Do not issue "redefined" warnings on C++ function overrides with different...

Do not issue "redefined" warnings on C++ function overrides with different signatures (previously only applied to methods).
Closes #2013.

CHANGES.rst

@@ -146,6 +146,9 @@ Bugs fixed
 * The builtin ``bytearray`` type could not be used as base type of cdef classes.
   (Github issue #2106)
 
+* Overloaded C++ functions no longer issue warnings about redeclarations.
+  (Github issue #2013)
+
 Other changes
 -------------
 

Cython/Compiler/CythonScope.py

@@ -26,6 +26,10 @@ class CythonScope(ModuleScope):
                                          cname='<error>')
             entry.in_cinclude = True
 
+    def is_cpp(self):
+        # Alow C++ utility code in C++ contexts.
+        return self.context.cpp
+
     def lookup_type(self, name):
         # This function should go away when types are all first-level objects.
         type = parse_basic_type(name)

Cython/Compiler/Symtab.py

@@ -446,9 +446,22 @@ class Scope(object):
             warning(pos, "'%s' is a reserved name in C." % cname, -1)
         entries = self.entries
         if name and name in entries and not shadow:
-            old_type = entries[name].type
-            if self.is_cpp_class_scope and type.is_cfunction and old_type.is_cfunction and type != old_type:
-                # C++ method overrides are ok
+            old_entry = entries[name]
+
+            # Reject redeclared C++ functions only if they have the same type signature.
+            cpp_override_allowed = False
+            if type.is_cfunction and old_entry.type.is_cfunction and self.is_cpp():
+                for alt_entry in old_entry.all_alternatives():
+                    if type == alt_entry.type:
+                        if name == '<init>' and not type.args:
+                            # Cython pre-declares the no-args constructor - allow later user definitions.
+                            cpp_override_allowed = True
+                        break
+                else:
+                    cpp_override_allowed = True
+
+            if cpp_override_allowed:
+                # C++ function/method overrides with different signatures are ok.
                 pass
             elif self.is_cpp_class_scope and entries[name].is_inherited:
                 # Likewise ignore inherited classes.