Implement F704 (#66)

resources/test/src/F704.py

@@ -0,0 +1,10 @@
+def f() -> int:
+    yield 1
+
+
+class Foo:
+    yield 2
+
+
+yield 3
+yield from 3

resources/test/src/pyproject.toml

@@ -7,6 +7,7 @@ select = [
     "F403",
     "F541",
     "F634",
+    "F704",
     "F706",
     "F821",
     "F831",

src/check_ast.rs

@@ -349,6 +349,21 @@ impl Visitor for Checker<'_> {
             | ExprKind::DictComp { .. }
             | ExprKind::SetComp { .. } => self.push_scope(Scope::new(Generator)),
             ExprKind::Lambda { .. } => self.push_scope(Scope::new(Function)),
+            ExprKind::Yield { .. } | ExprKind::YieldFrom { .. } => {
+                let scope = self.scopes.last().expect("No current scope found.");
+                if self
+                    .settings
+                    .select
+                    .contains(CheckKind::YieldOutsideFunction.code())
+                    && matches!(scope.kind, ScopeKind::Class)
+                    || matches!(scope.kind, ScopeKind::Module)
+                {
+                    self.checks.push(Check {
+                        kind: CheckKind::YieldOutsideFunction,
+                        location: expr.location,
+                    });
+                }
+            }
             ExprKind::JoinedStr { values } => {
                 if !self.in_f_string
                     && self

src/checks.rs

@@ -12,6 +12,7 @@ pub enum CheckCode {
     F403,
     F541,
     F634,
+    F704,
     F706,
     F821,
     F831,
@@ -30,6 +31,7 @@ impl FromStr for CheckCode {
             "F403" => Ok(CheckCode::F403),
             "F541" => Ok(CheckCode::F541),
             "F634" => Ok(CheckCode::F634),
+            "F704" => Ok(CheckCode::F704),
             "F706" => Ok(CheckCode::F706),
             "F821" => Ok(CheckCode::F821),
             "F831" => Ok(CheckCode::F831),
@@ -49,6 +51,7 @@ impl CheckCode {
             CheckCode::F403 => "F403",
             CheckCode::F541 => "F541",
             CheckCode::F634 => "F634",
+            CheckCode::F704 => "F704",
             CheckCode::F706 => "F706",
             CheckCode::F821 => "F821",
             CheckCode::F831 => "F831",
@@ -66,6 +69,7 @@ impl CheckCode {
             CheckCode::F403 => &LintSource::AST,
             CheckCode::F541 => &LintSource::AST,
             CheckCode::F634 => &LintSource::AST,
+            CheckCode::F704 => &LintSource::AST,
             CheckCode::F706 => &LintSource::AST,
             CheckCode::F821 => &LintSource::AST,
             CheckCode::F831 => &LintSource::AST,
@@ -90,6 +94,7 @@ pub enum CheckKind {
     ImportStarUsage,
     LineTooLong,
     RaiseNotImplemented,
+    YieldOutsideFunction,
     ReturnOutsideFunction,
     UndefinedName(String),
     UndefinedLocal(String),
@@ -107,6 +112,7 @@ impl CheckKind {
             CheckKind::ImportStarUsage => &CheckCode::F403,
             CheckKind::LineTooLong => &CheckCode::E501,
             CheckKind::RaiseNotImplemented => &CheckCode::F901,
+            CheckKind::YieldOutsideFunction => &CheckCode::F704,
             CheckKind::ReturnOutsideFunction => &CheckCode::F706,
             CheckKind::UndefinedName(_) => &CheckCode::F821,
             CheckKind::UndefinedLocal(_) => &CheckCode::F832,
@@ -132,6 +138,9 @@ impl CheckKind {
             CheckKind::RaiseNotImplemented => {
                 "'raise NotImplemented' should be 'raise NotImplementedError".to_string()
             }
+            CheckKind::YieldOutsideFunction => {
+                "a `yield` or `yield from` statement outside of a function/method".to_string()
+            }
             CheckKind::ReturnOutsideFunction => {
                 "a `return` statement outside of a function/method".to_string()
             }

src/linter.rs

@@ -222,6 +222,42 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn f704() -> Result<()> {
+        let actual = check_path(
+            &Path::new("./resources/test/src/F704.py"),
+            &settings::Settings {
+                line_length: 88,
+                exclude: vec![],
+                select: BTreeSet::from([CheckCode::F704]),
+            },
+            &cache::Mode::None,
+        )?;
+        let expected = vec![
+            Message {
+                kind: CheckKind::YieldOutsideFunction,
+                location: Location::new(6, 5),
+                filename: "./resources/test/src/F704.py".to_string(),
+            },
+            Message {
+                kind: CheckKind::YieldOutsideFunction,
+                location: Location::new(9, 1),
+                filename: "./resources/test/src/F704.py".to_string(),
+            },
+            Message {
+                kind: CheckKind::YieldOutsideFunction,
+                location: Location::new(10, 1),
+                filename: "./resources/test/src/F704.py".to_string(),
+            },
+        ];
+        assert_eq!(actual.len(), expected.len());
+        for i in 0..actual.len() {
+            assert_eq!(actual[i], expected[i]);
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn f706() -> Result<()> {
         let actual = check_path(

src/pyproject.rs

@@ -235,6 +235,7 @@ other-attribute = 1
                     CheckCode::F403,
                     CheckCode::F541,
                     CheckCode::F634,
+                    CheckCode::F704,
                     CheckCode::F706,
                     CheckCode::F821,
                     CheckCode::F831,