py/runtime: Allow multiple **args in a function call.

This is a partial implementation of PEP 448 to allow multiple ** unpackings
when calling a function or method.

The compiler is modified to encode the argument as a None: obj key-value
pair (similar to how regular keyword arguments are encoded as str: obj
pairs).  The extra object that was pushed on the stack to hold a single **
unpacking object is no longer used and is removed.

The runtime is modified to decode this new format.

Signed-off-by: David Lechner <david@pybricks.com>

3 files changed, 33 insertions, 2 deletions

diff --git a/tests/basics/fun_calldblstar4.py b/tests/basics/fun_calldblstar4.py
new file mode 100644
index 000000000..acb332a8c
--- /dev/null
+++ b/tests/basics/fun_calldblstar4.py
@@ -0,0 +1,33 @@
+# test calling a function with multiple **args
+
+
+def f(a, b=None, c=None):
+    print(a, b, c)
+
+
+f(**{"a": 1}, **{"b": 2})
+f(**{"a": 1}, **{"b": 2}, c=3)
+f(**{"a": 1}, b=2, **{"c": 3})
+
+try:
+    f(1, **{"b": 2}, **{"b": 3})
+except TypeError:
+    print("TypeError")
+
+# test calling a method with multiple **args
+
+
+class A:
+    def f(self, a, b=None, c=None):
+        print(a, b, c)
+
+
+a = A()
+a.f(**{"a": 1}, **{"b": 2})
+a.f(**{"a": 1}, **{"b": 2}, c=3)
+a.f(**{"a": 1}, b=2, **{"c": 3})
+
+try:
+    a.f(1, **{"b": 2}, **{"b": 3})
+except TypeError:
+    print("TypeError")
diff --git a/tests/basics/python34.py b/tests/basics/python34.py
index 0f6e4bafd..609a8b6b8 100644
--- a/tests/basics/python34.py
+++ b/tests/basics/python34.py
@@ -25,7 +25,6 @@ def test_syntax(code):
     except SyntaxError:
         print("SyntaxError")
 test_syntax("f(*a, *b)") # can't have multiple * (in 3.5 we can)
-test_syntax("f(**a, **b)") # can't have multiple ** (in 3.5 we can)
 test_syntax("f(*a, b)") # can't have positional after *
 test_syntax("f(**a, b)") # can't have positional after **
 test_syntax("() = []") # can't assign to empty tuple (in 3.6 we can)
diff --git a/tests/basics/python34.py.exp b/tests/basics/python34.py.exp
index 848017130..75f1c2c05 100644
--- a/tests/basics/python34.py.exp
+++ b/tests/basics/python34.py.exp
@@ -8,7 +8,6 @@ SyntaxError
 SyntaxError
 SyntaxError
 SyntaxError
-SyntaxError
 3.4
 3 4
 IndexError('foo',)