From 1f7ce62bd61488d5d721896a36a1b43befab88b5 Mon Sep 17 00:00:00 2001
From: Nick Coghlan <ncoghlan@gmail.com>
Date: Fri, 13 Jan 2012 21:43:40 +1000
Subject: [PATCH] Implement PEP 380 - 'yield from' (closes #11682)

---
 Doc/library/dis.rst            |   7 +
 Doc/library/exceptions.rst     |  11 +-
 Doc/reference/expressions.rst  |  30 ++-
 Doc/reference/simple_stmts.rst |  24 ++-
 Doc/whatsnew/3.3.rst           |  17 +-
 Grammar/Grammar                |   5 +-
 Include/Python-ast.h           |   6 +-
 Include/frameobject.h          |  43 ++--
 Include/genobject.h            |  21 +-
 Include/graminit.h             |   1 +
 Include/opcode.h               | 169 ++++++++--------
 Include/pyerrors.h             |   7 +
 Lib/opcode.py                  |   1 +
 Lib/test/test_ast.py           |   3 +-
 Lib/test/test_generators.py    |  42 ----
 Lib/test/test_grammar.py       |  32 +++
 Lib/test/test_parser.py        |   5 +-
 Lib/test/test_sys.py           |   2 +-
 Misc/ACKS                      |   2 +
 Misc/NEWS                      |   4 +
 Modules/parsermodule.c         |  82 +++++---
 Objects/abstract.c             |   2 -
 Objects/exceptions.c           |  66 ++++++-
 Objects/frameobject.c          |  15 +-
 Objects/genobject.c            | 219 ++++++++++++++++++--
 Parser/Python.asdl             |   2 +-
 Python/Python-ast.c            |  27 ++-
 Python/ast.c                   |  21 +-
 Python/ceval.c                 |  46 +++++
 Python/compile.c               |   8 +-
 Python/graminit.c              | 352 +++++++++++++++++----------------
 Python/opcode_targets.h        |   2 +-
 Python/symtable.c              |  19 --
 33 files changed, 872 insertions(+), 421 deletions(-)

diff --git a/Doc/library/dis.rst b/Doc/library/dis.rst
index cb429c880c1..5ba66cb9049 100644
--- a/Doc/library/dis.rst
+++ b/Doc/library/dis.rst
@@ -431,6 +431,13 @@ the stack so that it is available for further iterations of the loop.
    Pops ``TOS`` and yields it from a :term:`generator`.
 
 
+.. opcode:: YIELD_FROM
+
+   Pops ``TOS`` and delegates to it as a subiterator from a :term:`generator`.
+
+   .. versionadded:: 3.3
+
+
 .. opcode:: IMPORT_STAR
 
    Loads all symbols not starting with ``'_'`` directly from the module TOS to the
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index 49cec1ec0ce..a9a16d3d9a5 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -250,7 +250,16 @@ The following exceptions are the exceptions that are usually raised.
 .. exception:: StopIteration
 
    Raised by built-in function :func:`next` and an :term:`iterator`\'s
-   :meth:`__next__` method to signal that there are no further values.
+   :meth:`__next__` method to signal that there are no further items to be
+   produced by the iterator.
+
+   The exception object has a single attribute :attr:`value`, which is
+   given as an argument when constructing the exception, and defaults
+   to :const:`None`.
+
+   When a generator function returns, a new :exc:`StopIteration` instance is
+   raised, and the value returned by the function is used as the
+   :attr:`value` parameter to the constructor of the exception.
 
 
 .. exception:: SyntaxError
diff --git a/Doc/reference/expressions.rst b/Doc/reference/expressions.rst
index 655ebdebc0f..7da54a2ddf2 100644
--- a/Doc/reference/expressions.rst
+++ b/Doc/reference/expressions.rst
@@ -318,7 +318,7 @@ Yield expressions
 
 .. productionlist::
    yield_atom: "(" `yield_expression` ")"
-   yield_expression: "yield" [`expression_list`]
+   yield_expression: "yield" [`expression_list` | "from" `expression`]
 
 The :keyword:`yield` expression is only used when defining a generator function,
 and can only be used in the body of a function definition.  Using a
@@ -336,7 +336,10 @@ the internal evaluation stack.  When the execution is resumed by calling one of
 the generator's methods, the function can proceed exactly as if the
 :keyword:`yield` expression was just another external call.  The value of the
 :keyword:`yield` expression after resuming depends on the method which resumed
-the execution.
+the execution. If :meth:`__next__` is used (typically via either a
+:keyword:`for` or the :func:`next` builtin) then the result is :const:`None`,
+otherwise, if :meth:`send` is used, then the result will be the value passed
+in to that method.
 
 .. index:: single: coroutine
 
@@ -346,12 +349,29 @@ suspended.  The only difference is that a generator function cannot control
 where should the execution continue after it yields; the control is always
 transferred to the generator's caller.
 
-The :keyword:`yield` statement is allowed in the :keyword:`try` clause of a
+:keyword:`yield` expressions are allowed in the :keyword:`try` clause of a
 :keyword:`try` ...  :keyword:`finally` construct.  If the generator is not
 resumed before it is finalized (by reaching a zero reference count or by being
 garbage collected), the generator-iterator's :meth:`close` method will be
 called, allowing any pending :keyword:`finally` clauses to execute.
 
+When ``yield from expression`` is used, it treats the supplied expression as
+a subiterator. All values produced by that subiterator are passed directly
+to the caller of the current generator's methods. Any values passed in with
+:meth:`send` and any exceptions passed in with :meth:`throw` are passed to
+the underlying iterator if it has the appropriate methods. If this is not the
+case, then :meth:`send` will raise :exc:`AttributeError` or :exc:`TypeError`,
+while :meth:`throw` will just raise the passed in exception immediately.
+
+When the underlying iterator is complete, the :attr:`~StopIteration.value`
+attribute of the raised :exc:`StopIteration` instance becomes the value of
+the yield expression. It can be either set explicitly when raising
+:exc:`StopIteration`, or automatically when the sub-iterator is a generator
+(by returning a value from the sub-generator).
+
+The parentheses can be omitted when the :keyword:`yield` expression is the
+sole expression on the right hand side of an assignment statement.
+
 .. index:: object: generator
 
 The following generator's methods can be used to control the execution of a
@@ -444,6 +464,10 @@ generator functions::
       The proposal to enhance the API and syntax of generators, making them
       usable as simple coroutines.
 
+   :pep:`0380` - Syntax for Delegating to a Subgenerator
+      The proposal to introduce the :token:`yield_from` syntax, making delegation
+      to sub-generators easy.
+
 
 .. _primaries:
 
diff --git a/Doc/reference/simple_stmts.rst b/Doc/reference/simple_stmts.rst
index 34ed92fc7ab..d98b829c97d 100644
--- a/Doc/reference/simple_stmts.rst
+++ b/Doc/reference/simple_stmts.rst
@@ -425,10 +425,10 @@ When :keyword:`return` passes control out of a :keyword:`try` statement with a
 :keyword:`finally` clause, that :keyword:`finally` clause is executed before
 really leaving the function.
 
-In a generator function, the :keyword:`return` statement is not allowed to
-include an :token:`expression_list`.  In that context, a bare :keyword:`return`
-indicates that the generator is done and will cause :exc:`StopIteration` to be
-raised.
+In a generator function, the :keyword:`return` statement indicates that the
+generator is done and will cause :exc:`StopIteration` to be raised. The returned
+value (if any) is used as an argument to construct :exc:`StopIteration` and
+becomes the :attr:`StopIteration.value` attribute.
 
 
 .. _yield:
@@ -450,6 +450,7 @@ The :keyword:`yield` statement is only used when defining a generator function,
 and is only used in the body of the generator function. Using a :keyword:`yield`
 statement in a function definition is sufficient to cause that definition to
 create a generator function instead of a normal function.
+
 When a generator function is called, it returns an iterator known as a generator
 iterator, or more commonly, a generator.  The body of the generator function is
 executed by calling the :func:`next` function on the generator repeatedly until
@@ -469,14 +470,25 @@ resumed before it is finalized (by reaching a zero reference count or by being
 garbage collected), the generator-iterator's :meth:`close` method will be
 called, allowing any pending :keyword:`finally` clauses to execute.
 
+When ``yield from expression`` is used, it treats the supplied expression as
+a subiterator, producing values from it until the underlying iterator is
+exhausted.
+
+For full details of :keyword:`yield` semantics, refer to the :ref:`yieldexpr`
+section.
+
 .. seealso::
 
    :pep:`0255` - Simple Generators
       The proposal for adding generators and the :keyword:`yield` statement to Python.
 
    :pep:`0342` - Coroutines via Enhanced Generators
-      The proposal that, among other generator enhancements, proposed allowing
-      :keyword:`yield` to appear inside a :keyword:`try` ... :keyword:`finally` block.
+      The proposal to enhance the API and syntax of generators, making them
+      usable as simple coroutines.
+
+   :pep:`0380` - Syntax for Delegating to a Subgenerator
+      The proposal to introduce the :token:`yield_from` syntax, making delegation
+      to sub-generators easy.
 
 
 .. _raise:
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index 0b0f8f6db68..07257f085e9 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -195,6 +195,22 @@ inspection of exception attributes::
         print("You are not allowed to read document.txt")
 
 
+PEP 380: Syntax for Delegating to a Subgenerator
+================================================
+
+PEP 380 adds the ``yield from`` expression, allowing a generator to delegate
+part of its operations to another generator. This allows a section of code
+containing 'yield' to be factored out and placed in another generator.
+Additionally, the subgenerator is allowed to return with a value, and the
+value is made available to the delegating generator.
+While designed primarily for use in delegating to a subgenerator, the ``yield
+from`` expression actually allows delegation to arbitrary subiterators.
+
+(Implementation by Greg Ewing, integrated into 3.3 by Renaud Blanch, Ryan
+Kelly and Nick Coghlan, documentation by Zbigniew Jędrzejewski-Szmek and
+Nick Coghlan)
+
+
 PEP 3155: Qualified name for classes and functions
 ==================================================
 
@@ -208,7 +224,6 @@ it provides better information about where they were actually defined, and
 how they might be accessible from the global scope.
 
