84 files changed, 325 insertions, 143 deletions

diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index c431c048ca0..2b580452a60 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -161,7 +161,15 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
 
         if let Some(must_use_op) = must_use_op {
             cx.struct_span_lint(UNUSED_MUST_USE, expr.span, |lint| {
-                lint.build(&format!("unused {} that must be used", must_use_op)).emit()
+                let mut lint = lint.build(&format!("unused {} that must be used", must_use_op));
+                lint.span_label(expr.span, &format!("the {} produces a value", must_use_op));
+                lint.span_suggestion_verbose(
+                    expr.span.shrink_to_lo(),
+                    "use `let _ = ...` to ignore the resulting value",
+                    "let _ = ".to_string(),
+                    Applicability::MachineApplicable,
+                );
+                lint.emit();
             });
             op_warned = true;
         }
diff --git a/src/test/ui/lint/fn_must_use.stderr b/src/test/ui/lint/fn_must_use.stderr
index d6b1cf3ae1f..6a5fdac4d91 100644
--- a/src/test/ui/lint/fn_must_use.stderr
+++ b/src/test/ui/lint/fn_must_use.stderr
@@ -47,13 +47,23 @@ warning: unused comparison that must be used
   --> $DIR/fn_must_use.rs:74:5
    |
 LL |     2 == 3;
-   |     ^^^^^^
+   |     ^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 2 == 3;
+   |     ^^^^^^^
 
 warning: unused comparison that must be used
   --> $DIR/fn_must_use.rs:75:5
    |
 LL |     m == n;
-   |     ^^^^^^
+   |     ^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = m == n;
+   |     ^^^^^^^
 
 warning: 8 warnings emitted
 
diff --git a/src/test/ui/lint/must-use-ops.stderr b/src/test/ui/lint/must-use-ops.stderr
deleted file mode 100644
index 3fb80f7e798..00000000000
--- a/src/test/ui/lint/must-use-ops.stderr
+++ /dev/null
@@ -1,134 +0,0 @@
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:12:5
-   |
-LL |     val == 1;
-   |     ^^^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/must-use-ops.rs:5:9
-   |
-LL | #![warn(unused_must_use)]
-   |         ^^^^^^^^^^^^^^^
-
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:13:5
-   |
-LL |     val < 1;
-   |     ^^^^^^^
-
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:14:5
-   |
-LL |     val <= 1;
-   |     ^^^^^^^^
-
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:15:5
-   |
-LL |     val != 1;
-   |     ^^^^^^^^
-
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:16:5
-   |
-LL |     val >= 1;
-   |     ^^^^^^^^
-
-warning: unused comparison that must be used
-  --> $DIR/must-use-ops.rs:17:5
-   |
-LL |     val > 1;
-   |     ^^^^^^^
-
-warning: unused arithmetic operation that must be used
-  --> $DIR/must-use-ops.rs:20:5
-   |
-LL |     val + 2;
-   |     ^^^^^^^
-
-warning: unused arithmetic operation that must be used
-  --> $DIR/must-use-ops.rs:21:5
-   |
-LL |     val - 2;
-   |     ^^^^^^^
-
-warning: unused arithmetic operation that must be used
-  --> $DIR/must-use-ops.rs:22:5
-   |
-LL |     val / 2;
-   |     ^^^^^^^
-
-warning: unused arithmetic operation that must be used
-  --> $DIR/must-use-ops.rs:23:5
-   |
-LL |     val * 2;
-   |     ^^^^^^^
-
-warning: unused arithmetic operation that must be used
-  --> $DIR/must-use-ops.rs:24:5
-   |
-LL |     val % 2;
-   |     ^^^^^^^
-
-warning: unused logical operation that must be used
-  --> $DIR/must-use-ops.rs:27:5
-   |
-LL |     true && true;
-   |     ^^^^^^^^^^^^
-
-warning: unused logical operation that must be used
-  --> $DIR/must-use-ops.rs:28:5
-   |
-LL |     false || true;
-   |     ^^^^^^^^^^^^^
-
-warning: unused bitwise operation that must be used
-  --> $DIR/must-use-ops.rs:31:5
-   |
-LL |     5 ^ val;
-   |     ^^^^^^^
-
-warning: unused bitwise operation that must be used
-  --> $DIR/must-use-ops.rs:32:5
-   |
-LL |     5 & val;
-   |     ^^^^^^^
-
-warning: unused bitwise operation that must be used
-  --> $DIR/must-use-ops.rs:33:5
-   |
-LL |     5 | val;
-   |     ^^^^^^^
-
-warning: unused bitwise operation that must be used
-  --> $DIR/must-use-ops.rs:34:5
-   |
-LL |     5 << val;
-   |     ^^^^^^^^
-
-warning: unused bitwise operation that must be used
-  --> $DIR/must-use-ops.rs:35:5
-   |
-LL |     5 >> val;
-   |     ^^^^^^^^
-
-warning: unused unary operation that must be used
-  --> $DIR/must-use-ops.rs:38:5
-   |
-LL |     !val;
-   |     ^^^^
-
-warning: unused unary operation that must be used
-  --> $DIR/must-use-ops.rs:39:5
-   |
-LL |     -val;
-   |     ^^^^
-
-warning: unused unary operation that must be used
-  --> $DIR/must-use-ops.rs:40:5
-   |
-LL |     *val_pointer;
-   |     ^^^^^^^^^^^^
-
-warning: 21 warnings emitted
-
diff --git a/src/test/ui/lint/unused-borrows.stderr b/src/test/ui/lint/unused-borrows.stderr
index 24899fe992b..e91e02df476 100644
--- a/src/test/ui/lint/unused-borrows.stderr
+++ b/src/test/ui/lint/unused-borrows.stderr
@@ -2,43 +2,72 @@ error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:6:5
    |
 LL |     &42;
-   |     ^^^
+   |     ^^^ the borrow produces a value
    |
 note: the lint level is defined here
   --> $DIR/unused-borrows.rs:1:9
    |
 LL | #![deny(unused_must_use)]
    |         ^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = &42;
+   |     ^^^^^^^
 
 error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:9:5
    |
 LL |     &mut foo(42);
-   |     ^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^ the borrow produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = &mut foo(42);
+   |     ^^^^^^^
 
 error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:12:5
    |
 LL |     &&42;
-   |     ^^^^
+   |     ^^^^ the borrow produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = &&42;
+   |     ^^^^^^^
 
 error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:15:5
    |
 LL |     &&mut 42;
-   |     ^^^^^^^^
+   |     ^^^^^^^^ the borrow produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = &&mut 42;
+   |     ^^^^^^^
 
 error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:18:5
    |
 LL |     &mut &42;
-   |     ^^^^^^^^
+   |     ^^^^^^^^ the borrow produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = &mut &42;
+   |     ^^^^^^^
 
 error: unused borrow that must be used
   --> $DIR/unused-borrows.rs:23:5
    |
 LL |     && foo(42);
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ the borrow produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = && foo(42);
+   |     ^^^^^^^
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/lint/auxiliary/lint_unused_extern_crate.rs b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate.rs
index b76b4321d62..b76b4321d62 100644
--- a/src/test/ui/lint/auxiliary/lint_unused_extern_crate.rs
+++ b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate.rs
diff --git a/src/test/ui/lint/auxiliary/lint_unused_extern_crate2.rs b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate2.rs
index b76b4321d62..b76b4321d62 100644
--- a/src/test/ui/lint/auxiliary/lint_unused_extern_crate2.rs
+++ b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate2.rs
diff --git a/src/test/ui/lint/auxiliary/lint_unused_extern_crate3.rs b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate3.rs
index b76b4321d62..b76b4321d62 100644
--- a/src/test/ui/lint/auxiliary/lint_unused_extern_crate3.rs
+++ b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate3.rs
diff --git a/src/test/ui/lint/auxiliary/lint_unused_extern_crate4.rs b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate4.rs
index d11c69f812a..d11c69f812a 100644
--- a/src/test/ui/lint/auxiliary/lint_unused_extern_crate4.rs
+++ b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate4.rs
diff --git a/src/test/ui/lint/auxiliary/lint_unused_extern_crate5.rs b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate5.rs
index d11c69f812a..d11c69f812a 100644
--- a/src/test/ui/lint/auxiliary/lint_unused_extern_crate5.rs
+++ b/src/test/ui/lint/unused/auxiliary/lint_unused_extern_crate5.rs
diff --git a/src/test/ui/unused/issue-30730.rs b/src/test/ui/lint/unused/issue-30730.rs
index d6be90c8148..d6be90c8148 100644
--- a/src/test/ui/unused/issue-30730.rs
+++ b/src/test/ui/lint/unused/issue-30730.rs
diff --git a/src/test/ui/unused/issue-30730.stderr b/src/test/ui/lint/unused/issue-30730.stderr
index b299e99a3a9..b299e99a3a9 100644
--- a/src/test/ui/unused/issue-30730.stderr
+++ b/src/test/ui/lint/unused/issue-30730.stderr
diff --git a/src/test/ui/unused/issue-46576.rs b/src/test/ui/lint/unused/issue-46576.rs
index 15f458f3844..15f458f3844 100644
--- a/src/test/ui/unused/issue-46576.rs
+++ b/src/test/ui/lint/unused/issue-46576.rs
diff --git a/src/test/ui/unused/issue-46576.stderr b/src/test/ui/lint/unused/issue-46576.stderr
index 6f4d97068b3..6f4d97068b3 100644
--- a/src/test/ui/unused/issue-46576.stderr
+++ b/src/test/ui/lint/unused/issue-46576.stderr
diff --git a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.rs b/src/test/ui/lint/unused/issue-47390-unused-variable-in-struct-pattern.rs
index 0ad014e3361..0ad014e3361 100644
--- a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.rs
+++ b/src/test/ui/lint/unused/issue-47390-unused-variable-in-struct-pattern.rs
diff --git a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr b/src/test/ui/lint/unused/issue-47390-unused-variable-in-struct-pattern.stderr
index 2ef655efdbd..2ef655efdbd 100644
--- a/src/test/ui/lint/issue-47390-unused-variable-in-struct-pattern.stderr
+++ b/src/test/ui/lint/unused/issue-47390-unused-variable-in-struct-pattern.stderr
diff --git a/src/test/ui/lint/issue-54180-unused-ref-field.fixed b/src/test/ui/lint/unused/issue-54180-unused-ref-field.fixed
index 1350b7ca699..1350b7ca699 100644
--- a/src/test/ui/lint/issue-54180-unused-ref-field.fixed
+++ b/src/test/ui/lint/unused/issue-54180-unused-ref-field.fixed
diff --git a/src/test/ui/lint/issue-54180-unused-ref-field.rs b/src/test/ui/lint/unused/issue-54180-unused-ref-field.rs
index 7b3392b609a..7b3392b609a 100644
--- a/src/test/ui/lint/issue-54180-unused-ref-field.rs
+++ b/src/test/ui/lint/unused/issue-54180-unused-ref-field.rs
diff --git a/src/test/ui/lint/issue-54180-unused-ref-field.stderr b/src/test/ui/lint/unused/issue-54180-unused-ref-field.stderr
index c501aa25f13..c501aa25f13 100644
--- a/src/test/ui/lint/issue-54180-unused-ref-field.stderr
+++ b/src/test/ui/lint/unused/issue-54180-unused-ref-field.stderr
diff --git a/src/test/ui/lint/issue-54538-unused-parens-lint.fixed b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.fixed
index 0b3fe9371f7..0b3fe9371f7 100644
--- a/src/test/ui/lint/issue-54538-unused-parens-lint.fixed
+++ b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.fixed
diff --git a/src/test/ui/lint/issue-54538-unused-parens-lint.rs b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.rs
index 1e78ec5f7d9..1e78ec5f7d9 100644
--- a/src/test/ui/lint/issue-54538-unused-parens-lint.rs
+++ b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.rs
diff --git a/src/test/ui/lint/issue-54538-unused-parens-lint.stderr b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.stderr
index e6d0a359c5c..e6d0a359c5c 100644
--- a/src/test/ui/lint/issue-54538-unused-parens-lint.stderr
+++ b/src/test/ui/lint/unused/issue-54538-unused-parens-lint.stderr
diff --git a/src/test/ui/unused/issue-59896.rs b/src/test/ui/lint/unused/issue-59896.rs
index ff9f19acf84..ff9f19acf84 100644
--- a/src/test/ui/unused/issue-59896.rs
+++ b/src/test/ui/lint/unused/issue-59896.rs
diff --git a/src/test/ui/unused/issue-59896.stderr b/src/test/ui/lint/unused/issue-59896.stderr
index 95b7938ae03..95b7938ae03 100644
--- a/src/test/ui/unused/issue-59896.stderr
+++ b/src/test/ui/lint/unused/issue-59896.stderr
diff --git a/src/test/ui/lint/issue-67691-unused-field-in-or-pattern.rs b/src/test/ui/lint/unused/issue-67691-unused-field-in-or-pattern.rs
index e3631d014d6..e3631d014d6 100644
--- a/src/test/ui/lint/issue-67691-unused-field-in-or-pattern.rs
+++ b/src/test/ui/lint/unused/issue-67691-unused-field-in-or-pattern.rs
diff --git a/src/test/ui/lint/issue-67691-unused-field-in-or-pattern.stderr b/src/test/ui/lint/unused/issue-67691-unused-field-in-or-pattern.stderr
index 8aefe243a94..8aefe243a94 100644
--- a/src/test/ui/lint/issue-67691-unused-field-in-or-pattern.stderr
+++ b/src/test/ui/lint/unused/issue-67691-unused-field-in-or-pattern.stderr
