Fix use of TypeAlias from aliased imports (#12180)

Fixes #12179

mypy/semanal.py

@@ -2643,7 +2643,7 @@ def check_and_set_up_type_alias(self, s: AssignmentStmt) -> bool:
 
         pep_613 = False
         if s.unanalyzed_type is not None and isinstance(s.unanalyzed_type, UnboundType):
-            lookup = self.lookup(s.unanalyzed_type.name, s, suppress_errors=True)
+            lookup = self.lookup_qualified(s.unanalyzed_type.name, s, suppress_errors=True)
             if lookup and lookup.fullname in TYPE_ALIAS_NAMES:
                 pep_613 = True
         if not pep_613 and s.unanalyzed_type is not None:

test-data/unit/check-type-aliases.test

@@ -57,7 +57,7 @@ Never = NoReturn
 a: Never  # Used to be an error here
 
 def f(a: Never): ...
-f(5)  # E: Argument 1 to "f" has incompatible type "int"; expected "NoReturn" 
+f(5)  # E: Argument 1 to "f" has incompatible type "int"; expected "NoReturn"
 [case testImportUnionAlias]
 import typing
 from _m import U
@@ -702,6 +702,30 @@ x: TypeAlias = list(int)  # E: Invalid type alias: expression is not a valid typ
 a: x
 [builtins fixtures/tuple.pyi]
 
+[case testAliasedImportPep613]
+import typing as tpp
+import typing_extensions as tpx
+from typing import TypeAlias as TPA
+from typing_extensions import TypeAlias as TXA
+import typing
+import typing_extensions
+
+Int1: tpp.TypeAlias = int
+Int2: tpx.TypeAlias = int
+Int3: TPA = int
+Int4: TXA = int
+Int5: typing.TypeAlias = int
+Int6: typing_extensions.TypeAlias = int
+
+x1: Int1 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+x2: Int2 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+x3: Int3 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+x4: Int4 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+x5: Int5 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+x6: Int6 = "str"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-medium.pyi]
+
 [case testFunctionScopePep613]
 from typing_extensions import TypeAlias
 

test-data/unit/fixtures/typing-medium.pyi

@@ -26,6 +26,7 @@ Literal = 0
 TypedDict = 0
 NoReturn = 0
 NewType = 0
+TypeAlias = 0
 
 T = TypeVar('T')
 T_co = TypeVar('T_co', covariant=True)