 Example with (non-bound) methods::
-
    >>> class C:
    ...     def meth(self):
    ...         pass
diff --git a/Grammar/Grammar b/Grammar/Grammar
index 544852cc485..38320ef26fd 100644
--- a/Grammar/Grammar
+++ b/Grammar/Grammar
@@ -121,7 +121,7 @@ arglist: (argument ',')* (argument [',']
                          |'**' test)
 # The reason that keywords are test nodes instead of NAME is that using NAME
 # results in an ambiguity. ast.c makes sure it's a NAME.
-argument: test [comp_for] | test '=' test  # Really [keyword '='] test
+argument: (test) [comp_for] | test '=' test  # Really [keyword '='] test
 comp_iter: comp_for | comp_if
 comp_for: 'for' exprlist 'in' or_test [comp_iter]
 comp_if: 'if' test_nocond [comp_iter]
@@ -129,4 +129,5 @@ comp_if: 'if' test_nocond [comp_iter]
 # not used in grammar, but may appear in "node" passed from Parser to Compiler
 encoding_decl: NAME
 
-yield_expr: 'yield' [testlist]
+yield_expr: 'yield' [yield_arg]
+yield_arg: 'from' test | testlist
diff --git a/Include/Python-ast.h b/Include/Python-ast.h
index 938904968f5..4e21674e09f 100644
--- a/Include/Python-ast.h
+++ b/Include/Python-ast.h
@@ -245,6 +245,7 @@ struct _expr {
                 } GeneratorExp;
                 
                 struct {
+                        int is_from;
                         expr_ty value;
                 } Yield;
                 
@@ -487,8 +488,9 @@ expr_ty _Py_DictComp(expr_ty key, expr_ty value, asdl_seq * generators, int
 #define GeneratorExp(a0, a1, a2, a3, a4) _Py_GeneratorExp(a0, a1, a2, a3, a4)
 expr_ty _Py_GeneratorExp(expr_ty elt, asdl_seq * generators, int lineno, int
                          col_offset, PyArena *arena);
-#define Yield(a0, a1, a2, a3) _Py_Yield(a0, a1, a2, a3)
-expr_ty _Py_Yield(expr_ty value, int lineno, int col_offset, PyArena *arena);
+#define Yield(a0, a1, a2, a3, a4) _Py_Yield(a0, a1, a2, a3, a4)
+expr_ty _Py_Yield(int is_from, expr_ty value, int lineno, int col_offset,
+                  PyArena *arena);
 #define Compare(a0, a1, a2, a3, a4, a5) _Py_Compare(a0, a1, a2, a3, a4, a5)
 expr_ty _Py_Compare(expr_ty left, asdl_int_seq * ops, asdl_seq * comparators,
                     int lineno, int col_offset, PyArena *arena);
diff --git a/Include/frameobject.h b/Include/frameobject.h
index 1fb64bb2681..55447b73e0f 100644
--- a/Include/frameobject.h
+++ b/Include/frameobject.h
@@ -9,45 +9,46 @@ extern "C" {
 #endif
 
 typedef struct {
-    int b_type;			/* what kind of block this is */
-    int b_handler;		/* where to jump to find handler */
-    int b_level;		/* value stack level to pop to */
+    int b_type;                 /* what kind of block this is */
+    int b_handler;              /* where to jump to find handler */
+    int b_level;                /* value stack level to pop to */
 } PyTryBlock;
 
 typedef struct _frame {
     PyObject_VAR_HEAD
-    struct _frame *f_back;	/* previous frame, or NULL */
-    PyCodeObject *f_code;	/* code segment */
-    PyObject *f_builtins;	/* builtin symbol table (PyDictObject) */
-    PyObject *f_globals;	/* global symbol table (PyDictObject) */
-    PyObject *f_locals;		/* local symbol table (any mapping) */
-    PyObject **f_valuestack;	/* points after the last local */
+    struct _frame *f_back;      /* previous frame, or NULL */
+    PyCodeObject *f_code;       /* code segment */
+    PyObject *f_builtins;       /* builtin symbol table (PyDictObject) */
+    PyObject *f_globals;        /* global symbol table (PyDictObject) */
+    PyObject *f_locals;         /* local symbol table (any mapping) */
+    PyObject **f_valuestack;    /* points after the last local */
     /* Next free slot in f_valuestack.  Frame creation sets to f_valuestack.
        Frame evaluation usually NULLs it, but a frame that yields sets it
        to the current stack top. */
     PyObject **f_stacktop;
-    PyObject *f_trace;		/* Trace function */
+    PyObject *f_trace;          /* Trace function */
+    PyObject *f_yieldfrom;      /* Iterator being delegated to by yield from */
 
-	/* In a generator, we need to be able to swap between the exception
-	   state inside the generator and the exception state of the calling
-	   frame (which shouldn't be impacted when the generator "yields"
-	   from an except handler).
-	   These three fields exist exactly for that, and are unused for
-	   non-generator frames. See the SAVE_EXC_STATE and SWAP_EXC_STATE
-	   macros in ceval.c for details of their use. */
+        /* In a generator, we need to be able to swap between the exception
+           state inside the generator and the exception state of the calling
+           frame (which shouldn't be impacted when the generator "yields"
+           from an except handler).
+           These three fields exist exactly for that, and are unused for
+           non-generator frames. See the SAVE_EXC_STATE and SWAP_EXC_STATE
+           macros in ceval.c for details of their use. */
     PyObject *f_exc_type, *f_exc_value, *f_exc_traceback;
 
     PyThreadState *f_tstate;
-    int f_lasti;		/* Last instruction if called */
+    int f_lasti;                /* Last instruction if called */
     /* Call PyFrame_GetLineNumber() instead of reading this field
        directly.  As of 2.3 f_lineno is only valid when tracing is
        active (i.e. when f_trace is set).  At other times we use
        PyCode_Addr2Line to calculate the line from the current
        bytecode index. */
-    int f_lineno;		/* Current line number */
-    int f_iblock;		/* index in f_blockstack */
+    int f_lineno;               /* Current line number */
+    int f_iblock;               /* index in f_blockstack */
     PyTryBlock f_blockstack[CO_MAXBLOCKS]; /* for try and loop blocks */
-    PyObject *f_localsplus[1];	/* locals+stack, dynamically sized */
+    PyObject *f_localsplus[1];  /* locals+stack, dynamically sized */
 } PyFrameObject;
 
 
diff --git a/Include/genobject.h b/Include/genobject.h
index d29fb1ed1df..13a385601f1 100644
--- a/Include/genobject.h
+++ b/Include/genobject.h
@@ -11,20 +11,20 @@ extern "C" {
 struct _frame; /* Avoid including frameobject.h */
 
 typedef struct {
-	PyObject_HEAD
-	/* The gi_ prefix is intended to remind of generator-iterator. */
+        PyObject_HEAD
+        /* The gi_ prefix is intended to remind of generator-iterator. */
 
-	/* Note: gi_frame can be NULL if the generator is "finished" */
-	struct _frame *gi_frame;
+        /* Note: gi_frame can be NULL if the generator is "finished" */
+        struct _frame *gi_frame;
 
-	/* True if generator is being executed. */
-	int gi_running;
+        /* True if generator is being executed. */
+        int gi_running;
     
-	/* The code object backing the generator */
-	PyObject *gi_code;
+        /* The code object backing the generator */
+        PyObject *gi_code;
 
-	/* List of weak reference. */
-	PyObject *gi_weakreflist;
+        /* List of weak reference. */
+        PyObject *gi_weakreflist;
 } PyGenObject;
 
 PyAPI_DATA(PyTypeObject) PyGen_Type;
@@ -34,6 +34,7 @@ PyAPI_DATA(PyTypeObject) PyGen_Type;
 
 PyAPI_FUNC(PyObject *) PyGen_New(struct _frame *);
 PyAPI_FUNC(int) PyGen_NeedsFinalizing(PyGenObject *);
+PyAPI_FUNC(int) PyGen_FetchStopIterationValue(PyObject **);
 
 #ifdef __cplusplus
 }
diff --git a/Include/graminit.h b/Include/graminit.h
index e0e27f98c38..3ec949ab462 100644
--- a/Include/graminit.h
+++ b/Include/graminit.h
@@ -81,3 +81,4 @@
 #define comp_if 334
 #define encoding_decl 335
 #define yield_expr 336
+#define yield_arg 337
diff --git a/Include/opcode.h b/Include/opcode.h
index ece713ee39d..a90184d0d78 100644
--- a/Include/opcode.h
+++ b/Include/opcode.h
@@ -7,116 +7,117 @@ extern "C" {
 
 /* Instruction opcodes for compiled code */
 
-#define POP_TOP		1
-#define ROT_TWO		2
-#define ROT_THREE	3
-#define DUP_TOP		4
+#define POP_TOP         1
+#define ROT_TWO         2
+#define ROT_THREE       3
+#define DUP_TOP         4
 #define DUP_TOP_TWO     5
-#define NOP		9
+#define NOP             9
 
-#define UNARY_POSITIVE	10
-#define UNARY_NEGATIVE	11
-#define UNARY_NOT	12
+#define UNARY_POSITIVE  10
+#define UNARY_NEGATIVE  11
+#define UNARY_NOT       12
 
-#define UNARY_INVERT	15
+#define UNARY_INVERT    15
 
-#define BINARY_POWER	19
+#define BINARY_POWER    19
 
-#define BINARY_MULTIPLY	20
+#define BINARY_MULTIPLY 20
 
-#define BINARY_MODULO	22
-#define BINARY_ADD	23
-#define BINARY_SUBTRACT	24
-#define BINARY_SUBSCR	25
+#define BINARY_MODULO   22
+#define BINARY_ADD      23
+#define BINARY_SUBTRACT 24
+#define BINARY_SUBSCR   25
 #define BINARY_FLOOR_DIVIDE 26
 #define BINARY_TRUE_DIVIDE 27
 #define INPLACE_FLOOR_DIVIDE 28
 #define INPLACE_TRUE_DIVIDE 29
 
-#define STORE_MAP	54
-#define INPLACE_ADD	55
-#define INPLACE_SUBTRACT	56
-#define INPLACE_MULTIPLY	57
+#define STORE_MAP       54
+#define INPLACE_ADD     55
+#define INPLACE_SUBTRACT        56
+#define INPLACE_MULTIPLY        57
 
-#define INPLACE_MODULO	59
-#define STORE_SUBSCR	60
-#define DELETE_SUBSCR	61
+#define INPLACE_MODULO  59
+#define STORE_SUBSCR    60
+#define DELETE_SUBSCR   61
 
