From f7804ea29da839e747cd40afcf4016bde76da19c Mon Sep 17 00:00:00 2001
From: Eric Mark Martin <ericmarkmartin@gmail.com>
Date: Wed, 22 Oct 2025 17:09:23 -0400
Subject: [PATCH] fix typeguard overriding logic

---
 .../resources/mdtest/narrow/type_guards.md    | 28 ++++++++++++++++++-
 crates/ty_python_semantic/src/types/narrow.rs | 14 ++++++++--
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/crates/ty_python_semantic/resources/mdtest/narrow/type_guards.md b/crates/ty_python_semantic/resources/mdtest/narrow/type_guards.md
index 9c88845f12..c2a5f8feb6 100644
--- a/crates/ty_python_semantic/resources/mdtest/narrow/type_guards.md
+++ b/crates/ty_python_semantic/resources/mdtest/narrow/type_guards.md
@@ -359,7 +359,33 @@ def narrowed_type_must_be_exact(a: object, b: Baz):
         reveal_type(a)  # revealed: Foo
 ```
 
-## Complex boolean logic with TypeGuard and TypeIs
+## TypeGuard overrides normal constraints
+
+TypeGuard constraints override any previous narrowing, but additional "regular" constraints can be
+added on to TypeGuard constraints.
+
+```py
+from typing_extensions import TypeGuard, TypeIs
+
+class A: ...
+class B: ...
+class C: ...
+
+def f(x: object) -> TypeGuard[A]:
+    return True
+
+def g(x: object) -> TypeGuard[B]:
+    return True
+
+def h(x: object) -> TypeIs[C]:
+    return True
+
+def _(x: object):
+    if f(x) and g(x) and h(x):
+        reveal_type(x)  # revealed: B & C
+```
+
+## Boolean logic with TypeGuard and TypeIs
 
 TypeGuard constraints need to properly distribute through boolean operations.
 
diff --git a/crates/ty_python_semantic/src/types/narrow.rs b/crates/ty_python_semantic/src/types/narrow.rs
index 72e34c83db..b7cdf10e02 100644
--- a/crates/ty_python_semantic/src/types/narrow.rs
+++ b/crates/ty_python_semantic/src/types/narrow.rs
@@ -317,8 +317,16 @@ impl<'db> Conjunction<'db> {
     /// Evaluate this conjunction to a single type.
     /// If there's a `TypeGuard` constraint, it replaces the regular constraint.
     /// Otherwise, returns the regular constraint.
-    fn evaluate_type_constraint(self) -> Type<'db> {
-        self.typeguard.unwrap_or(self.constraint)
+    fn evaluate_type_constraint(self, db: &'db dyn Db) -> Type<'db> {
+        self.typeguard.map_or_else(
+            || self.constraint,
+            |typeguard_constraint| {
+                IntersectionBuilder::new(db)
+                    .add_positive(typeguard_constraint)
+                    .add_positive(self.constraint)
+                    .build()
+            },
+        )
     }
 }
 
@@ -367,7 +375,7 @@ impl<'db> NarrowingConstraint<'db> {
             db,
             self.disjuncts
                 .into_iter()
-                .map(Conjunction::evaluate_type_constraint),
+                .map(|disjunct| Conjunction::evaluate_type_constraint(disjunct, db)),
         )
     }
 }