Skip more method bodies in third-party libraries (#19586)

A while ago we started stripping function bodies when checking
third-party libraries. This PR pushes this idea further:
* Tighten the check in `fastparse.py` to only consider `foo.bar` as
possible self attribute definition.
* Do not type-check bodies where we didn't find any `self` attribute
_definitions_ during semantic analysis.
* Skip method override checks in third-party libraries.

In total this makes e.g. `mypy -c 'import torch'` ~10% faster.
Surprisingly, this also has some visible impact on self-check.

Author: ilevkivskyi

mypy/checker.py

@@ -832,8 +832,10 @@ def check_overlapping_overloads(self, defn: OverloadedFuncDef) -> None:
         # At this point we should have set the impl already, and all remaining
         # items are decorators
 
-        if self.msg.errors.file in self.msg.errors.ignored_files or (
-            self.is_typeshed_stub and self.options.test_env
+        if (
+            self.options.ignore_errors
+            or self.msg.errors.file in self.msg.errors.ignored_files
+            or (self.is_typeshed_stub and self.options.test_env)
         ):
             # This is a little hacky, however, the quadratic check here is really expensive, this
             # method has no side effects, so we should skip it if we aren't going to report
@@ -1444,7 +1446,19 @@ def check_func_def(
                     # TODO: Find a way of working around this limitation
                     if _is_empty_generator_function(item) or len(expanded) >= 2:
                         self.binder.suppress_unreachable_warnings()
-                    self.accept(item.body)
+                    # When checking a third-party library, we can skip function body,
+                    # if during semantic analysis we found that there are no attributes
+                    # defined via self here.
+                    if (
+                        not (
+                            self.options.ignore_errors
+                            or self.msg.errors.file in self.msg.errors.ignored_files
+                        )
+                        or self.options.preserve_asts
+                        or not isinstance(defn, FuncDef)
+                        or defn.has_self_attr_def
+                    ):
+                        self.accept(item.body)
                 unreachable = self.binder.is_unreachable()
                 if new_frame is not None:
                     self.binder.pop_frame(True, 0)
@@ -2127,6 +2141,9 @@ def check_method_override(
 
         Return a list of base classes which contain an attribute with the method name.
         """
+        if self.options.ignore_errors or self.msg.errors.file in self.msg.errors.ignored_files:
+            # Method override checks may be expensive, so skip them in third-party libraries.
+            return None
         # Check against definitions in base classes.
         check_override_compatibility = (
             defn.name not in ("__init__", "__new__", "__init_subclass__", "__post_init__")

mypy/fastparse.py

@@ -2234,7 +2234,7 @@ def visit_index_expr(self, e: IndexExpr) -> None:
         pass
 
     def visit_member_expr(self, e: MemberExpr) -> None:
-        if self.lvalue:
+        if self.lvalue and isinstance(e.expr, NameExpr):
             self.found = True
 
 

mypy/nodes.py

@@ -818,6 +818,7 @@ class FuncDef(FuncItem, SymbolNode, Statement):
         "original_def",
         "is_trivial_body",
         "is_trivial_self",
+        "has_self_attr_def",
         "is_mypy_only",
         # Present only when a function is decorated with @typing.dataclass_transform or similar
         "dataclass_transform_spec",
@@ -856,6 +857,8 @@ def __init__(
         # the majority). In cases where self is not annotated and there are no Self
         # in the signature we can simply drop the first argument.
         self.is_trivial_self = False
+        # Keep track of functions where self attributes are defined.
+        self.has_self_attr_def = False
         # This is needed because for positional-only arguments the name is set to None,
         # but we sometimes still want to show it in error messages.
         if arguments:

mypy/semanal.py

@@ -4570,6 +4570,9 @@ def analyze_member_lvalue(
                     lval.node = v
                     # TODO: should we also set lval.kind = MDEF?
                     self.type.names[lval.name] = SymbolTableNode(MDEF, v, implicit=True)
+                    for func in self.scope.functions:
+                        if isinstance(func, FuncDef):
+                            func.has_self_attr_def = True
         self.check_lvalue_validity(lval.node, lval)
 
     def is_self_member_ref(self, memberexpr: MemberExpr) -> bool: