diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs index 54a0192d2e8a5..2136cd27e4306 100644 --- a/src/librustc/middle/liveness.rs +++ b/src/librustc/middle/liveness.rs @@ -1657,11 +1657,15 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> { fn report_dead_assign(&self, hir_id: HirId, sp: Span, var: Variable, is_argument: bool) { if let Some(name) = self.should_warn(var) { if is_argument { - self.ir.tcx.lint_hir(lint::builtin::UNUSED_ASSIGNMENTS, hir_id, sp, - &format!("value passed to `{}` is never read", name)); + self.ir.tcx.struct_span_lint_hir(lint::builtin::UNUSED_ASSIGNMENTS, hir_id, sp, + &format!("value passed to `{}` is never read", name)) + .help("maybe it is overwritten before being read?") + .emit(); } else { - self.ir.tcx.lint_hir(lint::builtin::UNUSED_ASSIGNMENTS, hir_id, sp, - &format!("value assigned to `{}` is never read", name)); + self.ir.tcx.struct_span_lint_hir(lint::builtin::UNUSED_ASSIGNMENTS, hir_id, sp, + &format!("value assigned to `{}` is never read", name)) + .help("maybe it is overwritten before being read?") + .emit(); } } } diff --git a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr b/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr index a8b0e3e4250ea..6b9e1dc70573e 100644 --- a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr +++ b/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr @@ -55,6 +55,7 @@ note: lint level defined here LL | #![warn(unused)] // UI tests pass `-A unused` (#43896) | ^^^^^^ = note: #[warn(unused_assignments)] implied by #[warn(unused)] + = help: maybe it is overwritten before being read? warning: unused variable: `fire` --> $DIR/issue-47390-unused-variable-in-struct-pattern.rs:54:32 diff --git a/src/test/ui/liveness/liveness-dead.stderr b/src/test/ui/liveness/liveness-dead.stderr index 6709fee0abb72..6e43cccdccff2 100644 --- a/src/test/ui/liveness/liveness-dead.stderr +++ b/src/test/ui/liveness/liveness-dead.stderr @@ -9,24 +9,31 @@ note: lint level defined here | LL | #![deny(unused_assignments)] | ^^^^^^^^^^^^^^^^^^ + = help: maybe it is overwritten before being read? error: value assigned to `x` is never read --> $DIR/liveness-dead.rs:27:5 | LL | x = 4; //~ ERROR: value assigned to `x` is never read | ^ + | + = help: maybe it is overwritten before being read? error: value passed to `x` is never read --> $DIR/liveness-dead.rs:30:11 | LL | fn f4(mut x: i32) { //~ ERROR: value passed to `x` is never read | ^ + | + = help: maybe it is overwritten before being read? error: value assigned to `x` is never read --> $DIR/liveness-dead.rs:37:5 | LL | x = 4; //~ ERROR: value assigned to `x` is never read | ^ + | + = help: maybe it is overwritten before being read? error: aborting due to 4 previous errors diff --git a/src/test/ui/liveness/liveness-unused.stderr b/src/test/ui/liveness/liveness-unused.stderr index 2846f242fbe4c..35ccc79a19ac0 100644 --- a/src/test/ui/liveness/liveness-unused.stderr +++ b/src/test/ui/liveness/liveness-unused.stderr @@ -60,6 +60,7 @@ note: lint level defined here | LL | #![deny(unused_assignments)] | ^^^^^^^^^^^^^^^^^^ + = help: maybe it is overwritten before being read? error: variable `z` is assigned to, but never used --> $DIR/liveness-unused.rs:47:13 @@ -106,6 +107,8 @@ error: value assigned to `x` is never read | LL | x = 0; //~ ERROR value assigned to `x` is never read | ^ + | + = help: maybe it is overwritten before being read? error: aborting due to 13 previous errors