Improve panic_fmt lint messages.

m-ou-se · estebank · m-ou-se · commit 9743f676843c · 2020-10-29T19:44:06.000+01:00
(From the PR feedback.)

Co-authored-by: Esteban Küber &lt;esteban@kuber.com.ar&gt;
diff --git a/compiler/rustc_lint/src/panic_fmt.rs b/compiler/rustc_lint/src/panic_fmt.rs
@@ -1,6 +1,6 @@
 use crate::{LateContext, LateLintPass, LintContext};
 use rustc_ast as ast;
-use rustc_errors::Applicability;
+use rustc_errors::{pluralize, Applicability};
 use rustc_hir as hir;
 use rustc_middle::ty;
 use rustc_parse_format::{ParseMode, Parser, Piece};
@@ -21,7 +21,7 @@ declare_lint! {
     ///
     /// `panic!("{}")` panics with the message `"{}"`, as a `panic!()` invocation
     /// with a single argument does not use `format_args!()`.
-    /// A future version of Rust will interpret this string as format string,
+    /// A future edition of Rust will interpret this string as format string,
     /// which would break this.
     PANIC_FMT,
     Warn,
@@ -97,11 +97,11 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                                 1 => "panic message contains an unused formatting placeholder",
                                 _ => "panic message contains unused formatting placeholders",
                             });
-                            l.note("this message is not used as a format string when given without arguments, but will be in a future Rust version");
+                            l.note("this message is not used as a format string when given without arguments, but will be in a future Rust edition");
                             if expn.call_site.contains(arg.span) {
                                 l.span_suggestion(
                                     arg.span.shrink_to_hi(),
-                                    "add the missing argument(s)",
+                                    &format!("add the missing argument{}", pluralize!(n_arguments)),
                                     ", ...".into(),
                                     Applicability::HasPlaceholders,
                                 );
@@ -131,7 +131,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                         };
                         cx.struct_span_lint(PANIC_FMT, brace_spans.unwrap_or(vec![expn.call_site]), |lint| {
                             let mut l = lint.build(msg);
-                            l.note("this message is not used as a format string, but will be in a future Rust version");
+                            l.note("this message is not used as a format string, but will be in a future Rust edition");
                             if expn.call_site.contains(arg.span) {
                                 l.span_suggestion(
                                     arg.span.shrink_to_lo(),
diff --git a/src/test/ui/panic-brace.stderr b/src/test/ui/panic-brace.stderr
@@ -5,7 +5,7 @@ LL |     panic!("here's a brace: {");
    |                             ^
    |
    = note: `#[warn(panic_fmt)]` on by default
-   = note: this message is not used as a format string, but will be in a future Rust version
+   = note: this message is not used as a format string, but will be in a future Rust edition
 help: add a "{}" format string to use the message literally
    |
 LL |     panic!("{}", "here's a brace: {");
@@ -17,7 +17,7 @@ warning: panic message contains a brace
 LL |     std::panic!("another one: }");
    |                               ^
    |
-   = note: this message is not used as a format string, but will be in a future Rust version
+   = note: this message is not used as a format string, but will be in a future Rust edition
 help: add a "{}" format string to use the message literally
    |
 LL |     std::panic!("{}", "another one: }");
@@ -29,8 +29,8 @@ warning: panic message contains an unused formatting placeholder
 LL |     core::panic!("Hello {}");
    |                         ^^
    |
-   = note: this message is not used as a format string when given without arguments, but will be in a future Rust version
-help: add the missing argument(s)
+   = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition
+help: add the missing argument
    |
 LL |     core::panic!("Hello {}", ...);
    |                            ^^^^^
@@ -45,8 +45,8 @@ warning: panic message contains unused formatting placeholders
 LL |     assert!(false, "{:03x} {test} bla");
    |                     ^^^^^^ ^^^^^^
    |
-   = note: this message is not used as a format string when given without arguments, but will be in a future Rust version
-help: add the missing argument(s)
+   = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition
+help: add the missing arguments
    |
 LL |     assert!(false, "{:03x} {test} bla", ...);
    |                                       ^^^^^
@@ -61,7 +61,7 @@ warning: panic message contains braces
 LL |     debug_assert!(false, "{{}} bla");
    |                           ^^^^
    |
-   = note: this message is not used as a format string, but will be in a future Rust version
+   = note: this message is not used as a format string, but will be in a future Rust edition
 help: add a "{}" format string to use the message literally
    |
 LL |     debug_assert!(false, "{}", "{{}} bla");
@@ -73,8 +73,8 @@ warning: panic message contains an unused formatting placeholder
 LL |     panic!(concat!("{", "}"));
    |            ^^^^^^^^^^^^^^^^^
    |
-   = note: this message is not used as a format string when given without arguments, but will be in a future Rust version
-help: add the missing argument(s)
+   = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition
+help: add the missing argument
    |
 LL |     panic!(concat!("{", "}"), ...);
    |                             ^^^^^
@@ -89,7 +89,7 @@ warning: panic message contains braces
 LL |     panic!(concat!("{", "{"));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: this message is not used as a format string, but will be in a future Rust version
+   = note: this message is not used as a format string, but will be in a future Rust edition
 help: add a "{}" format string to use the message literally
    |
 LL |     panic!("{}", concat!("{", "{"));

