Fix panic when filling up types vector during unpacking

astral-sh · Oct 30, 2024 · e44f117 · e44f117
1 parent c6b8215
commit e44f117
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diff --git a/crates/red_knot_python_semantic/resources/mdtest/unpacking.md b/crates/red_knot_python_semantic/resources/mdtest/unpacking.md
@@ -134,6 +134,20 @@ reveal_type(b)  # revealed: Literal[2]
 reveal_type(c)  # revealed: @Todo
 ```
 
+### Starred expression (6)
+
+```py
+# TODO: Remove 'not-iterable' diagnostic
+# TODO: Add diagnostic (need more values to unpack)
+(a, b, c, *d, e, f) = (1,)  # error: "Object of type `None` is not iterable"
+reveal_type(a)  # revealed: Literal[1]
+reveal_type(b)  # revealed: Unknown
+reveal_type(c)  # revealed: Unknown
+reveal_type(d)  # revealed: @Todo
+reveal_type(e)  # revealed: Unknown
+reveal_type(f)  # revealed: Unknown
+```
+
 ### Non-iterable unpacking
 
 TODO: Remove duplicate diagnostics. This is happening because for a sequence-like

diff --git a/crates/red_knot_python_semantic/src/types/infer.rs b/crates/red_knot_python_semantic/src/types/infer.rs
@@ -1282,6 +1282,8 @@ impl<'db> TypeInferenceBuilder<'db> {
                                 Cow::Owned(element_types)
                             } else {
                                 let mut element_types = tuple_ty.elements(builder.db).to_vec();
+                                element_types.resize(elts.len(), Type::Unknown);
+                                // TODO: This should be `list[Unknown]`
                                 element_types.insert(starred_index, Type::Todo);
                                 Cow::Owned(element_types)
                             }