diff --git a/src/test/ui/unused/issue-70041.rs b/src/test/ui/lint/unused/issue-70041.rs
index 22e42295eed..22e42295eed 100644
--- a/src/test/ui/unused/issue-70041.rs
+++ b/src/test/ui/lint/unused/issue-70041.rs
diff --git a/src/test/ui/unused/issue-70041.stderr b/src/test/ui/lint/unused/issue-70041.stderr
index ecd618eae8b..ecd618eae8b 100644
--- a/src/test/ui/unused/issue-70041.stderr
+++ b/src/test/ui/lint/unused/issue-70041.stderr
diff --git a/src/test/ui/lint/issue-71290-unused-paren-binop.rs b/src/test/ui/lint/unused/issue-71290-unused-paren-binop.rs
index 24d77e36d94..24d77e36d94 100644
--- a/src/test/ui/lint/issue-71290-unused-paren-binop.rs
+++ b/src/test/ui/lint/unused/issue-71290-unused-paren-binop.rs
diff --git a/src/test/ui/lint/issue-74883-unused-paren-baren-yield.rs b/src/test/ui/lint/unused/issue-74883-unused-paren-baren-yield.rs
index 8064c3a88d1..8064c3a88d1 100644
--- a/src/test/ui/lint/issue-74883-unused-paren-baren-yield.rs
+++ b/src/test/ui/lint/unused/issue-74883-unused-paren-baren-yield.rs
diff --git a/src/test/ui/lint/issue-74883-unused-paren-baren-yield.stderr b/src/test/ui/lint/unused/issue-74883-unused-paren-baren-yield.stderr
index 3f6260dc6e1..3f6260dc6e1 100644
--- a/src/test/ui/lint/issue-74883-unused-paren-baren-yield.stderr
+++ b/src/test/ui/lint/unused/issue-74883-unused-paren-baren-yield.stderr
diff --git a/src/test/ui/lint/issue-81314-unused-span-ident.fixed b/src/test/ui/lint/unused/issue-81314-unused-span-ident.fixed
index aac918f2bc8..aac918f2bc8 100644
--- a/src/test/ui/lint/issue-81314-unused-span-ident.fixed
+++ b/src/test/ui/lint/unused/issue-81314-unused-span-ident.fixed
diff --git a/src/test/ui/lint/issue-81314-unused-span-ident.rs b/src/test/ui/lint/unused/issue-81314-unused-span-ident.rs
index 78296f4258d..78296f4258d 100644
--- a/src/test/ui/lint/issue-81314-unused-span-ident.rs
+++ b/src/test/ui/lint/unused/issue-81314-unused-span-ident.rs
diff --git a/src/test/ui/lint/issue-81314-unused-span-ident.stderr b/src/test/ui/lint/unused/issue-81314-unused-span-ident.stderr
index 519c71e9413..519c71e9413 100644
--- a/src/test/ui/lint/issue-81314-unused-span-ident.stderr
+++ b/src/test/ui/lint/unused/issue-81314-unused-span-ident.stderr
diff --git a/src/test/ui/lint/unused/issue-85913.rs b/src/test/ui/lint/unused/issue-85913.rs
new file mode 100644
index 00000000000..7f3817b6ef1
--- /dev/null
+++ b/src/test/ui/lint/unused/issue-85913.rs
@@ -0,0 +1,13 @@
+#![deny(unused_must_use)]
+
+pub fn fun() -> i32 {
+    function() && return 1;
+    //~^ ERROR: unused logical operation that must be used
+    return 0;
+}
+
+fn function() -> bool {
+    true
+}
+
+fn main() {}
diff --git a/src/test/ui/lint/unused/issue-85913.stderr b/src/test/ui/lint/unused/issue-85913.stderr
new file mode 100644
index 00000000000..4835cfae46f
--- /dev/null
+++ b/src/test/ui/lint/unused/issue-85913.stderr
@@ -0,0 +1,18 @@
+error: unused logical operation that must be used
+  --> $DIR/issue-85913.rs:4:5
+   |
+LL |     function() && return 1;
+   |     ^^^^^^^^^^^^^^^^^^^^^^ the logical operation produces a value
+   |
+note: the lint level is defined here
+  --> $DIR/issue-85913.rs:1:9
+   |
+LL | #![deny(unused_must_use)]
+   |         ^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = function() && return 1;
+   |     ^^^^^^^
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/lint/lint-unused-extern-crate.rs b/src/test/ui/lint/unused/lint-unused-extern-crate.rs
index d5e4da526a1..d5e4da526a1 100644
--- a/src/test/ui/lint/lint-unused-extern-crate.rs
+++ b/src/test/ui/lint/unused/lint-unused-extern-crate.rs
diff --git a/src/test/ui/lint/lint-unused-extern-crate.stderr b/src/test/ui/lint/unused/lint-unused-extern-crate.stderr
index 46d8f3beeab..46d8f3beeab 100644
--- a/src/test/ui/lint/lint-unused-extern-crate.stderr
+++ b/src/test/ui/lint/unused/lint-unused-extern-crate.stderr
diff --git a/src/test/ui/lint/lint-unused-imports.rs b/src/test/ui/lint/unused/lint-unused-imports.rs
index 4754d888076..4754d888076 100644
--- a/src/test/ui/lint/lint-unused-imports.rs
+++ b/src/test/ui/lint/unused/lint-unused-imports.rs
diff --git a/src/test/ui/lint/lint-unused-imports.stderr b/src/test/ui/lint/unused/lint-unused-imports.stderr
index 0574ca4569f..0574ca4569f 100644
--- a/src/test/ui/lint/lint-unused-imports.stderr
+++ b/src/test/ui/lint/unused/lint-unused-imports.stderr
diff --git a/src/test/ui/lint/lint-unused-mut-self.fixed b/src/test/ui/lint/unused/lint-unused-mut-self.fixed
index 92ce103586c..92ce103586c 100644
--- a/src/test/ui/lint/lint-unused-mut-self.fixed
+++ b/src/test/ui/lint/unused/lint-unused-mut-self.fixed
diff --git a/src/test/ui/lint/lint-unused-mut-self.rs b/src/test/ui/lint/unused/lint-unused-mut-self.rs
index 70736ce216e..70736ce216e 100644
--- a/src/test/ui/lint/lint-unused-mut-self.rs
+++ b/src/test/ui/lint/unused/lint-unused-mut-self.rs
diff --git a/src/test/ui/lint/lint-unused-mut-self.stderr b/src/test/ui/lint/unused/lint-unused-mut-self.stderr
index 01a524bd323..01a524bd323 100644
--- a/src/test/ui/lint/lint-unused-mut-self.stderr
+++ b/src/test/ui/lint/unused/lint-unused-mut-self.stderr
diff --git a/src/test/ui/lint/lint-unused-mut-variables.rs b/src/test/ui/lint/unused/lint-unused-mut-variables.rs
index 67ec7facf17..67ec7facf17 100644
--- a/src/test/ui/lint/lint-unused-mut-variables.rs
+++ b/src/test/ui/lint/unused/lint-unused-mut-variables.rs
diff --git a/src/test/ui/lint/lint-unused-mut-variables.stderr b/src/test/ui/lint/unused/lint-unused-mut-variables.stderr
index 805ed2b40bb..805ed2b40bb 100644
--- a/src/test/ui/lint/lint-unused-mut-variables.stderr
+++ b/src/test/ui/lint/unused/lint-unused-mut-variables.stderr
diff --git a/src/test/ui/lint/lint-unused-variables.rs b/src/test/ui/lint/unused/lint-unused-variables.rs
index 6850e999242..6850e999242 100644
--- a/src/test/ui/lint/lint-unused-variables.rs
+++ b/src/test/ui/lint/unused/lint-unused-variables.rs
diff --git a/src/test/ui/lint/lint-unused-variables.stderr b/src/test/ui/lint/unused/lint-unused-variables.stderr
index d6e684e8306..d6e684e8306 100644
--- a/src/test/ui/lint/lint-unused-variables.stderr
+++ b/src/test/ui/lint/unused/lint-unused-variables.stderr
diff --git a/src/test/ui/lint/must-use-ops.rs b/src/test/ui/lint/unused/must-use-ops.rs
index 3e425727e78..3e425727e78 100644
--- a/src/test/ui/lint/must-use-ops.rs
+++ b/src/test/ui/lint/unused/must-use-ops.rs
diff --git a/src/test/ui/lint/unused/must-use-ops.stderr b/src/test/ui/lint/unused/must-use-ops.stderr
new file mode 100644
index 00000000000..4dd739088b9
--- /dev/null
+++ b/src/test/ui/lint/unused/must-use-ops.stderr
@@ -0,0 +1,238 @@
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:12:5
+   |
+LL |     val == 1;
+   |     ^^^^^^^^ the comparison produces a value
+   |
+note: the lint level is defined here
+  --> $DIR/must-use-ops.rs:5:9
+   |
+LL | #![warn(unused_must_use)]
+   |         ^^^^^^^^^^^^^^^
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val == 1;
+   |     ^^^^^^^
+
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:13:5
+   |
+LL |     val < 1;
+   |     ^^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val < 1;
+   |     ^^^^^^^
+
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:14:5
+   |
+LL |     val <= 1;
+   |     ^^^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val <= 1;
+   |     ^^^^^^^
+
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:15:5
+   |
+LL |     val != 1;
+   |     ^^^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val != 1;
+   |     ^^^^^^^
+
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:16:5
+   |
+LL |     val >= 1;
+   |     ^^^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val >= 1;
+   |     ^^^^^^^
+
+warning: unused comparison that must be used
+  --> $DIR/must-use-ops.rs:17:5
+   |
+LL |     val > 1;
+   |     ^^^^^^^ the comparison produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val > 1;
+   |     ^^^^^^^
+
+warning: unused arithmetic operation that must be used
+  --> $DIR/must-use-ops.rs:20:5
+   |
+LL |     val + 2;
+   |     ^^^^^^^ the arithmetic operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val + 2;
+   |     ^^^^^^^
+
+warning: unused arithmetic operation that must be used
+  --> $DIR/must-use-ops.rs:21:5
+   |
+LL |     val - 2;
