fixes #23765; Method calling proc with return value overlapping declared generic type generates invalid C

compiler/seminst.nim

@@ -81,7 +81,8 @@ proc sameInstantiation(a, b: TInstantiation): bool =
       if not compareTypes(a.concreteTypes[i], b.concreteTypes[i],
                           flags = {ExactTypeDescValues,
                                    ExactGcSafety,
-                                   PickyCAliases}): return
+                                   PickyCAliases,
+                                   PickyBackendAliases}): return
     result = true
   else:
     result = false

compiler/semtypinst.nim

@@ -52,7 +52,8 @@ proc searchInstTypes*(g: ModuleGraph; key: PType): PType =
       for j in FirstGenericParamAt..<key.kidsLen:
         # XXX sameType is not really correct for nested generics?
         if not compareTypes(inst[j], key[j],
-                            flags = {ExactGenericParams, PickyCAliases}):
+                            flags = {ExactGenericParams, PickyCAliases,
+                                     PickyBackendAliases}):
           break matchType
 
       return inst