From 5e87238f3391fe449d609dadab8f7e1405947853 Mon Sep 17 00:00:00 2001
From: Charlie Marsh <charlie.r.marsh@gmail.com>
Date: Sat, 13 Dec 2025 17:04:13 -0500
Subject: [PATCH] Add __doc__

---
 .../mdtest/scopes/class_implicit_attrs.md     |  5 ++--
 crates/ty_python_semantic/src/place.rs        | 11 +++++++--
 .../src/types/infer/builder.rs                | 24 +++++++++----------
 3 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/crates/ty_python_semantic/resources/mdtest/scopes/class_implicit_attrs.md b/crates/ty_python_semantic/resources/mdtest/scopes/class_implicit_attrs.md
index cf6ff80d71..7130538acf 100644
--- a/crates/ty_python_semantic/resources/mdtest/scopes/class_implicit_attrs.md
+++ b/crates/ty_python_semantic/resources/mdtest/scopes/class_implicit_attrs.md
@@ -2,14 +2,15 @@
 
 ## Class body implicit attributes
 
-Python makes certain names available implicitly inside class body scopes. These are `__qualname__`
-and `__module__`, as documented at
+Python makes certain names available implicitly inside class body scopes. These are `__qualname__`,
+`__module__`, and `__doc__`, as documented at
 <https://docs.python.org/3/reference/datamodel.html#creating-the-class-object>.
 
 ```py
 class Foo:
     reveal_type(__qualname__)  # revealed: str
     reveal_type(__module__)  # revealed: str
+    reveal_type(__doc__)  # revealed: str | None
 ```
 
 ## `__firstlineno__` (Python 3.13+)
diff --git a/crates/ty_python_semantic/src/place.rs b/crates/ty_python_semantic/src/place.rs
index 45bce10c18..21dfb955a9 100644
--- a/crates/ty_python_semantic/src/place.rs
+++ b/crates/ty_python_semantic/src/place.rs
@@ -1637,8 +1637,8 @@ mod implicit_globals {
 /// Looks up the type of an "implicit class body symbol". Returns [`Place::Undefined`] if
 /// `name` is not present as an implicit symbol in class bodies.
 ///
-/// Implicit class body symbols are symbols such as `__qualname__`, `__module__`, and
-/// `__firstlineno__` that Python implicitly makes available inside a class body during
+/// Implicit class body symbols are symbols such as `__qualname__`, `__module__`, `__doc__`,
+/// and `__firstlineno__` that Python implicitly makes available inside a class body during
 /// class creation.
 ///
 /// See <https://docs.python.org/3/reference/datamodel.html#creating-the-class-object>
@@ -1649,6 +1649,13 @@ pub(crate) fn class_body_implicit_symbol<'db>(
     match name {
         "__qualname__" => Place::bound(KnownClass::Str.to_instance(db)).into(),
         "__module__" => Place::bound(KnownClass::Str.to_instance(db)).into(),
+        // __doc__ is `str` if there's a docstring, `None` if there isn't
+        "__doc__" => Place::bound(UnionType::from_elements(
+            db,
+            [KnownClass::Str.to_instance(db), Type::none(db)],
+        ))
+        .into(),
+        // __firstlineno__ was added in Python 3.13
         "__firstlineno__" if Program::get(db).python_version(db) >= PythonVersion::PY313 => {
             Place::bound(KnownClass::Int.to_instance(db)).into()
         }
diff --git a/crates/ty_python_semantic/src/types/infer/builder.rs b/crates/ty_python_semantic/src/types/infer/builder.rs
index 8a43d06ac3..75286a7a7b 100644
--- a/crates/ty_python_semantic/src/types/infer/builder.rs
+++ b/crates/ty_python_semantic/src/types/infer/builder.rs
@@ -9173,18 +9173,18 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                 // If we're in a class body, check for implicit class body symbols first.
                 // These take precedence over globals.
                 .or_fall_back_to(db, || {
-                    if scope.node(db).scope_kind().is_class() {
-                        if let Some(symbol) = place_expr.as_symbol() {
-                            let implicit = class_body_implicit_symbol(db, symbol.name());
-                            if implicit.place.is_definitely_bound() {
-                                return implicit.map_type(|ty| {
-                                    self.narrow_place_with_applicable_constraints(
-                                        place_expr,
-                                        ty,
-                                        &constraint_keys,
-                                    )
-                                });
-                            }
+                    if scope.node(db).scope_kind().is_class()
+                        && let Some(symbol) = place_expr.as_symbol()
+                    {
+                        let implicit = class_body_implicit_symbol(db, symbol.name());
+                        if implicit.place.is_definitely_bound() {
+                            return implicit.map_type(|ty| {
+                                self.narrow_place_with_applicable_constraints(
+                                    place_expr,
+                                    ty,
+                                    &constraint_keys,
+                                )
+                            });
                         }
                     }
                     Place::Undefined.into()