From f53c145ef18db6543e8e5420e172e04b6054db2e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 14 Jul 2018 20:50:30 -0700
Subject: [PATCH 01/19] Improve suggestion for missing fmt str in println

Avoid using `concat!(fmt, "\n")` to improve the diagnostics being
emitted when the first `println!()` argument isn't a formatting string
literal.
---
 src/libstd/macros.rs                          | 10 ++++-
 src/libsyntax/ext/base.rs                     | 25 ++++++-----
 src/libsyntax_ext/concat.rs                   | 15 +++----
 src/libsyntax_ext/format.rs                   | 28 +++++++++---
 .../conditional_array_execution.nll.stderr    | 14 ++----
 src/test/ui/const-eval/issue-43197.nll.stderr | 14 ++----
 src/test/ui/const-eval/issue-44578.nll.stderr | 14 ++----
 src/test/ui/fmt/format-string-error.rs        |  2 +
 src/test/ui/fmt/format-string-error.stderr    | 20 ++++-----
 src/test/ui/macros/bad_hello.rs               |  5 ++-
 src/test/ui/macros/bad_hello.stderr           | 20 ++++++---
 src/test/ui/macros/format-foreign.stderr      |  5 ++-
 .../ui/macros/format-unused-lables.stderr     | 43 +++++++++----------
 src/test/ui/macros/trace-macro.stderr         |  9 ++--
 14 files changed, 122 insertions(+), 102 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 75f038407c127..a4a6ed73c61cf 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -155,8 +155,14 @@ macro_rules! print {
 #[stable(feature = "rust1", since = "1.0.0")]
 macro_rules! println {
     () => (print!("\n"));
-    ($fmt:expr) => (print!(concat!($fmt, "\n")));
-    ($fmt:expr, $($arg:tt)*) => (print!(concat!($fmt, "\n"), $($arg)*));
+    ($fmt:expr) => ({
+        print!($fmt);
+        print!("\n");
+    });
+    ($fmt:expr, $($arg:tt)*) => ({
+        print!($fmt, $($arg)*);
+        print!("\n");
+    });
 }
 
 /// Macro for printing to the standard error.
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 5ec44fb589818..b55c4f99206c4 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -959,29 +959,34 @@ impl<'a> ExtCtxt<'a> {
 /// Extract a string literal from the macro expanded version of `expr`,
 /// emitting `err_msg` if `expr` is not a string literal. This does not stop
 /// compilation on error, merely emits a non-fatal error and returns None.
-pub fn expr_to_spanned_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
-                              -> Option<Spanned<(Symbol, ast::StrStyle)>> {
+pub fn expr_to_spanned_string<'a>(
+    cx: &'a mut ExtCtxt,
+    expr: P<ast::Expr>,
+    err_msg: &str,
+) -> Result<Spanned<(Symbol, ast::StrStyle)>, DiagnosticBuilder<'a>> {
     // Update `expr.span`'s ctxt now in case expr is an `include!` macro invocation.
     let expr = expr.map(|mut expr| {
         expr.span = expr.span.apply_mark(cx.current_expansion.mark);
         expr
     });
 
-    // we want to be able to handle e.g. concat("foo", "bar")
+    // we want to be able to handle e.g. `concat!("foo", "bar")`
     let expr = cx.expander().fold_expr(expr);
-    match expr.node {
+    Err(match expr.node {
         ast::ExprKind::Lit(ref l) => match l.node {
-            ast::LitKind::Str(s, style) => return Some(respan(expr.span, (s, style))),
-            _ => cx.span_err(l.span, err_msg)
+            ast::LitKind::Str(s, style) => return Ok(respan(expr.span, (s, style))),
+            _ => cx.struct_span_err(l.span, err_msg)
         },
-        _ => cx.span_err(expr.span, err_msg)
-    }
-    None
+        _ => cx.struct_span_err(expr.span, err_msg)
+    })
 }
 
 pub fn expr_to_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
                       -> Option<(Symbol, ast::StrStyle)> {
-    expr_to_spanned_string(cx, expr, err_msg).map(|s| s.node)
+    expr_to_spanned_string(cx, expr, err_msg)
+        .map_err(|mut err| err.emit())
+        .ok()
+        .map(|s| s.node)
 }
 
 /// Non-fatally assert that `tts` is empty. Note that this function
diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index 69b4a83764e46..d58f4ce17e2f7 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -27,6 +27,7 @@ pub fn expand_syntax_ext(
         None => return base::DummyResult::expr(sp),
     };
     let mut accumulator = String::new();
+    let mut missing_literal = vec![];
     for e in es {
         match e.node {
             ast::ExprKind::Lit(ref lit) => match lit.node {
@@ -51,17 +52,15 @@ pub fn expand_syntax_ext(
                 }
             },
             _ => {
-                let mut err = cx.struct_span_err(e.span, "expected a literal");
-                let snippet = cx.codemap().span_to_snippet(e.span).unwrap();
-                err.span_suggestion(
-                    e.span,
-                    "you might be missing a string literal to format with",
-                    format!("\"{{}}\", {}", snippet),
-                );
-                err.emit();
+                missing_literal.push(e.span);
             }
         }
     }
+    if missing_literal.len() > 0 {
+        let mut err = cx.struct_span_err(missing_literal, "expected a literal");
+        err.note("only `&str` literals can be passed to `concat!()`");
+        err.emit();
+    }
     let sp = sp.apply_mark(cx.current_expansion.mark);
     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
 }
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 8587d11b22786..6abf987d0ab70 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -703,10 +703,24 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
     let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
     let mut macsp = ecx.call_site();
     macsp = macsp.apply_mark(ecx.current_expansion.mark);
-    let msg = "format argument must be a string literal.";
+    let msg = "format argument must be a string literal";
+    let fmt_sp = efmt.span;
     let fmt = match expr_to_spanned_string(ecx, efmt, msg) {
-        Some(fmt) => fmt,
-        None => return DummyResult::raw_expr(sp),
+        Ok(fmt) => fmt,
+        Err(mut err) => {
+            let sugg_fmt = match args.len() {
+                0 => "{}".to_string(),
+                _ => format!("{}{{}}", "{}, ".repeat(args.len())),
+
+            };
+            err.span_suggestion(
+                fmt_sp.shrink_to_lo(),
+                "you might be missing a string literal to format with",
+                format!("\"{}\", ", sugg_fmt),
+            );
+            err.emit();
+            return DummyResult::raw_expr(sp);
+        },
     };
 
     let mut cx = Context {
@@ -818,7 +832,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
                     errs.iter().map(|&(sp, _)| sp).collect::<Vec<Span>>(),
                     "multiple unused formatting arguments"
                 );
-                diag.span_label(cx.fmtsp, "multiple unused arguments in this statement");
+                diag.span_label(cx.fmtsp, "multiple missing formatting arguments");
                 diag
             }
         };
@@ -861,8 +875,10 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
                     }
 
                     if show_doc_note {
-                        diag.note(concat!(stringify!($kind), " formatting not supported; see \
-                                the documentation for `std::fmt`"));
+                        diag.note(concat!(
+                            stringify!($kind),
+                            " formatting not supported; see the documentation for `std::fmt`",
+                        ));
                     }
                 }};
             }
diff --git a/src/test/ui/const-eval/conditional_array_execution.nll.stderr b/src/test/ui/const-eval/conditional_array_execution.nll.stderr
index 8bc302a2befa4..3f82311d469ae 100644
--- a/src/test/ui/const-eval/conditional_array_execution.nll.stderr
+++ b/src/test/ui/const-eval/conditional_array_execution.nll.stderr
@@ -28,25 +28,19 @@ LL |     println!("{}", FOO);
    |                    ^^^ referenced constant has errors
 
 error[E0080]: referenced constant has errors
-  --> $DIR/conditional_array_execution.rs:19:5
+  --> $DIR/conditional_array_execution.rs:19:14
    |
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    |                   ----- attempt to subtract with overflow
 ...
 LL |     println!("{}", FOO);
-   |     ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^
 
 error[E0080]: erroneous constant used
-  --> $DIR/conditional_array_execution.rs:19:5
+  --> $DIR/conditional_array_execution.rs:19:14
    |
 LL |     println!("{}", FOO);
-   |     ^^^^^^^^^^^^^^^---^^
-   |                    |
-   |                    referenced constant has errors
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^  --- referenced constant has errors
 
