Auto merge of #100966 - compiler-errors:revert-remove-deferred-sized-checks, r=pnkfelix

[rust.git] / compiler / rustc_lint / src / let_underscore.rs

diff --git a/compiler/rustc_lint/src/let_underscore.rs b/compiler/rustc_lint/src/let_underscore.rs
index 18661e8c5059c714dab92c3a87a0211c59e75302..7e885e6c51aad42261b5da1eeb11ee618712875c 100644 (file)
--- a/compiler/rustc_lint/src/let_underscore.rs
+++ b/compiler/rustc_lint/src/let_underscore.rs
@@ -1,7 +1,7 @@
 use crate::{LateContext, LateLintPass, LintContext};
-use rustc_errors::Applicability;
+use rustc_errors::{Applicability, LintDiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
-use rustc_middle::{lint::LintDiagnosticBuilder, ty};
+use rustc_middle::ty;
 use rustc_span::Symbol;
 
 declare_lint! {
@@ -119,7 +119,16 @@ fn check_local(&mut self, cx: &LateContext<'_>, local: &hir::Local<'_>) {
             };
 
             if is_sync_lock {
-                cx.struct_span_lint(LET_UNDERSCORE_LOCK, local.span, |lint| {
+                let mut span = MultiSpan::from_spans(vec![local.pat.span, init.span]);
+                span.push_span_label(
+                    local.pat.span,
+                    "this lock is not assigned to a binding and is immediately dropped".to_string(),
+                );
+                span.push_span_label(
+                    init.span,
+                    "this binding will immediately drop the value assigned to it".to_string(),
+                );
+                cx.struct_span_lint(LET_UNDERSCORE_LOCK, span, |lint| {
                     build_and_emit_lint(
                         lint,
                         local,
@@ -150,14 +159,14 @@ fn build_and_emit_lint(
     lint.build(msg)
         .span_suggestion_verbose(
             local.pat.span,
-            "consider binding to an unused variable",
+            "consider binding to an unused variable to avoid immediately dropping the value",
             "_unused",
             Applicability::MachineApplicable,
         )
         .multipart_suggestion(
-            "consider explicitly droping with `std::mem::drop`",
+            "consider immediately dropping the value",
             vec![
-                (init_span.shrink_to_lo(), "drop(".to_string()),
+                (local.span.until(init_span), "drop(".to_string()),
                 (init_span.shrink_to_hi(), ")".to_string()),
             ],
             Applicability::MachineApplicable,