Improve messaging from PR feedback

Author: davidhewitt

src/librustc_builtin_macros/format.rs

@@ -507,8 +507,8 @@ impl<'a, 'b> Context<'a, 'b> {
                             .features
                             .map_or(false, |features| features.format_args_capture);
 
-                        // For the moment capturing variables from format strings expanded from
-                        // literals is disabled (see RFC #2795)
+                        // For the moment capturing variables from format strings expanded from macros is
+                        // disabled (see RFC #2795)
                         let can_capture = capture_feature_enabled && self.is_literal;
 
                         if can_capture {
@@ -541,15 +541,11 @@ impl<'a, 'b> Context<'a, 'b> {
                                      when the format string is expanded from a macro",
                                 );
                             } else if self.ecx.parse_sess().unstable_features.is_nightly_build() {
-                                err.note(&format!(
-                                    "did you intend to capture a variable `{}` from \
-                                     the surrounding scope?",
+                                err.help(&format!(
+                                    "if you intended to capture `{}` from the surrounding scope, add \
+                                     `#![feature(format_args_capture)]` to the crate attributes",
                                     name
                                 ));
-                                err.help(
-                                    "add `#![feature(format_args_capture)]` to the crate \
-                                     attributes to enable",
-                                );
                             }
 
                             err.emit();

src/test/ui/fmt/feature-gate-format-args-capture.stderr

@@ -4,17 +4,15 @@ error: there is no argument named `foo`
 LL |     format!("{foo}");
    |              ^^^^^
    |
-   = note: did you intend to capture a variable `foo` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: there is no argument named `foo`
   --> $DIR/feature-gate-format-args-capture.rs:5:13
    |
 LL |     panic!("{foo} {bar}", bar=1);
    |             ^^^^^
    |
-   = note: did you intend to capture a variable `foo` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: aborting due to 2 previous errors
 

src/test/ui/if/ifmt-bad-arg.stderr

@@ -64,26 +64,23 @@ error: there is no argument named `foo`
 LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
    |                 ^^^^^
    |
-   = note: did you intend to capture a variable `foo` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: there is no argument named `bar`
   --> $DIR/ifmt-bad-arg.rs:27:26
    |
 LL |     format!("{} {foo} {} {bar} {}", 1, 2, 3);
    |                          ^^^^^
    |
-   = note: did you intend to capture a variable `bar` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `bar` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: there is no argument named `foo`
   --> $DIR/ifmt-bad-arg.rs:31:14
    |
 LL |     format!("{foo}");
    |              ^^^^^
    |
-   = note: did you intend to capture a variable `foo` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: multiple unused formatting arguments
   --> $DIR/ifmt-bad-arg.rs:32:17
@@ -165,8 +162,7 @@ error: there is no argument named `valueb`
 LL |     format!("{valuea} {valueb}", valuea=5, valuec=7);
    |                       ^^^^^^^^
    |
-   = note: did you intend to capture a variable `valueb` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `valueb` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: named argument never used
   --> $DIR/ifmt-bad-arg.rs:45:51
@@ -218,8 +214,7 @@ error: there is no argument named `foo`
 LL |         {foo}
    |         ^^^^^
    |
-   = note: did you intend to capture a variable `foo` from the surrounding scope?
-   = help: add `#![feature(format_args_capture)]` to the crate attributes to enable
+   = help: if you intended to capture `foo` from the surrounding scope, add `#![feature(format_args_capture)]` to the crate attributes
 
 error: invalid format string: expected `'}'`, found `'t'`
   --> $DIR/ifmt-bad-arg.rs:75:1