implement support for extracting type declarations from signature annotations

CHANGES.rst

@@ -9,6 +9,9 @@ Latest
 Features added
 --------------
 
+* Simple support for declaring Python object types in Python signature
+  annotations.
+
 Bugs fixed
 ----------
 

Cython/Compiler/ExprNodes.py

@@ -289,15 +289,16 @@ class ExprNode(Node):
     #
     #
 
-    is_sequence_constructor = 0
-    is_string_literal = 0
-    is_attribute = 0
-    is_subscript = 0
+    is_sequence_constructor = False
+    is_dict_literal = False
+    is_string_literal = False
+    is_attribute = False
+    is_subscript = False
 
     saved_subexpr_nodes = None
-    is_temp = 0
-    is_target = 0
-    is_starred = 0
+    is_temp = False
+    is_target = False
+    is_starred = False
 
     constant_result = constant_value_not_set
 
@@ -1174,6 +1175,20 @@ class FloatNode(ConstNode):
             self.result_code = c_value
 
 
+def _analyse_name_as_type(name, pos, env):
+    type = PyrexTypes.parse_basic_type(name)
+    if type is not None:
+        return type
+    from TreeFragment import TreeFragment
+    pos = (pos[0], pos[1], pos[2]-7)
+    declaration = TreeFragment(u"sizeof(%s)" % name, name=pos[0].filename, initial_pos=pos)
+    sizeof_node = declaration.root.stats[0].expr
+    sizeof_node = sizeof_node.analyse_types(env)
+    if isinstance(sizeof_node, SizeofTypeNode):
+        return sizeof_node.arg_type
+    return None
+
+
 class BytesNode(ConstNode):
     # A char* or bytes literal
     #
@@ -1196,16 +1211,7 @@ class BytesNode(ConstNode):
         return self.value
 
     def analyse_as_type(self, env):
-        type = PyrexTypes.parse_basic_type(self.value)
-        if type is not None:
-            return type
-        from TreeFragment import TreeFragment
-        pos = (self.pos[0], self.pos[1], self.pos[2]-7)
-        declaration = TreeFragment(u"sizeof(%s)" % self.value, name=pos[0].filename, initial_pos=pos)
-        sizeof_node = declaration.root.stats[0].expr
-        sizeof_node = sizeof_node.analyse_types(env)
-        if isinstance(sizeof_node, SizeofTypeNode):
-            return sizeof_node.arg_type
+        return _analyse_name_as_type(self.value.decode('ISO8859-1'), self.pos, env)
 
     def can_coerce_to_char_literal(self):
         return len(self.value) == 1
@@ -1279,6 +1285,9 @@ class UnicodeNode(ConstNode):
     def calculate_constant_result(self):
         self.constant_result = self.value
 
+    def analyse_as_type(self, env):
+        return _analyse_name_as_type(self.value, self.pos, env)
+
     def as_sliced_node(self, start, stop, step=None):
         if StringEncoding.string_contains_surrogates(self.value[:stop]):
             # this is unsafe as it may give different results
@@ -1388,6 +1397,9 @@ class StringNode(PyConstNode):
             # only the Unicode value is portable across Py2/3
             self.constant_result = self.unicode_value
 
+    def analyse_as_type(self, env):
+        return _analyse_name_as_type(self.unicode_value or self.value.decode('ISO8859-1'), self.pos, env)
+
     def as_sliced_node(self, start, stop, step=None):
         value = type(self.value)(self.value[start:stop:step])
         value.encoding = self.value.encoding
@@ -6706,6 +6718,7 @@ class DictNode(ExprNode):
     is_temp = 1
     exclude_null_values = False
     type = dict_type
+    is_dict_literal = True
 
     obj_conversion_errors = []
 

Cython/Compiler/Nodes.py

@@ -612,8 +612,8 @@ class CFuncDeclaratorNode(CDeclaratorNode):
             nonempty -= 1
         func_type_args = []
         for i, arg_node in enumerate(self.args):
-            name_declarator, type = arg_node.analyse(env, nonempty = nonempty,
-                                                     is_self_arg = (i == 0 and env.is_c_class_scope))
+            name_declarator, type = arg_node.analyse(
+                env, nonempty=nonempty, is_self_arg=(i == 0 and env.is_c_class_scope))
             name = name_declarator.name
             if name in directive_locals:
                 type_node = directive_locals[name]
@@ -800,7 +800,7 @@ class CArgDeclNode(Node):
                 if nonempty:
                     if self.base_type.is_basic_c_type:
                         # char, short, long called "int"
-                        type = self.base_type.analyse(env, could_be_name = True)
+                        type = self.base_type.analyse(env, could_be_name=True)
                         arg_name = type.declaration_code("")
                     else:
                         arg_name = self.base_type.name
@@ -811,9 +811,10 @@ class CArgDeclNode(Node):
             else:
                 could_be_name = False
             self.base_type.is_arg = True
-            base_type = self.base_type.analyse(env, could_be_name = could_be_name)
+            base_type = self.base_type.analyse(env, could_be_name=could_be_name)
             if hasattr(self.base_type, 'arg_name') and self.base_type.arg_name:
                 self.declarator.name = self.base_type.arg_name
+
             # The parser is unable to resolve the ambiguity of [] as part of the
             # type (e.g. in buffers) or empty declarator (as with arrays).
             # This is only arises for empty multi-dimensional arrays.
@@ -825,10 +826,45 @@ class CArgDeclNode(Node):
                     declarator = declarator.base
                 declarator.base = self.base_type.array_declarator
                 base_type = base_type.base_type
-            return self.declarator.analyse(base_type, env, nonempty = nonempty)
+
+            # inject type declaration from annotations
+            if self.annotation and env.directives['annotation_typing'] and self.base_type.name is None:
+                arg_type = self.inject_type_from_annotations(env)
+                if arg_type is not None:
+                    base_type = arg_type
+            return self.declarator.analyse(base_type, env, nonempty=nonempty)
         else:
             return self.name_declarator, self.type
 
