Ammed the refactoring of add_unknown_symbol() (#6456)

Author: ilevkivskyi

mypy/newsemanal/semanal.py

@@ -1659,7 +1659,7 @@ def visit_import_from(self, imp: ImportFrom) -> None:
             else:
                 # Missing module.
                 missing_name = import_id + '.' + id
-                self.add_unknown_symbol(imported_id, imp, target_name=missing_name)
+                self.add_unknown_imported_symbol(imported_id, imp, target_name=missing_name)
 
     def report_missing_module_attribute(self, import_id: str, source_id: str, imported_id: str,
                                         context: Node) -> None:
@@ -1674,7 +1674,7 @@ def report_missing_module_attribute(self, import_id: str, source_id: str, import
         if extra:
             message += " {}".format(extra)
         self.fail(message, context)
-        self.add_unknown_symbol(imported_id, context)
+        self.add_unknown_imported_symbol(imported_id, context)
 
         if import_id == 'typing':
             # The user probably has a missing definition in a test fixture. Let's verify.
@@ -4045,7 +4045,7 @@ def add_module_symbol(self, id: str, as_id: str, module_public: bool,
                             module_public=module_public,
                             module_hidden=module_hidden)
         else:
-            self.add_unknown_symbol(as_id, context, target_name=id)
+            self.add_unknown_imported_symbol(as_id, context, target_name=id)
 
     def add_local(self, node: Union[Var, FuncDef, OverloadedFuncDef], context: Context) -> None:
         """Add local variable or function."""
@@ -4062,9 +4062,15 @@ def add_imported_symbol(self, name: str, node: SymbolTableNode, context: Context
                                  module_hidden=module_hidden)
         self.add_symbol_table_node(name, symbol, context)
 
-    def add_unknown_symbol(self, name: str, context: Context,
-                           target_name: Optional[str] = None) -> None:
-        """Add symbol that we don't know what it points to (due to error, for example)."""
+    def add_unknown_imported_symbol(self, name: str, context: Context,
+                                    target_name: Optional[str] = None) -> None:
+        """Add symbol that we don't know what it points to because resolving an import failed.
+
+        This can happen if a module is missing, or it is present, but doesn't have
+        the imported attribute. The `target_name` is the name of symbol in the namespace
+        it is imported from. For example, for 'from mod import x as y' the target_name is
+        'mod.x'. This is currently used only to track logical dependencies.
+        """
         existing = self.current_symbol_table().get(name)
         if existing and isinstance(existing.node, Var) and existing.node.is_suppressed_import:
             # This missing import was already added -- nothing to do here.