From 8a58b22d6402229773c93a82abfe5b3b33eb58d8 Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Tue, 16 Nov 2021 16:39:18 +0000
Subject: [PATCH] Fix crash related to AST diff of ParamSpec in mypy daemon
 (#11567)

Fixes #11566.
---
 mypy/server/astdiff.py   |  6 +++++-
 test-data/unit/diff.test | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/mypy/server/astdiff.py b/mypy/server/astdiff.py
index 789c7c909911..bf82c0385c3a 100644
--- a/mypy/server/astdiff.py
+++ b/mypy/server/astdiff.py
@@ -54,7 +54,7 @@ class level -- these are handled at attribute level (say, 'mod.Cls.method'
 
 from mypy.nodes import (
     SymbolTable, TypeInfo, Var, SymbolNode, Decorator, TypeVarExpr, TypeAlias,
-    FuncBase, OverloadedFuncDef, FuncItem, MypyFile, UNBOUND_IMPORTED
+    FuncBase, OverloadedFuncDef, FuncItem, MypyFile, ParamSpecExpr, UNBOUND_IMPORTED
 )
 from mypy.types import (
     Type, TypeVisitor, UnboundType, AnyType, NoneType, UninhabitedType,
@@ -151,6 +151,10 @@ def snapshot_symbol_table(name_prefix: str, table: SymbolTable) -> Dict[str, Sna
                             node.normalized,
                             node.no_args,
                             snapshot_optional_type(node.target))
+        elif isinstance(node, ParamSpecExpr):
+            result[name] = ('ParamSpec',
+                            node.variance,
+                            snapshot_type(node.upper_bound))
         else:
             assert symbol.kind != UNBOUND_IMPORTED
             if node and get_prefix(node.fullname) != name_prefix:
diff --git a/test-data/unit/diff.test b/test-data/unit/diff.test
index ee3519478c45..7369ea247e26 100644
--- a/test-data/unit/diff.test
+++ b/test-data/unit/diff.test
@@ -1470,3 +1470,17 @@ x: Union[Callable[[Arg(int, 'y')], None],
 [builtins fixtures/tuple.pyi]
 [out]
 __main__.x
+
+[case testChangeParamSpec]
+from typing import ParamSpec, TypeVar
+A = ParamSpec('A')
+B = ParamSpec('B')
+C = TypeVar('C')
+[file next.py]
+from typing import ParamSpec, TypeVar
+A = ParamSpec('A')
+B = TypeVar('B')
+C = ParamSpec('C')
+[out]
+__main__.B
+__main__.C