Fix type query for recursive aliases (#14136)

ilevkivskyi · web-flow · commit 6cd8e007923a · 2022-11-18T18:00:33.000-08:00
See #14130 for context. Btw it looks like these `Any` reports are quite broken in general. Some issues I found: * Many types are reported twice (even non-recursive) * Explicit `Any` in alias r.h.s are not counted (because of reckless `res = make_any_non_explicit(res)` in semanal.py) * For generic aliases we count their r.h.s. as containing `Any` from omitted generics I tried to fix these things, but it is not trivial, so maybe we can do it later in a separate PR.
diff --git a/mypy/type_visitor.py b/mypy/type_visitor.py
@@ -404,24 +404,16 @@ def visit_placeholder_type(self, t: PlaceholderType) -> T:
         return self.query_types(t.args)
 
     def visit_type_alias_type(self, t: TypeAliasType) -> T:
+        # Skip type aliases already visited types to avoid infinite recursion.
+        # TODO: Ideally we should fire subvisitors here (or use caching) if we care
+        #       about duplicates.
+        if t in self.seen_aliases:
+            return self.strategy([])
+        self.seen_aliases.add(t)
         if self.skip_alias_target:
             return self.query_types(t.args)
         return get_proper_type(t).accept(self)
 
     def query_types(self, types: Iterable[Type]) -> T:
-        """Perform a query for a list of types.
-
-        Use the strategy to combine the results.
-        Skip type aliases already visited types to avoid infinite recursion.
-        """
-        res: list[T] = []
-        for t in types:
-            if isinstance(t, TypeAliasType):
-                # Avoid infinite recursion for recursive type aliases.
-                # TODO: Ideally we should fire subvisitors here (or use caching) if we care
-                #       about duplicates.
-                if t in self.seen_aliases:
-                    continue
-                self.seen_aliases.add(t)
-            res.append(t.accept(self))
-        return self.strategy(res)
+        """Perform a query for a list of types using the strategy to combine the results."""
+        return self.strategy([t.accept(self) for t in types])
diff --git a/mypy/typeanal.py b/mypy/typeanal.py
@@ -450,7 +450,7 @@ def try_analyze_special_unbound_type(self, t: UnboundType, fullname: str) -> Typ
         if fullname == "builtins.None":
             return NoneType()
         elif fullname == "typing.Any" or fullname == "builtins.Any":
-            return AnyType(TypeOfAny.explicit)
+            return AnyType(TypeOfAny.explicit, line=t.line, column=t.column)
         elif fullname in FINAL_TYPE_NAMES:
             self.fail(
                 "Final can be only used as an outermost qualifier in a variable annotation",
diff --git a/test-data/unit/reports.test b/test-data/unit/reports.test
@@ -103,6 +103,28 @@ class A(object):
 </body>
 </html>
 
+[case testNoCrashRecursiveAliasInReport]
+# cmd: mypy --any-exprs-report report n.py
+
+[file n.py]
+from typing import Union, List, Any, TypeVar
+
+Nested = List[Union[Any, Nested]]
+T = TypeVar("T")
+NestedGen = List[Union[T, NestedGen[T]]]
+
+x: Nested
+y: NestedGen[int]
+z: NestedGen[Any]
+
+[file report/any-exprs.txt]
+[outfile report/types-of-anys.txt]
+ Name   Unannotated   Explicit   Unimported   Omitted Generics   Error   Special Form   Implementation Artifact
+-----------------------------------------------------------------------------------------------------------------
+    n             0          4            0                  8       0              0                         0
+-----------------------------------------------------------------------------------------------------------------
+Total             0          4            0                  8       0              0                         0
+
 [case testTypeVarTreatedAsEmptyLine]
 # cmd: mypy --html-report report n.py
 
@@ -480,7 +502,7 @@ namespace_packages = True
 <link rel="stylesheet" type="text/css" href="../../../mypy-html.css">
 </head>
 <body>
-<h2>folder.subfolder.something</h2>           
+<h2>folder.subfolder.something</h2>
 <table>
 <caption>folder/subfolder/something.py</caption>
 <tbody><tr>
