Check class references to catch non-existant classes in match cases (#20042)

Fixes #20018.

Author: A5rocks

mypy/checkpattern.py

@@ -14,7 +14,7 @@
 from mypy.maptype import map_instance_to_supertype
 from mypy.meet import narrow_declared_type
 from mypy.messages import MessageBuilder
-from mypy.nodes import ARG_POS, Context, Expression, NameExpr, TypeAlias, TypeInfo, Var
+from mypy.nodes import ARG_POS, Context, Expression, NameExpr, TypeAlias, Var
 from mypy.options import Options
 from mypy.patterns import (
     AsPattern,
@@ -37,6 +37,7 @@
 )
 from mypy.types import (
     AnyType,
+    FunctionLike,
     Instance,
     LiteralType,
     NoneType,
@@ -538,27 +539,20 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
         # Check class type
         #
         type_info = o.class_ref.node
-        if type_info is None:
-            typ: Type = AnyType(TypeOfAny.from_error)
-        elif isinstance(type_info, TypeAlias) and not type_info.no_args:
+        typ = self.chk.expr_checker.accept(o.class_ref)
+        p_typ = get_proper_type(typ)
+        if isinstance(type_info, TypeAlias) and not type_info.no_args:
             self.msg.fail(message_registry.CLASS_PATTERN_GENERIC_TYPE_ALIAS, o)
             return self.early_non_match()
-        elif isinstance(type_info, TypeInfo):
-            typ = fill_typevars_with_any(type_info)
-        elif isinstance(type_info, TypeAlias):
-            typ = type_info.target
-        elif (
-            isinstance(type_info, Var)
-            and type_info.type is not None
-            and isinstance(get_proper_type(type_info.type), AnyType)
-        ):
-            typ = type_info.type
-        else:
-            if isinstance(type_info, Var) and type_info.type is not None:
-                name = type_info.type.str_with_options(self.options)
-            else:
-                name = type_info.name
-            self.msg.fail(message_registry.CLASS_PATTERN_TYPE_REQUIRED.format(name), o)
+        elif isinstance(p_typ, FunctionLike) and p_typ.is_type_obj():
+            typ = fill_typevars_with_any(p_typ.type_object())
+        elif not isinstance(p_typ, AnyType):
+            self.msg.fail(
+                message_registry.CLASS_PATTERN_TYPE_REQUIRED.format(
+                    typ.str_with_options(self.options)
+                ),
+                o,
+            )
             return self.early_non_match()
 
         new_type, rest_type = self.chk.conditional_types_with_intersection(
@@ -697,6 +691,8 @@ def should_self_match(self, typ: Type) -> bool:
         typ = get_proper_type(typ)
         if isinstance(typ, TupleType):
             typ = typ.partial_fallback
+        if isinstance(typ, AnyType):
+            return False
         if isinstance(typ, Instance) and typ.type.get("__match_args__") is not None:
             # Named tuples and other subtypes of builtins that define __match_args__
             # should not self match.

mypyc/test-data/irbuild-match.test

@@ -563,10 +563,9 @@ def f():
 def f():
     r0, r1 :: object
     r2 :: bool
-    i :: int
-    r3 :: object
-    r4 :: str
-    r5, r6 :: object
+    r3, i, r4 :: object
+    r5 :: str
+    r6 :: object
     r7 :: object[1]
     r8 :: object_ptr
     r9, r10 :: object
@@ -576,21 +575,22 @@ L0:
     r2 = CPy_TypeCheck(r1, r0)
     if r2 goto L1 else goto L3 :: bool
 L1:
-    i = 246
+    r3 = object 123
+    i = r3
 L2:
-    r3 = builtins :: module
-    r4 = 'print'
-    r5 = CPyObject_GetAttr(r3, r4)
-    r6 = box(int, i)
-    r7 = [r6]
+    r4 = builtins :: module
+    r5 = 'print'
+    r6 = CPyObject_GetAttr(r4, r5)
+    r7 = [i]
     r8 = load_address r7
-    r9 = PyObject_Vectorcall(r5, r8, 1, 0)
-    keep_alive r6
+    r9 = PyObject_Vectorcall(r6, r8, 1, 0)
+    keep_alive i
     goto L4
 L3:
 L4:
     r10 = box(None, 1)
     return r10
+
 [case testMatchClassPatternWithPositionalArgs_python3_10]
 class Position:
     __match_args__ = ("x", "y", "z")
@@ -599,7 +599,7 @@ class Position:
     y: int
     z: int
 
-def f(x):
+def f(x) -> None:
     match x:
         case Position(1, 2, 3):
             print("matched")
@@ -641,7 +641,7 @@ def f(x):
     r28 :: object
     r29 :: object[1]
     r30 :: object_ptr
-    r31, r32 :: object
+    r31 :: object
 L0:
     r0 = __main__.Position :: type
     r1 = PyObject_IsInstance(x, r0)
@@ -687,8 +687,8 @@ L4:
     goto L6
 L5:
 L6:
-    r32 = box(None, 1)
-    return r32
+    return 1
+
 [case testMatchClassPatternWithKeywordPatterns_python3_10]
 class Position:
     x: int
@@ -848,7 +848,7 @@ class C:
     a: int
     b: int
 