 error[E0080]: referenced constant has errors
   --> $DIR/conditional_array_execution.rs:19:20
diff --git a/src/test/ui/const-eval/issue-43197.nll.stderr b/src/test/ui/const-eval/issue-43197.nll.stderr
index 5819e6a9254a7..e25cb29c11475 100644
--- a/src/test/ui/const-eval/issue-43197.nll.stderr
+++ b/src/test/ui/const-eval/issue-43197.nll.stderr
@@ -51,25 +51,19 @@ LL |     println!("{} {}", X, Y);
    |                          ^ referenced constant has errors
 
 error[E0080]: referenced constant has errors
-  --> $DIR/issue-43197.rs:24:5
+  --> $DIR/issue-43197.rs:24:14
    |
 LL |     const X: u32 = 0-1;
    |                    --- attempt to subtract with overflow
 ...
 LL |     println!("{} {}", X, Y);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^^^^
 
 error[E0080]: erroneous constant used
-  --> $DIR/issue-43197.rs:24:5
+  --> $DIR/issue-43197.rs:24:14
    |
 LL |     println!("{} {}", X, Y);
-   |     ^^^^^^^^^^^^^^^^^^-^^^^^
-   |                       |
-   |                       referenced constant has errors
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^^^^  - referenced constant has errors
 
 error[E0080]: referenced constant has errors
   --> $DIR/issue-43197.rs:24:26
diff --git a/src/test/ui/const-eval/issue-44578.nll.stderr b/src/test/ui/const-eval/issue-44578.nll.stderr
index eeb152e00ea47..da040747991a4 100644
--- a/src/test/ui/const-eval/issue-44578.nll.stderr
+++ b/src/test/ui/const-eval/issue-44578.nll.stderr
@@ -1,23 +1,17 @@
 error[E0080]: referenced constant has errors
-  --> $DIR/issue-44578.rs:35:5
+  --> $DIR/issue-44578.rs:35:14
    |
 LL |     const AMT: usize = [A::AMT][(A::AMT > B::AMT) as usize];
    |                        ------------------------------------ index out of bounds: the len is 1 but the index is 1
 ...
 LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^
 
 error[E0080]: erroneous constant used
-  --> $DIR/issue-44578.rs:35:5
+  --> $DIR/issue-44578.rs:35:14
    |
 LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT);
-   |     ^^^^^^^^^^^^^^^--------------------------^^
-   |                    |
-   |                    referenced constant has errors
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ^^^^  -------------------------- referenced constant has errors
 
 error[E0080]: referenced constant has errors
   --> $DIR/issue-44578.rs:35:20
diff --git a/src/test/ui/fmt/format-string-error.rs b/src/test/ui/fmt/format-string-error.rs
index 5b13686240e7c..e48aa489f4359 100644
--- a/src/test/ui/fmt/format-string-error.rs
+++ b/src/test/ui/fmt/format-string-error.rs
@@ -10,8 +10,10 @@
 
 fn main() {
     println!("{");
+    //~^ ERROR invalid format string: expected `'}'` but string was terminated
     println!("{{}}");
     println!("}");
+    //~^ ERROR invalid format string: unmatched `}` found
     let _ = format!("{_foo}", _foo = 6usize);
     //~^ ERROR invalid format string: invalid argument name `_foo`
     let _ = format!("{_}", _ = 6usize);
diff --git a/src/test/ui/fmt/format-string-error.stderr b/src/test/ui/fmt/format-string-error.stderr
index ff766ddc8fa67..4c7ef11b29ef0 100644
--- a/src/test/ui/fmt/format-string-error.stderr
+++ b/src/test/ui/fmt/format-string-error.stderr
@@ -1,23 +1,21 @@
 error: invalid format string: expected `'}'` but string was terminated
-  --> $DIR/format-string-error.rs:12:5
+  --> $DIR/format-string-error.rs:12:16
    |
 LL |     println!("{");
-   |     ^^^^^^^^^^^^^^ expected `'}'` in format string
+   |                ^ expected `'}'` in format string
    |
    = note: if you intended to print `{`, you can escape it using `{{`
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: invalid format string: unmatched `}` found
-  --> $DIR/format-string-error.rs:14:5
+  --> $DIR/format-string-error.rs:15:15
    |
 LL |     println!("}");
-   |     ^^^^^^^^^^^^^^ unmatched `}` in format string
+   |               ^ unmatched `}` in format string
    |
    = note: if you intended to print `}`, you can escape it using `}}`
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: invalid format string: invalid argument name `_foo`
-  --> $DIR/format-string-error.rs:15:23
+  --> $DIR/format-string-error.rs:17:23
    |
 LL |     let _ = format!("{_foo}", _foo = 6usize);
    |                       ^^^^ invalid argument name in format string
@@ -25,7 +23,7 @@ LL |     let _ = format!("{_foo}", _foo = 6usize);
    = note: argument names cannot start with an underscore
 
 error: invalid format string: invalid argument name `_`
-  --> $DIR/format-string-error.rs:17:23
+  --> $DIR/format-string-error.rs:19:23
    |
 LL |     let _ = format!("{_}", _ = 6usize);
    |                       ^ invalid argument name in format string
@@ -33,7 +31,7 @@ LL |     let _ = format!("{_}", _ = 6usize);
    = note: argument names cannot start with an underscore
 
 error: invalid format string: expected `'}'` but string was terminated
-  --> $DIR/format-string-error.rs:19:23
+  --> $DIR/format-string-error.rs:21:23
    |
 LL |     let _ = format!("{");
    |                       ^ expected `'}'` in format string
@@ -41,7 +39,7 @@ LL |     let _ = format!("{");
    = note: if you intended to print `{`, you can escape it using `{{`
 
 error: invalid format string: unmatched `}` found
-  --> $DIR/format-string-error.rs:21:22
+  --> $DIR/format-string-error.rs:23:22
    |
 LL |     let _ = format!("}");
    |                      ^ unmatched `}` in format string
@@ -49,7 +47,7 @@ LL |     let _ = format!("}");
    = note: if you intended to print `}`, you can escape it using `}}`
 
 error: invalid format string: expected `'}'`, found `'/'`
-  --> $DIR/format-string-error.rs:23:23
+  --> $DIR/format-string-error.rs:25:23
    |
 LL |     let _ = format!("{/}");
    |                       ^ expected `}` in format string
diff --git a/src/test/ui/macros/bad_hello.rs b/src/test/ui/macros/bad_hello.rs
index 174dcc9b6cd3f..cccaf7998c98b 100644
--- a/src/test/ui/macros/bad_hello.rs
+++ b/src/test/ui/macros/bad_hello.rs
@@ -9,5 +9,8 @@
 // except according to those terms.
 
 fn main() {
-    println!(3 + 4); //~ ERROR expected a literal
+    println!(3 + 4);
+    //~^ ERROR format argument must be a string literal
+    println!(3, 4);
+    //~^ ERROR format argument must be a string literal
 }
diff --git a/src/test/ui/macros/bad_hello.stderr b/src/test/ui/macros/bad_hello.stderr
index 0bfb060f84416..87ea515182f15 100644
--- a/src/test/ui/macros/bad_hello.stderr
+++ b/src/test/ui/macros/bad_hello.stderr
@@ -1,12 +1,22 @@
-error: expected a literal
+error: format argument must be a string literal
   --> $DIR/bad_hello.rs:12:14
    |
-LL |     println!(3 + 4); //~ ERROR expected a literal
+LL |     println!(3 + 4);
    |              ^^^^^
 help: you might be missing a string literal to format with
    |
-LL |     println!("{}", 3 + 4); //~ ERROR expected a literal
-   |              ^^^^^^^^^^^
+LL |     println!("{}", 3 + 4);
+   |              ^^^^^
+
+error: format argument must be a string literal
+  --> $DIR/bad_hello.rs:14:14
+   |
+LL |     println!(3, 4);
+   |              ^
+help: you might be missing a string literal to format with
+   |
+LL |     println!("{}, {}", 3, 4);
+   |              ^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/macros/format-foreign.stderr b/src/test/ui/macros/format-foreign.stderr
index 6804ce95fa873..401b2f6d67e39 100644
--- a/src/test/ui/macros/format-foreign.stderr
+++ b/src/test/ui/macros/format-foreign.stderr
@@ -2,12 +2,13 @@ error: multiple unused formatting arguments
   --> $DIR/format-foreign.rs:12:30
    |
 LL |     println!("%.*3$s %s!/n", "Hello,", "World", 4); //~ ERROR multiple unused formatting arguments
-   |     -------------------------^^^^^^^^--^^^^^^^--^-- multiple unused arguments in this statement
+   |              --------------  ^^^^^^^^  ^^^^^^^  ^
+   |              |
+   |              multiple missing formatting arguments
    |
    = help: `%.*3$s` should be written as `{:.2$}`
    = help: `%s` should be written as `{}`
    = note: printf formatting not supported; see the documentation for `std::fmt`
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: argument never used
   --> $DIR/format-foreign.rs:13:29
diff --git a/src/test/ui/macros/format-unused-lables.stderr b/src/test/ui/macros/format-unused-lables.stderr
index 777b492dcb65f..f764190438f33 100644
--- a/src/test/ui/macros/format-unused-lables.stderr
+++ b/src/test/ui/macros/format-unused-lables.stderr
@@ -2,24 +2,21 @@ error: multiple unused formatting arguments
   --> $DIR/format-unused-lables.rs:12:22
    |
 LL |     println!("Test", 123, 456, 789);
-   |     -----------------^^^--^^^--^^^-- multiple unused arguments in this statement
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+   |              ------  ^^^  ^^^  ^^^
+   |              |
+   |              multiple missing formatting arguments
 
