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Lint against iterator functions that panics when N is zero
1 parent 4b51b1d commit e3bb247

4 files changed

Lines changed: 154 additions & 4 deletions

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‎compiler/rustc_mir_transform/src/errors.rs‎

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Original file line numberDiff line numberDiff line change
@@ -159,6 +159,14 @@ impl AssertLintKind {
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}
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}
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#[derive(Diagnostic)]
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#[diag("this operation will panic at runtime")]
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pub(crate) struct ConstNIsZero {
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#[label("const parameter `{$const_param_name}` is zero")]
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pub const_param_span: Span,
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pub const_param_name: Symbol,
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}
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#[derive(Diagnostic)]
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#[diag("call to inline assembly that may unwind")]
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pub(crate) struct AsmUnwindCall {

‎compiler/rustc_mir_transform/src/known_panics_lint.rs‎

Lines changed: 39 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -10,19 +10,23 @@ use rustc_const_eval::interpret::{
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ImmTy, InterpCx, InterpResult, Projectable, Scalar, format_interp_error, interp_ok,
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};
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use rustc_data_structures::fx::FxHashSet;
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use rustc_hir::HirId;
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use rustc_hir::def::DefKind;
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use rustc_hir::{HirId, find_attr};
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use rustc_index::IndexVec;
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use rustc_index::bit_set::DenseBitSet;
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use rustc_middle::bug;
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use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
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use rustc_middle::mir::*;
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use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
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use rustc_middle::ty::{self, ConstInt, ScalarInt, Ty, TyCtxt, TypeVisitableExt, Unnormalized};
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use rustc_middle::ty::{
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self, ConstInt, GenericArgKind, GenericParamDefKind, ScalarInt, Ty, TyCtxt, TypeVisitableExt,
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Unnormalized,
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};
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use rustc_session::lint::builtin::UNCONDITIONAL_PANIC;
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use rustc_span::Span;
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use tracing::{debug, instrument, trace};
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use crate::errors::{AssertLint, AssertLintKind};
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use crate::errors::{AssertLint, AssertLintKind, ConstNIsZero};
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pub(super) struct KnownPanicsLint;
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@@ -768,6 +772,38 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
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}
769773
// We failed to evaluate the discriminant, fallback to visiting all successors.
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}
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TerminatorKind::Call { func, args: _, .. } => {
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if let Some((def_id, generic_args)) = func.const_fn_def() {
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for (index, arg) in generic_args.iter().enumerate() {
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if let GenericArgKind::Const(ct) = arg.kind() {
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let generics = self.tcx.generics_of(def_id);
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let param_def = generics.param_at(index, self.tcx);
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if let GenericParamDefKind::Const { .. } = param_def.kind
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&& find_attr!(self.tcx, param_def.def_id, RustcPanicsWhenZero)
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&& let Some(0) = ct.try_to_target_usize(self.tcx)
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{
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// We managed to figure-out that the value of a
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// `#[rustc_panics_when_zero]` const-generic parameter is zero.
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//
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// Let's report it as an unconditional panic.
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let source_info = self.body.source_info(location);
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if let Some(lint_root) = self.lint_root(*source_info) {
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self.tcx.emit_node_span_lint(
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UNCONDITIONAL_PANIC,
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lint_root,
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source_info.span,
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ConstNIsZero {
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const_param_span: source_info.span,
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const_param_name: param_def.name,
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},
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);
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}
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}
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}
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}
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}
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}
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// None of these have Operands to const-propagate.
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TerminatorKind::Goto { .. }
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| TerminatorKind::UnwindResume
@@ -780,7 +816,6 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
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| TerminatorKind::CoroutineDrop
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| TerminatorKind::FalseEdge { .. }
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| TerminatorKind::FalseUnwind { .. }
783-
| TerminatorKind::Call { .. }
784819
| TerminatorKind::InlineAsm { .. } => {}
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}
786821

‎tests/ui/lint/const-n-is-zero.rs‎

Lines changed: 55 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,55 @@
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// Test that core functions annotated with `#[rustc_panics_when_zero]` lint when `N` is zero
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//@ build-fail
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#![feature(iter_map_windows)]
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#![feature(iter_array_chunks)]
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const ZERO: usize = 0;
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const ONE: usize = 1;
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fn main() {
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let s = [1, 2, 3, 4];
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let _ = s.array_windows::<0>();
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//~^ ERROR this operation will panic at runtime
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//~| NOTE `#[deny(unconditional_panic)]` on by default
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//~| NOTE const parameter `N` is zero
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let _ = s.as_chunks::<{ 0 }>();
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
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//
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let _ = s.as_rchunks::<{ 1 - 1 }>();
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
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let mut m = [1, 2, 3, 4];
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let _ = m.as_chunks_mut::<ZERO>();
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
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let _ = m.as_rchunks_mut::<{ if ZERO == 0 { 0 } else { 1 } }>();
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
36+
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let _ = s.array_windows().any(|[]| true);
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
40+
41+
let _ = s.iter().map_windows(|[]| true);
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
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let _ = s.iter().array_chunks().any(|[]| true);
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//~^ ERROR this operation will panic at runtime
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//~| NOTE const parameter `N` is zero
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// Shouldn't lint
50+
let _ = s.array_windows::<2>();
51+
let _ = s.as_chunks::<1>();
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let _ = m.as_chunks_mut::<ONE>();
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let _ = m.as_rchunks::<{ 1 + 1 }>();
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let _ = m.as_rchunks_mut::<{ if ZERO == 1 { 0 } else { 5 } }>();
55+
}

‎tests/ui/lint/const-n-is-zero.stderr‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,52 @@
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error: this operation will panic at runtime
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--> $DIR/const-n-is-zero.rs:14:13
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|
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LL | let _ = s.array_windows::<0>();
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| ^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
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|
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= note: `#[deny(unconditional_panic)]` on by default
8+
9+
error: this operation will panic at runtime
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--> $DIR/const-n-is-zero.rs:19:13
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|
12+
LL | let _ = s.as_chunks::<{ 0 }>();
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| ^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
14+
15+
error: this operation will panic at runtime
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--> $DIR/const-n-is-zero.rs:23:13
17+
|
18+
LL | let _ = s.as_rchunks::<{ 1 - 1 }>();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
20+
21+
error: this operation will panic at runtime
22+
--> $DIR/const-n-is-zero.rs:29:13
23+
|
24+
LL | let _ = m.as_chunks_mut::<ZERO>();
25+
| ^^^^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
26+
27+
error: this operation will panic at runtime
28+
--> $DIR/const-n-is-zero.rs:33:13
29+
|
30+
LL | let _ = m.as_rchunks_mut::<{ if ZERO == 0 { 0 } else { 1 } }>();
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
32+
33+
error: this operation will panic at runtime
34+
--> $DIR/const-n-is-zero.rs:37:13
35+
|
36+
LL | let _ = s.array_windows().any(|[]| true);
37+
| ^^^^^^^^^^^^^^^^^ const parameter `N` is zero
38+
39+
error: this operation will panic at runtime
40+
--> $DIR/const-n-is-zero.rs:41:13
41+
|
42+
LL | let _ = s.iter().map_windows(|[]| true);
43+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
44+
45+
error: this operation will panic at runtime
46+
--> $DIR/const-n-is-zero.rs:45:13
47+
|
48+
LL | let _ = s.iter().array_chunks().any(|[]| true);
49+
| ^^^^^^^^^^^^^^^^^^^^^^^ const parameter `N` is zero
50+
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error: aborting due to 8 previous errors
52+

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