-#define BINARY_LSHIFT	62
-#define BINARY_RSHIFT	63
-#define BINARY_AND	64
-#define BINARY_XOR	65
-#define BINARY_OR	66
-#define INPLACE_POWER	67
-#define GET_ITER	68
-#define STORE_LOCALS	69
-#define PRINT_EXPR	70
+#define BINARY_LSHIFT   62
+#define BINARY_RSHIFT   63
+#define BINARY_AND      64
+#define BINARY_XOR      65
+#define BINARY_OR       66
+#define INPLACE_POWER   67
+#define GET_ITER        68
+#define STORE_LOCALS    69
+#define PRINT_EXPR      70
 #define LOAD_BUILD_CLASS 71
+#define YIELD_FROM      72
 
-#define INPLACE_LSHIFT	75
-#define INPLACE_RSHIFT	76
-#define INPLACE_AND	77
-#define INPLACE_XOR	78
-#define INPLACE_OR	79
-#define BREAK_LOOP	80
+#define INPLACE_LSHIFT  75
+#define INPLACE_RSHIFT  76
+#define INPLACE_AND     77
+#define INPLACE_XOR     78
+#define INPLACE_OR      79
+#define BREAK_LOOP      80
 #define WITH_CLEANUP    81
 
-#define RETURN_VALUE	83
-#define IMPORT_STAR	84
+#define RETURN_VALUE    83
+#define IMPORT_STAR     84
 
-#define YIELD_VALUE	86
-#define POP_BLOCK	87
-#define END_FINALLY	88
-#define POP_EXCEPT	89
+#define YIELD_VALUE     86
+#define POP_BLOCK       87
+#define END_FINALLY     88
+#define POP_EXCEPT      89
 
-#define HAVE_ARGUMENT	90	/* Opcodes from here have an argument: */
+#define HAVE_ARGUMENT   90      /* Opcodes from here have an argument: */
 
-#define STORE_NAME	90	/* Index in name list */
-#define DELETE_NAME	91	/* "" */
-#define UNPACK_SEQUENCE	92	/* Number of sequence items */
-#define FOR_ITER	93
+#define STORE_NAME      90      /* Index in name list */
+#define DELETE_NAME     91      /* "" */
+#define UNPACK_SEQUENCE 92      /* Number of sequence items */
+#define FOR_ITER        93
 #define UNPACK_EX       94      /* Num items before variable part +
                                    (Num items after variable part << 8) */
 
-#define STORE_ATTR	95	/* Index in name list */
-#define DELETE_ATTR	96	/* "" */
-#define STORE_GLOBAL	97	/* "" */
-#define DELETE_GLOBAL	98	/* "" */
+#define STORE_ATTR      95      /* Index in name list */
+#define DELETE_ATTR     96      /* "" */
+#define STORE_GLOBAL    97      /* "" */
+#define DELETE_GLOBAL   98      /* "" */
 
-#define LOAD_CONST	100	/* Index in const list */
-#define LOAD_NAME	101	/* Index in name list */
-#define BUILD_TUPLE	102	/* Number of tuple items */
-#define BUILD_LIST	103	/* Number of list items */
-#define BUILD_SET	104     /* Number of set items */
-#define BUILD_MAP	105	/* Always zero for now */
-#define LOAD_ATTR	106	/* Index in name list */
-#define COMPARE_OP	107	/* Comparison operator */
-#define IMPORT_NAME	108	/* Index in name list */
-#define IMPORT_FROM	109	/* Index in name list */
+#define LOAD_CONST      100     /* Index in const list */
+#define LOAD_NAME       101     /* Index in name list */
+#define BUILD_TUPLE     102     /* Number of tuple items */
+#define BUILD_LIST      103     /* Number of list items */
+#define BUILD_SET       104     /* Number of set items */
+#define BUILD_MAP       105     /* Always zero for now */
+#define LOAD_ATTR       106     /* Index in name list */
+#define COMPARE_OP      107     /* Comparison operator */
+#define IMPORT_NAME     108     /* Index in name list */
+#define IMPORT_FROM     109     /* Index in name list */
 
-#define JUMP_FORWARD	110	/* Number of bytes to skip */
-#define JUMP_IF_FALSE_OR_POP 111	/* Target byte offset from beginning of code */
-#define JUMP_IF_TRUE_OR_POP 112	/* "" */
-#define JUMP_ABSOLUTE	113	/* "" */
-#define POP_JUMP_IF_FALSE 114	/* "" */
-#define POP_JUMP_IF_TRUE 115	/* "" */
+#define JUMP_FORWARD    110     /* Number of bytes to skip */
+#define JUMP_IF_FALSE_OR_POP 111        /* Target byte offset from beginning of code */
+#define JUMP_IF_TRUE_OR_POP 112 /* "" */
+#define JUMP_ABSOLUTE   113     /* "" */
+#define POP_JUMP_IF_FALSE 114   /* "" */
+#define POP_JUMP_IF_TRUE 115    /* "" */
 
-#define LOAD_GLOBAL	116	/* Index in name list */
+#define LOAD_GLOBAL     116     /* Index in name list */
 
-#define CONTINUE_LOOP	119	/* Start of loop (absolute) */
-#define SETUP_LOOP	120	/* Target address (relative) */
-#define SETUP_EXCEPT	121	/* "" */
-#define SETUP_FINALLY	122	/* "" */
+#define CONTINUE_LOOP   119     /* Start of loop (absolute) */
+#define SETUP_LOOP      120     /* Target address (relative) */
+#define SETUP_EXCEPT    121     /* "" */
+#define SETUP_FINALLY   122     /* "" */
 
-#define LOAD_FAST	124	/* Local variable number */
-#define STORE_FAST	125	/* Local variable number */
-#define DELETE_FAST	126	/* Local variable number */
+#define LOAD_FAST       124     /* Local variable number */
+#define STORE_FAST      125     /* Local variable number */
+#define DELETE_FAST     126     /* Local variable number */
 
-#define RAISE_VARARGS	130	/* Number of raise arguments (1, 2 or 3) */
+#define RAISE_VARARGS   130     /* Number of raise arguments (1, 2 or 3) */
 /* CALL_FUNCTION_XXX opcodes defined below depend on this definition */
-#define CALL_FUNCTION	131	/* #args + (#kwargs<<8) */
-#define MAKE_FUNCTION	132	/* #defaults + #kwdefaults<<8 + #annotations<<16 */
-#define BUILD_SLICE 	133	/* Number of items */
+#define CALL_FUNCTION   131     /* #args + (#kwargs<<8) */
+#define MAKE_FUNCTION   132     /* #defaults + #kwdefaults<<8 + #annotations<<16 */
+#define BUILD_SLICE     133     /* Number of items */
 
 #define MAKE_CLOSURE    134     /* same as MAKE_FUNCTION */
 #define LOAD_CLOSURE    135     /* Load free variable from closure */
@@ -126,9 +127,9 @@ extern "C" {
 
 /* The next 3 opcodes must be contiguous and satisfy
    (CALL_FUNCTION_VAR - CALL_FUNCTION) & 3 == 1  */
-#define CALL_FUNCTION_VAR          140	/* #args + (#kwargs<<8) */
-#define CALL_FUNCTION_KW           141	/* #args + (#kwargs<<8) */
-#define CALL_FUNCTION_VAR_KW       142	/* #args + (#kwargs<<8) */
+#define CALL_FUNCTION_VAR          140  /* #args + (#kwargs<<8) */
+#define CALL_FUNCTION_KW           141  /* #args + (#kwargs<<8) */
+#define CALL_FUNCTION_VAR_KW       142  /* #args + (#kwargs<<8) */
 
 #define SETUP_WITH 143
 
@@ -148,7 +149,7 @@ extern "C" {
 
 
 enum cmp_op {PyCmp_LT=Py_LT, PyCmp_LE=Py_LE, PyCmp_EQ=Py_EQ, PyCmp_NE=Py_NE, PyCmp_GT=Py_GT, PyCmp_GE=Py_GE,
-	     PyCmp_IN, PyCmp_NOT_IN, PyCmp_IS, PyCmp_IS_NOT, PyCmp_EXC_MATCH, PyCmp_BAD};
+             PyCmp_IN, PyCmp_NOT_IN, PyCmp_IS, PyCmp_IS_NOT, PyCmp_EXC_MATCH, PyCmp_BAD};
 
 #define HAS_ARG(op) ((op) >= HAVE_ARGUMENT)
 
diff --git a/Include/pyerrors.h b/Include/pyerrors.h
index 44eb3d9fc22..1bd04425465 100644
--- a/Include/pyerrors.h
+++ b/Include/pyerrors.h
@@ -51,6 +51,11 @@ typedef struct {
     Py_ssize_t written;   /* only for BlockingIOError, -1 otherwise */
 } PyOSErrorObject;
 
+typedef struct {
+    PyException_HEAD
+    PyObject *value;
+} PyStopIterationObject;
+
 /* Compatibility typedefs */
 typedef PyOSErrorObject PyEnvironmentErrorObject;
 #ifdef MS_WINDOWS
@@ -380,6 +385,8 @@ PyAPI_FUNC(int) PyUnicodeTranslateError_SetReason(
     const char *reason          /* UTF-8 encoded string */
     );
 
+/* create a StopIteration exception with the given value */
+PyAPI_FUNC(PyObject *) PyStopIteration_Create(PyObject *);
 
 /* These APIs aren't really part of the error implementation, but
    often needed to format error messages; the native C lib APIs are
diff --git a/Lib/opcode.py b/Lib/opcode.py
index b631b257c46..6fe20c72207 100644
--- a/Lib/opcode.py
+++ b/Lib/opcode.py
@@ -87,6 +87,7 @@ def_op('STORE_LOCALS', 69)
 
 def_op('PRINT_EXPR', 70)
 def_op('LOAD_BUILD_CLASS', 71)
+def_op('YIELD_FROM', 72)
 
 def_op('INPLACE_LSHIFT', 75)
 def_op('INPLACE_RSHIFT', 76)
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index b1656bc4ff7..2022ee20c9c 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -813,7 +813,8 @@ class ASTValidatorTests(unittest.TestCase):
         self._check_comprehension(factory)
 
     def test_yield(self):
-        self.expr(ast.Yield(ast.Name("x", ast.Store())), "must have Load")
+        self.expr(ast.Yield(0, ast.Name("x", ast.Store())), "must have Load")
+        self.expr(ast.Yield(1, ast.Name("x", ast.Store())), "must have Load")
 
     def test_compare(self):
         left = ast.Name("x", ast.Load())
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 5f47b3eae03..06f67c2ea69 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -728,29 +728,6 @@ Ye olde Fibonacci generator, tee style.
 
