(subplotlib-derive): use Write macro for cleaner string update

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/subplotlib-derive/src/lib.rs b/subplotlib-derive/src/lib.rs
index 7fd1810..86f5c5e 100644
--- a/subplotlib-derive/src/lib.rs
+++ b/subplotlib-derive/src/lib.rs
@@ -1,5 +1,6 @@
 use proc_macro::TokenStream;
 use proc_macro2::Span;
+use std::fmt::Write;
 use syn::{
     parse_macro_input, parse_quote, Error, FnArg, Ident, ItemFn, Pat, PathArguments, ReturnType,
     Type,
@@ -372,7 +373,7 @@ fn process_step(mut input: ItemFn) -> proc_macro2::TokenStream {
             Some(&contexttype)
         };
         for context in outer_ctx.into_iter().chain(contexts.iter()) {
-            contextattrs.push_str(&format!("\n    #[context({:?})]", ty_as_path(context)?));
+            write!(contextattrs, "\n    #[context({:?})]", ty_as_path(context)?).unwrap();
         }
         let func_args: Vec<_> = fields
             .iter()