make ctuples available in pure python code

CHANGES.rst

@@ -16,6 +16,8 @@ Features added
 
 * Cpdef enums are now first-class iterable, callable types in Python.
 
+* Ctuples can now be declared in pure Python code.
+
 * Posix declarations for DLL loading and stdio extensions were added.
   Patch by Lars Buitinck.
 

Cython/Compiler/ExprNodes.py

@@ -7172,6 +7172,16 @@ class TupleNode(SequenceNode):
             node.is_partly_literal = True
         return node
 
+    def analyse_as_type(self, env):
+        # ctuple type
+        if not self.args:
+            return None
+        item_types = [arg.analyse_as_type(env) for arg in self.args]
+        if any(t is None for t in item_types):
+            return None
+        entry = env.declare_tuple_type(self.pos, item_types)
+        return entry.type
+
     def coerce_to(self, dst_type, env):
         if self.type.is_ctuple:
             if dst_type.is_ctuple and self.type.size == dst_type.size:

docs/src/tutorial/pure.rst

@@ -222,6 +222,8 @@ The Python types int, long and bool are interpreted as C ``int``, ``long``
 and ``bint`` respectively. Also, the Python builtin types ``list``, ``dict``,
 ``tuple``, etc. may be used, as well as any user defined types.
 
+Typed C-tuples can be declared as a tuple of C types.
+
 
 Extension types and cdef functions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/run/ctuple.pyx

@@ -141,6 +141,7 @@ cpdef (int, double) cpdef_ctuple_return_type(int x, double y):
     """
     return x, y
 
+
 @cython.infer_types(True)
 def test_type_inference():
     """
@@ -155,6 +156,28 @@ def test_type_inference():
     assert cython.typeof(xo) == "tuple object", cython.typeof(xo)
 
 
+@cython.locals(a=(int,int), b=(cython.long,cython.float))
+def test_pure_python_declaration(x, y):
+    """
+    >>> test_pure_python_declaration(1, 2)
+    (int, int)
+    (long, float)
+    ((1, 2), (1, 2.0))
+    >>> test_pure_python_declaration(1.0, 2.0)
+    (int, int)
+    (long, float)
+    ((1, 2), (1, 2.0))
+    >>> test_pure_python_declaration('x', 'y')
+    Traceback (most recent call last):
+    TypeError: an integer is required
+    """
+    a = (x, y)
+    b = (x, y)
+    print(cython.typeof(a))
+    print(cython.typeof(b))
+    return (a, b)
+
+
 def test_equality((int, int) ab, (int, int) cd, (int, int) ef):
     """
     >>> test_equality((1, 2), (3, 4), (5, 6))