 syntax_tests = """
 
->>> def f():
-...     return 22
-...     yield 1
-Traceback (most recent call last):
-  ..
-SyntaxError: 'return' with argument inside generator
-
->>> def f():
-...     yield 1
-...     return 22
-Traceback (most recent call last):
-  ..
-SyntaxError: 'return' with argument inside generator
-
-"return None" is not the same as "return" in a generator:
-
->>> def f():
-...     yield 1
-...     return None
-Traceback (most recent call last):
-  ..
-SyntaxError: 'return' with argument inside generator
-
 These are fine:
 
 >>> def f():
@@ -866,20 +843,6 @@ These are fine:
 >>> type(f())
 <class 'generator'>
 
-
->>> def f():
-...     if 0:
-...         lambda x:  x        # shouldn't trigger here
-...         return              # or here
-...         def f(i):
-...             return 2*i      # or here
-...         if 0:
-...             return 3        # but *this* sucks (line 8)
-...     if 0:
-...         yield 2             # because it's a generator (line 10)
-Traceback (most recent call last):
-SyntaxError: 'return' with argument inside generator
-
 This one caused a crash (see SF bug 567538):
 
 >>> def f():
@@ -1566,11 +1529,6 @@ Traceback (most recent call last):
   ...
 SyntaxError: 'yield' outside function
 
->>> def f(): return lambda x=(yield): 1
-Traceback (most recent call last):
-  ...
-SyntaxError: 'return' with argument inside generator
-
 >>> def f(): x = yield = y
 Traceback (most recent call last):
   ...
diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index eff763e6570..6b326bdaa11 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -458,7 +458,39 @@ class GrammarTests(unittest.TestCase):
         check_syntax_error(self, "class foo:return 1")
 
     def test_yield(self):
+        # Allowed as standalone statement
+        def g(): yield 1
+        def g(): yield from ()
+        # Allowed as RHS of assignment
+        def g(): x = yield 1
+        def g(): x = yield from ()
+        # Ordinary yield accepts implicit tuples
+        def g(): yield 1, 1
+        def g(): x = yield 1, 1
+        # 'yield from' does not
+        check_syntax_error(self, "def g(): yield from (), 1")
+        check_syntax_error(self, "def g(): x = yield from (), 1")
+        # Requires parentheses as subexpression
+        def g(): 1, (yield 1)
+        def g(): 1, (yield from ())
+        check_syntax_error(self, "def g(): 1, yield 1")
+        check_syntax_error(self, "def g(): 1, yield from ()")
+        # Requires parentheses as call argument
+        def g(): f((yield 1))
+        def g(): f((yield 1), 1)
+        def g(): f((yield from ()))
+        def g(): f((yield from ()), 1)
+        check_syntax_error(self, "def g(): f(yield 1)")
+        check_syntax_error(self, "def g(): f(yield 1, 1)")
+        check_syntax_error(self, "def g(): f(yield from ())")
+        check_syntax_error(self, "def g(): f(yield from (), 1)")
+        # Not allowed at top level
+        check_syntax_error(self, "yield")
+        check_syntax_error(self, "yield from")
+        # Not allowed at class scope
         check_syntax_error(self, "class foo:yield 1")
+        check_syntax_error(self, "class foo:yield from ()")
+
 
     def test_raise(self):
         # 'raise' test [',' test]
diff --git a/Lib/test/test_parser.py b/Lib/test/test_parser.py
index 2b50fca818a..b6f81fbf38e 100644
--- a/Lib/test/test_parser.py
+++ b/Lib/test/test_parser.py
@@ -50,6 +50,10 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
         self.check_suite("def f(): (yield 1)*2")
         self.check_suite("def f(): return; yield 1")
         self.check_suite("def f(): yield 1; return")
+        self.check_suite("def f(): yield from 1")
+        self.check_suite("def f(): x = yield from 1")
+        self.check_suite("def f(): f((yield from 1))")
+        self.check_suite("def f(): yield 1; return 1")
         self.check_suite("def f():\n"
                          "    for x in range(30):\n"
                          "        yield x\n")
@@ -621,7 +625,6 @@ class OtherParserCase(unittest.TestCase):
         with self.assertRaises(TypeError):
             parser.expr("a", "b")
 
-
 def test_main():
     support.run_unittest(
         RoundtripLegalSyntaxTestCase,
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index f89514f8190..6dc0e422a6d 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -727,7 +727,7 @@ class SizeofTest(unittest.TestCase):
         nfrees = len(x.f_code.co_freevars)
         extras = x.f_code.co_stacksize + x.f_code.co_nlocals +\
                   ncells + nfrees - 1
-        check(x, size(vh + '12P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
+        check(x, size(vh + '13P3i' + CO_MAXBLOCKS*'3i' + 'P' + extras*'P'))
         # function
         def func(): pass
         check(func, size(h + '12P'))
diff --git a/Misc/ACKS b/Misc/ACKS
index 169262f6be9..02742af60c1 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -96,6 +96,7 @@ Dominic Binks
 Philippe Biondi
 Stuart Bishop
 Roy Bixler
+Renaud Blanch
 Mike Bland
 Martin Bless
 Pablo Bleyer
@@ -482,6 +483,7 @@ Geert Jansen
 Jack Jansen
 Bill Janssen
 Thomas Jarosch
+Zbigniew Jędrzejewski-Szmek
 Julien Jehannet
 Drew Jenkins
 Flemming Kjær Jensen
diff --git a/Misc/NEWS b/Misc/NEWS
index d930f158fd9..9e27e303b52 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@ What's New in Python 3.3 Alpha 1?
 Core and Builtins
 -----------------
 
+- PEP 380, Issue #11682: Add "yield from <x>" to support easy delegation to
+  subgenerators (initial patch by Greg Ewing, integration into 3.3 by
+  Renaud Blanch, Ryan Kelly, Zbigniew Jędrzejewski-Szmek and Nick Coghlan)
+
 - Issue #13748: Raw bytes literals can now be written with the ``rb`` prefix
   as well as ``br``.
 
diff --git a/Modules/parsermodule.c b/Modules/parsermodule.c
index 2f2e0457ea9..9d1bca5da46 100644
--- a/Modules/parsermodule.c
+++ b/Modules/parsermodule.c
@@ -298,25 +298,25 @@ parser_richcompare(PyObject *left, PyObject *right, int op)
 
     /* Convert return value to a Boolean */
     switch (op) {
-    case Py_EQ:
+      case Py_EQ:
         v = TEST_COND(result == 0);
         break;
-    case Py_NE:
+      case Py_NE:
         v = TEST_COND(result != 0);
         break;
-    case Py_LE:
+      case Py_LE:
         v = TEST_COND(result <= 0);
         break;
-    case Py_GE:
+      case Py_GE:
         v = TEST_COND(result >= 0);
         break;
-    case Py_LT:
+      case Py_LT:
         v = TEST_COND(result < 0);
         break;
-    case Py_GT:
+      case Py_GT:
         v = TEST_COND(result > 0);
         break;
-    default:
+      default:
         PyErr_BadArgument();
         return NULL;
     }
@@ -976,6 +976,7 @@ VALIDATER(comp_iter);           VALIDATER(comp_if);
 VALIDATER(testlist_comp);       VALIDATER(yield_expr);
 VALIDATER(or_test);
 VALIDATER(test_nocond);         VALIDATER(lambdef_nocond);
+VALIDATER(yield_arg);
 
 #undef VALIDATER
 
@@ -1636,22 +1637,49 @@ validate_raise_stmt(node *tree)
 }
 
 
-/* yield_expr: 'yield' [testlist]
+/* yield_expr: 'yield' [yield_arg]
  */
 static int
 validate_yield_expr(node *tree)
 {
     int nch = NCH(tree);
-    int res = (validate_ntype(tree, yield_expr)
-               && ((nch == 1) || (nch == 2))
-               && validate_name(CHILD(tree, 0), "yield"));
-
-    if (res && (nch == 2))
-        res = validate_testlist(CHILD(tree, 1));
-
-    return (res);
+    if (nch < 1 || nch > 2)
+        return 0;
+    if (!validate_ntype(tree, yield_expr))
+        return 0;
+    if (!validate_name(CHILD(tree, 0), "yield"))
+        return 0;
+    if (nch == 2) {
+        if (!validate_yield_arg(CHILD(tree, 1)))
+            return 0;
+    }
+    return 1;
 }
 
+/* yield_arg: 'from' test | testlist
+ */
+static int
+validate_yield_arg(node *tree)
+{
+    int nch = NCH(tree);
+    if (!validate_ntype(tree, yield_arg))
+        return 0;
+    switch (nch) {
+      case 1:
+        if (!validate_testlist(CHILD(tree, nch - 1)))
+            return 0;
+        break;
+      case 2:
+        if (!validate_name(CHILD(tree, 0), "from"))
+            return 0;
+        if (!validate_test(CHILD(tree, 1)))
+            return 0;
+        break;
+      default:
+        return 0;
+    }
+    return 1;
+}
 
 /* yield_stmt: yield_expr
  */
@@ -2120,16 +2148,16 @@ validate_comp_op(node *tree)
          */
         tree = CHILD(tree, 0);
         switch (TYPE(tree)) {
-            case LESS:
-            case GREATER:
-            case EQEQUAL:
-            case EQUAL:
-            case LESSEQUAL:
-            case GREATEREQUAL:
-            case NOTEQUAL:
+          case LESS:
+          case GREATER:
+          case EQEQUAL:
+          case EQUAL:
+          case LESSEQUAL:
+          case GREATEREQUAL:
+          case NOTEQUAL:
               res = 1;
               break;
-            case NAME:
+          case NAME:
               res = ((strcmp(STR(tree), "in") == 0)
                      || (strcmp(STR(tree), "is") == 0));
               if (!res) {
@@ -2665,9 +2693,9 @@ validate_argument(node *tree)
 {
     int nch = NCH(tree);
     int res = (validate_ntype(tree, argument)
-               && ((nch == 1) || (nch == 2) || (nch == 3))
-               && validate_test(CHILD(tree, 0)));
-
+               && ((nch == 1) || (nch == 2) || (nch == 3)));
+    if (res) 
+        res = validate_test(CHILD(tree, 0));
     if (res && (nch == 2))
         res = validate_comp_for(CHILD(tree, 1));
     else if (res && (nch == 3))
diff --git a/Objects/abstract.c b/Objects/abstract.c
index a44bec69022..4d73a3b5349 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2267,7 +2267,6 @@ PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
 
     func = PyObject_GetAttrString(o, name);
     if (func == NULL) {
-        PyErr_SetString(PyExc_AttributeError, name);
         return 0;
     }
 
