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.

10 files changed, 70 insertions, 76 deletions

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 8bc302a2bef..3f82311d469 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 5819e6a9254..e25cb29c114 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 eeb152e00ea..da040747991 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 5b13686240e..e48aa489f43 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 ff766ddc8fa..4c7ef11b29e 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 174dcc9b6cd..cccaf7998c9 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 0bfb060f844..87ea515182f 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 6804ce95fa8..401b2f6d67e 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 777b492dcb6..f764190438f 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 938f876872f..c98e42ea647 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" ) )`