Improve the __new__ error message to have a line number

Author: msullivan

mypy/semanal_namedtuple.py

@@ -51,7 +51,7 @@ def analyze_namedtuple_classdef(self, defn: ClassDef) -> Optional[TypeInfo]:
                         node.kind = GDEF  # TODO in process_namedtuple_definition also applies here
                         items, types, default_items = self.check_namedtuple_classdef(defn)
                         info = self.build_namedtuple_typeinfo(
-                            defn.name, items, types, default_items)
+                            defn.name, items, types, default_items, defn.line)
                         node.node = info
                         defn.info.replaced = info
                         defn.info = info
@@ -160,7 +160,7 @@ def check_namedtuple(self,
                 name = var_name
             else:
                 name = 'namedtuple@' + str(call.line)
-            info = self.build_namedtuple_typeinfo(name, [], [], {})
+            info = self.build_namedtuple_typeinfo(name, [], [], {}, node.line)
             self.store_namedtuple_info(info, name, call, is_typed)
             return info
         name = cast(Union[StrExpr, BytesExpr, UnicodeExpr], call.args[0]).value
@@ -174,7 +174,7 @@ def check_namedtuple(self,
             }
         else:
             default_items = {}
-        info = self.build_namedtuple_typeinfo(name, items, types, default_items)
+        info = self.build_namedtuple_typeinfo(name, items, types, default_items, node.line)
         # Store it as a global just in case it would remain anonymous.
         # (Or in the nearest class if there is one.)
         self.store_namedtuple_info(info, name, call, is_typed)
@@ -290,7 +290,8 @@ def fail_namedtuple_arg(self, message: str, context: Context
         return [], [], [], False
 
     def build_namedtuple_typeinfo(self, name: str, items: List[str], types: List[Type],
-                                  default_items: Mapping[str, Expression]) -> TypeInfo:
+                                  default_items: Mapping[str, Expression],
+                                  line: int) -> TypeInfo:
         strtype = self.api.named_type('__builtins__.str')
         implicit_any = AnyType(TypeOfAny.special_form)
         basetuple_type = self.api.named_type('__builtins__.tuple', [implicit_any])
@@ -363,6 +364,7 @@ def add_method(funcname: str,
                                      function_type)
             signature.variables = [tvd]
             func = FuncDef(funcname, args, Block([]))
+            func.line = line
             func.info = info
             func.is_class = is_classmethod
             func.type = set_callable_name(signature, func)

test-data/unit/check-class-namedtuple.test

@@ -587,7 +587,7 @@ class XMethBad(NamedTuple):
 class MagicalFields(NamedTuple):
     x: int
     def __slots__(self) -> None: pass  # E: Cannot overwrite NamedTuple attribute "__slots__"
-    def __new__(cls) -> None: pass  # E: Name '__new__' already defined (possibly by an import)
+    def __new__(cls) -> None: pass  # E: Name '__new__' already defined on line 8
     def _source(self) -> int: pass  # E: Cannot overwrite NamedTuple attribute "_source"
     __annotations__ = {'x': float}  # E: NamedTuple field name cannot start with an underscore: __annotations__ \
         # E: Invalid statement in NamedTuple definition; expected "field_name: field_type [= default]" \