Fix the type of the 'self' argument in a cdef staticmethod declared in a pxd file (GH-4085)

Fixes https://github.com/cython/cython/issues/3174
Closes https://github.com/cython/cython/pull/3175

I've removed all identification of is_self_arg from the parser, since I think it's better dealt with when analysing the declarations.

Original test copied from https://github.com/cython/cython/pull/3175

Cython/Compiler/Nodes.py

@@ -902,7 +902,7 @@ class CArgDeclNode(Node):
 
     def analyse(self, env, nonempty=0, is_self_arg=False):
         if is_self_arg:
-            self.base_type.is_self_arg = self.is_self_arg = True
+            self.base_type.is_self_arg = self.is_self_arg = is_self_arg
         if self.type is not None:
             return self.name_declarator, self.type
 
@@ -1024,6 +1024,7 @@ class CSimpleBaseTypeNode(CBaseTypeNode):
     module_path = []
     is_basic_c_type = False
     complex = False
+    is_self_arg = False
 
     def analyse(self, env, could_be_name=False):
         # Return type descriptor.

Cython/Compiler/Parsing.pxd

@@ -141,10 +141,10 @@ cdef tuple p_suite_with_docstring(PyrexScanner s, ctx, bint with_doc_only=*)
 cdef tuple _extract_docstring(node)
 cdef p_positional_and_keyword_args(PyrexScanner s, end_sy_set, templates = *)
 
-cpdef p_c_base_type(PyrexScanner s, bint self_flag = *, bint nonempty = *, templates = *)
+cpdef p_c_base_type(PyrexScanner s, bint nonempty = *, templates = *)
 cdef p_calling_convention(PyrexScanner s)
 cdef p_c_complex_base_type(PyrexScanner s, templates = *)
-cdef p_c_simple_base_type(PyrexScanner s, bint self_flag, bint nonempty, templates = *)
+cdef p_c_simple_base_type(PyrexScanner s, bint nonempty, templates = *)
 cdef p_buffer_or_template(PyrexScanner s, base_type_node, templates)
 cdef p_bracketed_base_type(PyrexScanner s, base_type_node, nonempty, empty)
 cdef is_memoryviewslice_access(PyrexScanner s)

Cython/Compiler/Parsing.py

@@ -2477,13 +2477,11 @@ def p_positional_and_keyword_args(s, end_sy_set, templates = None):
         s.next()
     return positional_args, keyword_args
 
-def p_c_base_type(s, self_flag = 0, nonempty = 0, templates = None):
-    # If self_flag is true, this is the base type for the
-    # self argument of a C method of an extension type.
+def p_c_base_type(s, nonempty=False, templates=None):
     if s.sy == '(':
         return p_c_complex_base_type(s, templates = templates)
     else:
-        return p_c_simple_base_type(s, self_flag, nonempty = nonempty, templates = templates)
+        return p_c_simple_base_type(s, nonempty=nonempty, templates=templates)
 
 def p_calling_convention(s):
     if s.sy == 'IDENT' and s.systring in calling_convention_words:
@@ -2527,8 +2525,7 @@ def p_c_complex_base_type(s, templates = None):
     return type_node
 
 
-def p_c_simple_base_type(s, self_flag, nonempty, templates = None):
-    #print "p_c_simple_base_type: self_flag =", self_flag, nonempty
+def p_c_simple_base_type(s, nonempty, templates=None):
     is_basic = 0
     signed = 1
     longness = 0
@@ -2549,7 +2546,7 @@ def p_c_simple_base_type(s, self_flag, nonempty, templates = None):
             break
         s.next()
     if is_const or is_volatile:
-        base_type = p_c_base_type(s, self_flag=self_flag, nonempty=nonempty, templates=templates)
+        base_type = p_c_base_type(s, nonempty=nonempty, templates=templates)
         if isinstance(base_type, Nodes.MemoryViewSliceTypeNode):
             # reverse order to avoid having to write "(const int)[:]"
             base_type.base_type_node = Nodes.CConstOrVolatileTypeNode(pos,
@@ -2607,7 +2604,7 @@ def p_c_simple_base_type(s, self_flag, nonempty, templates = None):
         name = name, module_path = module_path,
         is_basic_c_type = is_basic, signed = signed,
         complex = complex, longness = longness,
-        is_self_arg = self_flag, templates = templates)
+        templates = templates)
 
     #    declarations here.
     if s.sy == '[':
@@ -3052,7 +3049,7 @@ def p_c_arg_decl(s, ctx, in_pyfunc, cmethod_flag = 0, nonempty = 0,
             complex = 0, longness = 0,
             is_self_arg = cmethod_flag, templates = None)
     else:
-        base_type = p_c_base_type(s, cmethod_flag, nonempty = nonempty)
+        base_type = p_c_base_type(s, nonempty=nonempty)
     declarator = p_c_declarator(s, ctx, nonempty = nonempty)
     if s.sy in ('not', 'or') and not s.in_python_file:
         kind = s.sy

tests/run/static_methods.pxd

 cdef class FromPxd:
     @staticmethod
     cdef static_cdef(int* x)
+
+    @staticmethod
+    cdef static_cdef_with_implicit_object(obj)

tests/run/static_methods.pyx

@@ -87,6 +87,10 @@ cdef class FromPxd:
     cdef static_cdef(int* x):
         return 'pxd_cdef', x[0]
 
+    @staticmethod
+    cdef static_cdef_with_implicit_object(obj):
+        return obj+1
+
 def call_static_pxd_cdef(int x):
     """
     >>> call_static_pxd_cdef(2)
@@ -94,3 +98,11 @@ def call_static_pxd_cdef(int x):
     """
     cdef int *x_ptr = &x
     return FromPxd.static_cdef(x_ptr)
+
+def call_static_pxd_cdef_with_implicit_object(int x):
+    """
+    # https://github.com/cython/cython/issues/3174
+    >>> call_static_pxd_cdef_with_implicit_object(2)
+    3
+    """
+    return FromPxd.static_cdef_with_implicit_object(x)