Original file line number	Diff line number	Diff line change
`@@ -5,7 +5,7 @@ LL \| panic!("here's a brace: {");`
`5`	`5`	`\| ^`
`6`	`6`	`\|`
`7`	`7`	= note: `#[warn(panic_fmt)]` on by default
`8`		`- = note: this message is not used as a format string, but will be in a future Rust version`
	`8`	`+ = note: this message is not used as a format string, but will be in a future Rust edition`
`9`	`9`	`help: add a "{}" format string to use the message literally`
`10`	`10`	`\|`
`11`	`11`	`LL \| panic!("{}", "here's a brace: {");`
`@@ -17,7 +17,7 @@ warning: panic message contains a brace`
`17`	`17`	`LL \| std::panic!("another one: }");`
`18`	`18`	`\| ^`
`19`	`19`	`\|`
`20`		`- = note: this message is not used as a format string, but will be in a future Rust version`
	`20`	`+ = note: this message is not used as a format string, but will be in a future Rust edition`
`21`	`21`	`help: add a "{}" format string to use the message literally`
`22`	`22`	`\|`
`23`	`23`	`LL \| std::panic!("{}", "another one: }");`
`@@ -29,8 +29,8 @@ warning: panic message contains an unused formatting placeholder`
`29`	`29`	`LL \| core::panic!("Hello {}");`
`30`	`30`	`\| ^^`
`31`	`31`	`\|`
`32`		`- = note: this message is not used as a format string when given without arguments, but will be in a future Rust version`
`33`		`-help: add the missing argument(s)`
	`32`	`+ = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition`
	`33`	`+help: add the missing argument`
`34`	`34`	`\|`
`35`	`35`	`LL \| core::panic!("Hello {}", ...);`
`36`	`36`	`\| ^^^^^`
`@@ -45,8 +45,8 @@ warning: panic message contains unused formatting placeholders`
`45`	`45`	`LL \| assert!(false, "{:03x} {test} bla");`
`46`	`46`	`\| ^^^^^^ ^^^^^^`
`47`	`47`	`\|`
`48`		`- = note: this message is not used as a format string when given without arguments, but will be in a future Rust version`
`49`		`-help: add the missing argument(s)`
	`48`	`+ = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition`
	`49`	`+help: add the missing arguments`
`50`	`50`	`\|`
`51`	`51`	`LL \| assert!(false, "{:03x} {test} bla", ...);`
`52`	`52`	`\| ^^^^^`
`@@ -61,7 +61,7 @@ warning: panic message contains braces`
`61`	`61`	`LL \| debug_assert!(false, "{{}} bla");`
`62`	`62`	`\| ^^^^`
`63`	`63`	`\|`
`64`		`- = note: this message is not used as a format string, but will be in a future Rust version`
	`64`	`+ = note: this message is not used as a format string, but will be in a future Rust edition`
`65`	`65`	`help: add a "{}" format string to use the message literally`
`66`	`66`	`\|`
`67`	`67`	`LL \| debug_assert!(false, "{}", "{{}} bla");`
`@@ -73,8 +73,8 @@ warning: panic message contains an unused formatting placeholder`
`73`	`73`	`LL \| panic!(concat!("{", "}"));`
`74`	`74`	`\| ^^^^^^^^^^^^^^^^^`
`75`	`75`	`\|`
`76`		`- = note: this message is not used as a format string when given without arguments, but will be in a future Rust version`
`77`		`-help: add the missing argument(s)`
	`76`	`+ = note: this message is not used as a format string when given without arguments, but will be in a future Rust edition`
	`77`	`+help: add the missing argument`
`78`	`78`	`\|`
`79`	`79`	`LL \| panic!(concat!("{", "}"), ...);`
`80`	`80`	`\| ^^^^^`
`@@ -89,7 +89,7 @@ warning: panic message contains braces`
`89`	`89`	`LL \| panic!(concat!("{", "{"));`
`90`	`90`	`\| ^^^^^^^^^^^^^^^^^^^^^^^^^^`
`91`	`91`	`\|`
`92`		`- = note: this message is not used as a format string, but will be in a future Rust version`
	`92`	`+ = note: this message is not used as a format string, but will be in a future Rust edition`
`93`	`93`	`help: add a "{}" format string to use the message literally`
`94`	`94`	`\|`
`95`	`95`	`LL \| panic!("{}", concat!("{", "{"));`