Clean up new_semantic_analyzer config (#18071)

This has been very dead for years, no plugin I can tell is using it

Author: hauntsaninja

mypy/config_parser.py

@@ -472,12 +472,7 @@ def parse_section(
             )
             continue
         else:
-            dv = None
-            # We have to keep new_semantic_analyzer in Options
-            # for plugin compatibility but it is not a valid option anymore.
-            assert hasattr(template, "new_semantic_analyzer")
-            if key != "new_semantic_analyzer":
-                dv = getattr(template, key, None)
+            dv = getattr(template, key, None)
             if dv is None:
                 if key.endswith("_report"):
                     report_type = key[:-7].replace("_", "-")

mypy/options.py

@@ -400,17 +400,12 @@ def use_or_syntax(self) -> bool:
     def use_star_unpack(self) -> bool:
         return self.python_version >= (3, 11)
 
-    # To avoid breaking plugin compatibility, keep providing new_semantic_analyzer
-    @property
-    def new_semantic_analyzer(self) -> bool:
-        return True
-
     def snapshot(self) -> dict[str, object]:
         """Produce a comparable snapshot of this Option"""
         # Under mypyc, we don't have a __dict__, so we need to do worse things.
         d = dict(getattr(self, "__dict__", ()))
         for k in get_class_descriptors(Options):
-            if hasattr(self, k) and k != "new_semantic_analyzer":
+            if hasattr(self, k):
                 d[k] = getattr(self, k)
         # Remove private attributes from snapshot
         d = {k: v for k, v in d.items() if not k.startswith("_")}

mypy/plugin.py

@@ -114,9 +114,6 @@ class C: pass
 Note that a forward reference in a function signature won't trigger another
 pass, since all functions are processed only after the top level has been fully
 analyzed.
-
-You can use `api.options.new_semantic_analyzer` to check whether the new
-semantic analyzer is enabled (it's always true in mypy 0.730 and later).
 """
 
 from __future__ import annotations

mypyc/irbuild/builder.py

@@ -594,7 +594,7 @@ def get_assignment_target(
             if isinstance(symbol, Decorator):
                 symbol = symbol.func
             if symbol is None:
-                # New semantic analyzer doesn't create ad-hoc Vars for special forms.
+                # Semantic analyzer doesn't create ad-hoc Vars for special forms.
                 assert lvalue.is_special_form
                 symbol = Var(lvalue.name)
             if not for_read and isinstance(symbol, Var) and symbol.is_cls: