Use original source for _simple_arg

Signed-off-by: Anders Kaseorg <[email protected]>

pyupgrade.py

@@ -2190,16 +2190,11 @@ def _replace(i: int, mapping: Dict[str, str], node: NameOrAttr) -> None:
     return tokens_to_src(tokens)
 
 
-def _simple_arg(arg: ast.expr) -> bool:
-    return (
-        isinstance(arg, ast.Name) or
-        (isinstance(arg, ast.Attribute) and _simple_arg(arg.value)) or
-        (
-            isinstance(arg, ast.Call) and
-            _simple_arg(arg.func) and
-            not arg.args and not arg.keywords
-        )
-    )
+def _simple_arg(arg: ast.expr, lines: List[str]) -> bool:
+    if arg.lineno != arg.end_lineno:
+        return False
+    s = _unparse(arg, lines)
+    return '\\' not in s and "'" not in s and '"' not in s
 
 
 def _starargs(call: ast.Call) -> bool:
@@ -2256,8 +2251,10 @@ def _parse(self, node: ast.Call) -> Optional[Tuple[DotFormatPart, ...]]:
                 isinstance(node.func, ast.Attribute) and
                 isinstance(node.func.value, ast.Str) and
                 node.func.attr == 'format' and
-                all(_simple_arg(arg) for arg in node.args) and
-                all(_simple_arg(k.value) for k in node.keywords) and
+                all(_simple_arg(arg, self.lines) for arg in node.args) and
+                all(
+                    _simple_arg(k.value, self.lines) for k in node.keywords
+                ) and
                 not _starargs(node)
         ):
             return None