+   |     ^^^^^^^ the arithmetic operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val - 2;
+   |     ^^^^^^^
+
+warning: unused arithmetic operation that must be used
+  --> $DIR/must-use-ops.rs:22:5
+   |
+LL |     val / 2;
+   |     ^^^^^^^ the arithmetic operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val / 2;
+   |     ^^^^^^^
+
+warning: unused arithmetic operation that must be used
+  --> $DIR/must-use-ops.rs:23:5
+   |
+LL |     val * 2;
+   |     ^^^^^^^ the arithmetic operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val * 2;
+   |     ^^^^^^^
+
+warning: unused arithmetic operation that must be used
+  --> $DIR/must-use-ops.rs:24:5
+   |
+LL |     val % 2;
+   |     ^^^^^^^ the arithmetic operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = val % 2;
+   |     ^^^^^^^
+
+warning: unused logical operation that must be used
+  --> $DIR/must-use-ops.rs:27:5
+   |
+LL |     true && true;
+   |     ^^^^^^^^^^^^ the logical operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = true && true;
+   |     ^^^^^^^
+
+warning: unused logical operation that must be used
+  --> $DIR/must-use-ops.rs:28:5
+   |
+LL |     false || true;
+   |     ^^^^^^^^^^^^^ the logical operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = false || true;
+   |     ^^^^^^^
+
+warning: unused bitwise operation that must be used
+  --> $DIR/must-use-ops.rs:31:5
+   |
+LL |     5 ^ val;
+   |     ^^^^^^^ the bitwise operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 5 ^ val;
+   |     ^^^^^^^
+
+warning: unused bitwise operation that must be used
+  --> $DIR/must-use-ops.rs:32:5
+   |
+LL |     5 & val;
+   |     ^^^^^^^ the bitwise operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 5 & val;
+   |     ^^^^^^^
+
+warning: unused bitwise operation that must be used
+  --> $DIR/must-use-ops.rs:33:5
+   |
+LL |     5 | val;
+   |     ^^^^^^^ the bitwise operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 5 | val;
+   |     ^^^^^^^
+
+warning: unused bitwise operation that must be used
+  --> $DIR/must-use-ops.rs:34:5
+   |
+LL |     5 << val;
+   |     ^^^^^^^^ the bitwise operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 5 << val;
+   |     ^^^^^^^
+
+warning: unused bitwise operation that must be used
+  --> $DIR/must-use-ops.rs:35:5
+   |
+LL |     5 >> val;
+   |     ^^^^^^^^ the bitwise operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = 5 >> val;
+   |     ^^^^^^^
+
+warning: unused unary operation that must be used
+  --> $DIR/must-use-ops.rs:38:5
+   |
+LL |     !val;
+   |     ^^^^ the unary operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = !val;
+   |     ^^^^^^^
+
+warning: unused unary operation that must be used
+  --> $DIR/must-use-ops.rs:39:5
+   |
+LL |     -val;
+   |     ^^^^ the unary operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = -val;
+   |     ^^^^^^^
+
+warning: unused unary operation that must be used
+  --> $DIR/must-use-ops.rs:40:5
+   |
+LL |     *val_pointer;
+   |     ^^^^^^^^^^^^ the unary operation produces a value
+   |
+help: use `let _ = ...` to ignore the resulting value
+   |
+LL |     let _ = *val_pointer;
+   |     ^^^^^^^
+
+warning: 21 warnings emitted
+
diff --git a/src/test/ui/lint/must_use-array.rs b/src/test/ui/lint/unused/must_use-array.rs
index 97825dd2f6c..97825dd2f6c 100644
--- a/src/test/ui/lint/must_use-array.rs
+++ b/src/test/ui/lint/unused/must_use-array.rs
diff --git a/src/test/ui/lint/must_use-array.stderr b/src/test/ui/lint/unused/must_use-array.stderr
index c42223b5198..c42223b5198 100644
--- a/src/test/ui/lint/must_use-array.stderr
+++ b/src/test/ui/lint/unused/must_use-array.stderr
diff --git a/src/test/ui/lint/must_use-in-stdlib-traits.rs b/src/test/ui/lint/unused/must_use-in-stdlib-traits.rs
index 70dddf61fb7..70dddf61fb7 100644
--- a/src/test/ui/lint/must_use-in-stdlib-traits.rs
+++ b/src/test/ui/lint/unused/must_use-in-stdlib-traits.rs
diff --git a/src/test/ui/lint/must_use-in-stdlib-traits.stderr b/src/test/ui/lint/unused/must_use-in-stdlib-traits.stderr
index 76978d29dc8..76978d29dc8 100644
--- a/src/test/ui/lint/must_use-in-stdlib-traits.stderr