 error: multiple unused formatting arguments
   --> $DIR/format-unused-lables.rs:16:9
    |
-LL | /     println!("Test2",
-LL | |         123,  //~ ERROR multiple unused formatting arguments
-   | |         ^^^
-LL | |         456,
-   | |         ^^^
-LL | |         789
-   | |         ^^^
-LL | |     );
-   | |______- multiple unused arguments in this statement
-   |
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+LL |     println!("Test2",
+   |              ------- multiple missing formatting arguments
+LL |         123,  //~ ERROR multiple unused formatting arguments
+   |         ^^^
+LL |         456,
+   |         ^^^
+LL |         789
+   |         ^^^
 
 error: named argument never used
   --> $DIR/format-unused-lables.rs:21:35
@@ -30,18 +27,18 @@ LL |     println!("Some stuff", UNUSED="args"); //~ ERROR named argument never u
 error: multiple unused formatting arguments
   --> $DIR/format-unused-lables.rs:24:9
    |
-LL | /     println!("Some more $STUFF",
-LL | |         "woo!",  //~ ERROR multiple unused formatting arguments
-   | |         ^^^^^^
-LL | |             STUFF=
-LL | |        "things"
-   | |        ^^^^^^^^
-LL | |              , UNUSED="args");
-   | |_______________________^^^^^^_- multiple unused arguments in this statement
+LL |     println!("Some more $STUFF",
+   |              ------------------ multiple missing formatting arguments
+LL |         "woo!",  //~ ERROR multiple unused formatting arguments
+   |         ^^^^^^
+LL |             STUFF=
+LL |        "things"
+   |        ^^^^^^^^
+LL |              , UNUSED="args");
+   |                       ^^^^^^
    |
    = help: `$STUFF` should be written as `{STUFF}`
    = note: shell formatting not supported; see the documentation for `std::fmt`
-   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/macros/trace-macro.stderr b/src/test/ui/macros/trace-macro.stderr
index 938f876872f2f..c98e42ea647d0 100644
--- a/src/test/ui/macros/trace-macro.stderr
+++ b/src/test/ui/macros/trace-macro.stderr
@@ -5,8 +5,9 @@ LL |     println!("Hello, World!");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: expanding `println! { "Hello, World!" }`
-   = note: to `print ! ( concat ! ( "Hello, World!" , "/n" ) )`
-   = note: expanding `print! { concat ! ( "Hello, World!" , "/n" ) }`
-   = note: to `$crate :: io :: _print ( format_args ! ( concat ! ( "Hello, World!" , "/n" ) )
-           )`
+   = note: to `{ print ! ( "Hello, World!" ) ; print ! ( "/n" ) ; }`
+   = note: expanding `print! { "Hello, World!" }`
+   = note: to `$crate :: io :: _print ( format_args ! ( "Hello, World!" ) )`
+   = note: expanding `print! { "/n" }`
+   = note: to `$crate :: io :: _print ( format_args ! ( "/n" ) )`
 

From fbce952193d38328c39262cf2fb7f7bfbe088a70 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 15 Jul 2018 11:52:11 -0700
Subject: [PATCH 02/19] review comments: modify note wording and change
 `println`

- Don't print the newline on its own to avoid the possibility of
  printing it out of order due to `stdout` locking.
- Modify wording of `concat!()` with non-literals to not mislead into
  believing that only `&str` literals are accepted.
- Add test for `concat!()` with non-literals.
---
 src/libstd/macros.rs                  |  9 +--------
 src/libsyntax_ext/concat.rs           |  2 +-
 src/test/ui/macros/bad-concat.rs      | 18 ++++++++++++++++++
 src/test/ui/macros/bad-concat.stderr  | 10 ++++++++++
 src/test/ui/macros/trace-macro.stderr |  9 ++++-----
 5 files changed, 34 insertions(+), 14 deletions(-)
 create mode 100644 src/test/ui/macros/bad-concat.rs
 create mode 100644 src/test/ui/macros/bad-concat.stderr

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index a4a6ed73c61cf..7f3c8fcdd5aa9 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -155,14 +155,7 @@ macro_rules! print {
 #[stable(feature = "rust1", since = "1.0.0")]
 macro_rules! println {
     () => (print!("\n"));
-    ($fmt:expr) => ({
-        print!($fmt);
-        print!("\n");
-    });
-    ($fmt:expr, $($arg:tt)*) => ({
-        print!($fmt, $($arg)*);
-        print!("\n");
-    });
+    ($($arg:tt)*) => (print!("{}\n", format_args!($($arg)*)));
 }
 
 /// Macro for printing to the standard error.
diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index d58f4ce17e2f7..99dba8af754fa 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -58,7 +58,7 @@ pub fn expand_syntax_ext(
     }
     if missing_literal.len() > 0 {
         let mut err = cx.struct_span_err(missing_literal, "expected a literal");
-        err.note("only `&str` literals can be passed to `concat!()`");
+        err.note("only literals (like `\"foo\"`, `42` and `3.14`) can be passed to `concat!()`");
         err.emit();
     }
     let sp = sp.apply_mark(cx.current_expansion.mark);
diff --git a/src/test/ui/macros/bad-concat.rs b/src/test/ui/macros/bad-concat.rs
new file mode 100644
index 0000000000000..e7adee8ce8597
--- /dev/null
+++ b/src/test/ui/macros/bad-concat.rs
@@ -0,0 +1,18 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    let x: u32 = 42;
+    let y: f64 = 3.14;
+    let z = "foo";
+    let _ = concat!(x, y, z, "bar");
+    //~^ ERROR expected a literal
+    //~| NOTE only literals
+}
diff --git a/src/test/ui/macros/bad-concat.stderr b/src/test/ui/macros/bad-concat.stderr
new file mode 100644
index 0000000000000..b97e4f268241c
--- /dev/null
+++ b/src/test/ui/macros/bad-concat.stderr
@@ -0,0 +1,10 @@
+error: expected a literal
+  --> $DIR/bad-concat.rs:15:21
+   |
+LL |     let _ = concat!(x, y, z, "bar");
+   |                     ^  ^  ^
+   |
+   = note: only literals (like `"foo"`, `42` and `3.14`) can be passed to `concat!()`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/macros/trace-macro.stderr b/src/test/ui/macros/trace-macro.stderr
index c98e42ea647d0..6d8a329be8048 100644
--- a/src/test/ui/macros/trace-macro.stderr
+++ b/src/test/ui/macros/trace-macro.stderr
@@ -5,9 +5,8 @@ LL |     println!("Hello, World!");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: expanding `println! { "Hello, World!" }`
-   = note: to `{ print ! ( "Hello, World!" ) ; print ! ( "/n" ) ; }`
-   = note: expanding `print! { "Hello, World!" }`
-   = note: to `$crate :: io :: _print ( format_args ! ( "Hello, World!" ) )`
-   = note: expanding `print! { "/n" }`
-   = note: to `$crate :: io :: _print ( format_args ! ( "/n" ) )`
+   = note: to `print ! ( "{}/n" , format_args ! ( "Hello, World!" ) )`
+   = note: expanding `print! { "{}/n" , format_args ! ( "Hello, World!" ) }`
+   = note: to `$crate :: io :: _print (
+           format_args ! ( "{}/n" , format_args ! ( "Hello, World!" ) ) )`
 

