improve

Author: AlexWaygood

crates/ty_python_semantic/resources/mdtest/loops/for.md

@@ -264,19 +264,20 @@ def g(
         reveal_type(y)  # revealed: str | int
 ```
 
-## Union type as iterable where all elements in the union have precise tuple specs
+## Union type as iterable where some elements in the union have precise tuple specs
 
-If all elements in a union can be heterogeneously unpacked, we "union together" their "tuple specs"
-and are able to infer the iterable element precisely when iterating over the union, in the same way
-that we infer a precise type for the iterable element when iterating over a `Literal` string or
-bytes type:
+If all elements in a union can be iterated over, we "union together" their "tuple specs" and are
+able to infer the iterable element precisely when iterating over the union, in the same way that we
+infer a precise type for the iterable element when iterating over a `Literal` string or bytes type:
 
 ```py
 from typing import Literal
 
-def f(x: Literal["foo", b"bar"]):
+def f(x: Literal["foo", b"bar"], y: Literal["foo"] | range):
     for item in x:
         reveal_type(item)  # revealed: Literal["f", "o", 98, 97, 114]
+    for item in y:
+        reveal_type(item)  # revealed: Literal["f", "o"] | int
 ```
 
 ## Union type as iterable where one union element has no `__iter__` method

crates/ty_python_semantic/src/types.rs

@@ -5358,10 +5358,10 @@ impl<'db> Type<'db> {
                     let elements = union.elements(db);
                     if elements.len() < MAX_TUPLE_LENGTH {
                         let mut elements_iter = elements.iter();
-                        let first_element_spec = non_async_special_case(db, *elements_iter.next()?)?;
+                        let first_element_spec = elements_iter.next()?.try_iterate_with_mode(db, EvaluationMode::Sync).ok()?;
                         let mut builder = TupleSpecBuilder::from(&*first_element_spec);
                         for element in elements_iter {
-                            builder = builder.union(db, non_async_special_case(db, *element).as_deref()?);
+                            builder = builder.union(db, &*element.try_iterate_with_mode(db, EvaluationMode::Sync).ok()?);
                         }
                         Some(Cow::Owned(builder.build()))
                     } else {