rework println

2 files changed, 30 insertions, 2 deletions

diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 6abf987d0ab..d3e5adf6835 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -683,7 +683,20 @@ pub fn expand_format_args<'cx>(ecx: &'cx mut ExtCtxt,
     sp = sp.apply_mark(ecx.current_expansion.mark);
     match parse_args(ecx, sp, tts) {
         Some((efmt, args, names)) => {
-            MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names))
+            MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, false))
+        }
+        None => DummyResult::expr(sp),
+    }
+}
+
+pub fn expand_format_args_nl<'cx>(ecx: &'cx mut ExtCtxt,
+                                  mut sp: Span,
+                                  tts: &[tokenstream::TokenTree])
+                                  -> Box<dyn base::MacResult + 'cx> {
+    sp = sp.apply_mark(ecx.current_expansion.mark);
+    match parse_args(ecx, sp, tts) {
+        Some((efmt, args, names)) => {
+            MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, true))
         }
         None => DummyResult::expr(sp),
     }
@@ -695,7 +708,8 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
                                     sp: Span,
                                     efmt: P<ast::Expr>,
                                     args: Vec<P<ast::Expr>>,
-                                    names: HashMap<String, usize>)
+                                    names: HashMap<String, usize>,
+                                    append_newline: bool)
                                     -> P<ast::Expr> {
     // NOTE: this verbose way of initializing `Vec<Vec<ArgumentType>>` is because
     // `ArgumentType` does not derive `Clone`.
@@ -706,6 +720,10 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
     let msg = "format argument must be a string literal";
     let fmt_sp = efmt.span;
     let fmt = match expr_to_spanned_string(ecx, efmt, msg) {
+        Ok(mut fmt) if append_newline => {
+            fmt.node.0 = Symbol::intern(&format!("{}\n", fmt.node.0));
+            fmt
+        }
         Ok(fmt) => fmt,
         Err(mut err) => {
             let sugg_fmt = match args.len() {
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index bdf7a8d7040..ff76e788b3c 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -139,6 +139,16 @@ pub fn register_builtins(resolver: &mut dyn syntax::ext::base::Resolver,
                 unstable_feature: None,
                 edition: hygiene::default_edition(),
             });
+    register(Symbol::intern("format_args_nl"),
+             NormalTT {
+                 expander: Box::new(format::expand_format_args_nl),
+                 def_info: None,
+                 allow_internal_unstable: true,
+                 allow_internal_unsafe: false,
+                 local_inner_macros: false,
+                 unstable_feature: None,
+                 edition: hygiene::default_edition(),
+             });
 
     for (name, ext) in user_exts {
         register(name, ext);