From e613bfb7015744c25ce838b64bf8db31acff49f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 15 Jul 2018 12:28:42 -0700
Subject: [PATCH 03/19] Same change as `println` for `eprintln`

---
 src/libstd/macros.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 7f3c8fcdd5aa9..527bab759b04b 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -211,8 +211,7 @@ macro_rules! eprint {
 #[stable(feature = "eprint", since = "1.19.0")]
 macro_rules! eprintln {
     () => (eprint!("\n"));
-    ($fmt:expr) => (eprint!(concat!($fmt, "\n")));
-    ($fmt:expr, $($arg:tt)*) => (eprint!(concat!($fmt, "\n"), $($arg)*));
+    ($($arg:tt)*) => (eprint!("{}\n", format_args!($($arg)*)));
 }
 
 #[macro_export]

From a47653214f8f8561196acf25b8898e7148f1c052 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 15 Jul 2018 14:36:19 -0700
Subject: [PATCH 04/19] Fix hir tree test

---
 src/test/run-make-fulldeps/hir-tree/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/run-make-fulldeps/hir-tree/Makefile b/src/test/run-make-fulldeps/hir-tree/Makefile
index 2e100b269e14b..483d68fd64656 100644
--- a/src/test/run-make-fulldeps/hir-tree/Makefile
+++ b/src/test/run-make-fulldeps/hir-tree/Makefile
@@ -5,4 +5,4 @@
 
 all:
 	$(RUSTC) -o $(TMPDIR)/input.hir -Z unpretty=hir-tree input.rs
-	$(CGREP) '"Hello, Rustaceans!\n"' < $(TMPDIR)/input.hir
+	$(CGREP) '"Hello, Rustaceans!"' < $(TMPDIR)/input.hir

From 154dee2dccd45f929b0a3d2ce2d45739513f77c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Thu, 19 Jul 2018 18:53:26 -0700
Subject: [PATCH 05/19] rework println

---
 src/libfmt_macros/lib.rs              |  6 +++++-
 src/libstd/macros.rs                  | 26 ++++++++++++++++++++++++--
 src/libsyntax_ext/format.rs           | 22 ++++++++++++++++++++--
 src/libsyntax_ext/lib.rs              | 10 ++++++++++
 src/test/ui/macros/trace-macro.stderr |  8 ++++----
 5 files changed, 63 insertions(+), 9 deletions(-)

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 51c3efb41ad97..ee590bc3b5ecf 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -273,7 +273,11 @@ impl<'a> Parser<'a> {
             }
         } else {
             let msg = format!("expected `{:?}` but string was terminated", c);
-            let pos = self.input.len() + 1; // point at closing `"`
+            // point at closing `"`, unless the last char is `\n` to account for `println`
+            let pos = match self.input.chars().last() {
+                Some('\n') => self.input.len(),
+                _ => self.input.len() + 1,
+            };
             if c == '}' {
                 self.err_with_note(msg,
                                    format!("expected `{:?}`", c),
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 527bab759b04b..a4bcf7fd26c5c 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -153,9 +153,17 @@ macro_rules! print {
 /// ```
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[allow_internal_unstable]
 macro_rules! println {
     () => (print!("\n"));
-    ($($arg:tt)*) => (print!("{}\n", format_args!($($arg)*)));
+    ($($arg:tt)*) => ({
+        #[cfg(not(stage0))] {
+            ($crate::io::_print(format_args_nl!($($arg)*)));
+        }
+        #[cfg(stage0)] {
+            print!("{}\n", format_args!($($arg)*))
+        }
+    })
 }
 
 /// Macro for printing to the standard error.
@@ -211,7 +219,8 @@ macro_rules! eprint {
 #[stable(feature = "eprint", since = "1.19.0")]
 macro_rules! eprintln {
     () => (eprint!("\n"));
-    ($($arg:tt)*) => (eprint!("{}\n", format_args!($($arg)*)));
+    ($fmt:expr) => (eprint!(concat!($fmt, "\n")));
+    ($fmt:expr, $($arg:tt)*) => (eprint!(concat!($fmt, "\n"), $($arg)*));
 }
 
 #[macro_export]
@@ -397,6 +406,19 @@ pub mod builtin {
         ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ });
     }
 
+    /// Internal version of [`format_args`].
+    ///
+    /// This macro differs from [`format_args`] in that it appends a newline to the format string
+    /// and nothing more. It is perma-unstable.
+    ///
+    /// [`format_args`]: ../std/macro.format_args.html
+    #[doc(hidden)]
+    #[unstable(feature = "println_format_args", issue="0")]
+    #[macro_export]
+    macro_rules! format_args_nl {
+        ($fmt:expr) => ({ /* compiler built-in */ });
+        ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ });
+    }
     /// Inspect an environment variable at compile time.
     ///
     /// This macro will expand to the value of the named environment variable at
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 6abf987d0ab70..d3e5adf683505 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 bdf7a8d704042..ff76e788b3c29 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);
diff --git a/src/test/ui/macros/trace-macro.stderr b/src/test/ui/macros/trace-macro.stderr
index 6d8a329be8048..2a30d9837517e 100644
--- a/src/test/ui/macros/trace-macro.stderr
+++ b/src/test/ui/macros/trace-macro.stderr
@@ -5,8 +5,8 @@ LL |     println!("Hello, World!");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: expanding `println! { "Hello, World!" }`
-   = note: to `print ! ( "{}/n" , format_args ! ( "Hello, World!" ) )`
-   = note: expanding `print! { "{}/n" , format_args ! ( "Hello, World!" ) }`
-   = note: to `$crate :: io :: _print (
-           format_args ! ( "{}/n" , format_args ! ( "Hello, World!" ) ) )`
+   = note: to `{
+           # [ cfg ( not ( stage0 ) ) ] {
+           ( $crate :: io :: _print ( format_args_nl ! ( "Hello, World!" ) ) ) ; } # [
+           cfg ( stage0 ) ] { print ! ( "{}/n" , format_args ! ( "Hello, World!" ) ) } }`
 

From f4306ffbfcb2280f180e51ce6421e1c6c28dccec Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Thu, 19 Jul 2018 23:14:00 -0700
Subject: [PATCH 06/19] Use correct spans for format string errors
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When encountering format string errors in a raw string, or regular
string literal with embedded newlines, account for the positional
change to use correct spans.

:drive by fix: 🚗
---
 src/Cargo.lock                             |  3 ++
 src/libfmt_macros/Cargo.toml               |  3 ++
 src/libfmt_macros/lib.rs                   | 40 ++++++++++++----
 src/librustc/traits/on_unimplemented.rs    |  6 +--
 src/libsyntax_ext/format.rs                |  2 +-
 src/test/ui/fmt/format-string-error.rs     | 34 +++++++++++++
 src/test/ui/fmt/format-string-error.stderr | 56 ++++++++++++++++++----
 7 files changed, 123 insertions(+), 21 deletions(-)

diff --git a/src/Cargo.lock b/src/Cargo.lock
index 8299dea1c4b0e..c59c110849577 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -715,6 +715,9 @@ dependencies = [
 [[package]]
 name = "fmt_macros"
 version = "0.0.0"
+dependencies = [
+ "syntax 0.0.0",
+]
 
 [[package]]
 name = "fnv"
diff --git a/src/libfmt_macros/Cargo.toml b/src/libfmt_macros/Cargo.toml
index b3f4d2deae2fc..6e6af9c2ff5e7 100644
--- a/src/libfmt_macros/Cargo.toml
+++ b/src/libfmt_macros/Cargo.toml
@@ -7,3 +7,6 @@ version = "0.0.0"
 name = "fmt_macros"
 path = "lib.rs"
 crate-type = ["dylib"]
+
+[dependencies]
+syntax = { path = "../libsyntax" }
diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index ee590bc3b5ecf..54cf3d24173f7 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -28,6 +28,8 @@ pub use self::Alignment::*;
 pub use self::Flag::*;
 pub use self::Count::*;
 
