Support functional API for Enum.

Fixes #2306.

Author: Guido van Rossum

mypy/checker.py

@@ -17,12 +17,17 @@
     TupleExpr, ListExpr, ExpressionStmt, ReturnStmt, IfStmt,
     WhileStmt, OperatorAssignmentStmt, WithStmt, AssertStmt,
     RaiseStmt, TryStmt, ForStmt, DelStmt, CallExpr, IntExpr, StrExpr,
-    UnicodeExpr, OpExpr, UnaryExpr, LambdaExpr, TempNode, SymbolTableNode,
-    Context, Decorator, PrintStmt, LITERAL_TYPE, BreakStmt, PassStmt, ContinueStmt,
-    ComparisonExpr, StarExpr, EllipsisExpr, RefExpr, ImportFrom, ImportAll, ImportBase,
-    ARG_POS, CONTRAVARIANT, COVARIANT, ExecStmt, GlobalDecl, Import, NonlocalDecl,
-    MDEF, Node
-)
+    BytesExpr, UnicodeExpr, FloatExpr, OpExpr, UnaryExpr, CastExpr, RevealTypeExpr, SuperExpr,
+    TypeApplication, DictExpr, SliceExpr, LambdaExpr, TempNode, SymbolTableNode,
+    Context, ListComprehension, ConditionalExpr, GeneratorExpr,
+    Decorator, SetExpr, TypeVarExpr, NewTypeExpr, PrintStmt,
+    LITERAL_TYPE, BreakStmt, PassStmt, ContinueStmt, ComparisonExpr, StarExpr,
+    YieldFromExpr, NamedTupleExpr, TypedDictExpr, SetComprehension,
+    DictionaryComprehension, ComplexExpr, EllipsisExpr, TypeAliasExpr,
+    RefExpr, YieldExpr, BackquoteExpr, Import, ImportFrom, ImportAll, ImportBase,
+    AwaitExpr, PromoteExpr, Node, EnumCallExpr,
+    ARG_POS, MDEF,
+    CONTRAVARIANT, COVARIANT)
 from mypy import nodes
 from mypy.types import (
     Type, AnyType, CallableType, FunctionLike, Overloaded, TupleType, TypedDictType,
@@ -44,7 +49,7 @@
 from mypy.semanal import set_callable_name, refers_to_fullname
 from mypy.erasetype import erase_typevars
 from mypy.expandtype import expand_type, expand_type_by_instance
-from mypy.visitor import StatementVisitor
+from mypy.visitor import NodeVisitor
 from mypy.join import join_types
 from mypy.treetransform import TransformVisitor
 from mypy.meet import is_overlapping_types
@@ -69,7 +74,7 @@
     ])
 
 
-class TypeChecker(StatementVisitor[None]):
+class TypeChecker(NodeVisitor[None]):
     """Mypy type checker.
 
     Type check mypy source files that have been semantically analyzed.
@@ -2212,21 +2217,13 @@ def visit_break_stmt(self, s: BreakStmt) -> None:
 
     def visit_continue_stmt(self, s: ContinueStmt) -> None:
         self.binder.handle_continue()
+        return None
 
-    def visit_exec_stmt(self, s: ExecStmt) -> None:
-        pass
-
-    def visit_global_decl(self, s: GlobalDecl) -> None:
-        pass
-
-    def visit_nonlocal_decl(self, s: NonlocalDecl) -> None:
-        pass
+    def visit_typeddict_expr(self, e: TypedDictExpr) -> Type:
+        return self.expr_checker.visit_typeddict_expr(e)
 
-    def visit_var(self, s: Var) -> None:
-        pass
-
-    def visit_pass_stmt(self, s: PassStmt) -> None:
-        pass
+    def visit_enum_call_expr(self, o: 'mypy.nodes.EnumCallExpr') -> Type:
+        return self.expr_checker.visit_enum_call_expr(o)
 
