python · gvanrossum · Oct 19, 2016 · Oct 1, 2016 · Oct 11, 2016 · Oct 11, 2016
diff --git a/extensions/mypy_extensions.py b/extensions/mypy_extensions.py
@@ -7,4 +7,16 @@
 
 # NOTE: This module must support Python 2.7 in addition to Python 3.x
 
-# (TODO: Declare TypedDict and other extensions here)
+
+def TypedDict(typename, fields):
+    """TypedDict creates a dictionary type that expects all of its
+    instances to have a certain set of keys, with each key
+    associated with a value of a consistent type. This expectation
+    is not checked at runtime but is only enforced by typecheckers.
+    """
+    def new_dict(*args, **kwargs):
+        return dict(*args, **kwargs)
+
+    new_dict.__name__ = typename
+    new_dict.__supertype__ = dict
+    return new_dict
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -20,7 +20,7 @@
     Context, ListComprehension, ConditionalExpr, GeneratorExpr,
     Decorator, SetExpr, TypeVarExpr, NewTypeExpr, PrintStmt,
     LITERAL_TYPE, BreakStmt, PassStmt, ContinueStmt, ComparisonExpr, StarExpr,
-    YieldFromExpr, NamedTupleExpr, SetComprehension,
+    YieldFromExpr, NamedTupleExpr, TypedDictExpr, SetComprehension,
     DictionaryComprehension, ComplexExpr, EllipsisExpr, TypeAliasExpr,
     RefExpr, YieldExpr, BackquoteExpr, ImportFrom, ImportAll, ImportBase,
     AwaitExpr,
@@ -2082,6 +2082,10 @@ def visit_namedtuple_expr(self, e: NamedTupleExpr) -> Type:
         # TODO: Perhaps return a type object type?
         return AnyType()
 
+    def visit_typeddict_expr(self, e: TypedDictExpr) -> Type:
+        # TODO: Perhaps return a type object type?
+        return AnyType()
+
     def visit_list_expr(self, e: ListExpr) -> Type:
         return self.expr_checker.visit_list_expr(e)
 

diff --git a/mypy/nodes.py b/mypy/nodes.py
@@ -1747,7 +1747,7 @@ def accept(self, visitor: NodeVisitor[T]) -> T:
 
 
 class NamedTupleExpr(Expression):
-    """Named tuple expression namedtuple(...)."""
+    """Named tuple expression namedtuple(...) or NamedTuple(...)."""
 
     # The class representation of this named tuple (its tuple_type attribute contains
     # the tuple item types)
@@ -1760,6 +1760,19 @@ def accept(self, visitor: NodeVisitor[T]) -> T:
         return visitor.visit_namedtuple_expr(self)
 
 
+class TypedDictExpr(Expression):
+    """Typed dict expression TypedDict(...)."""
+
+    # The class representation of this typed dict
+    info = None  # type: TypeInfo
+
+    def __init__(self, info: 'TypeInfo') -> None:
+        self.info = info
+
+    def accept(self, visitor: NodeVisitor[T]) -> T:
+        return visitor.visit_typeddict_expr(self)
+
+
 class PromoteExpr(Expression):
     """Ducktype class decorator expression _promote(...)."""
 
@@ -1882,6 +1895,9 @@ class is generic then it will be a type constructor of higher kind.
     # Is this a named tuple type?
     is_named_tuple = False
 
+    # Is this a typed dict type?
+    is_typed_dict = False
+
     # Is this a newtype type?
     is_newtype = False
 
@@ -1893,7 +1909,7 @@ class is generic then it will be a type constructor of higher kind.
 
     FLAGS = [
         'is_abstract', 'is_enum', 'fallback_to_any', 'is_named_tuple',
-        'is_newtype', 'is_dummy'
+        'is_typed_dict', 'is_newtype', 'is_dummy'
     ]
 
     def __init__(self, names: 'SymbolTable', defn: ClassDef, module_name: str) -> None:

