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

This is a partial implementation of PEP 448 to allow unpacking multiple
star args in a function or method call.

This is implemented by changing the emitted bytecodes so that both
positional args and star args are stored as positional args.  A bitmap is
added to indicate if an argument at a given position is a positional
argument or a star arg.

In the generated code, this new bitmap takes the place of the old star arg.
It is stored as a small int, so this means only the first N arguments can
be star args where N is the number of bits in a small int.

The runtime is modified to interpret this new bytecode format while still
trying to perform as few memory reallocations as possible.

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

5 files changed, 39 insertions, 12 deletions

diff --git a/tests/basics/fun_callstar.py b/tests/basics/fun_callstar.py
index a27a288a3c..53d2ece3e1 100644
--- a/tests/basics/fun_callstar.py
+++ b/tests/basics/fun_callstar.py
@@ -3,10 +3,16 @@
 def foo(a, b, c):
     print(a, b, c)
 
+foo(*(), 1, 2, 3)
+foo(*(1,), 2, 3)
+foo(*(1, 2), 3)
 foo(*(1, 2, 3))
 foo(1, *(2, 3))
 foo(1, 2, *(3,))
 foo(1, 2, 3, *())
+foo(*(1,), 2, *(3,))
+foo(*(1, 2), *(3,))
+foo(*(1,), *(2, 3))
 
 # Another sequence type
 foo(1, 2, *[100])
@@ -29,10 +35,16 @@ class A:
         print(a, b, c)
 
 a = A()
+a.foo(*(), 1, 2, 3)
+a.foo(*(1,), 2, 3)
+a.foo(*(1, 2), 3)
 a.foo(*(1, 2, 3))
 a.foo(1, *(2, 3))
 a.foo(1, 2, *(3,))
 a.foo(1, 2, 3, *())
+a.foo(*(1,), 2, *(3,))
+a.foo(*(1, 2), *(3,))
+a.foo(*(1,), *(2, 3))
 
 # Another sequence type
 a.foo(1, 2, *[100])
diff --git a/tests/basics/fun_callstardblstar.py b/tests/basics/fun_callstardblstar.py
index f2fd29107e..aceb04a843 100644
--- a/tests/basics/fun_callstardblstar.py
+++ b/tests/basics/fun_callstardblstar.py
@@ -6,6 +6,11 @@ def f(a, b, c, d):
 f(*(1, 2), **{'c':3, 'd':4})
 f(*(1, 2), **{['c', 'd'][i]:(3 + i) for i in range(2)})
 
+try:
+    eval("f(**{'a': 1}, *(2, 3, 4))")
+except SyntaxError:
+    print("SyntaxError")
+
 # test calling a method with *tuple and **dict
 
 class A:
@@ -15,3 +20,8 @@ class A:
 a = A()
 a.f(*(1, 2), **{'c':3, 'd':4})
 a.f(*(1, 2), **{['c', 'd'][i]:(3 + i) for i in range(2)})
+
+try:
+    eval("a.f(**{'a': 1}, *(2, 3, 4))")
+except SyntaxError:
+    print("SyntaxError")
diff --git a/tests/basics/fun_kwvarargs.py b/tests/basics/fun_kwvarargs.py
index bdc10fcf14..e9fd0720e9 100644
--- a/tests/basics/fun_kwvarargs.py
+++ b/tests/basics/fun_kwvarargs.py
@@ -23,3 +23,16 @@ def f4(*vargs, **kwargs):
 f4(*(1, 2))
 f4(kw_arg=3)
 f4(*(1, 2), kw_arg=3)
+
+
+# test evaluation order of arguments
+def f5(*vargs, **kwargs):
+    print(vargs, kwargs)
+
+
+def print_ret(x):
+    print(x)
+    return x
+
+
+f5(*print_ret(["a", "b"]), kw_arg=print_ret(None))
diff --git a/tests/basics/python34.py b/tests/basics/python34.py
index 609a8b6b84..36e25e20dd 100644
--- a/tests/basics/python34.py
+++ b/tests/basics/python34.py
@@ -6,26 +6,23 @@ except NameError:
     print("SKIP")
     raise SystemExit
 
-# from basics/fun_kwvarargs.py
-# test evaluation order of arguments (in 3.4 it's backwards, 3.5 it's fixed)
-def f4(*vargs, **kwargs):
-    print(vargs, kwargs)
+
 def print_ret(x):
     print(x)
     return x
-f4(*print_ret(['a', 'b']), kw_arg=print_ret(None))
 
 # test evaluation order of dictionary key/value pair (in 3.4 it's backwards)
 {print_ret(1):print_ret(2)}
 
+
 # from basics/syntaxerror.py
 def test_syntax(code):
     try:
         exec(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 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)
 test_syntax("del ()") # can't delete empty tuple (in 3.6 we can)
diff --git a/tests/basics/python34.py.exp b/tests/basics/python34.py.exp
index 75f1c2c056..a56c1a50b6 100644
--- a/tests/basics/python34.py.exp
+++ b/tests/basics/python34.py.exp
@@ -1,13 +1,8 @@
-None
-['a', 'b']
-('a', 'b') {'kw_arg': None}
 2
 1
 SyntaxError
 SyntaxError
 SyntaxError
-SyntaxError
-SyntaxError
 3.4
 3 4
 IndexError('foo',)