     #
     # Helpers

mypy/checkexpr.py

@@ -20,7 +20,8 @@
     ConditionalExpr, ComparisonExpr, TempNode, SetComprehension,
     DictionaryComprehension, ComplexExpr, EllipsisExpr, StarExpr, AwaitExpr, YieldExpr,
     YieldFromExpr, TypedDictExpr, PromoteExpr, NewTypeExpr, NamedTupleExpr, TypeVarExpr,
-    TypeAliasExpr, BackquoteExpr, ARG_POS, ARG_NAMED, ARG_STAR, ARG_STAR2, MODULE_REF,
+    TypeAliasExpr, BackquoteExpr, EnumCallExpr,
+    ARG_POS, ARG_NAMED, ARG_STAR, ARG_STAR2, MODULE_REF,
     UNBOUND_TVAR, BOUND_TVAR, LITERAL_TYPE
 )
 from mypy import nodes
@@ -354,6 +355,12 @@ def check_call(self, callee: Type, args: List[Expression],
         """
         arg_messages = arg_messages or self.msg
         if isinstance(callee, CallableType):
+            if (isinstance(callable_node, RefExpr)
+                and callable_node.fullname in ('enum.Enum', 'enum.IntEnum',
+                                               'enum.Flag', 'enum.IntFlag')):
+                # An Enum() call that failed SemanticAnalyzer.check_enum_call().
+                return callee.ret_type, callee
+
             if callee.is_concrete_type_obj() and callee.type_object().is_abstract:
                 type = callee.type_object()
                 self.msg.cannot_instantiate_abstract_class(
@@ -2191,6 +2198,22 @@ def visit_namedtuple_expr(self, e: NamedTupleExpr) -> Type:
         # TODO: Perhaps return a type object type?
         return AnyType()
 
+    def visit_enum_call_expr(self, e: EnumCallExpr) -> Type:
+        for name, value in zip(e.items, e.values):
+            if value is not None:
+                typ = self.accept(value)
+                if not isinstance(typ, AnyType):
+                    var = e.info.names[name].node
+                    if isinstance(var, Var):
+                        # Inline TypeCheker.set_inferred_type(),
+                        # without the lvalue.  (This doesn't really do
+                        # much, since the value attribute is defined
+                        # to have type Any in the typeshed stub.)
+                        var.type = typ
+                        var.is_inferred = True
+        # 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()

mypy/nodes.py

@@ -1818,6 +1818,25 @@ def accept(self, visitor: ExpressionVisitor[T]) -> T:
         return visitor.visit_typeddict_expr(self)
 
 
+class EnumCallExpr(Expression):
+    """Named tuple expression Enum('name', 'val1 val2 ...')."""
+
+    # The class representation of this enumerated type
+    info = None  # type: TypeInfo
+    # The item names (for debugging)
+    items = None  # type: List[str]
+    values = None  # type: List[Optional[Expression]]
+
+    def __init__(self, info: 'TypeInfo', items: List[str],
+                 values: List[Optional[Expression]]) -> None:
+        self.info = info
+        self.items = items
+        self.values = values
+
+    def accept(self, visitor: ExpressionVisitor[T]) -> T:
+        return visitor.visit_enum_call_expr(self)
+
+
 class PromoteExpr(Expression):
     """Ducktype class decorator expression _promote(...)."""
 

mypy/semanal.py

@@ -64,7 +64,7 @@
     YieldFromExpr, NamedTupleExpr, TypedDictExpr, NonlocalDecl, SymbolNode,
     SetComprehension, DictionaryComprehension, TYPE_ALIAS, TypeAliasExpr,
     YieldExpr, ExecStmt, Argument, BackquoteExpr, ImportBase, AwaitExpr,
-    IntExpr, FloatExpr, UnicodeExpr, EllipsisExpr, TempNode,
+    IntExpr, FloatExpr, UnicodeExpr, EllipsisExpr, TempNode, EnumCallExpr,
     COVARIANT, CONTRAVARIANT, INVARIANT, UNBOUND_IMPORTED, LITERAL_YES, ARG_OPT, nongen_builtins,
     collections_type_aliases, get_member_expr_fullname,
 )
@@ -1434,6 +1434,7 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
         self.process_typevar_declaration(s)
         self.process_namedtuple_definition(s)
         self.process_typeddict_definition(s)
+        self.process_enum_call(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
@@ -2263,6 +2264,139 @@ def is_classvar(self, typ: Type) -> bool:
     def fail_invalid_classvar(self, context: Context) -> None:
         self.fail('ClassVar can only be used for assignments in class body', context)
 
