Fix more crashes in class scoped imports

More context in python#12197

This essentially walks back changes in python#12023 that apply to
function-like things that are imported in class-scope. We just issue a
(non-blocking) error and mark the type as Any. Inference for variables
still works fine; I'm yet to think of any problems that could cause.

A full fix seems quite difficult, but this is better than both a crash
and a blocking error.

Author: hauntsaninja

mypy/semanal.py

@@ -48,7 +48,6 @@
   reduce memory use).
 """
 
-import copy
 from contextlib import contextmanager
 
 from typing import (
@@ -4791,6 +4790,48 @@ def add_module_symbol(self,
                 module_hidden=module_hidden
             )
 
+    def _get_node_for_class_scoped_import(
+        self, name: str, symbol_node: Optional[SymbolNode], context: Context
+    ) -> Optional[SymbolNode]:
+        if symbol_node is None:
+            return None
+        # I promise this type checks; I'm just making mypyc issues go away.
+        # mypyc is absolutely convinced that `symbol_node` narrows to a Var in the following,
+        # when it can also be a FuncBase. Once fixed, `f` in the following can be removed.
+        # See also https://github.com/mypyc/mypyc/issues/892
+        f = cast(Any, lambda x: x)
+        if isinstance(f(symbol_node), (FuncBase, Var)):
+            # For imports in class scope, we construct a new node to represent the symbol and
+            # set its `info` attribute to `self.type`.
+            existing = self.current_symbol_table().get(name)
+            if (
+                # The redefinition checks in `add_symbol_table_node` don't work for our
+                # constructed Var / FuncBase, so check for possible redefinitions here.
+                existing is not None
+                and isinstance(f(existing.node), (FuncBase, Var))
+                and (
+                    isinstance(f(existing.type), AnyType)
+                    or f(existing.type) == f(symbol_node).type
+                )
+            ):
+                return existing.node
+
+            # Construct the new node
+            if isinstance(f(symbol_node), FuncBase):
+                # In theory we could construct a new node here as well, but in practice
+                # it doesn't work well, see #12197
+                typ = AnyType(TypeOfAny.from_error)
+                self.fail('Unsupported class scoped import', context)
+            else:
+                typ = f(symbol_node).type
+            symbol_node = Var(name, typ)
+            symbol_node._fullname = self.qualified_name(name)
+            assert self.type is not None  # guaranteed by is_class_scope
+            symbol_node.info = self.type
+            symbol_node.line = context.line
+            symbol_node.column = context.column
+        return symbol_node
+
     def add_imported_symbol(self,
                             name: str,
                             node: SymbolTableNode,
@@ -4803,32 +4844,7 @@ def add_imported_symbol(self,
         symbol_node: Optional[SymbolNode] = node.node
 
         if self.is_class_scope():
-            # I promise this type checks; I'm just making mypyc issues go away.
-            # mypyc is absolutely convinced that `symbol_node` narrows to a Var in the following,
-            # when it can also be a FuncBase. Once fixed, `f` in the following can be removed.
-            # See also https://github.com/mypyc/mypyc/issues/892
-            f = cast(Any, lambda x: x)
-            if isinstance(f(symbol_node), (FuncBase, Var)):
-                # For imports in class scope, we construct a new node to represent the symbol and
-                # set its `info` attribute to `self.type`.
-                existing = self.current_symbol_table().get(name)
-                if (
-                    # The redefinition checks in `add_symbol_table_node` don't work for our
-                    # constructed Var / FuncBase, so check for possible redefinitions here.
-                    existing is not None
-                    and isinstance(f(existing.node), (FuncBase, Var))
-                    and f(existing.type) == f(symbol_node).type
-                ):
-                    symbol_node = existing.node
-                else:
-                    # Construct the new node
-                    constructed_node = copy.copy(f(symbol_node))
-                    assert self.type is not None  # guaranteed by is_class_scope
-                    constructed_node.line = context.line
-                    constructed_node.column = context.column
-                    constructed_node.info = self.type
-                    constructed_node._fullname = self.qualified_name(name)
-                    symbol_node = constructed_node
+            symbol_node = self._get_node_for_class_scoped_import(name, symbol_node, context)
 
         symbol = SymbolTableNode(node.kind, symbol_node,
                                  module_public=module_public,

test-data/unit/check-classes.test

@@ -7135,24 +7135,20 @@ class B(A):  # E: Final class __main__.B has abstract attributes "foo"
 class C:
     class C1(XX): pass  # E: Name "XX" is not defined
 
-[case testClassScopeImportFunction]
+[case testClassScopeImports]
 class Foo:
-    from mod import foo
+    from mod import plain_function  # E: Unsupported class scoped import
+    from mod import plain_var
 
-reveal_type(Foo.foo)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
-reveal_type(Foo().foo)  # E: Invalid self argument "Foo" to attribute function "foo" with type "Callable[[int, int], int]" \
-                        # N: Revealed type is "def (y: builtins.int) -> builtins.int"
-[file mod.py]
-def foo(x: int, y: int) -> int: ...
+reveal_type(Foo.plain_function)  # N: Revealed type is "Any"
+reveal_type(Foo().plain_function)  # N: Revealed type is "Any"
 
-[case testClassScopeImportVariable]
-class Foo:
-    from mod import foo
+reveal_type(Foo.plain_var)  # N: Revealed type is "builtins.int"
+reveal_type(Foo().plain_var)  # N: Revealed type is "builtins.int"
 