+extern crate syntax;
+
 use std::str;
 use std::string;
 use std::iter;
@@ -150,18 +152,27 @@ pub struct Parser<'a> {
     pub errors: Vec<ParseError>,
     /// Current position of implicit positional argument pointer
     curarg: usize,
+    /// The style of the string (raw or not), used to position spans correctly
+    style: syntax::ast::StrStyle,
+    /// How many newlines have been seen in the string so far, to adjust the error spans
+    seen_newlines: usize,
 }
 
 impl<'a> Iterator for Parser<'a> {
     type Item = Piece<'a>;
 
     fn next(&mut self) -> Option<Piece<'a>> {
+        let raw = match self.style {
+            syntax::ast::StrStyle::Raw(raw) => raw as usize + self.seen_newlines,
+            _ => 0,
+        };
         if let Some(&(pos, c)) = self.cur.peek() {
             match c {
                 '{' => {
+                    let pos = pos + raw + 1;
                     self.cur.next();
                     if self.consume('{') {
-                        Some(String(self.string(pos + 1)))
+                        Some(String(self.string(pos)))
                     } else {
                         let ret = Some(NextArgument(self.argument()));
                         self.must_consume('}');
@@ -169,8 +180,8 @@ impl<'a> Iterator for Parser<'a> {
                     }
                 }
                 '}' => {
+                    let pos = pos + raw + 1;
                     self.cur.next();
-                    let pos = pos + 1;
                     if self.consume('}') {
                         Some(String(self.string(pos)))
                     } else {
@@ -184,6 +195,10 @@ impl<'a> Iterator for Parser<'a> {
                         None
                     }
                 }
+                '\n' => {
+                    self.seen_newlines += 1;
+                    Some(String(self.string(pos)))
+                }
                 _ => Some(String(self.string(pos))),
             }
         } else {
@@ -194,12 +209,14 @@ impl<'a> Iterator for Parser<'a> {
 
 impl<'a> Parser<'a> {
     /// Creates a new parser for the given format string
-    pub fn new(s: &'a str) -> Parser<'a> {
+    pub fn new(s: &'a str, style: syntax::ast::StrStyle) -> Parser<'a> {
         Parser {
             input: s,
             cur: s.char_indices().peekable(),
             errors: vec![],
             curarg: 0,
+            style,
+            seen_newlines: 0,
         }
     }
 
@@ -262,14 +279,19 @@ impl<'a> Parser<'a> {
     /// found, an error is emitted.
     fn must_consume(&mut self, c: char) {
         self.ws();
+        let raw = match self.style {
+            syntax::ast::StrStyle::Raw(raw) => raw as usize,
+            _ => 0,
+        };
+        let padding = raw + self.seen_newlines;
         if let Some(&(pos, maybe)) = self.cur.peek() {
             if c == maybe {
                 self.cur.next();
             } else {
                 self.err(format!("expected `{:?}`, found `{:?}`", c, maybe),
                          format!("expected `{}`", c),
-                         pos + 1,
-                         pos + 1);
+                         pos + padding + 1,
+                         pos + padding + 1);
             }
         } else {
             let msg = format!("expected `{:?}` but string was terminated", c);
@@ -282,8 +304,8 @@ impl<'a> Parser<'a> {
                 self.err_with_note(msg,
                                    format!("expected `{:?}`", c),
                                    "if you intended to print `{`, you can escape it using `{{`",
-                                   pos,
-                                   pos);
+                                   pos + padding,
+                                   pos + padding);
             } else {
                 self.err(msg, format!("expected `{:?}`", c), pos, pos);
             }
@@ -540,7 +562,7 @@ mod tests {
     use super::*;
 
     fn same(fmt: &'static str, p: &[Piece<'static>]) {
-        let parser = Parser::new(fmt);
+        let parser = Parser::new(fmt, syntax::ast::StrStyle::Cooked);
         assert!(parser.collect::<Vec<Piece<'static>>>() == p);
     }
 
@@ -556,7 +578,7 @@ mod tests {
     }
 
     fn musterr(s: &str) {
-        let mut p = Parser::new(s);
+        let mut p = Parser::new(fmt, syntax::ast::StrStyle::Cooked);
         p.next();
         assert!(!p.errors.is_empty());
     }
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
index 0550cf7c6d2c0..33d5502eba000 100644
--- a/src/librustc/traits/on_unimplemented.rs
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -15,7 +15,7 @@ use ty::{self, TyCtxt, GenericParamDefKind};
 use util::common::ErrorReported;
 use util::nodemap::FxHashMap;
 
-use syntax::ast::{MetaItem, NestedMetaItem};
+use syntax::ast::{self, MetaItem, NestedMetaItem};
 use syntax::attr;
 use syntax_pos::Span;
 use syntax_pos::symbol::LocalInternedString;
@@ -242,7 +242,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
     {
         let name = tcx.item_name(trait_def_id);
         let generics = tcx.generics_of(trait_def_id);
-        let parser = Parser::new(&self.0);
+        let parser = Parser::new(&self.0, ast::StrStyle::Cooked);
         let mut result = Ok(());
         for token in parser {
             match token {
@@ -298,7 +298,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
             Some((name, value))
         }).collect::<FxHashMap<String, String>>();
 
-        let parser = Parser::new(&self.0);
+        let parser = Parser::new(&self.0, ast::StrStyle::Cooked);
         parser.map(|p| {
             match p {
                 Piece::String(s) => s,
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index d3e5adf683505..7acfb08020fd9 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -763,7 +763,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
     };
 
     let fmt_str = &*fmt.node.0.as_str();
-    let mut parser = parse::Parser::new(fmt_str);
+    let mut parser = parse::Parser::new(fmt_str, fmt.node.1);
     let mut pieces = vec![];
 
     while let Some(mut piece) = parser.next() {
diff --git a/src/test/ui/fmt/format-string-error.rs b/src/test/ui/fmt/format-string-error.rs
index e48aa489f4359..f39110ebc5dcc 100644
--- a/src/test/ui/fmt/format-string-error.rs
+++ b/src/test/ui/fmt/format-string-error.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-tidy-tab
+
 fn main() {
     println!("{");
     //~^ ERROR invalid format string: expected `'}'` but string was terminated
@@ -24,4 +26,36 @@ fn main() {
     //~^ ERROR invalid format string: unmatched `}` found
     let _ = format!("{\\}");
     //~^ ERROR invalid format string: expected `'}'`, found `'\\'`
+    let _ = format!("\n\n\n{\n\n\n");
+    //~^ ERROR invalid format string
+    let _ = format!(r###"
+
+
+
+	{"###);
+    //~^ ERROR invalid format string
+    let _ = format!(r###"
+
+
+
+	{
+
+"###);
+    //~^^ ERROR invalid format string
+    let _ = format!(r###"
+
+
+
+	}
+
+"###);
+    //~^^^ ERROR invalid format string
+    let _ = format!(r###"
+
+
+
+        }
+
+"###);
+    //~^^^ ERROR invalid format string: unmatched `}` found
 }
diff --git a/src/test/ui/fmt/format-string-error.stderr b/src/test/ui/fmt/format-string-error.stderr
index 4c7ef11b29ef0..9c84fd2521891 100644
--- a/src/test/ui/fmt/format-string-error.stderr
+++ b/src/test/ui/fmt/format-string-error.stderr
@@ -1,5 +1,5 @@
 error: invalid format string: expected `'}'` but string was terminated
-  --> $DIR/format-string-error.rs:12:16
+  --> $DIR/format-string-error.rs:14:16
    |
 LL |     println!("{");
    |                ^ expected `'}'` in format string
@@ -7,7 +7,7 @@ LL |     println!("{");
    = note: if you intended to print `{`, you can escape it using `{{`
 
 error: invalid format string: unmatched `}` found
-  --> $DIR/format-string-error.rs:15:15
+  --> $DIR/format-string-error.rs:17:15
    |
 LL |     println!("}");
    |               ^ unmatched `}` in format string
@@ -15,7 +15,7 @@ LL |     println!("}");
    = note: if you intended to print `}`, you can escape it using `}}`
 
 error: invalid format string: invalid argument name `_foo`
-  --> $DIR/format-string-error.rs:17:23
+  --> $DIR/format-string-error.rs:19:23
    |
 LL |     let _ = format!("{_foo}", _foo = 6usize);
    |                       ^^^^ invalid argument name in format string
@@ -23,7 +23,7 @@ LL |     let _ = format!("{_foo}", _foo = 6usize);
    = note: argument names cannot start with an underscore
 