@@ -2311,7 +2310,6 @@ _PyObject_CallMethod_SizeT(PyObject *o, char *name, char *format, ...)
 
     func = PyObject_GetAttrString(o, name);
     if (func == NULL) {
-        PyErr_SetString(PyExc_AttributeError, name);
         return 0;
     }
     va_start(va, format);
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 331811500d8..a529a3cd111 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -487,8 +487,70 @@ SimpleExtendsException(PyExc_Exception, TypeError,
 /*
  *    StopIteration extends Exception
  */
-SimpleExtendsException(PyExc_Exception, StopIteration,
-                       "Signal the end from iterator.__next__().");
+
+static PyMemberDef StopIteration_members[] = {
+    {"value", T_OBJECT, offsetof(PyStopIterationObject, value), 0,
+        PyDoc_STR("generator return value")},
+    {NULL}  /* Sentinel */
+};
+
+static int
+StopIteration_init(PyStopIterationObject *self, PyObject *args, PyObject *kwds)
+{
+    Py_ssize_t size = PyTuple_GET_SIZE(args);
+    PyObject *value;
+
+    if (BaseException_init((PyBaseExceptionObject *)self, args, kwds) == -1)
+        return -1;
+    Py_CLEAR(self->value);
+    if (size > 0)
+        value = PyTuple_GET_ITEM(args, 0);
+    else
+        value = Py_None;
+    Py_INCREF(value);
+    self->value = value;
+    return 0;
+}
+
+static int
+StopIteration_clear(PyStopIterationObject *self)
+{
+    Py_CLEAR(self->value);
+    return BaseException_clear((PyBaseExceptionObject *)self);
+}
+
+static void
+StopIteration_dealloc(PyStopIterationObject *self)
+{
+    _PyObject_GC_UNTRACK(self);
+    StopIteration_clear(self);
+    Py_TYPE(self)->tp_free((PyObject *)self);
+}
+
+static int
+StopIteration_traverse(PyStopIterationObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->value);
+    return BaseException_traverse((PyBaseExceptionObject *)self, visit, arg);
+}
+
+PyObject *
+PyStopIteration_Create(PyObject *value)
+{
+    return PyObject_CallFunctionObjArgs(PyExc_StopIteration, value, NULL);
+}
+
+ComplexExtendsException(
+    PyExc_Exception,       /* base */
+    StopIteration,         /* name */
+    StopIteration,         /* prefix for *_init, etc */
+    0,                     /* new */
+    0,                     /* methods */
+    StopIteration_members, /* members */
+    0,                     /* getset */
+    0,                     /* str */
+    "Signal the end from iterator.__next__()."
+);
 
 
 /*
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 10fb8b350eb..9b05b9d0930 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -15,11 +15,12 @@
 #define OFF(x) offsetof(PyFrameObject, x)
 
 static PyMemberDef frame_memberlist[] = {
-    {"f_back",          T_OBJECT,       OFF(f_back),    READONLY},
-    {"f_code",          T_OBJECT,       OFF(f_code),    READONLY},
-    {"f_builtins",      T_OBJECT,       OFF(f_builtins),READONLY},
-    {"f_globals",       T_OBJECT,       OFF(f_globals), READONLY},
-    {"f_lasti",         T_INT,          OFF(f_lasti),   READONLY},
+    {"f_back",          T_OBJECT,       OFF(f_back),      READONLY},
+    {"f_code",          T_OBJECT,       OFF(f_code),      READONLY},
+    {"f_builtins",      T_OBJECT,       OFF(f_builtins),  READONLY},
+    {"f_globals",       T_OBJECT,       OFF(f_globals),   READONLY},
+    {"f_lasti",         T_INT,          OFF(f_lasti),     READONLY},
+    {"f_yieldfrom",     T_OBJECT,       OFF(f_yieldfrom), READONLY},
     {NULL}      /* Sentinel */
 };
 
@@ -444,6 +445,7 @@ frame_dealloc(PyFrameObject *f)
     Py_CLEAR(f->f_exc_type);
     Py_CLEAR(f->f_exc_value);
     Py_CLEAR(f->f_exc_traceback);
+    Py_CLEAR(f->f_yieldfrom);
 
     co = f->f_code;
     if (co->co_zombieframe == NULL)
@@ -475,6 +477,7 @@ frame_traverse(PyFrameObject *f, visitproc visit, void *arg)
     Py_VISIT(f->f_exc_type);
     Py_VISIT(f->f_exc_value);
     Py_VISIT(f->f_exc_traceback);
+    Py_VISIT(f->f_yieldfrom);
 
     /* locals */
     slots = f->f_code->co_nlocals + PyTuple_GET_SIZE(f->f_code->co_cellvars) + PyTuple_GET_SIZE(f->f_code->co_freevars);
@@ -508,6 +511,7 @@ frame_clear(PyFrameObject *f)
     Py_CLEAR(f->f_exc_value);
     Py_CLEAR(f->f_exc_traceback);
     Py_CLEAR(f->f_trace);
+    Py_CLEAR(f->f_yieldfrom);
 
     /* locals */
     slots = f->f_code->co_nlocals + PyTuple_GET_SIZE(f->f_code->co_cellvars) + PyTuple_GET_SIZE(f->f_code->co_freevars);
@@ -711,6 +715,7 @@ PyFrame_New(PyThreadState *tstate, PyCodeObject *code, PyObject *globals,
     f->f_lasti = -1;
     f->f_lineno = code->co_firstlineno;
     f->f_iblock = 0;
+    f->f_yieldfrom = NULL;
 
     _PyObject_GC_TRACK(f);
     return f;
diff --git a/Objects/genobject.c b/Objects/genobject.c
index c6612e26d5b..20c926b79f4 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -5,6 +5,9 @@
 #include "structmember.h"
 #include "opcode.h"
 
+static PyObject *gen_close(PyGenObject *gen, PyObject *args);
+static void gen_undelegate(PyGenObject *gen);
+
 static int
 gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
 {
@@ -90,12 +93,18 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
 
     /* If the generator just returned (as opposed to yielding), signal
      * that the generator is exhausted. */
-    if (result == Py_None && f->f_stacktop == NULL) {
-        Py_DECREF(result);
-        result = NULL;
-        /* Set exception if not called by gen_iternext() */
-        if (arg)
+    if (result && f->f_stacktop == NULL) {
+        if (result == Py_None) {
+            /* Delay exception instantiation if we can */
             PyErr_SetNone(PyExc_StopIteration);
+        } else {
+            PyObject *e = PyStopIteration_Create(result);
+            if (e != NULL) {
+                PyErr_SetObject(PyExc_StopIteration, e);
+                Py_DECREF(e);
+            }
+        }
+        Py_CLEAR(result);
     }
 
     if (!result || f->f_stacktop == NULL) {
@@ -111,8 +120,8 @@ gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
         Py_XDECREF(t);
         Py_XDECREF(v);
         Py_XDECREF(tb);
-        Py_DECREF(f);
         gen->gi_frame = NULL;
+        Py_DECREF(f);
     }
 
     return result;
@@ -125,17 +134,91 @@ return next yielded value or raise StopIteration.");
 static PyObject *
 gen_send(PyGenObject *gen, PyObject *arg)
 {
-    return gen_send_ex(gen, arg, 0);
+    int exc = 0;
+    PyObject *ret;
+    PyObject *yf = gen->gi_frame ? gen->gi_frame->f_yieldfrom : NULL;
+    /* XXX (ncoghlan): Are the incref/decref on arg and yf strictly needed?
+     *                 Or would it be valid to rely on borrowed references?
+     */
+    Py_INCREF(arg);
+    if (yf) {
+        Py_INCREF(yf);
+        if (PyGen_CheckExact(yf)) {
+            ret = gen_send((PyGenObject *)yf, arg);
+        } else {
+            if (arg == Py_None)
+                ret = PyIter_Next(yf);
+            else
+                ret = PyObject_CallMethod(yf, "send", "O", arg);
+        }
+        if (ret) {
+            Py_DECREF(yf);
+            goto done;
+        }
+        gen_undelegate(gen);
+        Py_CLEAR(arg);
+        if (PyGen_FetchStopIterationValue(&arg) < 0) {
+            exc = 1;
+        }
+        Py_DECREF(yf);
+    }
+    ret = gen_send_ex(gen, arg, exc);
+done:
+    Py_XDECREF(arg);
+    return ret;
 }
 
 PyDoc_STRVAR(close_doc,
 "close(arg) -> raise GeneratorExit inside generator.");
 
+/*
+ *   This helper function is used by gen_close and gen_throw to
+ *   close a subiterator being delegated to by yield-from.
+ */
+
+static int
+gen_close_iter(PyObject *yf)
+{
+    PyObject *retval = NULL;
+    
+    if (PyGen_CheckExact(yf)) {
+        retval = gen_close((PyGenObject *)yf, NULL);
+        if (retval == NULL) {
+            return -1;
+        }
+    } else {
+        PyObject *meth = PyObject_GetAttrString(yf, "close");
+        if (meth == NULL) {
+            if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+                PyErr_WriteUnraisable(yf);
+            }
+            PyErr_Clear();
+        } else {
+            retval = PyObject_CallFunction(meth, "");
+            Py_DECREF(meth);
+            if (!retval)
+                return -1;
+        }
+    }
+    Py_XDECREF(retval);
+    return 0;
+}       
+
 static PyObject *
 gen_close(PyGenObject *gen, PyObject *args)
 {
     PyObject *retval;
-    PyErr_SetNone(PyExc_GeneratorExit);
+    PyObject *yf = gen->gi_frame ? gen->gi_frame->f_yieldfrom : NULL;
+    int err = 0;
+
+    if (yf) {
+        Py_INCREF(yf);
+        err = gen_close_iter(yf);
+        gen_undelegate(gen);
+        Py_DECREF(yf);
+    }
+    if (err == 0)
+        PyErr_SetNone(PyExc_GeneratorExit);
     retval = gen_send_ex(gen, Py_None, 1);
     if (retval) {
         Py_DECREF(retval);
@@ -196,7 +279,7 @@ gen_del(PyObject *self)
         _Py_NewReference(self);
         self->ob_refcnt = refcnt;
     }
-    assert(PyType_IS_GC(self->ob_type) &&
+    assert(PyType_IS_GC(Py_TYPE(self)) &&
            _Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
 
