From 8d98aea6c41f4f8c71ab2727f46b5319392b91bd Mon Sep 17 00:00:00 2001
From: Alex Waygood <Alex.Waygood@Gmail.com>
Date: Tue, 29 Oct 2024 11:06:44 +0000
Subject: [PATCH] [red-knot] Infer attribute expressions in type annotations
 (#13967)

---
 .../resources/mdtest/assignment/annotations.md | 17 +++++++++++++++++
 .../src/types/infer.rs                         | 18 +++++++-----------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md b/crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md
index 84d9ab943f..30ea843523 100644
--- a/crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md
+++ b/crates/red_knot_python_semantic/resources/mdtest/assignment/annotations.md
@@ -91,3 +91,20 @@ def baz() -> str | str:
 
 reveal_type(baz())  # revealed: str
 ```
+
+## Attribute expressions in type annotations are understood
+
+```py
+import builtins
+
+int = "foo"
+a: builtins.int = 42
+
+# error: [invalid-assignment] "Object of type `Literal["bar"]` is not assignable to `int`"
+b: builtins.int = "bar"
+
+c: builtins.tuple[builtins.tuple[builtins.int, builtins.int], builtins.int] = ((42, 42), 42)
+
+# error: [invalid-assignment] "Object of type `Literal["foo"]` is not assignable to `tuple[tuple[int, int], int]`"
+c: builtins.tuple[builtins.tuple[builtins.int, builtins.int], builtins.int] = "foo"
+```
diff --git a/crates/red_knot_python_semantic/src/types/infer.rs b/crates/red_knot_python_semantic/src/types/infer.rs
index 30429850a4..19a97f71c9 100644
--- a/crates/red_knot_python_semantic/src/types/infer.rs
+++ b/crates/red_knot_python_semantic/src/types/infer.rs
@@ -3542,15 +3542,16 @@ impl<'db> TypeInferenceBuilder<'db> {
 
         let ty = match expression {
             ast::Expr::Name(name) => {
-                debug_assert!(
-                    name.ctx.is_load(),
-                    "name in a type expression is always 'load' but got: '{:?}'",
-                    name.ctx
-                );
-
+                debug_assert_eq!(name.ctx, ast::ExprContext::Load);
                 self.infer_name_expression(name).to_instance(self.db)
             }
 
+            ast::Expr::Attribute(attribute_expression) => {
+                debug_assert_eq!(attribute_expression.ctx, ast::ExprContext::Load);
+                self.infer_attribute_expression(attribute_expression)
+                    .to_instance(self.db)
+            }
+
             ast::Expr::NoneLiteral(_literal) => Type::None,
 
             // TODO: parse the expression and check whether it is a string annotation.
@@ -3684,11 +3685,6 @@ impl<'db> TypeInferenceBuilder<'db> {
                 self.infer_fstring_expression(fstring);
                 Type::Unknown
             }
-            //
-            ast::Expr::Attribute(attribute) => {
-                self.infer_attribute_expression(attribute);
-                Type::Unknown
-            }
             ast::Expr::List(list) => {
                 self.infer_list_expression(list);
                 Type::Unknown