut expr) = parser::parse_expression(expression, path) {
                 relocate_expr(&mut expr, location);
                 allocator.push(expr);
+            } else if self.settings.select.contains(&CheckCode::F722) {
+                self.checks.push(Check::new(
+                    CheckKind::ForwardAnnotationSyntaxError(expression.to_string()),
+                    location,
+                ));
             }
         }
         for expr in allocator {

src/checks.rs

@@ -37,6 +37,7 @@ pub enum CheckCode {
     F704,
     F706,
     F707,
+    F722,
     F821,
     F822,
     F823,
@@ -126,6 +127,7 @@ impl CheckCode {
             CheckCode::F704 => "F704",
             CheckCode::F706 => "F706",
             CheckCode::F707 => "F707",
+            CheckCode::F722 => "F722",
             CheckCode::F821 => "F821",
             CheckCode::F822 => "F822",
             CheckCode::F823 => "F823",
@@ -172,6 +174,7 @@ pub enum CheckKind {
     DoNotAssignLambda,
     DoNotUseBareExcept,
     DuplicateArgumentName,
+    ForwardAnnotationSyntaxError(String),
     FStringMissingPlaceholders,
     FutureFeatureNotDefined(String),
     IOError(String),
@@ -215,6 +218,7 @@ impl CheckKind {
             CheckKind::DoNotAssignLambda => "DoNotAssignLambda",
             CheckKind::DoNotUseBareExcept => "DoNotUseBareExcept",
             CheckKind::DuplicateArgumentName => "DuplicateArgumentName",
+            CheckKind::ForwardAnnotationSyntaxError(_) => "ForwardAnnotationSyntaxError",
             CheckKind::FStringMissingPlaceholders => "FStringMissingPlaceholders",
             CheckKind::FutureFeatureNotDefined(_) => "FutureFeatureNotDefined",
             CheckKind::IOError(_) => "IOError",
@@ -260,6 +264,7 @@ impl CheckKind {
             CheckKind::DoNotAssignLambda => &CheckCode::E731,
             CheckKind::DoNotUseBareExcept => &CheckCode::E722,
             CheckKind::DuplicateArgumentName => &CheckCode::F831,
+            CheckKind::ForwardAnnotationSyntaxError(_) => &CheckCode::F722,
             CheckKind::FStringMissingPlaceholders => &CheckCode::F541,
             CheckKind::FutureFeatureNotDefined(_) => &CheckCode::F407,
             CheckKind::IOError(_) => &CheckCode::E902,
@@ -317,6 +322,9 @@ impl CheckKind {
             CheckKind::DuplicateArgumentName => {
                 "Duplicate argument name in function definition".to_string()
             }
+            CheckKind::ForwardAnnotationSyntaxError(body) => {
+                format!("syntax error in forward annotation '{body}'")
+            }
             CheckKind::FStringMissingPlaceholders => {
                 "f-string without any placeholders".to_string()
             }

src/linter.rs

@@ -1073,6 +1073,31 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn f722() -> Result<()> {
+        let mut actual = check_path(
+            Path::new("./resources/test/fixtures/F722.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::F722]),
+            },
+            &fixer::Mode::Generate,
+        )?;
+        actual.sort_by_key(|check| check.location);
+        let expected = vec![Check {
+            kind: CheckKind::ForwardAnnotationSyntaxError("///".to_string()),
+            location: Location::new(9, 13),
+            fix: None,
+        }];
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn f821() -> Result<()> {
         let mut actual = check_path(

src/pyproject.rs

@@ -288,6 +288,7 @@ other-attribute = 1
                     CheckCode::F704,
                     CheckCode::F706,
                     CheckCode::F707,
+                    CheckCode::F722,
                     CheckCode::F821,
                     CheckCode::F822,
                     CheckCode::F823,

src/settings.rs

@@ -72,6 +72,7 @@ impl Settings {
                     CheckCode::F704,
                     CheckCode::F706,
                     CheckCode::F707,
+                    CheckCode::F722,
                     CheckCode::F821,
                     CheckCode::F822,
                     CheckCode::F823,