Add replace_args method for rustc_errors::diagnostic::Diagnostic

compiler/rustc_errors/src/diagnostic.rs

@@ -940,6 +940,10 @@ impl Diagnostic {
         self
     }
 
+    pub fn replace_args(&mut self, args: FxHashMap<DiagnosticArgName<'static>, DiagnosticArgValue<'static>>) {
+        self.args = args;
+    }
+
     pub fn styled_message(&self) -> &[(DiagnosticMessage, Style)] {
         &self.message
     }