 error: invalid format string: invalid argument name `_`
-  --> $DIR/format-string-error.rs:19:23
+  --> $DIR/format-string-error.rs:21:23
    |
 LL |     let _ = format!("{_}", _ = 6usize);
    |                       ^ invalid argument name in format string
@@ -31,7 +31,7 @@ LL |     let _ = format!("{_}", _ = 6usize);
    = note: argument names cannot start with an underscore
 
 error: invalid format string: expected `'}'` but string was terminated
-  --> $DIR/format-string-error.rs:21:23
+  --> $DIR/format-string-error.rs:23:23
    |
 LL |     let _ = format!("{");
    |                       ^ expected `'}'` in format string
@@ -39,7 +39,7 @@ LL |     let _ = format!("{");
    = note: if you intended to print `{`, you can escape it using `{{`
 
 error: invalid format string: unmatched `}` found
-  --> $DIR/format-string-error.rs:23:22
+  --> $DIR/format-string-error.rs:25:22
    |
 LL |     let _ = format!("}");
    |                      ^ unmatched `}` in format string
@@ -47,10 +47,50 @@ LL |     let _ = format!("}");
    = note: if you intended to print `}`, you can escape it using `}}`
 
 error: invalid format string: expected `'}'`, found `'/'`
-  --> $DIR/format-string-error.rs:25:23
+  --> $DIR/format-string-error.rs:27:23
    |
 LL |     let _ = format!("{/}");
    |                       ^ expected `}` in format string
 
-error: aborting due to 7 previous errors
+error: invalid format string: expected `'}'` but string was terminated
+  --> $DIR/format-string-error.rs:29:29
+   |
+LL |     let _ = format!("/n/n/n{/n/n/n");
+   |                             ^ expected `'}'` in format string
+   |
+   = note: if you intended to print `{`, you can escape it using `{{`
+
+error: invalid format string: expected `'}'` but string was terminated
+  --> $DIR/format-string-error.rs:35:3
+   |
+LL |     {"###);
+   |      ^ expected `'}'` in format string
+   |
+   = note: if you intended to print `{`, you can escape it using `{{`
+
+error: invalid format string: expected `'}'` but string was terminated
+  --> $DIR/format-string-error.rs:42:1
+   |
+LL | 
+   | ^ expected `'}'` in format string
+   |
+   = note: if you intended to print `{`, you can escape it using `{{`
+
+error: invalid format string: unmatched `}` found
+  --> $DIR/format-string-error.rs:49:2
+   |
+LL |     }
+   |     ^ unmatched `}` in format string
+   |
+   = note: if you intended to print `}`, you can escape it using `}}`
+
+error: invalid format string: unmatched `}` found
+  --> $DIR/format-string-error.rs:57:9
+   |
+LL |         }
+   |         ^ unmatched `}` in format string
+   |
+   = note: if you intended to print `}`, you can escape it using `}}`
+
+error: aborting due to 12 previous errors
 

From 85da68cb6d5e0fa69da4ae2c64ed56ce3622f73d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Thu, 19 Jul 2018 23:19:13 -0700
Subject: [PATCH 07/19] Rebase and fix text changed by master

---
 src/test/ui/issue-11692-1.stderr | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/test/ui/issue-11692-1.stderr b/src/test/ui/issue-11692-1.stderr
index daf53af3ace99..bee73e9f568b6 100644
--- a/src/test/ui/issue-11692-1.stderr
+++ b/src/test/ui/issue-11692-1.stderr
@@ -1,8 +1,12 @@
-error: format argument must be a string literal.
+error: format argument must be a string literal
   --> $DIR/issue-11692-1.rs:12:12
    |
 LL |     print!(test!());
    |            ^^^^^^^
+help: you might be missing a string literal to format with
+   |
+LL |     print!("{}", test!());
+   |            ^^^^^
 
 error: aborting due to previous error
 

From 052159be5349338f872b676c6593ee74cc1d5eb8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Fri, 20 Jul 2018 09:15:22 -0700
Subject: [PATCH 08/19] fix incorrect position of chars in fmt str

---
 src/libfmt_macros/lib.rs | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 54cf3d24173f7..6f4989c3e87d8 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -169,10 +169,9 @@ impl<'a> Iterator for Parser<'a> {
         if let Some(&(pos, c)) = self.cur.peek() {
             match c {
                 '{' => {
-                    let pos = pos + raw + 1;
                     self.cur.next();
                     if self.consume('{') {
-                        Some(String(self.string(pos)))
+                        Some(String(self.string(pos + 1)))
                     } else {
                         let ret = Some(NextArgument(self.argument()));
                         self.must_consume('}');
@@ -180,17 +179,17 @@ impl<'a> Iterator for Parser<'a> {
                     }
                 }
                 '}' => {
-                    let pos = pos + raw + 1;
                     self.cur.next();
                     if self.consume('}') {
-                        Some(String(self.string(pos)))
+                        Some(String(self.string(pos + 1)))
                     } else {
+                        let err_pos = pos + raw + 1;
                         self.err_with_note(
                             "unmatched `}` found",
                             "unmatched `}`",
                             "if you intended to print `}`, you can escape it using `}}`",
-                            pos,
-                            pos,
+                            err_pos,
+                            err_pos,
                         );
                         None
                     }
@@ -283,15 +282,17 @@ impl<'a> Parser<'a> {
             syntax::ast::StrStyle::Raw(raw) => raw as usize,
             _ => 0,
         };
+
         let padding = raw + self.seen_newlines;
         if let Some(&(pos, maybe)) = self.cur.peek() {
             if c == maybe {
                 self.cur.next();
             } else {
+                let pos = pos + padding + 1;
                 self.err(format!("expected `{:?}`, found `{:?}`", c, maybe),
                          format!("expected `{}`", c),
-                         pos + padding + 1,
-                         pos + padding + 1);
+                         pos,
+                         pos);
             }
         } else {
             let msg = format!("expected `{:?}` but string was terminated", c);

From 9112e1a4cdbc549ef58d496ff02f146c85857717 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Fri, 20 Jul 2018 11:04:23 -0700
Subject: [PATCH 09/19] fix rebase

---
 src/libfmt_macros/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 6f4989c3e87d8..52223b2343ca8 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -579,7 +579,7 @@ mod tests {
     }
 
     fn musterr(s: &str) {
-        let mut p = Parser::new(fmt, syntax::ast::StrStyle::Cooked);
+        let mut p = Parser::new(s, syntax::ast::StrStyle::Cooked);
         p.next();
         assert!(!p.errors.is_empty());
     }

From 8b59fbc951dabc714ff882674db01e58d44db98b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Fri, 20 Jul 2018 13:43:06 -0700
Subject: [PATCH 10/19] fix grep test looking for newline

---
 src/test/run-make-fulldeps/hir-tree/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/test/run-make-fulldeps/hir-tree/Makefile b/src/test/run-make-fulldeps/hir-tree/Makefile
index 483d68fd64656..2e100b269e14b 100644
--- a/src/test/run-make-fulldeps/hir-tree/Makefile
+++ b/src/test/run-make-fulldeps/hir-tree/Makefile
@@ -5,4 +5,4 @@
 
 all:
 	$(RUSTC) -o $(TMPDIR)/input.hir -Z unpretty=hir-tree input.rs
-	$(CGREP) '"Hello, Rustaceans!"' < $(TMPDIR)/input.hir
+	$(CGREP) '"Hello, Rustaceans!\n"' < $(TMPDIR)/input.hir

From 83a8af50bbf704b5cdf2cbbab481e0e936ed03a8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 12:16:06 -0700
Subject: [PATCH 11/19] Suggest space separated format str literal

---
 src/libsyntax_ext/format.rs         | 2 +-
 src/test/ui/macros/bad_hello.stderr | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 7acfb08020fd9..9f153c36733b3 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -728,7 +728,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
         Err(mut err) => {
             let sugg_fmt = match args.len() {
                 0 => "{}".to_string(),
-                _ => format!("{}{{}}", "{}, ".repeat(args.len())),
+                _ => format!("{}{{}}", "{} ".repeat(args.len())),
 
