From efeeeb0c6cedba649352a271983e19f8ad6132a4 Mon Sep 17 00:00:00 2001
From: Yurii Karabas <1998uriyyo@gmail.com>
Date: Sun, 29 Jan 2023 16:03:38 +0200
Subject: [PATCH 1/2] Fix internal crash when resolve same partial type twice

---
 mypy/checkexpr.py                   | 3 ++-
 test-data/unit/check-inference.test | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index dfac5be27d95..0ec7d1097da8 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -630,7 +630,8 @@ def try_infer_partial_type(self, e: CallExpr) -> None:
                 return
             var, partial_types = ret
             typ = self.try_infer_partial_value_type_from_call(e, callee.name, var)
-            if typ is not None:
+            # Var may be deleted from partial_types in try_infer_partial_value_type_from_call
+            if typ is not None and var in partial_types:
                 var.type = typ
                 del partial_types[var]
         elif isinstance(callee.expr, IndexExpr) and isinstance(callee.expr.base, RefExpr):
diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
index adf4a7b60420..be9e22416a49 100644
--- a/test-data/unit/check-inference.test
+++ b/test-data/unit/check-inference.test
@@ -1940,6 +1940,12 @@ class A:
 [out]
 main:4: error: "None" has no attribute "__iter__" (not iterable)
 
+[case testPartialTypeErrorSpecialCase4]
+# This used to crash.
+arr = []
+arr.append(arr.append(1))
+[out]
+main:3: error: "List[int]" has no attribute "append"
 
 -- Multipass
 -- ---------

From 999453b06d60d3d16ae14df90c9a7652364393d7 Mon Sep 17 00:00:00 2001
From: Yurii Karabas <1998uriyyo@gmail.com>
Date: Sun, 29 Jan 2023 18:08:58 +0200
Subject: [PATCH 2/2] Add fixture to correctly show error message

---
 test-data/unit/check-inference.test | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
index 541672015979..fc8113766f1a 100644
--- a/test-data/unit/check-inference.test
+++ b/test-data/unit/check-inference.test
@@ -1955,8 +1955,9 @@ main:4: error: "None" has no attribute "__iter__" (not iterable)
 # This used to crash.
 arr = []
 arr.append(arr.append(1))
+[builtins fixtures/list.pyi]
 [out]
-main:3: error: "List[int]" has no attribute "append"
+main:3: error: "append" of "list" does not return a value
 
 -- Multipass
 -- ---------