Fix single item enum match type exhaustion

Author: superosku

mypy/checkpattern.py

@@ -202,7 +202,7 @@ def visit_value_pattern(self, o: ValuePattern) -> PatternType:
         typ = self.chk.expr_checker.accept(o.expr)
         typ = coerce_to_literal(typ)
         narrowed_type, rest_type = self.chk.conditional_types_with_intersection(
-            current_type, [get_type_range(typ)], o, default=current_type
+            current_type, [get_type_range(typ)], o, default=get_type_range(typ).item
         )
         if not isinstance(get_proper_type(narrowed_type), (LiteralType, UninhabitedType)):
             return PatternType(narrowed_type, UnionType.make_union([narrowed_type, rest_type]), {})

test-data/unit/check-python310.test

@@ -1369,6 +1369,40 @@ match m3:
         reveal_type(m3)  # N: Revealed type is "Tuple[Union[builtins.int, builtins.str]]"
 [builtins fixtures/tuple.pyi]
 
+[case testMatchEnumMultipleChoices]
+from enum import Enum
+class Medal(Enum):
+    gold = 1
+    silver = 1
+
+def f(m: Medal) -> int:
+    match m:
+        case Medal.gold:
+            reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.gold]"
+            return 0
+        case Medal.silver:
+            reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.silver]"
+            return 2
+        case _:
+            reveal_type(m)
+            return 2
+[builtins fixtures/bool.pyi]
+
+[case testMatchEnumSingleChoice]
+from enum import Enum
+class Medal(Enum):
+    gold = 1
+
+def f(m: Medal) -> int:
+    match m:
+        case Medal.gold:
+            reveal_type(m)  # N: Revealed type is "Literal[__main__.Medal.gold]"
+            return 0
+        case _:
+            reveal_type(m)
+            return 1
+[builtins fixtures/bool.pyi]
+
 [case testMatchLiteralPatternEnumNegativeNarrowing]
 from enum import Enum
 class Medal(Enum):