+    def process_enum_call(self, s: AssignmentStmt) -> None:
+        """Check if s defines an Enum; 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
+        enum_call = self.check_enum_call(s.rvalue, name)
+        if enum_call is None:
+            return
+        # Yes, it's a valid Enum definition. Add it to the symbol table.
+        node = self.lookup(name, s)
+        if node:
+            node.kind = GDEF   # TODO locally defined Enum
+            node.node = enum_call
+
+    def check_enum_call(self, node: Expression, var_name: str = None) -> Optional[TypeInfo]:
+        """Check if a call defines an Enum.
+
+        Example:
+
+          A = enum.Enum('A', 'foo bar')
+
+        is equivalent to:
+
+          class A(enum.Enum):
+              foo = 1
+              bar = 2
+        """
+        if not isinstance(node, CallExpr):
+            return None
+        call = node
+        callee = call.callee
+        if not isinstance(callee, RefExpr):
+            return None
+        fullname = callee.fullname
+        if fullname not in ('enum.Enum', 'enum.IntEnum', 'enum.Flag', 'enum.IntFlag'):
+            return None
+        items, values, ok = self.parse_enum_call_args(call, fullname.split('.')[-1])
+        if not ok:
+            # Error. Construct dummy return value.
+            return self.build_enum_call_typeinfo('Enum', [], fullname)
+        name = cast(StrExpr, call.args[0]).value
+        if name != var_name or self.is_func_scope():
+            # Give it a unique name derived from the line number.
+            name += '@' + str(call.line)
+        info = self.build_enum_call_typeinfo(name, items, fullname)
+        # Store it as a global just in case it would remain anonymous.
+        # (Or in the nearest class if there is one.)
+        stnode = SymbolTableNode(GDEF, info, self.cur_mod_id)
+        if self.type:
+            self.type.names[name] = stnode
+        else:
+            self.globals[name] = stnode
+        call.analyzed = EnumCallExpr(info, items, values)
+        call.analyzed.set_line(call.line, call.column)
+        return info
+
+    def build_enum_call_typeinfo(self, name: str, items: List[str], fullname: str) -> TypeInfo:
+        base = self.named_type_or_none(fullname)
+        assert base is not None
+        info = self.basic_new_typeinfo(name, base)
+        info.is_enum = True
+        for item in items:
+            var = Var(item)
+            var.info = info
+            var.is_property = True
+            info.names[item] = SymbolTableNode(MDEF, var)
+        return info
+
+    def parse_enum_call_args(self, call: CallExpr,
+                             class_name: str) -> Tuple[List[str],
+                                                       List[Optional[Expression]], bool]:
+        args = call.args
+        if len(args) < 2:
+            return self.fail_enum_call_arg("Too few arguments for %s()" % class_name, call)
+        if len(args) > 2:
+            return self.fail_enum_call_arg("Too many arguments for %s()" % class_name, call)
+        if call.arg_kinds != [ARG_POS, ARG_POS]:
+            return self.fail_enum_call_arg("Unexpected arguments to %s()" % class_name, call)
+        if not isinstance(args[0], (StrExpr, UnicodeExpr)):
+            return self.fail_enum_call_arg(
+                "%s() expects a string literal as the first argument" % class_name, call)
+        items = []
+        values = []  # type: List[Optional[Expression]]
+        if isinstance(args[1], (StrExpr, UnicodeExpr)):
+            fields = args[1].value
+            for field in fields.replace(',', ' ').split():
+                items.append(field)
+        elif isinstance(args[1], (TupleExpr, ListExpr)):
+            seq_items = args[1].items
+            if all(isinstance(seq_item, (StrExpr, UnicodeExpr)) for seq_item in seq_items):
+                items = [cast(StrExpr, seq_item).value for seq_item in seq_items]
+            elif all(isinstance(seq_item, (TupleExpr, ListExpr))
+                     and len(seq_item.items) == 2
+                     and isinstance(seq_item.items[0], (StrExpr, UnicodeExpr))
+                     for seq_item in seq_items):
+                for seq_item in seq_items:
+                    assert isinstance(seq_item, (TupleExpr, ListExpr))
+                    name, value = seq_item.items
+                    assert isinstance(name, (StrExpr, UnicodeExpr))
+                    items.append(name.value)
+                    values.append(value)
+            else:
+                return self.fail_enum_call_arg(
+                    "%s() with tuple or list expects strings or (name, value) pairs" %
+                    class_name,
+                    call)
+        elif isinstance(args[1], DictExpr):
+            for key, value in args[1].items:
+                if not isinstance(key, (StrExpr, UnicodeExpr)):
+                    return self.fail_enum_call_arg(
+                        "%s() with dict literal requires string literals" % class_name, call)
+                items.append(key.value)
+                values.append(value)
+        else:
+            # TODO: Allow dict(x=1, y=2) as a substitute for {'x': 1, 'y': 2}?
+            return self.fail_enum_call_arg(
+                "%s() expects a string, tuple, list or dict literal as the second argument" %
+                class_name,
+                call)
+        if len(items) == 0:
+            return self.fail_enum_call_arg("%s() needs at least one item" % class_name, call)
+        if not values:
+            values = [None] * len(items)
+        assert len(items) == len(values)
+        return items, values, True
+
+    def fail_enum_call_arg(self, message: str,
+                           context: Context) -> Tuple[List[str],
+                                                      List[Optional[Expression]], bool]:
+        self.fail(message, context)
+        return [], [], False
+
     def visit_decorator(self, dec: Decorator) -> None:
         for d in dec.decorators:
             d.accept(self)