             };
             err.span_suggestion(
diff --git a/src/test/ui/macros/bad_hello.stderr b/src/test/ui/macros/bad_hello.stderr
index 87ea515182f15..c675eede2152b 100644
--- a/src/test/ui/macros/bad_hello.stderr
+++ b/src/test/ui/macros/bad_hello.stderr
@@ -15,8 +15,8 @@ LL |     println!(3, 4);
    |              ^
 help: you might be missing a string literal to format with
    |
-LL |     println!("{}, {}", 3, 4);
-   |              ^^^^^^^^^
+LL |     println!("{} {}", 3, 4);
+   |              ^^^^^^^^
 
 error: aborting due to 2 previous errors
 

From 00d500052c72775ab994b5634195976f85b4e0d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 15:50:46 -0700
Subject: [PATCH 12/19] Gate `format_args_nll` behind feature flag

---
 src/libstd/macros.rs          |  2 +-
 src/libsyntax/ext/expand.rs   |  1 +
 src/libsyntax/feature_gate.rs |  4 ++++
 src/libsyntax_ext/format.rs   | 15 +++++++++++++++
 4 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index a4bcf7fd26c5c..49de9f8027164 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -413,7 +413,7 @@ pub mod builtin {
     ///
     /// [`format_args`]: ../std/macro.format_args.html
     #[doc(hidden)]
-    #[unstable(feature = "println_format_args", issue="0")]
+    #[unstable(feature = "format_args_nl", issue="0")]
     #[macro_export]
     macro_rules! format_args_nl {
         ($fmt:expr) => ({ /* compiler built-in */ });
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 1241e230b26d6..4d1ca50a89375 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -1592,6 +1592,7 @@ impl<'feat> ExpansionConfig<'feat> {
         fn enable_trace_macros = trace_macros,
         fn enable_allow_internal_unstable = allow_internal_unstable,
         fn enable_custom_derive = custom_derive,
+        fn enable_format_args_nl = format_args_nl,
         fn use_extern_macros_enabled = use_extern_macros,
         fn macros_in_extern_enabled = macros_in_extern,
         fn proc_macro_mod = proc_macro_mod,
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 0f200479fe282..5b5453d5502ab 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -129,6 +129,7 @@ declare_features! (
     // rustc internal, for now:
     (active, intrinsics, "1.0.0", None, None),
     (active, lang_items, "1.0.0", None, None),
+    (active, format_args_nl, "1.29.0", None, None),
 
     (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
     (active, linkage, "1.0.0", Some(29603), None),
@@ -1327,6 +1328,9 @@ pub const EXPLAIN_LOG_SYNTAX: &'static str =
 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
     "`concat_idents` is not stable enough for use and is subject to change";
 
+pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
+    "`format_args_nl` is only for internal language use and is subject to change";
+
 pub const EXPLAIN_TRACE_MACROS: &'static str =
     "`trace_macros` is not stable enough for use and is subject to change";
 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 9f153c36733b3..5b8f059fd141b 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -17,6 +17,7 @@ use syntax::ast;
 use syntax::ext::base::*;
 use syntax::ext::base;
 use syntax::ext::build::AstBuilder;
+use syntax::feature_gate;
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax::symbol::Symbol;
@@ -693,6 +694,20 @@ pub fn expand_format_args_nl<'cx>(ecx: &'cx mut ExtCtxt,
                                   mut sp: Span,
                                   tts: &[tokenstream::TokenTree])
                                   -> Box<dyn base::MacResult + 'cx> {
+    //if !ecx.ecfg.enable_allow_internal_unstable() {
+
+    // For some reason, the only one that actually works for `println` is the first check
+    if !sp.allows_unstable()   // the enclosing span is marked as `#[allow_insternal_unsable]`
+        || !ecx.ecfg.enable_allow_internal_unstable()  // NOTE: when is this enabled?
+        || !ecx.ecfg.enable_format_args_nl()  // enabled using `#[feature(format_args_nl]`
+    {
+        feature_gate::emit_feature_err(&ecx.parse_sess,
+                                       "format_args_nl",
+                                       sp,
+                                       feature_gate::GateIssue::Language,
+                                       feature_gate::EXPLAIN_FORMAT_ARGS_NL);
+        return base::DummyResult::expr(sp);
+    }
     sp = sp.apply_mark(ecx.current_expansion.mark);
     match parse_args(ecx, sp, tts) {
         Some((efmt, args, names)) => {

From a7a68370a72cc553c8ca983fe593062235360b9b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 15:56:37 -0700
Subject: [PATCH 13/19] Change `eprintln!()`

Address #30143 as well. `writeln!()` hasn't been changed.
---
 src/libstd/macros.rs | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 49de9f8027164..f06b8f621f263 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -217,10 +217,17 @@ macro_rules! eprint {
 /// ```
 #[macro_export]
 #[stable(feature = "eprint", since = "1.19.0")]
+#[allow_internal_unstable]
 macro_rules! eprintln {
     () => (eprint!("\n"));
-    ($fmt:expr) => (eprint!(concat!($fmt, "\n")));
-    ($fmt:expr, $($arg:tt)*) => (eprint!(concat!($fmt, "\n"), $($arg)*));
+    ($($arg:tt)*) => ({
+        #[cfg(not(stage0))] {
+            ($crate::io::_eprint(format_args_nl!($($arg)*)));
+        }
+        #[cfg(stage0)] {
+            eprint!("{}\n", format_args!($($arg)*))
+        }
+    })
 }
 
 #[macro_export]

From 93b2bb01a961fdb61a4aeaf6bc6bdcab9ccedbe2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 16:18:06 -0700
Subject: [PATCH 14/19] Remove dependency on `libsyntax`

---
 src/Cargo.lock                          |  3 ---
 src/libfmt_macros/Cargo.toml            |  3 ---
 src/libfmt_macros/lib.rs                | 18 +++++-------------
 src/librustc/traits/on_unimplemented.rs |  6 +++---
 src/libsyntax_ext/format.rs             |  6 +++++-
 5 files changed, 13 insertions(+), 23 deletions(-)

diff --git a/src/Cargo.lock b/src/Cargo.lock
index c59c110849577..8299dea1c4b0e 100644
--- a/src/Cargo.lock
+++ b/src/Cargo.lock
@@ -715,9 +715,6 @@ dependencies = [
 [[package]]
 name = "fmt_macros"
 version = "0.0.0"
-dependencies = [
- "syntax 0.0.0",
-]
 
 [[package]]
 name = "fnv"
diff --git a/src/libfmt_macros/Cargo.toml b/src/libfmt_macros/Cargo.toml
index 6e6af9c2ff5e7..b3f4d2deae2fc 100644
--- a/src/libfmt_macros/Cargo.toml
+++ b/src/libfmt_macros/Cargo.toml
@@ -7,6 +7,3 @@ version = "0.0.0"
 name = "fmt_macros"
 path = "lib.rs"
 crate-type = ["dylib"]
-
-[dependencies]
-syntax = { path = "../libsyntax" }
diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 52223b2343ca8..3d17ccec12161 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -28,8 +28,6 @@ pub use self::Alignment::*;
 pub use self::Flag::*;
 pub use self::Count::*;
 
-extern crate syntax;
-
 use std::str;
 use std::string;
 use std::iter;
@@ -152,8 +150,8 @@ pub struct Parser<'a> {
     pub errors: Vec<ParseError>,
     /// Current position of implicit positional argument pointer
     curarg: usize,
-    /// The style of the string (raw or not), used to position spans correctly
-    style: syntax::ast::StrStyle,
+    /// `Some(raw count)` when the string is "raw", used to position spans correctly
+    style: Option<usize>,
     /// How many newlines have been seen in the string so far, to adjust the error spans
     seen_newlines: usize,
 }
@@ -162,10 +160,7 @@ impl<'a> Iterator for Parser<'a> {
     type Item = Piece<'a>;
 
     fn next(&mut self) -> Option<Piece<'a>> {
-        let raw = match self.style {
-            syntax::ast::StrStyle::Raw(raw) => raw as usize + self.seen_newlines,
-            _ => 0,
-        };
+        let raw = self.style.map(|raw| raw + self.seen_newlines).unwrap_or(0);
         if let Some(&(pos, c)) = self.cur.peek() {
             match c {
                 '{' => {
@@ -208,7 +203,7 @@ impl<'a> Iterator for Parser<'a> {
 
 impl<'a> Parser<'a> {
     /// Creates a new parser for the given format string
-    pub fn new(s: &'a str, style: syntax::ast::StrStyle) -> Parser<'a> {
+    pub fn new(s: &'a str, style: Option<usize>) -> Parser<'a> {
         Parser {
             input: s,
             cur: s.char_indices().peekable(),
@@ -278,10 +273,7 @@ impl<'a> Parser<'a> {
     /// found, an error is emitted.
     fn must_consume(&mut self, c: char) {
         self.ws();
-        let raw = match self.style {
-            syntax::ast::StrStyle::Raw(raw) => raw as usize,
-            _ => 0,
-        };
+        let raw = self.style.unwrap_or(0);
 
         let padding = raw + self.seen_newlines;
         if let Some(&(pos, maybe)) = self.cur.peek() {
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
index 33d5502eba000..925d3504f75fc 100644
--- a/src/librustc/traits/on_unimplemented.rs
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -15,7 +15,7 @@ use ty::{self, TyCtxt, GenericParamDefKind};
 use util::common::ErrorReported;
 use util::nodemap::FxHashMap;
 