     /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
@@ -209,8 +292,8 @@ gen_del(PyObject *self)
      * undone.
      */
 #ifdef COUNT_ALLOCS
-    --self->ob_type->tp_frees;
-    --self->ob_type->tp_allocs;
+    --(Py_TYPE(self)->tp_frees);
+    --(Py_TYPE(self)->tp_allocs);
 #endif
 }
 
@@ -226,10 +309,55 @@ gen_throw(PyGenObject *gen, PyObject *args)
     PyObject *typ;
     PyObject *tb = NULL;
     PyObject *val = NULL;
+    PyObject *yf = gen->gi_frame ? gen->gi_frame->f_yieldfrom : NULL;
 
     if (!PyArg_UnpackTuple(args, "throw", 1, 3, &typ, &val, &tb))
         return NULL;
 
+    if (yf) {
+        PyObject *ret;
+        int err;
+        Py_INCREF(yf);
+        if (PyErr_GivenExceptionMatches(typ, PyExc_GeneratorExit)) {
+            err = gen_close_iter(yf);
+            Py_DECREF(yf);
+            gen_undelegate(gen);
+            if (err < 0)
+                return gen_send_ex(gen, Py_None, 1);
+            goto throw_here;
+        }
+        if (PyGen_CheckExact(yf)) {
+            ret = gen_throw((PyGenObject *)yf, args);
+        } else {
+            PyObject *meth = PyObject_GetAttrString(yf, "throw");
+            if (meth == NULL) {
+                if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+                    Py_DECREF(yf);
+                    return NULL;
+                }
+                PyErr_Clear();
+                Py_DECREF(yf);
+                gen_undelegate(gen);
+                goto throw_here;
+            }
+            ret = PyObject_CallObject(meth, args);
+            Py_DECREF(meth);
+        }
+        Py_DECREF(yf);
+        if (!ret) {
+            PyObject *val;
+            gen_undelegate(gen);
+            if (PyGen_FetchStopIterationValue(&val) == 0) {
+                ret = gen_send_ex(gen, val, 0);
+                Py_DECREF(val);
+            } else {
+                ret = gen_send_ex(gen, Py_None, 1);
+            }
+        }
+        return ret;
+    }
+
+throw_here:
     /* First, check the traceback argument, replacing None with
        NULL. */
     if (tb == Py_None) {
@@ -272,7 +400,7 @@ gen_throw(PyGenObject *gen, PyObject *args)
         PyErr_Format(PyExc_TypeError,
                      "exceptions must be classes or instances "
                      "deriving from BaseException, not %s",
-                     typ->ob_type->tp_name);
+                     Py_TYPE(typ)->tp_name);
             goto failed_throw;
     }
 
@@ -291,9 +419,74 @@ failed_throw:
 static PyObject *
 gen_iternext(PyGenObject *gen)
 {
-    return gen_send_ex(gen, NULL, 0);
+    PyObject *val = NULL;
+    PyObject *ret;
+    int exc = 0;
+    PyObject *yf = gen->gi_frame ? gen->gi_frame->f_yieldfrom : NULL;
+    if (yf) {
+        Py_INCREF(yf);
+        /* ceval.c ensures that yf is an iterator */
+        ret = Py_TYPE(yf)->tp_iternext(yf);
+        if (ret) {
+            Py_DECREF(yf);
+            return ret;
+        }
+        gen_undelegate(gen);
+        if (PyGen_FetchStopIterationValue(&val) < 0)
+            exc = 1;
+        Py_DECREF(yf);
+    }
+    ret = gen_send_ex(gen, val, exc);
+    Py_XDECREF(val);
+    return ret;
 }
 
+/*
+ *   In certain recursive situations, a generator may lose its frame
+ *   before we get a chance to clear f_yieldfrom, so we use this
+ *   helper function.
+ */
+
+static void
+gen_undelegate(PyGenObject *gen) {
+    if (gen->gi_frame) {
+        Py_XDECREF(gen->gi_frame->f_yieldfrom);
+        gen->gi_frame->f_yieldfrom = NULL;
+    }
+}
+
+/*
+ *   If StopIteration exception is set, fetches its 'value'
+ *   attribute if any, otherwise sets pvalue to None.
+ *
+ *   Returns 0 if no exception or StopIteration is set.
+ *   If any other exception is set, returns -1 and leaves
+ *   pvalue unchanged.
+ */
+
+int
+PyGen_FetchStopIterationValue(PyObject **pvalue) {
+    PyObject *et, *ev, *tb;
+    PyObject *value = NULL;
+    
+    if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
+        PyErr_Fetch(&et, &ev, &tb);
+        Py_XDECREF(et);
+        Py_XDECREF(tb);
+        if (ev) {
+            value = ((PyStopIterationObject *)ev)->value;
+            Py_DECREF(ev);
+        }
+    } else if (PyErr_Occurred()) {
+        return -1;
+    }
+    if (value == NULL) {
+        value = Py_None;
+    }
+    Py_INCREF(value);
+    *pvalue = value;
+    return 0;
+}
 
 static PyObject *
 gen_repr(PyGenObject *gen)
diff --git a/Parser/Python.asdl b/Parser/Python.asdl
index 6955199280c..8ae4e5992f8 100644
--- a/Parser/Python.asdl
+++ b/Parser/Python.asdl
@@ -59,7 +59,7 @@ module Python
 	     | DictComp(expr key, expr value, comprehension* generators)
 	     | GeneratorExp(expr elt, comprehension* generators)
 	     -- the grammar constrains where yield expressions can occur
-	     | Yield(expr? value)
+	     | Yield(int is_from, expr? value)
 	     -- need sequences for compare to distinguish between
 	     -- x < 4 < 3 and (x < 4) < 3
 	     | Compare(expr left, cmpop* ops, expr* comparators)
diff --git a/Python/Python-ast.c b/Python/Python-ast.c
index 8a101cf3b05..3121eb1bb72 100644
--- a/Python/Python-ast.c
+++ b/Python/Python-ast.c
@@ -231,7 +231,9 @@ static char *GeneratorExp_fields[]={
         "generators",
 };
 static PyTypeObject *Yield_type;
+_Py_IDENTIFIER(is_from);
 static char *Yield_fields[]={
+        "is_from",
         "value",
 };
 static PyTypeObject *Compare_type;
@@ -810,7 +812,7 @@ static int init_types(void)
         GeneratorExp_type = make_type("GeneratorExp", expr_type,
                                       GeneratorExp_fields, 2);
         if (!GeneratorExp_type) return 0;
-        Yield_type = make_type("Yield", expr_type, Yield_fields, 1);
+        Yield_type = make_type("Yield", expr_type, Yield_fields, 2);
         if (!Yield_type) return 0;
         Compare_type = make_type("Compare", expr_type, Compare_fields, 3);
         if (!Compare_type) return 0;
@@ -1747,13 +1749,14 @@ GeneratorExp(expr_ty elt, asdl_seq * generators, int lineno, int col_offset,
 }
 
 expr_ty
-Yield(expr_ty value, int lineno, int col_offset, PyArena *arena)
+Yield(int is_from, expr_ty value, int lineno, int col_offset, PyArena *arena)
 {
         expr_ty p;
         p = (expr_ty)PyArena_Malloc(arena, sizeof(*p));
         if (!p)
                 return NULL;
         p->kind = Yield_kind;
+        p->v.Yield.is_from = is_from;
         p->v.Yield.value = value;
         p->lineno = lineno;
         p->col_offset = col_offset;
@@ -2795,6 +2798,11 @@ ast2obj_expr(void* _o)
         case Yield_kind:
                 result = PyType_GenericNew(Yield_type, NULL, NULL);
                 if (!result) goto failed;
+                value = ast2obj_int(o->v.Yield.is_from);
+                if (!value) goto failed;
+                if (PyObject_SetAttrString(result, "is_from", value) == -1)
+                        goto failed;
+                Py_DECREF(value);
                 value = ast2obj_expr(o->v.Yield.value);
                 if (!value) goto failed;
                 if (_PyObject_SetAttrId(result, &PyId_value, value) == -1)
@@ -5337,8 +5345,21 @@ obj2ast_expr(PyObject* obj, expr_ty* out, PyArena* arena)
                 return 1;
         }
         if (isinstance) {
+                int is_from;
                 expr_ty value;
 
