Add tests to stress test type references

Author: MichaelLeeDBX

mypy/indirection.py

@@ -10,7 +10,7 @@
 
 
 def extract_module_names(symbol_name: str) -> Iterable[str]:
-    """Returns the module and parent modules of a fully qualified symbol name."""
+    """Return the module and parent modules of a fully qualified symbol name."""
     if symbol_name is not None:
         while '.' in symbol_name:
             symbol_name = symbol_name.rsplit('.', 1)[0]

test-data/unit/check-incremental.test

@@ -351,18 +351,96 @@ import mod2.mod3 as mod3
 [file mod2/mod3/__init__.py]
 import mod2.mod3.mod4 as mod4
 
+[file mod2/mod3/__init__.py.next]
+# Import is gone!
+
 [file mod2/mod3/mod4.py]
 const = 3
 
+[rechecked mod1, mod2, mod2.mod3]
+[stale mod2.mod3]
+[builtins fixtures/module.pyi]
+[out2]
+main:1: note: In module imported here:
+tmp/mod1.py:3: error: "module" has no attribute "mod4"
+
+[case testIncrementalNestedBrokenCascadeWithType1]
+import mod1, mod2.mod3.mod5
+
+[file mod1.py]
+import mod2
+def accept_int(x: int) -> None: pass
+def produce() -> mod2.CustomType:
+    return mod2.CustomType()
+a = produce()
+accept_int(a.foo())
+
+[file mod2/__init__.py]
+from mod2.mod3 import CustomType 
+
+[file mod2/mod3/__init__.py]
+from mod2.mod3.mod4 import CustomType
+
 [file mod2/mod3/__init__.py.next]
-# Import is gone!
+# Import a different class that also happens to be called 'CustomType'
+from mod2.mod3.mod5 import CustomType
+def produce() -> CustomType:
+    return CustomType()
+
+[file mod2/mod3/mod4.py]
+class CustomType:
+    def foo(self) -> int: return 1
+
+[file mod2/mod3/mod5.py]
+class CustomType:
+    def foo(self) -> str: return "a"
+
+[rechecked mod1, mod2, mod2.mod3]
+[stale mod2, mod2.mod3]
+[builtins fixtures/module.pyi]
+[out1]
+[out2]
+main:1: note: In module imported here:
+tmp/mod1.py:6: error: Argument 1 to "accept_int" has incompatible type "str"; expected "int"
+
+[case testIncrementalNestedBrokenCascadeWithType2]
+import mod1, mod2.mod3.mod5
+
+[file mod1.py]
+from mod2 import produce 
+def accept_int(x: int) -> None: pass
+a = produce()
+accept_int(a.foo())
+
+[file mod2/__init__.py]
+from mod2.mod3 import produce 
+
+[file mod2/mod3/__init__.py]
+from mod2.mod3.mod4 import CustomType
+def produce() -> CustomType:
+    return CustomType()
+
+[file mod2/mod3/__init__.py.next]
+# Import a different class that also happens to be called 'CustomType'
+from mod2.mod3.mod5 import CustomType
+def produce() -> CustomType:
+    return CustomType()
+
+[file mod2/mod3/mod4.py]
+class CustomType:
+    def foo(self) -> int: return 1
+
+[file mod2/mod3/mod5.py]
+class CustomType:
+    def foo(self) -> str: return "a"
 
 [rechecked mod1, mod2, mod2.mod3]
 [stale mod2.mod3]
 [builtins fixtures/module.pyi]
+[out1]
 [out2]
 main:1: note: In module imported here:
-tmp/mod1.py:3: error: "module" has no attribute "mod4"
+tmp/mod1.py:4: error: Argument 1 to "accept_int" has incompatible type "str"; expected "int"
 
 [case testIncrementalRemoteChange]
 import mod1