-def f(x):
+def f(x) -> None:
     match x:
         case C(1, 2) as y:
             print("matched")
@@ -885,7 +885,7 @@ def f(x):
     r22 :: object
     r23 :: object[1]
     r24 :: object_ptr
-    r25, r26 :: object
+    r25 :: object
 L0:
     r0 = __main__.C :: type
     r1 = PyObject_IsInstance(x, r0)
@@ -925,8 +925,8 @@ L4:
     goto L6
 L5:
 L6:
-    r26 = box(None, 1)
-    return r26
+    return 1
+
 [case testMatchClassPatternPositionalCapture_python3_10]
 class C:
     __match_args__ = ("x",)
@@ -953,15 +953,14 @@ def f(x):
     r2 :: bit
     r3 :: bool
     r4 :: str
-    r5 :: object
-    r6, num :: int
-    r7 :: str
-    r8 :: object
-    r9 :: str
-    r10 :: object
-    r11 :: object[1]
-    r12 :: object_ptr
-    r13, r14 :: object
+    r5, num :: object
+    r6 :: str
+    r7 :: object
+    r8 :: str
+    r9 :: object
+    r10 :: object[1]
+    r11 :: object_ptr
+    r12, r13 :: object
 L0:
     r0 = __main__.C :: type
     r1 = PyObject_IsInstance(x, r0)
@@ -971,22 +970,22 @@ L0:
 L1:
     r4 = 'x'
     r5 = CPyObject_GetAttr(x, r4)
-    r6 = unbox(int, r5)
-    num = r6
+    num = r5
 L2:
-    r7 = 'matched'
-    r8 = builtins :: module
-    r9 = 'print'
-    r10 = CPyObject_GetAttr(r8, r9)
-    r11 = [r7]
-    r12 = load_address r11
-    r13 = PyObject_Vectorcall(r10, r12, 1, 0)
-    keep_alive r7
+    r6 = 'matched'
+    r7 = builtins :: module
+    r8 = 'print'
+    r9 = CPyObject_GetAttr(r7, r8)
+    r10 = [r6]
+    r11 = load_address r10
+    r12 = PyObject_Vectorcall(r9, r11, 1, 0)
+    keep_alive r6
     goto L4
 L3:
 L4:
-    r14 = box(None, 1)
-    return r14
+    r13 = box(None, 1)
+    return r13
+
 [case testMatchMappingEmpty_python3_10]
 def f(x):
     match x:
@@ -1601,35 +1600,35 @@ def f(x):
 def f(x):
     x, r0 :: object
     r1 :: bool
-    r2, y :: int
-    r3 :: str
-    r4 :: object
-    r5 :: str
-    r6 :: object
-    r7 :: object[1]
-    r8 :: object_ptr
-    r9, r10 :: object
+    y :: object
+    r2 :: str
+    r3 :: object
+    r4 :: str
+    r5 :: object
+    r6 :: object[1]
+    r7 :: object_ptr
+    r8, r9 :: object
 L0:
     r0 = load_address PyLong_Type
     r1 = CPy_TypeCheck(x, r0)
     if r1 goto L1 else goto L3 :: bool
 L1:
-    r2 = unbox(int, x)
-    y = r2
+    y = x
 L2:
-    r3 = 'matched'
-    r4 = builtins :: module
-    r5 = 'print'
-    r6 = CPyObject_GetAttr(r4, r5)
-    r7 = [r3]
-    r8 = load_address r7
-    r9 = PyObject_Vectorcall(r6, r8, 1, 0)
-    keep_alive r3
+    r2 = 'matched'
+    r3 = builtins :: module
+    r4 = 'print'
+    r5 = CPyObject_GetAttr(r3, r4)
+    r6 = [r2]
+    r7 = load_address r6
+    r8 = PyObject_Vectorcall(r5, r7, 1, 0)
+    keep_alive r2
     goto L4
 L3:
 L4:
-    r10 = box(None, 1)
-    return r10
+    r9 = box(None, 1)
+    return r9
+
 [case testMatchSequenceCaptureAll_python3_10]
 def f(x):
     match x:

test-data/unit/check-python310.test

@@ -2990,3 +2990,19 @@ def foo(e: Literal[0, 1]) -> None:
             ...
 
 defer = unknown_module.foo
+
+[case testMatchErrorsIncorrectName]
+class A:
+    pass
+
+match 5:
+    case A.blah():  # E: "type[A]" has no attribute "blah"
+        pass
+
+[case testMatchAllowsAnyClassArgsForAny]
+match 5:
+    case BlahBlah(a, b):  # E: Name "BlahBlah" is not defined
+        reveal_type(a)  # N: Revealed type is "Any"
+        reveal_type(b)  # N: Revealed type is "Any"
+    case BlahBlah(c=c):  # E: Name "BlahBlah" is not defined
+        reveal_type(c)  # N: Revealed type is "Any"