Fix incorrect "Incompatible types in capture pattern" error for narrowed types

mypy/checker.py

@@ -35,7 +35,7 @@
     analyze_member_access,
     type_object_type,
 )
-from mypy.checkpattern import PatternChecker
+from mypy.checkpattern import PatternChecker, PatternType
 from mypy.constraints import SUPERTYPE_OF
 from mypy.erasetype import erase_type, erase_typevars, remove_instance_last_known_values
 from mypy.errorcodes import TYPE_VAR, UNUSED_AWAITABLE, UNUSED_COROUTINE, ErrorCode
@@ -5296,7 +5296,20 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
             # capture variable may depend on multiple patterns (it
             # will be a union of all capture types). This pass ignores
             # guard expressions.
-            pattern_types = [self.pattern_checker.accept(p, subject_type) for p in s.patterns]
+            pattern_types: list[PatternType] = []
+            type_context = subject_type
+            for p in s.patterns:
+                pattern_type = self.pattern_checker.accept(p, type_context)
+                pattern_types.append(pattern_type)
+                new_type_context = get_proper_type(pattern_type.rest_type)
+                if isinstance(new_type_context, UninhabitedType):
+                    continue
+                if isinstance(new_type_context, UnionType) and any(
+                    isinstance(get_proper_type(t), UninhabitedType) for t in new_type_context.items
+                ):
+                    continue
+                type_context = new_type_context
+
             type_maps: list[TypeMap] = [t.captures for t in pattern_types]
             inferred_types = self.infer_variable_types_from_type_maps(type_maps)
 

test-data/unit/check-python310.test

@@ -8,6 +8,16 @@ match m:
     case a:
         reveal_type(a)  # N: Revealed type is "__main__.A"
 
+[case testMatchCapturePatternNarrows]
+x: int | None
+y: int
+
+match x:
+    case None:
+        pass
+    case y:
+        reveal_type(y) # N: Revealed type is "builtins.int"
+
 -- Literal Pattern --
 
 [case testMatchLiteralPatternNarrows]
@@ -1466,7 +1476,7 @@ m3: Tuple[Union[int, str]]
 match m3:
     case (1,):
         reveal_type(m3)  # N: Revealed type is "Tuple[Literal[1]]"
-    case r2:
+    case r3:
         reveal_type(m3)  # N: Revealed type is "Tuple[Union[builtins.int, builtins.str]]"
 
 m4: Tuple[Literal[1], int]