mypy/strconv.py

@@ -429,6 +429,9 @@ def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> str:
                                                   o.info.name(),
                                                   o.info.tuple_type)
 
+    def visit_enum_call_expr(self, o: 'mypy.nodes.EnumCallExpr') -> str:
+        return 'EnumCallExpr:{}({}, {})'.format(o.line, o.info.name(), o.items)
+
     def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> str:
         return 'TypedDictExpr:{}({})'.format(o.line,
                                              o.info.name())

mypy/treetransform.py

@@ -19,7 +19,7 @@
     ComparisonExpr, TempNode, StarExpr, Statement, Expression,
     YieldFromExpr, NamedTupleExpr, TypedDictExpr, NonlocalDecl, SetComprehension,
     DictionaryComprehension, ComplexExpr, TypeAliasExpr, EllipsisExpr,
-    YieldExpr, ExecStmt, Argument, BackquoteExpr, AwaitExpr,
+    YieldExpr, ExecStmt, Argument, BackquoteExpr, AwaitExpr, EnumCallExpr,
 )
 from mypy.types import Type, FunctionLike
 from mypy.traverser import TraverserVisitor
@@ -485,6 +485,9 @@ def visit_newtype_expr(self, node: NewTypeExpr) -> NewTypeExpr:
     def visit_namedtuple_expr(self, node: NamedTupleExpr) -> NamedTupleExpr:
         return NamedTupleExpr(node.info)
 
+    def visit_enum_call_expr(self, node: EnumCallExpr) -> EnumCallExpr:
+        return EnumCallExpr(node.info, node.items, node.values)
+
     def visit_typeddict_expr(self, node: TypedDictExpr) -> Node:
         return TypedDictExpr(node.info)
 

mypy/visitor.py

@@ -156,6 +156,10 @@ def visit_type_alias_expr(self, o: 'mypy.nodes.TypeAliasExpr') -> T:
     def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> T:
         pass
 
+    @abstractmethod
+    def visit_enum_call_expr(self, o: 'mypy.nodes.EnumCallExpr') -> T:
+        pass
+
     @abstractmethod
     def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> T:
         pass
@@ -514,6 +518,9 @@ def visit_type_alias_expr(self, o: 'mypy.nodes.TypeAliasExpr') -> T:
     def visit_namedtuple_expr(self, o: 'mypy.nodes.NamedTupleExpr') -> T:
         pass
 
+    def visit_enum_call_expr(self, o: 'mypy.nodes.EnumCallExpr') -> T:
+        pass
+
     def visit_typeddict_expr(self, o: 'mypy.nodes.TypedDictExpr') -> T:
         pass