+    def inject_type_from_annotations(self, env):
+        annotation = self.annotation
+        if not annotation:
+            return
+        explicit_pytype = explicit_ctype = False
+        if annotation.is_dict_literal:
+            for name, value in annotation.key_value_pairs:
+                if not name.is_string_literal:
+                    continue
+                if name.value == 'type':
+                    explicit_pytype = True
+                    if not explicit_ctype:
+                        annotation = value
+                elif name.value == 'ctype':
+                    explicit_ctype = True
+                    annotation = value
+            if explicit_pytype and explicit_ctype:
+                warning(annotation.pos, "Duplicate type declarations found in signature annotation")
+        arg_type = annotation.analyse_as_type(env)
+        if arg_type is not None:
+            if explicit_pytype and not explicit_ctype and not arg_type.is_pyobject:
+                warning(annotation.pos,
+                        "Python type declaration in signature annotation does not refer to a Python type")
+            self.base_type = CAnalysedBaseTypeNode(
+                annotation.pos, type=arg_type, is_arg=True)
+        else:
+            warning(annotation.pos, "Unknown type declaration found in signature annotation")
+        return arg_type
+
     def calculate_default_value_code(self, code):
         if self.default_value is None:
             if self.default:
@@ -1524,19 +1560,25 @@ class FuncDefNode(StatNode, BlockNode):
                 error(arg.pos, "Non-default argument following default argument")
 
     def align_argument_type(self, env, arg):
+        # @cython.locals()
         directive_locals = self.directive_locals
-        type = arg.type
+        orig_type = arg.type
         if arg.name in directive_locals:
             type_node = directive_locals[arg.name]
             other_type = type_node.analyse_as_type(env)
-            if other_type is None:
-                error(type_node.pos, "Not a type")
-            elif (type is not PyrexTypes.py_object_type
-                    and not type.same_as(other_type)):
-                error(arg.base_type.pos, "Signature does not agree with previous declaration")
-                error(type_node.pos, "Previous declaration here")
-            else:
-                arg.type = other_type
+        elif isinstance(arg, CArgDeclNode) and arg.annotation:
+            type_node = arg.annotation
+            other_type = arg.inject_type_from_annotations(env)
+        else:
+            return arg
+        if other_type is None:
+            error(type_node.pos, "Not a type")
+        elif (orig_type is not PyrexTypes.py_object_type
+                and not orig_type.same_as(other_type)):
+            error(arg.base_type.pos, "Signature does not agree with previous declaration")
+            error(type_node.pos, "Previous declaration here")
+        else:
+            arg.type = other_type
         return arg
 
     def need_gil_acquisition(self, lenv):

Cython/Compiler/Options.py

@@ -101,6 +101,7 @@ directive_defaults = {
     'profile': False,
     'no_gc_clear': False,
     'linetrace': False,
+    'annotation_typing': False,  # read type declarations from Python function annotations
     'infer_types': None,
     'infer_types.verbose': False,
     'autotestdict': True,
@@ -228,6 +229,7 @@ directive_scopes = { # defaults to available everywhere
     'test_assert_path_exists' : ('function', 'class', 'cclass'),
     'test_fail_if_path_exists' : ('function', 'class', 'cclass'),
     'freelist': ('cclass',),
+    'annotation_typing': ('module',),  # FIXME: analysis currently lacks more specific function scope
     # Avoid scope-specific to/from_py_functions for c_string.
     'c_string_type': ('module',),
     'c_string_encoding': ('module',),

docs/src/tutorial/pure.rst

@@ -36,6 +36,16 @@ The currently supported attributes of the ``cython`` module are:
     def foo(a, b, x, y):
         ...
 
+* Starting with Cython 0.21, Python signature annotations can be used to
+  declare argument types.  Cython recognises three ways to do this, as
+  shown in the following example::
+
+    def func(plain_python_type: dict,
+             named_python_type: 'dict',
+             explicit_python_type: {'type': dict},
+             explicit_c_type: {'ctype': 'int'}):
+        ...
+
 * ``address`` is used in place of the ``&`` operator::
 
     cython.declare(x=cython.int, x_ptr=cython.p_int)