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estebankalexcrichton
estebank
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alexcrichton
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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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‎src/librustc_lint/unused.rs‎

Lines changed: 28 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -189,11 +189,38 @@ impl LintPass for UnusedUnsafe {
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190190
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, _, _, _, _),
200+
..
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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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}
192210
if let hir::ExprBlock(ref blk) = e.node {
193211
// Don't warn about generated blocks, that'll just pollute the output.
194212
if blk.rules == hir::UnsafeBlock(hir::UserProvided) &&
195213
!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();
197224
}
198225
}
199226
}

‎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

Lines changed: 116 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,116 @@
1+
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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13+
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
18+
19+
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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|
25+
note: because it's nested under this `unsafe` fn
26+
--> $DIR/lint-unused-unsafe.rs:28:1
27+
|
28+
28 | unsafe fn bad3() { unsafe {} } //~ ERROR: unnecessary `unsafe` block
29+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
30+
31+
error: unnecessary `unsafe` block
32+
--> $DIR/lint-unused-unsafe.rs:29:13
33+
|
34+
29 | fn bad4() { unsafe { callback(||{}) } } //~ ERROR: unnecessary `unsafe` block
35+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
36+
37+
error: unnecessary `unsafe` block
38+
--> $DIR/lint-unused-unsafe.rs:30:20
39+
|
40+
30 | unsafe fn bad5() { unsafe { unsf() } } //~ ERROR: unnecessary `unsafe` block
41+
| ^^^^^^^^^^^^^^^^^ unnecessary `unsafe` block
42+
|
43+
note: because it's nested under this `unsafe` fn
44+
--> $DIR/lint-unused-unsafe.rs:30:1
45+
|
46+
30 | unsafe fn bad5() { unsafe { unsf() } } //~ ERROR: unnecessary `unsafe` block
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
48+
49+
error: unnecessary `unsafe` block
50+
--> $DIR/lint-unused-unsafe.rs:33:9
51+
|
52+
33 | unsafe { //~ ERROR: unnecessary `unsafe` block
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| _________^ starting here...
54+
34 | | unsf()
55+
35 | | }
56+
| |_________^ ...ending here: unnecessary `unsafe` block
57+
|
58+
note: because it's nested under this `unsafe` block
59+
--> $DIR/lint-unused-unsafe.rs:32:5
60+
|
61+
32 | unsafe { // don't put the warning here
62+
| _____^ starting here...
63+
33 | | unsafe { //~ ERROR: unnecessary `unsafe` block
64+
34 | | unsf()
65+
35 | | }
66+
36 | | }
67+
| |_____^ ...ending here
68+
69+
error: unnecessary `unsafe` block
70+
--> $DIR/lint-unused-unsafe.rs:39:5
71+
|
72+
39 | unsafe { //~ ERROR: unnecessary `unsafe` block
73+
| _____^ starting here...
74+
40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
75+
41 | | unsf()
76+
42 | | }
77+
43 | | }
78+
| |_____^ ...ending here: unnecessary `unsafe` block
79+
|
80+
note: because it's nested under this `unsafe` fn
81+
--> $DIR/lint-unused-unsafe.rs:38:1
82+
|
83+
38 | unsafe fn bad7() {
84+
| _^ starting here...
85+
39 | | unsafe { //~ ERROR: unnecessary `unsafe` block
86+
40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
87+
41 | | unsf()
88+
42 | | }
89+
43 | | }
90+
44 | | }
91+
| |_^ ...ending here
92+
93+
error: unnecessary `unsafe` block
94+
--> $DIR/lint-unused-unsafe.rs:40:9
95+
|
96+
40 | unsafe { //~ ERROR: unnecessary `unsafe` block
97+
| _________^ starting here...
98+
41 | | unsf()
99+
42 | | }
100+
| |_________^ ...ending here: unnecessary `unsafe` block
101+
|
102+
note: because it's nested under this `unsafe` fn
103+
--> $DIR/lint-unused-unsafe.rs:38:1
104+
|
105+
38 | unsafe fn bad7() {
106+
| _^ starting here...
107+
39 | | unsafe { //~ ERROR: unnecessary `unsafe` block
108+
40 | | unsafe { //~ ERROR: unnecessary `unsafe` block
109+
41 | | unsf()
110+
42 | | }
111+
43 | | }
112+
44 | | }
113+
| |_^ ...ending here
114+
115+
error: aborting due to 8 previous errors
116+

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