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Remove top-level or-pattern hack
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@Nadrieril
Nadrieril committed Dec 2, 2019
1 parent ef087d9 commit 1c1bec2
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Showing 3 changed files with 85 additions and 114 deletions.
182 changes: 80 additions & 102 deletions src/librustc_mir/hair/pattern/check_match.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -139,39 +139,22 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {
MatchCheckCtxt::create_and_enter(self.tcx, self.param_env, module, |ref mut cx| {
let mut have_errors = false;

let inlined_arms: Vec<(Vec<_>, _)> = arms
let inlined_arms: Vec<_> = arms
.iter()
.map(|arm| {
(
// HACK(or_patterns; Centril | dlrobertson): Remove this and
// correctly handle exhaustiveness checking for nested or-patterns.
match &arm.pat.kind {
hir::PatKind::Or(pats) => pats,
_ => std::slice::from_ref(&arm.pat),
}
.iter()
.map(|pat| {
let mut patcx = PatCtxt::new(
self.tcx,
self.param_env.and(self.identity_substs),
self.tables,
);
patcx.include_lint_checks();
let pattern = cx
.pattern_arena
.alloc(expand_pattern(cx, patcx.lower_pattern(&pat)))
as &_;
if !patcx.errors.is_empty() {
patcx.report_inlining_errors(pat.span);
have_errors = true;
}
(pattern, &**pat)
})
.collect(),
arm.guard.as_ref().map(|g| match g {
hir::Guard::If(ref e) => &**e,
}),
)
let mut patcx = PatCtxt::new(
self.tcx,
self.param_env.and(self.identity_substs),
self.tables,
);
patcx.include_lint_checks();
let pattern: &_ =
cx.pattern_arena.alloc(expand_pattern(cx, patcx.lower_pattern(&arm.pat)));
if !patcx.errors.is_empty() {
patcx.report_inlining_errors(arm.pat.span);
have_errors = true;
}
(pattern, &*arm.pat, arm.guard.is_some())
})
.collect();

Expand Down Expand Up @@ -399,95 +382,90 @@ fn pat_is_catchall(pat: &Pat) -> bool {
// Check for unreachable patterns
fn check_arms<'p, 'tcx>(
cx: &mut MatchCheckCtxt<'p, 'tcx>,
arms: &[(Vec<(&'p super::Pat<'tcx>, &hir::Pat)>, Option<&hir::Expr>)],
arms: &[(&'p super::Pat<'tcx>, &hir::Pat, bool)],
source: hir::MatchSource,
) -> Matrix<'p, 'tcx> {
let mut seen = Matrix::empty();
let mut catchall = None;
for (arm_index, &(ref pats, guard)) in arms.iter().enumerate() {
for &(pat, hir_pat) in pats {
let v = PatStack::from_pattern(pat);

match is_useful(cx, &seen, &v, LeaveOutWitness, hir_pat.hir_id) {
NotUseful => {
match source {
hir::MatchSource::IfDesugar { .. } | hir::MatchSource::WhileDesugar => {
bug!()
}

hir::MatchSource::IfLetDesugar { .. }
| hir::MatchSource::WhileLetDesugar => {
// check which arm we're on.
match arm_index {
// The arm with the user-specified pattern.
0 => {
cx.tcx.lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
}
// The arm with the wildcard pattern.
1 => {
let msg = match source {
hir::MatchSource::IfLetDesugar { .. } => {
"irrefutable if-let pattern"
}
hir::MatchSource::WhileLetDesugar => {
"irrefutable while-let pattern"
}
_ => bug!(),
};
cx.tcx.lint_hir(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.hir_id,
pat.span,
msg,
);
}
_ => bug!(),
for (arm_index, (pat, hir_pat, has_guard)) in arms.iter().enumerate() {
let v = PatStack::from_pattern(pat);

match is_useful(cx, &seen, &v, LeaveOutWitness, hir_pat.hir_id) {
NotUseful => {
match source {
hir::MatchSource::IfDesugar { .. } | hir::MatchSource::WhileDesugar => bug!(),

hir::MatchSource::IfLetDesugar { .. } | hir::MatchSource::WhileLetDesugar => {
// check which arm we're on.
match arm_index {
// The arm with the user-specified pattern.
0 => {
cx.tcx.lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
}
}

hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
let mut err = cx.tcx.struct_span_lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
// if we had a catchall pattern, hint at that
if let Some(catchall) = catchall {
err.span_label(pat.span, "unreachable pattern");
err.span_label(catchall, "matches any value");
// The arm with the wildcard pattern.
1 => {
let msg = match source {
hir::MatchSource::IfLetDesugar { .. } => {
"irrefutable if-let pattern"
}
hir::MatchSource::WhileLetDesugar => {
"irrefutable while-let pattern"
}
_ => bug!(),
};
cx.tcx.lint_hir(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.hir_id,
pat.span,
msg,
);
}
err.emit();
_ => bug!(),
}

// Unreachable patterns in try and await expressions occur when one of
// the arms are an uninhabited type. Which is OK.
hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
}
}
Useful(unreachable_subpatterns) => {
for pat in unreachable_subpatterns {
cx.tcx.lint_hir(

hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
let mut err = cx.tcx.struct_span_lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
// if we had a catchall pattern, hint at that
if let Some(catchall) = catchall {
err.span_label(pat.span, "unreachable pattern");
err.span_label(catchall, "matches any value");
}
err.emit();
}

// Unreachable patterns in try and await expressions occur when one of
// the arms are an uninhabited type. Which is OK.
hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
}
UsefulWithWitness(_) => bug!(),
}
if guard.is_none() {
seen.push(v);
if catchall.is_none() && pat_is_catchall(hir_pat) {
catchall = Some(pat.span);
Useful(unreachable_subpatterns) => {
for pat in unreachable_subpatterns {
cx.tcx.lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
}
}
UsefulWithWitness(_) => bug!(),
}
if !has_guard {
seen.push(v);
if catchall.is_none() && pat_is_catchall(hir_pat) {
catchall = Some(pat.span);
}
}
}
seen
Expand Down
3 changes: 1 addition & 2 deletions src/test/ui/pattern/usefulness/top-level-alternation.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -46,8 +46,7 @@ fn main() {
match Some(0u8) {
Some(_) => {}
None => {}
None //~ ERROR unreachable pattern
| Some(_) => {} //~ ERROR unreachable pattern
None | Some(_) => {} //~ ERROR unreachable pattern
}
match 0u8 {
1 | 2 => {},
Expand Down
14 changes: 4 additions & 10 deletions src/test/ui/pattern/usefulness/top-level-alternation.stderr
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,20 +55,14 @@ LL | None => {}
error: unreachable pattern
--> $DIR/top-level-alternation.rs:49:9
|
LL | None
| ^^^^

error: unreachable pattern
--> $DIR/top-level-alternation.rs:50:15
|
LL | | Some(_) => {}
| ^^^^^^^
LL | None | Some(_) => {}
| ^^^^^^^^^^^^^^

error: unreachable pattern
--> $DIR/top-level-alternation.rs:54:9
--> $DIR/top-level-alternation.rs:53:9
|
LL | 1..=2 => {},
| ^^^^^

error: aborting due to 11 previous errors
error: aborting due to 10 previous errors

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