-reveal_type(Foo.foo)  # N: Revealed type is "builtins.int"
-reveal_type(Foo().foo)  # N: Revealed type is "builtins.int"
 [file mod.py]
-foo: int
+def plain_function(x: int, y: int) -> int: ...
+plain_var: int
 
 [case testClassScopeImportModule]
 class Foo:
@@ -7165,40 +7161,42 @@ foo: int
 
 [case testClassScopeImportFunctionAlias]
 class Foo:
-    from mod import foo
+    from mod import foo  # E: Unsupported class scoped import
     bar = foo
 
     from mod import const_foo
     const_bar = const_foo
 
-reveal_type(Foo.foo)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
-reveal_type(Foo.bar)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
+reveal_type(Foo.foo)  # N: Revealed type is "Any"
+reveal_type(Foo.bar)  # N: Revealed type is "Any"
 reveal_type(Foo.const_foo)  # N: Revealed type is "builtins.int"
 reveal_type(Foo.const_bar)  # N: Revealed type is "builtins.int"
+
 [file mod.py]
 def foo(x: int, y: int) -> int: ...
 const_foo: int
 
 [case testClassScopeImportModuleStar]
 class Foo:
-    from mod import *
+    from mod import *  # E: Unsupported class scoped import
 
 reveal_type(Foo.foo)  # N: Revealed type is "builtins.int"
-reveal_type(Foo.bar)  # N: Revealed type is "def (x: builtins.int) -> builtins.int"
+reveal_type(Foo.bar)  # N: Revealed type is "Any"
 reveal_type(Foo.baz)  # E: "Type[Foo]" has no attribute "baz" \
                       # N: Revealed type is "Any"
+
 [file mod.py]
 foo: int
 def bar(x: int) -> int: ...
 
 [case testClassScopeImportFunctionNested]
 class Foo:
     class Bar:
-        from mod import baz
+        from mod import baz  # E: Unsupported class scoped import
+
+reveal_type(Foo.Bar.baz)  # N: Revealed type is "Any"
+reveal_type(Foo.Bar().baz)  # N: Revealed type is "Any"
 
-reveal_type(Foo.Bar.baz)  # N: Revealed type is "def (x: builtins.int) -> builtins.int"
-reveal_type(Foo.Bar().baz)  # E: Invalid self argument "Bar" to attribute function "baz" with type "Callable[[int], int]" \
-                            # N: Revealed type is "def () -> builtins.int"
 [file mod.py]
 def baz(x: int) -> int: ...
 
@@ -7221,25 +7219,44 @@ def foo(x: int, y: int) -> int: ...
 
 [case testClassScopeImportVarious]
 class Foo:
-    from mod1 import foo
-    from mod2 import foo  # E: Name "foo" already defined on line 2
+    from mod1 import foo  # E: Unsupported class scoped import
+    from mod2 import foo
 
-    from mod1 import meth1
+    from mod1 import meth1  # E: Unsupported class scoped import
     def meth1(self, a: str) -> str: ...  # E: Name "meth1" already defined on line 5
 
     def meth2(self, a: str) -> str: ...
-    from mod1 import meth2  # E: Name "meth2" already defined on line 8
+    from mod1 import meth2  # E: Unsupported class scoped import \
+                            # E: Name "meth2" already defined on line 8
 
 class Bar:
-    from mod1 import foo
+    from mod1 import foo  # E: Unsupported class scoped import
 
 import mod1
-reveal_type(Foo.foo)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
-reveal_type(Bar.foo)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
+reveal_type(Foo.foo)  # N: Revealed type is "Any"
+reveal_type(Bar.foo)  # N: Revealed type is "Any"
 reveal_type(mod1.foo)  # N: Revealed type is "def (x: builtins.int, y: builtins.int) -> builtins.int"
+
 [file mod1.py]
 def foo(x: int, y: int) -> int: ...
 def meth1(x: int) -> int: ...
 def meth2(x: int) -> int: ...
 [file mod2.py]
 def foo(z: str) -> int: ...
+
+
+[case testClassScopeImportWithError]
+class Foo:
+    from mod import meth1  # E: Unsupported class scoped import
+    from mod import meth2  # E: Unsupported class scoped import
+
+[file mod.pyi]
+from typing import Any, TypeVar, overload
+
+@overload
+def meth1(self: Any, y: int) -> int: ...
+@overload
+def meth1(self: Any, y: str) -> str: ...
+
+T = TypeVar("T")
+def meth2(self: Any, y: T) -> T: ...

test-data/unit/check-modules.test

@@ -131,9 +131,10 @@ def f() -> None: pass
 [case testImportWithinClassBody2]
 import typing
 class C:
-    from m import f  # E: Method must have at least one argument
+    from m import f  # E: Unsupported class scoped import
     f()
-    f(C) # E: Too many arguments for "f" of "C"
+    # ideally, the following should error:
+    f(C)
 [file m.py]
 def f() -> None: pass
 [out]

test-data/unit/check-newsemanal.test

@@ -2722,7 +2722,7 @@ import m
 
 [file m.py]
 class C:
-    from mm import f  # E: Method must have at least one argument
+    from mm import f  # E: Unsupported class scoped import
     @dec(f)
     def m(self): pass
 
@@ -2742,7 +2742,7 @@ import m
 
 [file m/__init__.py]
 class C:
-    from m.m import f  # E: Method must have at least one argument
+    from m.m import f  # E: Unsupported class scoped import
     @dec(f)
     def m(self): pass