WIP: adds better namedtuple semantic analyzer

docs/source/error_code_list.rst

@@ -654,7 +654,7 @@ consistently when using the call-based syntax. Example:
 
     from typing import NamedTuple
 
-    # Error: First argument to namedtuple() should be "Point2D", not "Point"
+    # Error: First argument to "NamedTuple()" should be "Point2D", not "Point"
     Point2D = NamedTuple("Point", [("x", int), ("y", int)])
 
 Report syntax errors [syntax]

mypy/checkexpr.py

@@ -4181,6 +4181,8 @@ def visit_newtype_expr(self, e: NewTypeExpr) -> Type:
         return AnyType(TypeOfAny.special_form)
 
     def visit_namedtuple_expr(self, e: NamedTupleExpr) -> Type:
+        if e.call:
+            self.accept(e.call)
         tuple_type = e.info.tuple_type
         if tuple_type:
             if (self.chk.options.disallow_any_unimported and

mypy/nodes.py

@@ -2305,16 +2305,23 @@ def accept(self, visitor: ExpressionVisitor[T]) -> T:
 class NamedTupleExpr(Expression):
     """Named tuple expression namedtuple(...) or NamedTuple(...)."""
 
-    __slots__ = ('info', 'is_typed')
+    __slots__ = ('info', 'call', 'is_typed')
 
     # The class representation of this named tuple (its tuple_type attribute contains
     # the tuple item types)
     info: "TypeInfo"
+    # We store original expr, if named tuple was created by an inline-call.
+    # We construct it during "semanal" phase and
+    # use it to type check that call is valid during "check" phase.
+    call: Optional[CallExpr]
     is_typed: bool  # whether this class was created with typing.NamedTuple
 
-    def __init__(self, info: 'TypeInfo', is_typed: bool = False) -> None:
+    def __init__(self, info: 'TypeInfo',
+                 call: Optional[CallExpr] = None,
+                 is_typed: bool = False) -> None:
         super().__init__()
         self.info = info
+        self.call = call
         self.is_typed = is_typed
 
     def accept(self, visitor: ExpressionVisitor[T]) -> T:

mypy/semanal.py

@@ -2295,12 +2295,8 @@ def analyze_namedtuple_assign(self, s: AssignmentStmt) -> bool:
         if internal_name is None:
             return False
         if isinstance(lvalue, MemberExpr):
-            self.fail("NamedTuple type as an attribute is not supported", lvalue)
+            self.fail('Namedtuples as attributes are not supported', lvalue)
             return False
-        if internal_name != name:
-            self.fail('First argument to namedtuple() should be "{}", not "{}"'.format(
-                name, internal_name), s.rvalue, code=codes.NAME_MATCH)
-            return True
         # Yes, it's a valid namedtuple, but defer if it is not ready.
         if not info:
             self.mark_incomplete(name, lvalue, becomes_typeinfo=True)