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Point to enclosing block/fn on nested unsafe
When declaring nested unsafe blocks (`unsafe {unsafe {}}`) that trigger the "unnecessary `unsafe` block" error, point out the enclosing `unsafe block` or `unsafe fn` that makes it unnecessary.
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lines changed

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‎src/librustc_lint/unused.rs

+28-1
Original file line numberDiff line numberDiff line change
@@ -189,11 +189,38 @@ impl LintPass for UnusedUnsafe {
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedUnsafe {
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fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
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/// Return the NodeId for an enclosing scope that is also `unsafe`
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fn is_enclosed(cx: &LateContext, id: ast::NodeId) -> Option<(String, ast::NodeId)> {
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let parent_id = cx.tcx.hir.get_parent_node(id);
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if parent_id != id {
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if cx.tcx.used_unsafe.borrow().contains(&parent_id) {
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Some(("block".to_string(), parent_id))
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} else if let Some(hir::map::NodeItem(&hir::Item {
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node: hir::ItemFn(_, hir::Unsafety::Unsafe, _, _, _, _),
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..
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})) = cx.tcx.hir.find(parent_id) {
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Some(("fn".to_string(), parent_id))
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} else {
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is_enclosed(cx, parent_id)
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}
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} else {
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None
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}
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}
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if let hir::ExprBlock(ref blk) = e.node {
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// Don't warn about generated blocks, that'll just pollute the output.
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if blk.rules == hir::UnsafeBlock(hir::UserProvided) &&
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!cx.tcx.used_unsafe.borrow().contains(&blk.id) {
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cx.span_lint(UNUSED_UNSAFE, blk.span, "unnecessary `unsafe` block");
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let mut db = cx.struct_span_lint(UNUSED_UNSAFE, blk.span,
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"unnecessary `unsafe` block");
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db.span_label(blk.span, &"unnecessary `unsafe` block");
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if let Some((kind, id)) = is_enclosed(cx, blk.id) {
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db.span_note(cx.tcx.hir.span(id),
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&format!("because it's nested under this `unsafe` {}", kind));
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}
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db.emit();
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}
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}
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}

‎src/test/compile-fail/lint-unused-unsafe.rs renamed to ‎src/test/ui/span/lint-unused-unsafe.rs

File renamed without changes.

‎src/test/ui/span/lint-unused-unsafe.stderr

+116
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,116 @@
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:26:13
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|
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26 | fn bad1() { unsafe {} } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^ unnecessary `unsafe` block
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|
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note: lint level defined here
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--> $DIR/lint-unused-unsafe.rs:14:9
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|
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14 | #![deny(unused_unsafe)]
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| ^^^^^^^^^^^^^
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:27:13
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|
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27 | fn bad2() { unsafe { bad1() } } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:28:20
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|
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28 | unsafe fn bad3() { unsafe {} } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^ unnecessary `unsafe` block
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|
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note: because it's nested under this `unsafe` fn
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--> $DIR/lint-unused-unsafe.rs:28:1
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|
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28 | unsafe fn bad3() { unsafe {} } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:29:13
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|
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29 | fn bad4() { unsafe { callback(||{}) } } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:30:20
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|
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30 | unsafe fn bad5() { unsafe { unsf() } } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
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|
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note: because it's nested under this `unsafe` fn
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--> $DIR/lint-unused-unsafe.rs:30:1
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|
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30 | unsafe fn bad5() { unsafe { unsf() } } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:33:9
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|
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33 | unsafe { //~ ERROR: unnecessary `unsafe` block
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| _________^ starting here...
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34 | | unsf()
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35 | | }
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| |_________^ ...ending here: unnecessary `unsafe` block
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|
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note: because it's nested under this `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:32:5
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|
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32 | unsafe { // don't put the warning here
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| _____^ starting here...
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33 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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34 | | unsf()
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35 | | }
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36 | | }
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| |_____^ ...ending here
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:39:5
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|
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39 | unsafe { //~ ERROR: unnecessary `unsafe` block
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| _____^ starting here...
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40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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41 | | unsf()
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42 | | }
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43 | | }
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| |_____^ ...ending here: unnecessary `unsafe` block
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|
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note: because it's nested under this `unsafe` fn
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--> $DIR/lint-unused-unsafe.rs:38:1
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|
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38 | unsafe fn bad7() {
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| _^ starting here...
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39 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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41 | | unsf()
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42 | | }
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43 | | }
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44 | | }
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| |_^ ...ending here
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error: unnecessary `unsafe` block
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--> $DIR/lint-unused-unsafe.rs:40:9
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|
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40 | unsafe { //~ ERROR: unnecessary `unsafe` block
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| _________^ starting here...
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41 | | unsf()
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42 | | }
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| |_________^ ...ending here: unnecessary `unsafe` block
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|
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note: because it's nested under this `unsafe` fn
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--> $DIR/lint-unused-unsafe.rs:38:1
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|
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38 | unsafe fn bad7() {
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| _^ starting here...
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39 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
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41 | | unsf()
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42 | | }
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43 | | }
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44 | | }
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| |_^ ...ending here
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error: aborting due to 8 previous errors
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