Fix initialize-to-...-in-stub behavior

Summary:
This commit separates Pyre2's decision about whether to type check the
value in an `AnnAssign` versus whether to treat it as initialized.

We need this so that we can correctly skip typing `...` assignment in stubs,
while also correctly treating it as indicating initialization.

This fixes a bug in class-and-instance attribute handling from stubs.

Reviewed By: rchen152

Differential Revision: D68279121

fbshipit-source-id: f0a896e86b1bd84c392566bd7e81ca255aa71c87

pyre2/pyre2/bin/binding/bindings.rs

@@ -1648,10 +1648,20 @@ impl<'a> BindingsBuilder<'a> {
                     };
                     let ann_key = self.table.insert(ann_key, ann_val);
 
-                    let (binding, is_initialized) = if let Some(mut value) = x.value
-                        && (!self.module_info.is_interface()
-                            || !matches!(&*value, Expr::EllipsisLiteral(_)))
-                    {
+                    let (value, is_initialized) = if let Some(value) = x.value {
+                        // Treat a name as initialized, but skip actually checking the value, if we are assigning `...` in a stub.
+                        if self.module_info.is_interface()
+                            && matches!(&*value, Expr::EllipsisLiteral(_))
+                        {
+                            (None, true)
+                        } else {
+                            (Some(value), true)
+                        }
+                    } else {
+                        (None, false)
+                    };
+
+                    let binding = if let Some(mut value) = value {
                         // Handle forward references in explicit type aliases.
                         if let Expr::Name(name) = *x.annotation
                             && name.id == "TypeAlias"
@@ -1661,22 +1671,16 @@ impl<'a> BindingsBuilder<'a> {
                             self.ensure_expr(&value);
                         }
                         let range = value.range();
-                        (
-                            Binding::NameAssign(
-                                name.id.clone(),
-                                Some(ann_key),
-                                Box::new(Binding::Expr(Some(ann_key), *value)),
-                                range,
-                            ),
-                            true,
+                        Binding::NameAssign(
+                            name.id.clone(),
+                            Some(ann_key),
+                            Box::new(Binding::Expr(Some(ann_key), *value)),
+                            range,
                         )
                     } else {
-                        (
-                            Binding::AnnotatedType(
-                                ann_key,
-                                Box::new(Binding::AnyType(AnyStyle::Implicit)),
-                            ),
-                            false,
+                        Binding::AnnotatedType(
+                            ann_key,
+                            Box::new(Binding::AnyType(AnyStyle::Implicit)),
                         )
                     };
                     self.bind_definition(&name, binding, Some(ann_key), is_initialized);

pyre2/pyre2/bin/test/attributes.rs

@@ -7,7 +7,6 @@
 
 use crate::test::util::TestEnv;
 use crate::testcase;
-use crate::testcase_with_bug;
 
 testcase!(
     test_set_attribute,
@@ -427,16 +426,14 @@ class A:
     t
 }
 
-testcase_with_bug!(
-    "We are incorrectly treating `...` assignment as not initializing attributes in stubs",
+testcase!(
     test_stub_initializes_attr_with_ellipses,
     env_with_stub(),
     r#"
 from typing import assert_type
 from foo import A
 
-# TODO(stroxler) The error on the second line below is correct, but the first line should have no errors.
-assert_type(A.x, int)  # E: Instance-only attribute `x` of class `A` is not visible on the class  # E: assert_type(Any, int)
+assert_type(A.x, int)
 A.y  # E: Instance-only attribute `y` of class `A` is not visible on the class
     "#,
 );