Warn on PEP 604 syntax not in an annotation, but don't autofix (#4170)

crates/ruff/src/checkers/ast/mod.rs

@@ -2281,8 +2281,7 @@ where
         match &expr.node {
             ExprKind::Subscript { value, slice, .. } => {
                 // Ex) Optional[...], Union[...]
-                if self.ctx.in_type_definition
-                    && !self.settings.pyupgrade.keep_runtime_typing
+                if !self.settings.pyupgrade.keep_runtime_typing
                     && self.settings.rules.enabled(Rule::NonPEP604Annotation)
                     && (self.settings.target_version >= PythonVersion::Py310
                         || (self.settings.target_version >= PythonVersion::Py37

crates/ruff/src/rules/pyupgrade/rules/use_pep604_annotation.rs

@@ -100,12 +100,13 @@ pub fn use_pep604_annotation(checker: &mut Checker, expr: &Expr, value: &Expr, s
         return;
     };
 
-    // Avoid fixing forward references.
-    let fixable = checker
-        .ctx
-        .in_deferred_string_type_definition
-        .as_ref()
-        .map_or(true, AnnotationKind::is_simple);
+    // Avoid fixing forward references, or types not in an annotation.
+    let fixable = checker.ctx.in_type_definition
+        && checker
+            .ctx
+            .in_deferred_string_type_definition
+            .as_ref()
+            .map_or(true, AnnotationKind::is_simple);
 
     match typing_member {
         TypingMember::Optional => {

crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP007.py.snap

@@ -200,6 +200,26 @@ UP007.py:47:8: UP007 [*] Use `X | Y` for type annotations
 49 49 | 
 50 50 |     x = Union[str, int]
 
+UP007.py:48:9: UP007 Use `X | Y` for type annotations
+   |
+48 | def f() -> None:
+49 |     x: Optional[str]
+50 |     x = Optional[str]
+   |         ^^^^^^^^^^^^^ UP007
+51 | 
+52 |     x = Union[str, int]
+   |
+
+UP007.py:50:9: UP007 Use `X | Y` for type annotations
+   |
+50 |     x = Optional[str]
+51 | 
+52 |     x = Union[str, int]
+   |         ^^^^^^^^^^^^^^^ UP007
+53 |     x = Union["str", "int"]
+54 |     x: Union[str, int]
+   |
+
 UP007.py:52:8: UP007 [*] Use `X | Y` for type annotations
    |
 52 |     x = Union[str, int]