+                if (_PyObject_HasAttrId(obj, &PyId_is_from)) {
+                        int res;
+                        tmp = _PyObject_GetAttrId(obj, &PyId_is_from);
+                        if (tmp == NULL) goto failed;
+                        res = obj2ast_int(tmp, &is_from, arena);
+                        if (res != 0) goto failed;
+                        Py_XDECREF(tmp);
+                        tmp = NULL;
+                } else {
+                        PyErr_SetString(PyExc_TypeError, "required field \"is_from\" missing from Yield");
+                        return 1;
+                }
                 if (_PyObject_HasAttrId(obj, &PyId_value)) {
                         int res;
                         tmp = _PyObject_GetAttrId(obj, &PyId_value);
@@ -5350,7 +5371,7 @@ obj2ast_expr(PyObject* obj, expr_ty* out, PyArena* arena)
                 } else {
                         value = NULL;
                 }
-                *out = Yield(value, lineno, col_offset, arena);
+                *out = Yield(is_from, value, lineno, col_offset, arena);
                 if (*out == NULL) goto failed;
                 return 0;
         }
diff --git a/Python/ast.c b/Python/ast.c
index 110754bfd47..7080c65f34b 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -2369,13 +2369,24 @@ ast_for_expr(struct compiling *c, const node *n)
             }
             return ast_for_binop(c, n);
         case yield_expr: {
+            node *an = NULL;
+            node *en = NULL;
+            int is_from = 0;
             expr_ty exp = NULL;
-            if (NCH(n) == 2) {
-                exp = ast_for_testlist(c, CHILD(n, 1));
+            if (NCH(n) > 1)
+                an = CHILD(n, 1); /* yield_arg */
+            if (an) {
+                en = CHILD(an, NCH(an) - 1);
+                if (NCH(an) == 2) {
+                    is_from = 1;
+                    exp = ast_for_expr(c, en);
+                }
+                else
+                    exp = ast_for_testlist(c, en);
                 if (!exp)
                     return NULL;
             }
-            return Yield(exp, LINENO(n), n->n_col_offset, c->c_arena);
+            return Yield(is_from, exp, LINENO(n), n->n_col_offset, c->c_arena);
         }
         case factor:
             if (NCH(n) == 1) {
@@ -2399,7 +2410,7 @@ ast_for_call(struct compiling *c, const node *n, expr_ty func)
     /*
       arglist: (argument ',')* (argument [',']| '*' test [',' '**' test]
                | '**' test)
-      argument: [test '='] test [comp_for]        # Really [keyword '='] test
+      argument: [test '='] (test) [comp_for]        # Really [keyword '='] test
     */
 
     int i, nargs, nkeywords, ngens;
@@ -2693,7 +2704,7 @@ ast_for_flow_stmt(struct compiling *c, const node *n)
       continue_stmt: 'continue'
       return_stmt: 'return' [testlist]
       yield_stmt: yield_expr
-      yield_expr: 'yield' testlist
+      yield_expr: 'yield' testlist | 'yield' 'from' test
       raise_stmt: 'raise' [test [',' test [',' test]]]
     */
     node *ch;
diff --git a/Python/ceval.c b/Python/ceval.c
index ed82b9411a0..134d1eec4b7 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1828,6 +1828,52 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             why = WHY_RETURN;
             goto fast_block_end;
 
+        TARGET(YIELD_FROM)
+            u = POP();
+            x = PyObject_GetIter(u);
+            Py_DECREF(u);
+            if (x == NULL)
+                break;
+            /* x is now the iterator, make the first next() call */
+            retval = (*Py_TYPE(x)->tp_iternext)(x);
+            if (!retval) {
+                /* iter may be exhausted */
+                Py_CLEAR(x);
+                if (!PyErr_ExceptionMatches(PyExc_StopIteration)) {
+                    /* some other exception */
+                    break;
+                }
+                /* try to get return value from exception */
+                PyObject *et, *ev, *tb;
+                PyErr_Fetch(&et, &ev, &tb);
+                Py_XDECREF(et);
+                Py_XDECREF(tb);
+                /* u is return value */
+                u = NULL;
+                if (ev) {
+                    u = PyObject_GetAttrString(ev, "value");
+                    Py_DECREF(ev);
+                    if (u == NULL) {
+                        if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+                            /* some other exception */
+                            break;
+                        }
+                        PyErr_Clear();
+                    }
+                }
+                if (u == NULL) {
+                    u = Py_None;
+                    Py_INCREF(u);
+                }
+                PUSH(u);
+                continue;
+            }
+            /* x is iterator, retval is value to be yielded */
+            f->f_yieldfrom = x;
+            f->f_stacktop = stack_pointer;
+            why = WHY_YIELD;
+            goto fast_yield;
+
         TARGET(YIELD_VALUE)
             retval = POP();
             f->f_stacktop = stack_pointer;
diff --git a/Python/compile.c b/Python/compile.c
index 849f48785dc..4d91f5024b5 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -840,6 +840,7 @@ opcode_stack_effect(int opcode, int oparg)
         case IMPORT_STAR:
             return -1;
         case YIELD_VALUE:
+        case YIELD_FROM:
             return 0;
 
