diff --git a/mypy/checker.py b/mypy/checker.py
index dde8a3441c35..556f0ee13104 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -2796,7 +2796,9 @@ def check_lvalue(self, lvalue: Lvalue) -> Tuple[Optional[Type],
         index_lvalue = None
         inferred = None
 
-        if self.is_definition(lvalue):
+        if self.is_definition(lvalue) and (
+            not isinstance(lvalue, NameExpr) or isinstance(lvalue.node, Var)
+        ):
             if isinstance(lvalue, NameExpr):
                 inferred = cast(Var, lvalue.node)
                 assert isinstance(inferred, Var)
@@ -3420,7 +3422,8 @@ def visit_try_without_finally(self, s: TryStmt, try_frame: bool) -> None:
                                 source = ('(exception variable "{}", which we do not '
                                           'accept outside except: blocks even in '
                                           'python 2)'.format(var.name))
-                            cast(Var, var.node).type = DeletedType(source=source)
+                            if isinstance(var.node, Var):
+                                var.node.type = DeletedType(source=source)
                             self.binder.cleanse(var)
             if s.else_body:
                 self.accept(s.else_body)
diff --git a/test-data/unit/check-redefine.test b/test-data/unit/check-redefine.test
index 5530777dd4db..4ac56edb24ef 100644
--- a/test-data/unit/check-redefine.test
+++ b/test-data/unit/check-redefine.test
@@ -474,3 +474,12 @@ with A() as x:
     reveal_type(x) # N: Revealed type is "builtins.int"
 with B() as x:
     x = 0 # E: Incompatible types in assignment (expression has type "int", variable has type "str")
+
+
+[case testRedefineModuleAsException]
+import typing
+try:
+    pass
+except Exception as typing:
+    pass
+[builtins fixtures/exception.pyi]
diff --git a/test-data/unit/check-unreachable-code.test b/test-data/unit/check-unreachable-code.test
index e4235e82fc98..21b0f1f0c60f 100644
--- a/test-data/unit/check-unreachable-code.test
+++ b/test-data/unit/check-unreachable-code.test
@@ -1305,3 +1305,19 @@ async def f_malformed_2() -> int:
 
 [typing fixtures/typing-full.pyi]
 [builtins fixtures/tuple.pyi]
+
+
+[case testConditionalTypeVarException]
+# every part of this test case was necessary to trigger the crash
+import sys
+from typing import TypeVar
+
+T = TypeVar("T", int, str)
+
+def f(t: T) -> None:
+    if sys.platform == "lol":
+        try:
+            pass
+        except BaseException as e:
+            pass
+[builtins fixtures/dict.pyi]