diff --git a/mypy/semanal.py b/mypy/semanal.py
@@ -60,7 +60,7 @@
     FuncExpr, MDEF, FuncBase, Decorator, SetExpr, TypeVarExpr, NewTypeExpr,
     StrExpr, BytesExpr, PrintStmt, ConditionalExpr, PromoteExpr,
     ComparisonExpr, StarExpr, ARG_POS, ARG_NAMED, MroError, type_aliases,
-    YieldFromExpr, NamedTupleExpr, NonlocalDecl, SymbolNode,
+    YieldFromExpr, NamedTupleExpr, TypedDictExpr, NonlocalDecl, SymbolNode,
     SetComprehension, DictionaryComprehension, TYPE_ALIAS, TypeAliasExpr,
     YieldExpr, ExecStmt, Argument, BackquoteExpr, ImportBase, AwaitExpr,
     IntExpr, FloatExpr, UnicodeExpr, EllipsisExpr,
@@ -1127,6 +1127,7 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
         self.process_newtype_declaration(s)
         self.process_typevar_declaration(s)
         self.process_namedtuple_definition(s)
+        self.process_typeddict_definition(s)
 
         if (len(s.lvalues) == 1 and isinstance(s.lvalues[0], NameExpr) and
                 s.lvalues[0].name == '__all__' and s.lvalues[0].kind == GDEF and
@@ -1498,9 +1499,9 @@ def get_typevar_declaration(self, s: AssignmentStmt) -> Optional[CallExpr]:
         if not isinstance(s.rvalue, CallExpr):
             return None
         call = s.rvalue
-        if not isinstance(call.callee, RefExpr):
-            return None
         callee = call.callee
+        if not isinstance(callee, RefExpr):
+            return None
         if callee.fullname != 'typing.TypeVar':
             return None
         return call
@@ -1579,10 +1580,9 @@ def process_namedtuple_definition(self, s: AssignmentStmt) -> None:
         # Yes, it's a valid namedtuple definition. Add it to the symbol table.
         node = self.lookup(name, s)
         node.kind = GDEF   # TODO locally defined namedtuple
-        # TODO call.analyzed
         node.node = named_tuple
 
-    def check_namedtuple(self, node: Expression, var_name: str = None) -> TypeInfo:
+    def check_namedtuple(self, node: Expression, var_name: str = None) -> Optional[TypeInfo]:
         """Check if a call defines a namedtuple.
 
         The optional var_name argument is the name of the variable to
@@ -1596,9 +1596,9 @@ def check_namedtuple(self, node: Expression, var_name: str = None) -> TypeInfo:
         if not isinstance(node, CallExpr):
             return None
         call = node
-        if not isinstance(call.callee, RefExpr):
-            return None
         callee = call.callee
+        if not isinstance(callee, RefExpr):
+            return None
         fullname = callee.fullname
         if fullname not in ('collections.namedtuple', 'typing.NamedTuple'):
             return None
@@ -1607,9 +1607,9 @@ def check_namedtuple(self, node: Expression, var_name: str = None) -> TypeInfo:
             # Error. Construct dummy return value.
             return self.build_namedtuple_typeinfo('namedtuple', [], [])
         else:
-            # Give it a unique name derived from the line number.
             name = cast(StrExpr, call.args[0]).value
             if name != var_name:
+                # Give it a unique name derived from the line number.
                 name += '@' + str(call.line)
             info = self.build_namedtuple_typeinfo(name, items, types)
             # Store it as a global just in case it would remain anonymous.
@@ -1620,7 +1620,7 @@ def check_namedtuple(self, node: Expression, var_name: str = None) -> TypeInfo:
 
     def parse_namedtuple_args(self, call: CallExpr,
                               fullname: str) -> Tuple[List[str], List[Type], bool]:
-        # TODO Share code with check_argument_count in checkexpr.py?
+        # TODO: Share code with check_argument_count in checkexpr.py?
         args = call.args
         if len(args) < 2:
             return self.fail_namedtuple_arg("Too few arguments for namedtuple()", call)
@@ -1777,6 +1777,114 @@ def analyze_types(self, items: List[Expression]) -> List[Type]:
                 result.append(AnyType())
         return result
 
