[ty] Don't warn yield not in function when yield is in function (#18008)

crates/ruff_linter/resources/test/fixtures/pyflakes/F704.py

@@ -9,3 +9,11 @@ class Foo:
 yield 3
 yield from 3
 await f()
+
+def _():
+    # Invalid yield scopes; but not outside a function
+    type X[T: (yield 1)] = int
+    type Y = (yield 2)
+
+    # Valid yield scope
+    yield 3

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

@@ -681,6 +681,17 @@ impl SemanticSyntaxContext for Checker<'_> {
         false
     }
 
+    fn in_yield_allowed_context(&self) -> bool {
+        for scope in self.semantic.current_scopes() {
+            match scope.kind {
+                ScopeKind::Class(_) | ScopeKind::Generator { .. } => return false,
+                ScopeKind::Function(_) | ScopeKind::Lambda(_) => return true,
+                ScopeKind::Module | ScopeKind::Type => {}
+            }
+        }
+        false
+    }
+
     fn in_sync_comprehension(&self) -> bool {
         for scope in self.semantic.current_scopes() {
             if let ScopeKind::Generator {

crates/ruff_linter/src/rules/pyflakes/snapshots/ruff_linter__rules__pyflakes__tests__F704_F704.py.snap

@@ -1,6 +1,5 @@
 ---
 source: crates/ruff_linter/src/rules/pyflakes/mod.rs
-snapshot_kind: text
 ---
 F704.py:6:5: F704 `yield` statement outside of a function
   |
@@ -31,4 +30,6 @@ F704.py:11:1: F704 `await` statement outside of a function
 10 | yield from 3
 11 | await f()
    | ^^^^^^^^^ F704
+12 |
+13 | def _():
    |