+++ b/src/test/ui/lint/unused/must_use-in-stdlib-traits.stderr
diff --git a/src/test/ui/lint/must_use-trait.rs b/src/test/ui/lint/unused/must_use-trait.rs
index 0aa751443a0..0aa751443a0 100644
--- a/src/test/ui/lint/must_use-trait.rs
+++ b/src/test/ui/lint/unused/must_use-trait.rs
diff --git a/src/test/ui/lint/must_use-trait.stderr b/src/test/ui/lint/unused/must_use-trait.stderr
index 11555d80825..11555d80825 100644
--- a/src/test/ui/lint/must_use-trait.stderr
+++ b/src/test/ui/lint/unused/must_use-trait.stderr
diff --git a/src/test/ui/lint/must_use-tuple.rs b/src/test/ui/lint/unused/must_use-tuple.rs
index 0f0aa20253c..0f0aa20253c 100644
--- a/src/test/ui/lint/must_use-tuple.rs
+++ b/src/test/ui/lint/unused/must_use-tuple.rs
diff --git a/src/test/ui/lint/must_use-tuple.stderr b/src/test/ui/lint/unused/must_use-tuple.stderr
index 0532d89e039..0532d89e039 100644
--- a/src/test/ui/lint/must_use-tuple.stderr
+++ b/src/test/ui/lint/unused/must_use-tuple.stderr
diff --git a/src/test/ui/lint/must_use-unit.rs b/src/test/ui/lint/unused/must_use-unit.rs
index 4dd4798abb7..4dd4798abb7 100644
--- a/src/test/ui/lint/must_use-unit.rs
+++ b/src/test/ui/lint/unused/must_use-unit.rs
diff --git a/src/test/ui/lint/must_use-unit.stderr b/src/test/ui/lint/unused/must_use-unit.stderr
index 7f25a193508..7f25a193508 100644
--- a/src/test/ui/lint/must_use-unit.stderr
+++ b/src/test/ui/lint/unused/must_use-unit.stderr
diff --git a/src/test/ui/lint/no-unused-parens-return-block.rs b/src/test/ui/lint/unused/no-unused-parens-return-block.rs
index 37dc519a204..37dc519a204 100644
--- a/src/test/ui/lint/no-unused-parens-return-block.rs
+++ b/src/test/ui/lint/unused/no-unused-parens-return-block.rs
diff --git a/src/test/ui/unused/unused-attr-macro-rules.rs b/src/test/ui/lint/unused/unused-attr-macro-rules.rs
index 396137a11d0..396137a11d0 100644
--- a/src/test/ui/unused/unused-attr-macro-rules.rs
+++ b/src/test/ui/lint/unused/unused-attr-macro-rules.rs
diff --git a/src/test/ui/unused/unused-attr-macro-rules.stderr b/src/test/ui/lint/unused/unused-attr-macro-rules.stderr
index 4606be01ac0..4606be01ac0 100644
--- a/src/test/ui/unused/unused-attr-macro-rules.stderr
+++ b/src/test/ui/lint/unused/unused-attr-macro-rules.stderr
diff --git a/src/test/ui/unused/unused-attr.rs b/src/test/ui/lint/unused/unused-attr.rs
index cb8ac0e6a05..cb8ac0e6a05 100644
--- a/src/test/ui/unused/unused-attr.rs
+++ b/src/test/ui/lint/unused/unused-attr.rs
diff --git a/src/test/ui/unused/unused-attr.stderr b/src/test/ui/lint/unused/unused-attr.stderr
index 707521b7802..707521b7802 100644
--- a/src/test/ui/unused/unused-attr.stderr
+++ b/src/test/ui/lint/unused/unused-attr.stderr
diff --git a/src/test/ui/unused/unused-closure.rs b/src/test/ui/lint/unused/unused-closure.rs
index c96c907318c..c96c907318c 100644
--- a/src/test/ui/unused/unused-closure.rs
+++ b/src/test/ui/lint/unused/unused-closure.rs
diff --git a/src/test/ui/unused/unused-closure.stderr b/src/test/ui/lint/unused/unused-closure.stderr
index 265d3e8e075..265d3e8e075 100644
--- a/src/test/ui/unused/unused-closure.stderr
+++ b/src/test/ui/lint/unused/unused-closure.stderr
diff --git a/src/test/ui/unused/unused-doc-comments-edge-cases.rs b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
index fd9baf8c6b9..fd9baf8c6b9 100644
--- a/src/test/ui/unused/unused-doc-comments-edge-cases.rs
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.rs
diff --git a/src/test/ui/unused/unused-doc-comments-edge-cases.stderr b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
index 14db5f64b0c..14db5f64b0c 100644
--- a/src/test/ui/unused/unused-doc-comments-edge-cases.stderr
+++ b/src/test/ui/lint/unused/unused-doc-comments-edge-cases.stderr
diff --git a/src/test/ui/unused/unused-doc-comments-for-macros.rs b/src/test/ui/lint/unused/unused-doc-comments-for-macros.rs
index 05828ebb2c3..05828ebb2c3 100644
--- a/src/test/ui/unused/unused-doc-comments-for-macros.rs
+++ b/src/test/ui/lint/unused/unused-doc-comments-for-macros.rs
diff --git a/src/test/ui/unused/unused-doc-comments-for-macros.stderr b/src/test/ui/lint/unused/unused-doc-comments-for-macros.stderr
