Micro-optimize type indirection visitor (#19460)

Specialize iteration for the concrete types `list` and `tuple`, since
this is faster than iterating over an abstract iterable in compiled
code. Also avoid constructing many temporary lists.

Duplicate some very hot code in the hopes further improving performance
slightly, through inlining and possibly also better branch prediction.

The approach is similar to what I used in #19459.

This is a part of a set of micro-optimizations that improve self check
performance by ~5.5%.

Author: JukkaL

mypy/indirection.py

@@ -32,11 +32,29 @@ def find_modules(self, typs: Iterable[types.Type]) -> set[str]:
         self.modules = set()
         self.seen_fullnames = set()
         self.seen_aliases = set()
-        self._visit(typs)
+        for typ in typs:
+            self._visit(typ)
         return self.modules
 
-    def _visit(self, typ_or_typs: types.Type | Iterable[types.Type]) -> None:
-        typs = [typ_or_typs] if isinstance(typ_or_typs, types.Type) else typ_or_typs
+    def _visit(self, typ: types.Type) -> None:
+        if isinstance(typ, types.TypeAliasType):
+            # Avoid infinite recursion for recursive type aliases.
+            if typ not in self.seen_aliases:
+                self.seen_aliases.add(typ)
+        typ.accept(self)
+
+    def _visit_type_tuple(self, typs: tuple[types.Type, ...]) -> None:
+        # Micro-optimization: Specialized version of _visit for lists
+        for typ in typs:
+            if isinstance(typ, types.TypeAliasType):
+                # Avoid infinite recursion for recursive type aliases.
+                if typ in self.seen_aliases:
+                    continue
+                self.seen_aliases.add(typ)
+            typ.accept(self)
+
+    def _visit_type_list(self, typs: list[types.Type]) -> None:
+        # Micro-optimization: Specialized version of _visit for tuples
         for typ in typs:
             if isinstance(typ, types.TypeAliasType):
                 # Avoid infinite recursion for recursive type aliases.
@@ -50,7 +68,7 @@ def _visit_module_name(self, module_name: str) -> None:
             self.modules.update(split_module_names(module_name))
 
     def visit_unbound_type(self, t: types.UnboundType) -> None:
-        self._visit(t.args)
+        self._visit_type_tuple(t.args)
 
     def visit_any(self, t: types.AnyType) -> None:
         pass
@@ -68,7 +86,7 @@ def visit_deleted_type(self, t: types.DeletedType) -> None:
         pass
 
     def visit_type_var(self, t: types.TypeVarType) -> None:
-        self._visit(t.values)
+        self._visit_type_list(t.values)
         self._visit(t.upper_bound)
         self._visit(t.default)
 
@@ -84,10 +102,10 @@ def visit_unpack_type(self, t: types.UnpackType) -> None:
         t.type.accept(self)
 
     def visit_parameters(self, t: types.Parameters) -> None:
-        self._visit(t.arg_types)
+        self._visit_type_list(t.arg_types)
 
     def visit_instance(self, t: types.Instance) -> None:
-        self._visit(t.args)
+        self._visit_type_tuple(t.args)
         if t.type:
             # Uses of a class depend on everything in the MRO,
             # as changes to classes in the MRO can add types to methods,
@@ -98,7 +116,7 @@ def visit_instance(self, t: types.Instance) -> None:
                 self._visit_module_name(t.type.metaclass_type.type.module_name)
 
     def visit_callable_type(self, t: types.CallableType) -> None:
-        self._visit(t.arg_types)
+        self._visit_type_list(t.arg_types)
         self._visit(t.ret_type)
         if t.definition is not None:
             fullname = t.definition.fullname
@@ -107,22 +125,22 @@ def visit_callable_type(self, t: types.CallableType) -> None:
                 self.seen_fullnames.add(fullname)
 
     def visit_overloaded(self, t: types.Overloaded) -> None:
-        self._visit(t.items)
+        self._visit_type_list(list(t.items))
         self._visit(t.fallback)
 
     def visit_tuple_type(self, t: types.TupleType) -> None:
-        self._visit(t.items)
+        self._visit_type_list(t.items)
         self._visit(t.partial_fallback)
 
     def visit_typeddict_type(self, t: types.TypedDictType) -> None:
-        self._visit(t.items.values())
+        self._visit_type_list(list(t.items.values()))
         self._visit(t.fallback)
 
     def visit_literal_type(self, t: types.LiteralType) -> None:
         self._visit(t.fallback)
 
     def visit_union_type(self, t: types.UnionType) -> None:
-        self._visit(t.items)
+        self._visit_type_list(t.items)
 
     def visit_partial_type(self, t: types.PartialType) -> None:
         pass