Highlight redundant arguments instead of the whole format string

Author: francorbacho

compiler/rustc_builtin_macros/src/errors.rs

@@ -650,7 +650,7 @@ pub(crate) struct FormatPositionalMismatch {
 #[diag(builtin_macros_format_redundant_args)]
 pub(crate) struct FormatRedundantArgs {
     #[primary_span]
-    pub(crate) fmt_span: Span,
+    pub(crate) span: MultiSpan,
     pub(crate) n: usize,
 
     #[note]

compiler/rustc_builtin_macros/src/format.rs

@@ -619,7 +619,7 @@ fn report_missing_placeholders(
 
     if !placeholders.is_empty() {
         if let Some(mut new_diag) =
-            report_redundant_format_arguments(ecx, fmt_span, &args, used, placeholders)
+            report_redundant_format_arguments(ecx, &args, used, placeholders)
         {
             diag.cancel();
             new_diag.emit();
@@ -718,7 +718,6 @@ fn report_missing_placeholders(
 /// redundant due to implicit captures (e.g. `format!("{x}", x)`).
 fn report_redundant_format_arguments<'a>(
     ecx: &mut ExtCtxt<'a>,
-    fmt_span: Span,
     args: &FormatArguments,
     used: &[bool],
     placeholders: Vec<(Span, &str)>,
@@ -769,9 +768,9 @@ fn report_redundant_format_arguments<'a>(
         }
 
         return Some(ecx.create_err(errors::FormatRedundantArgs {
-            fmt_span,
-            note: multispan,
             n: args_spans.len(),
+            span: MultiSpan::from(args_spans),
+            note: multispan,
             sugg: errors::FormatRedundantArgsSugg { spans: suggestion_spans },
         }));
     }

tests/ui/did_you_mean/issue-105225.rs

@@ -1,5 +1,7 @@
 fn main() {
     let x = 0;
+    let y = 0;
+
     println!("{x}", x);
     //~^ ERROR: redundant argument
 
@@ -9,11 +11,9 @@ fn main() {
     println!("{} {x}", x, x);
     //~^ ERROR: redundant argument
 
-    let y = 0;
     println!("{x} {y}", x, y);
-    //~^ ERROR: redundant argument
+    //~^ ERROR: redundant arguments
 
-    let y = 0;
     println!("{} {} {x} {y} {}", x, x, x, y, y);
-    //~^ ERROR: redundant argument
+    //~^ ERROR: redundant arguments
 }

tests/ui/did_you_mean/issue-105225.stderr

@@ -1,47 +1,47 @@
 error: redundant argument
-  --> $DIR/issue-105225.rs:3:14
+  --> $DIR/issue-105225.rs:5:21
    |
 LL |     println!("{x}", x);
-   |              ^^^^^  - help: this can be removed
+   |                     ^ help: this can be removed
    |
 note: the formatting specifier is referencing the binding already
-  --> $DIR/issue-105225.rs:3:16
+  --> $DIR/issue-105225.rs:5:16
    |
 LL |     println!("{x}", x);
    |                ^
 
 error: redundant argument
-  --> $DIR/issue-105225.rs:6:14
+  --> $DIR/issue-105225.rs:8:27
    |
 LL |     println!("{x} {}", x, x);
-   |              ^^^^^^^^     - help: this can be removed
+   |                           ^ help: this can be removed
    |
 note: the formatting specifier is referencing the binding already
-  --> $DIR/issue-105225.rs:6:16
+  --> $DIR/issue-105225.rs:8:16
    |
 LL |     println!("{x} {}", x, x);
    |                ^
 
 error: redundant argument
-  --> $DIR/issue-105225.rs:9:14
+  --> $DIR/issue-105225.rs:11:27
    |
 LL |     println!("{} {x}", x, x);
-   |              ^^^^^^^^     - help: this can be removed
+   |                           ^ help: this can be removed
    |
 note: the formatting specifier is referencing the binding already
-  --> $DIR/issue-105225.rs:9:19
+  --> $DIR/issue-105225.rs:11:19
    |
 LL |     println!("{} {x}", x, x);
    |                   ^
 
 error: redundant arguments
-  --> $DIR/issue-105225.rs:13:14
+  --> $DIR/issue-105225.rs:14:25
    |
 LL |     println!("{x} {y}", x, y);
-   |              ^^^^^^^^^
+   |                         ^  ^
    |
 note: the formatting specifiers are referencing the bindings already
-  --> $DIR/issue-105225.rs:13:16
+  --> $DIR/issue-105225.rs:14:16
    |
 LL |     println!("{x} {y}", x, y);
    |                ^   ^
@@ -52,10 +52,10 @@ LL +     println!("{x} {y}", );
    |
 
 error: redundant arguments
-  --> $DIR/issue-105225.rs:17:14
+  --> $DIR/issue-105225.rs:17:43
    |
 LL |     println!("{} {} {x} {y} {}", x, x, x, y, y);
-   |              ^^^^^^^^^^^^^^^^^^
+   |                                           ^  ^
    |
 note: the formatting specifiers are referencing the bindings already
   --> $DIR/issue-105225.rs:17:26