index f4f5bb71e55..f4f5bb71e55 100644
--- a/src/test/ui/unused/unused-doc-comments-for-macros.stderr
+++ b/src/test/ui/lint/unused/unused-doc-comments-for-macros.stderr
diff --git a/src/test/ui/unused/unused-macro-rules.rs b/src/test/ui/lint/unused/unused-macro-rules.rs
index 1a714b8f0a0..1a714b8f0a0 100644
--- a/src/test/ui/unused/unused-macro-rules.rs
+++ b/src/test/ui/lint/unused/unused-macro-rules.rs
diff --git a/src/test/ui/unused/unused-macro-rules.stderr b/src/test/ui/lint/unused/unused-macro-rules.stderr
index 55072bd81bf..55072bd81bf 100644
--- a/src/test/ui/unused/unused-macro-rules.stderr
+++ b/src/test/ui/lint/unused/unused-macro-rules.stderr
diff --git a/src/test/ui/unused/unused-macro-with-bad-frag-spec.rs b/src/test/ui/lint/unused/unused-macro-with-bad-frag-spec.rs
index ce187047bb7..ce187047bb7 100644
--- a/src/test/ui/unused/unused-macro-with-bad-frag-spec.rs
+++ b/src/test/ui/lint/unused/unused-macro-with-bad-frag-spec.rs
diff --git a/src/test/ui/unused/unused-macro-with-bad-frag-spec.stderr b/src/test/ui/lint/unused/unused-macro-with-bad-frag-spec.stderr
index 6edf0a2cf8d..6edf0a2cf8d 100644
--- a/src/test/ui/unused/unused-macro-with-bad-frag-spec.stderr
+++ b/src/test/ui/lint/unused/unused-macro-with-bad-frag-spec.stderr
diff --git a/src/test/ui/unused/unused-macro-with-follow-violation.rs b/src/test/ui/lint/unused/unused-macro-with-follow-violation.rs
index 1666dae69b9..1666dae69b9 100644
--- a/src/test/ui/unused/unused-macro-with-follow-violation.rs
+++ b/src/test/ui/lint/unused/unused-macro-with-follow-violation.rs
diff --git a/src/test/ui/unused/unused-macro-with-follow-violation.stderr b/src/test/ui/lint/unused/unused-macro-with-follow-violation.stderr
index 5eced4f06c0..5eced4f06c0 100644
--- a/src/test/ui/unused/unused-macro-with-follow-violation.stderr
+++ b/src/test/ui/lint/unused/unused-macro-with-follow-violation.stderr
diff --git a/src/test/ui/unused/unused-macro.rs b/src/test/ui/lint/unused/unused-macro.rs
index 302b0727d77..302b0727d77 100644
--- a/src/test/ui/unused/unused-macro.rs
+++ b/src/test/ui/lint/unused/unused-macro.rs
diff --git a/src/test/ui/unused/unused-macro.stderr b/src/test/ui/lint/unused/unused-macro.stderr
index f5eb76179bf..f5eb76179bf 100644
--- a/src/test/ui/unused/unused-macro.stderr
+++ b/src/test/ui/lint/unused/unused-macro.stderr
diff --git a/src/test/ui/unused/unused-mut-warning-captured-var.fixed b/src/test/ui/lint/unused/unused-mut-warning-captured-var.fixed
index c21f18015c1..c21f18015c1 100644
--- a/src/test/ui/unused/unused-mut-warning-captured-var.fixed
+++ b/src/test/ui/lint/unused/unused-mut-warning-captured-var.fixed
diff --git a/src/test/ui/unused/unused-mut-warning-captured-var.rs b/src/test/ui/lint/unused/unused-mut-warning-captured-var.rs
index 3119d83a0eb..3119d83a0eb 100644
--- a/src/test/ui/unused/unused-mut-warning-captured-var.rs
+++ b/src/test/ui/lint/unused/unused-mut-warning-captured-var.rs
diff --git a/src/test/ui/unused/unused-mut-warning-captured-var.stderr b/src/test/ui/lint/unused/unused-mut-warning-captured-var.stderr
index 20aeedcc241..20aeedcc241 100644
--- a/src/test/ui/unused/unused-mut-warning-captured-var.stderr
+++ b/src/test/ui/lint/unused/unused-mut-warning-captured-var.stderr
diff --git a/src/test/ui/unused/unused-result.rs b/src/test/ui/lint/unused/unused-result.rs
index a65e98990dc..a65e98990dc 100644
--- a/src/test/ui/unused/unused-result.rs
+++ b/src/test/ui/lint/unused/unused-result.rs
diff --git a/src/test/ui/unused/unused-result.stderr b/src/test/ui/lint/unused/unused-result.stderr
index 1b1dcab3a1b..1b1dcab3a1b 100644
--- a/src/test/ui/unused/unused-result.stderr
+++ b/src/test/ui/lint/unused/unused-result.stderr
diff --git a/src/test/ui/unused/useless-comment.rs b/src/test/ui/lint/unused/useless-comment.rs
index 7d2e5ab6f2b..7d2e5ab6f2b 100644
--- a/src/test/ui/unused/useless-comment.rs
+++ b/src/test/ui/lint/unused/useless-comment.rs
diff --git a/src/test/ui/unused/useless-comment.stderr b/src/test/ui/lint/unused/useless-comment.stderr
index 0054426fb1e..0054426fb1e 100644
--- a/src/test/ui/unused/useless-comment.stderr
+++ b/src/test/ui/lint/unused/useless-comment.stderr