-use syntax::ast::{self, MetaItem, NestedMetaItem};
+use syntax::ast::{MetaItem, NestedMetaItem};
 use syntax::attr;
 use syntax_pos::Span;
 use syntax_pos::symbol::LocalInternedString;
@@ -242,7 +242,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
     {
         let name = tcx.item_name(trait_def_id);
         let generics = tcx.generics_of(trait_def_id);
-        let parser = Parser::new(&self.0, ast::StrStyle::Cooked);
+        let parser = Parser::new(&self.0, None);
         let mut result = Ok(());
         for token in parser {
             match token {
@@ -298,7 +298,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
             Some((name, value))
         }).collect::<FxHashMap<String, String>>();
 
-        let parser = Parser::new(&self.0, ast::StrStyle::Cooked);
+        let parser = Parser::new(&self.0, None);
         parser.map(|p| {
             match p {
                 Piece::String(s) => s,
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 5b8f059fd141b..c63cc3727eda0 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -778,7 +778,11 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
     };
 
     let fmt_str = &*fmt.node.0.as_str();
-    let mut parser = parse::Parser::new(fmt_str, fmt.node.1);
+    let str_style = match fmt.node.1 {
+        ast::StrStyle::Cooked => None,
+        ast::StrStyle::Raw(raw) => Some(raw as usize),
+    };
+    let mut parser = parse::Parser::new(fmt_str, str_style);
     let mut pieces = vec![];
 
     while let Some(mut piece) = parser.next() {

From 915ff0b9699c9cf39b5d80fc3aeb6c7e047dd280 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 17:17:49 -0700
Subject: [PATCH 15/19] fix logic bug

---
 src/libsyntax_ext/format.rs                | 4 ++--
 src/test/ui/feature-gate-format_args_nl.rs | 0
 2 files changed, 2 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/feature-gate-format_args_nl.rs

diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index c63cc3727eda0..755d2b476b716 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -698,8 +698,8 @@ pub fn expand_format_args_nl<'cx>(ecx: &'cx mut ExtCtxt,
 
     // For some reason, the only one that actually works for `println` is the first check
     if !sp.allows_unstable()   // the enclosing span is marked as `#[allow_insternal_unsable]`
-        || !ecx.ecfg.enable_allow_internal_unstable()  // NOTE: when is this enabled?
-        || !ecx.ecfg.enable_format_args_nl()  // enabled using `#[feature(format_args_nl]`
+        && !ecx.ecfg.enable_allow_internal_unstable()  // NOTE: when is this enabled?
+        && !ecx.ecfg.enable_format_args_nl()  // enabled using `#[feature(format_args_nl]`
     {
         feature_gate::emit_feature_err(&ecx.parse_sess,
                                        "format_args_nl",
diff --git a/src/test/ui/feature-gate-format_args_nl.rs b/src/test/ui/feature-gate-format_args_nl.rs
new file mode 100644
index 0000000000000..e69de29bb2d1d

From 118b0f9a02113fe7462ca5c94780912919dbce02 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 17:35:09 -0700
Subject: [PATCH 16/19] Fix tidy by adding new feature gate test

---
 src/test/ui/feature-gate-format_args_nl.rs     | 13 +++++++++++++
 src/test/ui/feature-gate-format_args_nl.stderr | 11 +++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 src/test/ui/feature-gate-format_args_nl.stderr

diff --git a/src/test/ui/feature-gate-format_args_nl.rs b/src/test/ui/feature-gate-format_args_nl.rs
index e69de29bb2d1d..b976d57f9c179 100644
--- a/src/test/ui/feature-gate-format_args_nl.rs
+++ b/src/test/ui/feature-gate-format_args_nl.rs
@@ -0,0 +1,13 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+fn main() {
+    format_args_nl!(""); //~ ERROR `format_args_nl` is only for internal language use
+}
diff --git a/src/test/ui/feature-gate-format_args_nl.stderr b/src/test/ui/feature-gate-format_args_nl.stderr
new file mode 100644
index 0000000000000..a79535641a627
--- /dev/null
+++ b/src/test/ui/feature-gate-format_args_nl.stderr
@@ -0,0 +1,11 @@
+error[E0658]: `format_args_nl` is only for internal language use and is subject to change
+  --> $DIR/feature-gate-format_args_nl.rs:12:5
+   |
+LL |     format_args_nl!(""); //~ ERROR `format_args_nl` is only for internal language use
+   |     ^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add #![feature(format_args_nl)] to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.

From 6aa17a3c687c3e78ba65953f88d763ab2b437384 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 17:59:17 -0700
Subject: [PATCH 17/19] Don't use the new `eprintln` for stage0 and stage1

I'm not entirely sure why (or if) this is needed.
---
 src/libstd/macros.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index f06b8f621f263..6309ca069fec1 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -221,10 +221,10 @@ macro_rules! eprint {
 macro_rules! eprintln {
     () => (eprint!("\n"));
     ($($arg:tt)*) => ({
-        #[cfg(not(stage0))] {
+        #[cfg(all(not(stage0), not(stage1)))] {
             ($crate::io::_eprint(format_args_nl!($($arg)*)));
         }
-        #[cfg(stage0)] {
+        #[cfg(any(stage0, stage1))] {
             eprint!("{}\n", format_args!($($arg)*))
         }
     })

From 3c817259e3ff08b673c74b48742d118a238befe6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 18:24:10 -0700
Subject: [PATCH 18/19] fix tidy ~ again

---
 src/libstd/macros.rs | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs
index 6309ca069fec1..76f38646308d8 100644
--- a/src/libstd/macros.rs
+++ b/src/libstd/macros.rs
@@ -413,19 +413,6 @@ pub mod builtin {
         ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ });
     }
 
-    /// Internal version of [`format_args`].
-    ///
-    /// This macro differs from [`format_args`] in that it appends a newline to the format string
-    /// and nothing more. It is perma-unstable.
-    ///
-    /// [`format_args`]: ../std/macro.format_args.html
-    #[doc(hidden)]
-    #[unstable(feature = "format_args_nl", issue="0")]
-    #[macro_export]
-    macro_rules! format_args_nl {
-        ($fmt:expr) => ({ /* compiler built-in */ });
-        ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ });
-    }
     /// Inspect an environment variable at compile time.
     ///
     /// This macro will expand to the value of the named environment variable at

From dc563d950017fedaa4690165d2d8b9b3e6cbd982 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@commure.com>
Date: Sat, 21 Jul 2018 20:48:15 -0700
Subject: [PATCH 19/19] fix test

---
 src/libfmt_macros/lib.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 3d17ccec12161..9952e5f64d6ab 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -555,7 +555,7 @@ mod tests {
     use super::*;
 
     fn same(fmt: &'static str, p: &[Piece<'static>]) {
-        let parser = Parser::new(fmt, syntax::ast::StrStyle::Cooked);
+        let parser = Parser::new(fmt, None);
         assert!(parser.collect::<Vec<Piece<'static>>>() == p);
     }
 
@@ -571,7 +571,7 @@ mod tests {
     }
 
     fn musterr(s: &str) {
-        let mut p = Parser::new(s, syntax::ast::StrStyle::Cooked);
+        let mut p = Parser::new(s, None);
         p.next();
         assert!(!p.errors.is_empty());
     }