         case POP_BLOCK:
@@ -3318,7 +3319,12 @@ compiler_visit_expr(struct compiler *c, expr_ty e)
         else {
             ADDOP_O(c, LOAD_CONST, Py_None, consts);
         }
-        ADDOP(c, YIELD_VALUE);
+        if (e->v.Yield.is_from) {
+            ADDOP(c, YIELD_FROM);
+        }
+        else {
+            ADDOP(c, YIELD_VALUE);
+        }
         break;
     case Compare_kind:
         return compiler_compare(c, e);
diff --git a/Python/graminit.c b/Python/graminit.c
index a8af5833a9a..e91e09ff93e 100644
--- a/Python/graminit.c
+++ b/Python/graminit.c
@@ -1791,7 +1791,7 @@ static arc arcs_80_0[1] = {
     {167, 1},
 };
 static arc arcs_80_1[2] = {
-    {9, 2},
+    {168, 2},
     {0, 1},
 };
 static arc arcs_80_2[1] = {
@@ -1802,171 +1802,188 @@ static state states_80[3] = {
     {2, arcs_80_1},
     {1, arcs_80_2},
 };
-static dfa dfas[81] = {
-    {256, "single_input", 0, 3, states_0,
-     "\004\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204"},
-    {257, "file_input", 0, 2, states_1,
-     "\204\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204"},
-    {258, "eval_input", 0, 3, states_2,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {259, "decorator", 0, 7, states_3,
-     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {260, "decorators", 0, 2, states_4,
-     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {261, "decorated", 0, 3, states_5,
-     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {262, "funcdef", 0, 8, states_6,
-     "\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {263, "parameters", 0, 4, states_7,
-     "\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {264, "typedargslist", 0, 18, states_8,
-     "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {265, "tfpdef", 0, 4, states_9,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {266, "varargslist", 0, 18, states_10,
-     "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {267, "vfpdef", 0, 2, states_11,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {268, "stmt", 0, 2, states_12,
-     "\000\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204"},
-    {269, "simple_stmt", 0, 4, states_13,
-     "\000\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200"},
-    {270, "small_stmt", 0, 2, states_14,
-     "\000\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200"},
-    {271, "expr_stmt", 0, 6, states_15,
-     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {272, "testlist_star_expr", 0, 3, states_16,
-     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {273, "augassign", 0, 2, states_17,
-     "\000\000\000\000\000\000\376\037\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {274, "del_stmt", 0, 3, states_18,
-     "\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {275, "pass_stmt", 0, 2, states_19,
-     "\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {276, "flow_stmt", 0, 2, states_20,
-     "\000\000\000\000\000\000\000\000\340\001\000\000\000\000\000\000\000\000\000\000\200"},
-    {277, "break_stmt", 0, 2, states_21,
-     "\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {278, "continue_stmt", 0, 2, states_22,
-     "\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {279, "return_stmt", 0, 3, states_23,
-     "\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {280, "yield_stmt", 0, 2, states_24,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\200"},
-    {281, "raise_stmt", 0, 5, states_25,
-     "\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000\000"},
-    {282, "import_stmt", 0, 2, states_26,
-     "\000\000\000\000\000\000\000\000\000\022\000\000\000\000\000\000\000\000\000\000\000"},
-    {283, "import_name", 0, 3, states_27,
-     "\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000"},
-    {284, "import_from", 0, 8, states_28,
-     "\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000\000\000\000"},
-    {285, "import_as_name", 0, 4, states_29,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {286, "dotted_as_name", 0, 4, states_30,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {287, "import_as_names", 0, 3, states_31,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {288, "dotted_as_names", 0, 2, states_32,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {289, "dotted_name", 0, 2, states_33,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {290, "global_stmt", 0, 3, states_34,
-     "\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000"},
-    {291, "nonlocal_stmt", 0, 3, states_35,
-     "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000"},
-    {292, "assert_stmt", 0, 5, states_36,
-     "\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000"},
-    {293, "compound_stmt", 0, 2, states_37,
-     "\000\010\020\000\000\000\000\000\000\000\000\220\045\000\000\000\000\000\000\000\004"},
-    {294, "if_stmt", 0, 8, states_38,
-     "\000\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000"},
-    {295, "while_stmt", 0, 8, states_39,
-     "\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000"},
-    {296, "for_stmt", 0, 10, states_40,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000"},
-    {297, "try_stmt", 0, 13, states_41,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\004\000\000\000\000\000\000\000\000"},
-    {298, "with_stmt", 0, 5, states_42,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000"},
-    {299, "with_item", 0, 4, states_43,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {300, "except_clause", 0, 5, states_44,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000"},
-    {301, "suite", 0, 5, states_45,
-     "\004\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200"},
-    {302, "test", 0, 6, states_46,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {303, "test_nocond", 0, 2, states_47,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {304, "lambdef", 0, 5, states_48,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000"},
-    {305, "lambdef_nocond", 0, 5, states_49,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000"},
-    {306, "or_test", 0, 2, states_50,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000"},
-    {307, "and_test", 0, 2, states_51,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000"},
-    {308, "not_test", 0, 3, states_52,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000"},
-    {309, "comparison", 0, 2, states_53,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {310, "comp_op", 0, 4, states_54,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\002\000\220\177\000\000\000\000\000"},
-    {311, "star_expr", 0, 3, states_55,
-     "\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {312, "expr", 0, 2, states_56,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {313, "xor_expr", 0, 2, states_57,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {314, "and_expr", 0, 2, states_58,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {315, "shift_expr", 0, 2, states_59,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {316, "arith_expr", 0, 2, states_60,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {317, "term", 0, 2, states_61,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {318, "factor", 0, 3, states_62,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {319, "power", 0, 4, states_63,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\120\076\000"},
-    {320, "atom", 0, 9, states_64,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\120\076\000"},
-    {321, "testlist_comp", 0, 5, states_65,
-     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {322, "trailer", 0, 7, states_66,
-     "\000\040\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\020\000\000"},
-    {323, "subscriptlist", 0, 3, states_67,
-     "\000\040\040\002\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {324, "subscript", 0, 5, states_68,
-     "\000\040\040\002\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {325, "sliceop", 0, 3, states_69,
-     "\000\000\000\002\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {326, "exprlist", 0, 3, states_70,
-     "\000\040\040\200\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000"},
-    {327, "testlist", 0, 3, states_71,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {328, "dictorsetmaker", 0, 11, states_72,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {329, "classdef", 0, 8, states_73,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\004"},
-    {330, "arglist", 0, 8, states_74,
-     "\000\040\040\200\001\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {331, "argument", 0, 4, states_75,
-     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000"},
-    {332, "comp_iter", 0, 2, states_76,
-     "\000\000\000\000\000\000\000\000\000\000\000\020\001\000\000\000\000\000\000\000\000"},
-    {333, "comp_for", 0, 6, states_77,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000"},
-    {334, "comp_if", 0, 4, states_78,
-     "\000\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000"},
-    {335, "encoding_decl", 0, 2, states_79,
-     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
-    {336, "yield_expr", 0, 3, states_80,
-     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\200"},
+static arc arcs_81_0[2] = {
+    {73, 1},
+    {9, 2},
 };
-static label labels[168] = {
+static arc arcs_81_1[1] = {
+    {24, 2},
+};
+static arc arcs_81_2[1] = {
+    {0, 2},
+};
+static state states_81[3] = {
+    {2, arcs_81_0},
+    {1, arcs_81_1},
+    {1, arcs_81_2},
+};
+static dfa dfas[82] = {
+    {256, "single_input", 0, 3, states_0,
+     "\004\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204\000"},
+    {257, "file_input", 0, 2, states_1,
+     "\204\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204\000"},
+    {258, "eval_input", 0, 3, states_2,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {259, "decorator", 0, 7, states_3,
+     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {260, "decorators", 0, 2, states_4,
+     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {261, "decorated", 0, 3, states_5,
+     "\000\010\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {262, "funcdef", 0, 8, states_6,
+     "\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {263, "parameters", 0, 4, states_7,
+     "\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {264, "typedargslist", 0, 18, states_8,
+     "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {265, "tfpdef", 0, 4, states_9,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {266, "varargslist", 0, 18, states_10,
+     "\000\000\040\200\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {267, "vfpdef", 0, 2, states_11,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {268, "stmt", 0, 2, states_12,
+     "\000\050\060\200\000\000\000\240\340\223\160\220\045\200\020\000\000\206\120\076\204\000"},
+    {269, "simple_stmt", 0, 4, states_13,
+     "\000\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200\000"},
+    {270, "small_stmt", 0, 2, states_14,
+     "\000\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200\000"},
+    {271, "expr_stmt", 0, 6, states_15,
+     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {272, "testlist_star_expr", 0, 3, states_16,
+     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {273, "augassign", 0, 2, states_17,
+     "\000\000\000\000\000\000\376\037\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {274, "del_stmt", 0, 3, states_18,
+     "\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {275, "pass_stmt", 0, 2, states_19,
+     "\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {276, "flow_stmt", 0, 2, states_20,
+     "\000\000\000\000\000\000\000\000\340\001\000\000\000\000\000\000\000\000\000\000\200\000"},
+    {277, "break_stmt", 0, 2, states_21,
+     "\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {278, "continue_stmt", 0, 2, states_22,
+     "\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {279, "return_stmt", 0, 3, states_23,
+     "\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {280, "yield_stmt", 0, 2, states_24,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000"},
+    {281, "raise_stmt", 0, 5, states_25,
+     "\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {282, "import_stmt", 0, 2, states_26,
+     "\000\000\000\000\000\000\000\000\000\022\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {283, "import_name", 0, 3, states_27,
+     "\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {284, "import_from", 0, 8, states_28,
+     "\000\000\000\000\000\000\000\000\000\002\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {285, "import_as_name", 0, 4, states_29,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {286, "dotted_as_name", 0, 4, states_30,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {287, "import_as_names", 0, 3, states_31,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {288, "dotted_as_names", 0, 2, states_32,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {289, "dotted_name", 0, 2, states_33,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {290, "global_stmt", 0, 3, states_34,
+     "\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000\000"},
+    {291, "nonlocal_stmt", 0, 3, states_35,
+     "\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000\000\000"},
+    {292, "assert_stmt", 0, 5, states_36,
+     "\000\000\000\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\000\000\000"},
+    {293, "compound_stmt", 0, 2, states_37,
+     "\000\010\020\000\000\000\000\000\000\000\000\220\045\000\000\000\000\000\000\000\004\000"},
+    {294, "if_stmt", 0, 8, states_38,
+     "\000\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000"},
+    {295, "while_stmt", 0, 8, states_39,
+     "\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\000\000"},
+    {296, "for_stmt", 0, 10, states_40,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000"},
+    {297, "try_stmt", 0, 13, states_41,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\004\000\000\000\000\000\000\000\000\000"},
+    {298, "with_stmt", 0, 5, states_42,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\040\000\000\000\000\000\000\000\000\000"},
+    {299, "with_item", 0, 4, states_43,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {300, "except_clause", 0, 5, states_44,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000"},
+    {301, "suite", 0, 5, states_45,
+     "\004\040\040\200\000\000\000\240\340\223\160\000\000\200\020\000\000\206\120\076\200\000"},
+    {302, "test", 0, 6, states_46,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {303, "test_nocond", 0, 2, states_47,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {304, "lambdef", 0, 5, states_48,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000"},
+    {305, "lambdef_nocond", 0, 5, states_49,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000"},
+    {306, "or_test", 0, 2, states_50,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000\000"},
+    {307, "and_test", 0, 2, states_51,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000\000"},
+    {308, "not_test", 0, 3, states_52,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\020\000\000\206\120\076\000\000"},
+    {309, "comparison", 0, 2, states_53,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {310, "comp_op", 0, 4, states_54,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\002\000\220\177\000\000\000\000\000\000"},
+    {311, "star_expr", 0, 3, states_55,
+     "\000\000\000\200\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {312, "expr", 0, 2, states_56,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {313, "xor_expr", 0, 2, states_57,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {314, "and_expr", 0, 2, states_58,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {315, "shift_expr", 0, 2, states_59,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {316, "arith_expr", 0, 2, states_60,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {317, "term", 0, 2, states_61,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {318, "factor", 0, 3, states_62,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {319, "power", 0, 4, states_63,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\120\076\000\000"},
+    {320, "atom", 0, 9, states_64,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\000\000\000\000\000\120\076\000\000"},
+    {321, "testlist_comp", 0, 5, states_65,
+     "\000\040\040\200\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {322, "trailer", 0, 7, states_66,
+     "\000\040\000\000\000\000\000\000\000\100\000\000\000\000\000\000\000\000\020\000\000\000"},
+    {323, "subscriptlist", 0, 3, states_67,
+     "\000\040\040\002\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {324, "subscript", 0, 5, states_68,
+     "\000\040\040\002\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {325, "sliceop", 0, 3, states_69,
+     "\000\000\000\002\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {326, "exprlist", 0, 3, states_70,
+     "\000\040\040\200\000\000\000\000\000\200\000\000\000\000\000\000\000\206\120\076\000\000"},
+    {327, "testlist", 0, 3, states_71,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {328, "dictorsetmaker", 0, 11, states_72,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {329, "classdef", 0, 8, states_73,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\004\000"},
+    {330, "arglist", 0, 8, states_74,
+     "\000\040\040\200\001\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {331, "argument", 0, 4, states_75,
+     "\000\040\040\000\000\000\000\000\000\200\000\000\000\200\020\000\000\206\120\076\000\000"},
+    {332, "comp_iter", 0, 2, states_76,
+     "\000\000\000\000\000\000\000\000\000\000\000\020\001\000\000\000\000\000\000\000\000\000"},
+    {333, "comp_for", 0, 6, states_77,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\000"},
+    {334, "comp_if", 0, 4, states_78,
+     "\000\000\000\000\000\000\000\000\000\000\000\020\000\000\000\000\000\000\000\000\000\000"},
+    {335, "encoding_decl", 0, 2, states_79,
+     "\000\000\040\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000"},
+    {336, "yield_expr", 0, 3, states_80,
+     "\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\200\000"},
+    {337, "yield_arg", 0, 3, states_81,
+     "\000\040\040\000\000\000\000\000\000\202\000\000\000\200\020\000\000\206\120\076\000\000"},
+};
+static label labels[169] = {
     {0, "EMPTY"},
     {256, 0},
     {4, 0},
@@ -2135,10 +2152,11 @@ static label labels[168] = {
     {334, 0},
     {335, 0},
     {1, "yield"},
+    {337, 0},
 };
 grammar _PyParser_Grammar = {
-    81,
+    82,
     dfas,
-    {168, labels},
+    {169, labels},
     256
 };
diff --git a/Python/opcode_targets.h b/Python/opcode_targets.h
index a91da79be69..2d6bcda513c 100644
--- a/Python/opcode_targets.h
+++ b/Python/opcode_targets.h
@@ -71,7 +71,7 @@ static void *opcode_targets[256] = {
     &&TARGET_STORE_LOCALS,
     &&TARGET_PRINT_EXPR,
     &&TARGET_LOAD_BUILD_CLASS,
-    &&_unknown_opcode,
+    &&TARGET_YIELD_FROM,
     &&_unknown_opcode,
     &&_unknown_opcode,
     &&TARGET_INPLACE_LSHIFT,
diff --git a/Python/symtable.c b/Python/symtable.c
index 824a53fc1b8..1ce7f7036f2 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -19,10 +19,6 @@
 
 #define IMPORT_STAR_WARNING "import * only allowed at module level"
 
-#define RETURN_VAL_IN_GENERATOR \
-    "'return' with argument inside generator"
-
-
 static PySTEntryObject *
 ste_new(struct symtable *st, identifier name, _Py_block_ty block,
         void *key, int lineno, int col_offset)
@@ -1133,14 +1129,6 @@ symtable_visit_stmt(struct symtable *st, stmt_ty s)
         if (s->v.Return.value) {
             VISIT(st, expr, s->v.Return.value);
             st->st_cur->ste_returns_value = 1;
-            if (st->st_cur->ste_generator) {
-                PyErr_SetString(PyExc_SyntaxError,
-                    RETURN_VAL_IN_GENERATOR);
-                PyErr_SyntaxLocationEx(st->st_filename,
-                                       s->lineno,
-                                       s->col_offset);
-                return 0;
-            }
         }
         break;
     case Delete_kind:
@@ -1345,13 +1333,6 @@ symtable_visit_expr(struct symtable *st, expr_ty e)
         if (e->v.Yield.value)
             VISIT(st, expr, e->v.Yield.value);
         st->st_cur->ste_generator = 1;
-        if (st->st_cur->ste_returns_value) {
-            PyErr_SetString(PyExc_SyntaxError,
-                RETURN_VAL_IN_GENERATOR);
-            PyErr_SyntaxLocationEx(st->st_filename,
-                                   e->lineno, e->col_offset);
-            return 0;
-        }
         break;
     case Compare_kind:
         VISIT(st, expr, e->v.Compare.left);