Allow trailing comma in format macro + fix tests.

src/collections/string.rs

@@ -95,7 +95,11 @@ macro_rules! format {
         let mut s = $crate::collections::String::new_in(bump);
         let _ = write!(&mut s, $fmt, $($args),*);
         s
-    }}
+    }};
+
+    ( in $bump:expr, $fmt:expr, $($args:expr,)* ) => {
+        $crate::format!(in $bump, $fmt, $($args),*)
+    };
 }
 
 /// A UTF-8 encoded, growable string.

tests/string.rs

@@ -1,5 +1,5 @@
 #![cfg(feature = "collections")]
-use bumpalo::{collections::String, Bump};
+use bumpalo::{collections::String, format, Bump};
 use std::fmt::Write;
 
 #[test]
@@ -10,3 +10,10 @@ fn format_a_bunch_of_strings() {
         write!(&mut s, " {}", i).unwrap();
     }
 }
+
+#[test]
+fn trailing_comma_in_format_macro() {
+    let b = Bump::new();
+    let v = format![in &b, "{}{}", 1, 2, ];
+    assert_eq!(v, "12");
+}

tests/vec.rs

@@ -1,8 +1,5 @@
 #![cfg(feature = "collections")]
-use bumpalo::{
-    collections::{vec, Vec},
-    Bump,
-};
+use bumpalo::{collections::Vec, vec, Bump};
 use std::cell::Cell;
 
 #[test]
@@ -17,7 +14,7 @@ fn push_a_bunch_of_items() {
 #[test]
 fn trailing_comma_in_vec_macro() {
     let b = Bump::new();
-    let mut v = vec![in b; 1, 2, 3,];
+    let v = vec![in &b; 1, 2, 3,];
     assert_eq!(v, [1, 2, 3]);
 }