+    def process_typeddict_definition(self, s: AssignmentStmt) -> None:
+        """Check if s defines a TypedDict; if yes, store the definition in symbol table."""
+        if len(s.lvalues) != 1 or not isinstance(s.lvalues[0], NameExpr):
+            return
+        lvalue = s.lvalues[0]
+        name = lvalue.name
+        typed_dict = self.check_typeddict(s.rvalue, name)
+        if typed_dict is None:
+            return
+        # Yes, it's a valid TypedDict definition. Add it to the symbol table.
+        node = self.lookup(name, s)
+        node.kind = GDEF   # TODO locally defined TypedDict
+        node.node = typed_dict
+
+    def check_typeddict(self, node: Expression, var_name: str = None) -> Optional[TypeInfo]:
+        """Check if a call defines a TypedDict.
+
+        The optional var_name argument is the name of the variable to
+        which this is assigned, if any.
+
+        If it does, return the corresponding TypeInfo. Return None otherwise.
+
+        If the definition is invalid but looks like a TypedDict,
+        report errors but return (some) TypeInfo.
+        """
+        if not isinstance(node, CallExpr):
+            return None
+        call = node
+        callee = call.callee
+        if not isinstance(callee, RefExpr):
+            return None
+        fullname = callee.fullname
+        if fullname != 'mypy_extensions.TypedDict':
+            return None
+        items, types, ok = self.parse_typeddict_args(call, fullname)
+        if not ok:
+            # Error. Construct dummy return value.
+            return self.build_typeddict_typeinfo('TypedDict', [], [])
+        else:
+            name = cast(StrExpr, call.args[0]).value
+            if name != var_name:
+                # Give it a unique name derived from the line number.
+                name += '@' + str(call.line)
+            info = self.build_typeddict_typeinfo(name, items, types)
+            # Store it as a global just in case it would remain anonymous.
+            self.globals[name] = SymbolTableNode(GDEF, info, self.cur_mod_id)
+        call.analyzed = TypedDictExpr(info)
+        call.analyzed.set_line(call.line, call.column)
+        return info
+
+    def parse_typeddict_args(self, call: CallExpr,
+                             fullname: str) -> Tuple[List[str], List[Type], bool]:
+        # TODO: Share code with check_argument_count in checkexpr.py?
+        args = call.args
+        if len(args) < 2:
+            return self.fail_typeddict_arg("Too few arguments for TypedDict()", call)
+        if len(args) > 2:
+            return self.fail_typeddict_arg("Too many arguments for TypedDict()", call)
+        # TODO: Support keyword arguments
+        if call.arg_kinds != [ARG_POS, ARG_POS]:
+            return self.fail_typeddict_arg("Unexpected arguments to TypedDict()", call)
+        if not isinstance(args[0], (StrExpr, BytesExpr, UnicodeExpr)):
+            return self.fail_typeddict_arg(
+                "TypedDict() expects a string literal as the first argument", call)
+        if not isinstance(args[1], DictExpr):
+            return self.fail_typeddict_arg(
+                "TypedDict() expects a dictionary literal as the second argument", call)
+        dictexpr = args[1]
+        items, types, ok = self.parse_typeddict_fields_with_types(dictexpr.items, call)
+        return items, types, ok
+
+    def parse_typeddict_fields_with_types(self, dict_items: List[Tuple[Expression, Expression]],
+                                          context: Context) -> Tuple[List[str], List[Type], bool]:
+        items = []  # type: List[str]
+        types = []  # type: List[Type]
+        for (field_name_expr, field_type_expr) in dict_items:
+            if isinstance(field_name_expr, (StrExpr, BytesExpr, UnicodeExpr)):
+                items.append(field_name_expr.value)
+            else:
+                return self.fail_typeddict_arg("Invalid TypedDict() field name", field_name_expr)
+            try:
+                type = expr_to_unanalyzed_type(field_type_expr)
+            except TypeTranslationError:
+                return self.fail_typeddict_arg('Invalid field type', field_type_expr)
+            types.append(self.anal_type(type))
+        return items, types, True
+
+    def fail_typeddict_arg(self, message: str,
+                           context: Context) -> Tuple[List[str], List[Type], bool]:
+        self.fail(message, context)
+        return [], [], False
+
+    def build_typeddict_typeinfo(self, name: str, items: List[str],
+                                 types: List[Type]) -> TypeInfo:
+        strtype = self.named_type('__builtins__.str')  # type: Type
+        dictype = (self.named_type_or_none('builtins.dict', [strtype, AnyType()])
+                   or self.object_type())
+        fallback = dictype
+
+        info = self.basic_new_typeinfo(name, fallback)
+        info.is_typed_dict = True
+
+        # (TODO: Store {items, types} inside "info" somewhere for use later.
+        #        Probably inside a new "info.keys" field which
+        #        would be analogous to "info.names".)
+
+        return info
+
     def visit_decorator(self, dec: Decorator) -> None:
         for d in dec.decorators:
             d.accept(self)

diff --git a/mypy/strconv.py b/mypy/strconv.py
@@ -422,6 +422,10 @@ def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> str:
                                                   o.info.name(),
                                                   o.info.tuple_type)
 
