Fix crash involving undefined cyclic import *

mypy/semanal.py

@@ -4612,7 +4612,11 @@ def add_symbol_table_node(self,
         names = self.current_symbol_table(escape_comprehensions=escape_comprehensions)
         existing = names.get(name)
         if isinstance(symbol.node, PlaceholderNode) and can_defer:
-            self.defer(context)
+            if context is not None:
+                self.process_placeholder(name, 'name', context)
+            else:
+                # see note in docstring describing None contexts
+                self.defer()
         if (existing is not None
                 and context is not None
                 and not is_valid_replacement(existing, symbol)):

test-data/unit/check-modules.test

@@ -3131,4 +3131,43 @@ main:2: error: Cannot find implementation or library stub for module named "blea
 # flags: --ignore-missing-imports
 import bleach.xyz
 from bleach.abc import fgh
-[file bleach/__init__.pyi]
+[file bleach/__init__.pyi]
+
+[case testCyclicUndefinedImportWithName]
+import a
+[file a.py]
+from b import no_such_export
+[file b.py]
+from a import no_such_export  # E: Module "a" has no attribute "no_such_export"
+
+[case testCyclicUndefinedImportWithStar1]
+import a
+[file a.py]
+from b import no_such_export
+[file b.py]
+from a import *
+[out]
+tmp/b.py:1: error: Cannot resolve name "no_such_export" (possible cyclic definition)
+tmp/a.py:1: error: Module "b" has no attribute "no_such_export"
+
+[case testCyclicUndefinedImportWithStar2]
+import a
+[file a.py]
+from b import no_such_export
+[file b.py]
+from c import *
+[file c.py]
+from a import *
+[out]
+tmp/c.py:1: error: Cannot resolve name "no_such_export" (possible cyclic definition)
+tmp/b.py:1: error: Cannot resolve name "no_such_export" (possible cyclic definition)
+tmp/a.py:1: error: Module "b" has no attribute "no_such_export"
+
+[case testCyclicUndefinedImportWithStar3]
+import test1
+[file test1.py]
+from dir1 import *
+[file dir1/__init__.py]
+from .test2 import *
+[file dir1/test2.py]
+from test1 import aaaa  # E: Module "test1" has no attribute "aaaa"