+    def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> str:
+        return 'TypedDictExpr:{}({})'.format(o.line,
+                                             o.info.name())
+
     def visit__promote_expr(self, o: 'mypy.nodes.PromoteExpr') -> str:
         return 'PromoteExpr:{}({})'.format(o.line, o.type)
 

diff --git a/mypy/test/testsemanal.py b/mypy/test/testsemanal.py
@@ -29,6 +29,7 @@
                  'semanal-statements.test',
                  'semanal-abstractclasses.test',
                  'semanal-namedtuple.test',
+                 'semanal-typeddict.test',
                  'semanal-python2.test']
 
 
@@ -78,6 +79,7 @@ def test_semanal(testcase):
             # TODO the test is not reliable
             if (not f.path.endswith((os.sep + 'builtins.pyi',
                                      'typing.pyi',
+                                     'mypy_extensions.pyi',
                                      'abc.pyi',
                                      'collections.pyi'))
                     and not os.path.basename(f.path).startswith('_')

diff --git a/mypy/treetransform.py b/mypy/treetransform.py
@@ -17,7 +17,7 @@
     SliceExpr, OpExpr, UnaryExpr, FuncExpr, TypeApplication, PrintStmt,
     SymbolTable, RefExpr, TypeVarExpr, NewTypeExpr, PromoteExpr,
     ComparisonExpr, TempNode, StarExpr, Statement, Expression,
-    YieldFromExpr, NamedTupleExpr, NonlocalDecl, SetComprehension,
+    YieldFromExpr, NamedTupleExpr, TypedDictExpr, NonlocalDecl, SetComprehension,
     DictionaryComprehension, ComplexExpr, TypeAliasExpr, EllipsisExpr,
     YieldExpr, ExecStmt, Argument, BackquoteExpr, AwaitExpr,
 )
@@ -492,6 +492,9 @@ def visit_newtype_expr(self, node: NewTypeExpr) -> NewTypeExpr:
     def visit_namedtuple_expr(self, node: NamedTupleExpr) -> NamedTupleExpr:
         return NamedTupleExpr(node.info)
 
+    def visit_typeddict_expr(self, node: TypedDictExpr) -> Node:
+        return TypedDictExpr(node.info)
+
     def visit__promote_expr(self, node: PromoteExpr) -> PromoteExpr:
         return PromoteExpr(node.type)
 

diff --git a/mypy/visitor.py b/mypy/visitor.py
@@ -225,6 +225,9 @@ def visit_type_alias_expr(self, o: 'mypy.nodes.TypeAliasExpr') -> T:
     def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> T:
         pass
 
+    def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> T:
+        pass
+
     def visit_newtype_expr(self, o: 'mypy.nodes.NewTypeExpr') -> T:
         pass
 

diff --git a/test-data/unit/lib-stub/mypy_extensions.pyi b/test-data/unit/lib-stub/mypy_extensions.pyi
@@ -0,0 +1,6 @@
+from typing import Dict, Type, TypeVar
+
+T = TypeVar('T')
+
+
+def TypedDict(typename: str, fields: Dict[str, Type[T]]) -> Type[dict]: ...
diff --git a/test-data/unit/semanal-namedtuple.test b/test-data/unit/semanal-namedtuple.test
@@ -154,9 +154,11 @@ N = namedtuple('N', 1) # E: List or tuple literal expected as the second argumen
 from collections import namedtuple
 N = namedtuple('N', ['x', 1]) # E: String literal expected as namedtuple() item
 
-[case testNamedTupleWithInvalidArgs]
+-- NOTE: The following code works at runtime but is not yet supported by mypy.
+--       Keyword arguments may potentially be supported in the future.
+[case testNamedTupleWithNonpositionalArgs]
 from collections import namedtuple
-N = namedtuple('N', x=['x']) # E: Unexpected arguments to namedtuple()
+N = namedtuple(typename='N', field_names=['x']) # E: Unexpected arguments to namedtuple()
 
 [case testInvalidNamedTupleBaseClass]
 from typing import NamedTuple
-Original file line number
+Diff line change
@@ Expand Up @@
         def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> T:
             pass
+        def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> T:
+            pass
         def visit_newtype_expr(self, o: 'mypy.nodes.NewTypeExpr') -> T:
             pass
@@ Expand Down @@