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check_match: simplify check_arm
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@Centril
Centril committed Jan 20, 2020
1 parent 78f0c7f commit 58eb03d
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Showing 4 changed files with 46 additions and 63 deletions.
1 change: 1 addition & 0 deletions Cargo.lock
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Original file line number Diff line number Diff line change
Expand Up @@ -3763,6 +3763,7 @@ dependencies = [
"rustc_hir",
"rustc_index",
"rustc_macros",
"rustc_session",
"rustc_span",
"rustc_target",
"serialize",
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1 change: 1 addition & 0 deletions src/librustc_mir_build/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ rustc_errors = { path = "../librustc_errors" }
rustc_hir = { path = "../librustc_hir" }
rustc_macros = { path = "../librustc_macros" }
rustc_serialize = { path = "../libserialize", package = "serialize" }
rustc_session = { path = "../librustc_session" }
rustc_span = { path = "../librustc_span" }
rustc_target = { path = "../librustc_target" }
syntax = { path = "../libsyntax" }
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103 changes: 41 additions & 62 deletions src/librustc_mir_build/hair/pattern/check_match.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,16 +5,17 @@ use super::_match::{expand_pattern, is_useful, MatchCheckCtxt, Matrix, PatStack}
use super::{PatCtxt, PatKind, PatternError};

use rustc::hir::map::Map;
use rustc::lint;
use rustc::session::parse::feature_err;
use rustc::session::Session;
use rustc::ty::{self, Ty, TyCtxt};
use rustc_errors::{error_code, struct_span_err, Applicability, DiagnosticBuilder};
use rustc_hir as hir;
use rustc_hir::def::*;
use rustc_hir::def_id::DefId;
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_hir::{HirId, Pat};
use rustc_session::lint::builtin::BINDINGS_WITH_VARIANT_NAME;
use rustc_session::lint::builtin::{IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS};
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::symbol::sym;
use rustc_span::{MultiSpan, Span};
use syntax::ast::Mutability;
Expand Down Expand Up @@ -156,9 +157,8 @@ impl<'tcx> MatchVisitor<'_, 'tcx> {

let inlined_arms: Vec<_> = arms
.iter()
.map(|arm| {
let (pattern, _) = self.lower_pattern(cx, &arm.pat, &mut have_errors);
(pattern, &*arm.pat, arm.guard.is_some())
.map(|hir::Arm { pat, guard, .. }| {
(self.lower_pattern(cx, pat, &mut have_errors).0, pat.hir_id, guard.is_some())
})
.collect();

Expand Down Expand Up @@ -285,7 +285,7 @@ fn check_for_bindings_named_same_as_variants(cx: &MatchVisitor<'_, '_>, pat: &Pa
let ty_path = cx.tcx.def_path_str(edef.did);
cx.tcx
.struct_span_lint_hir(
lint::builtin::BINDINGS_WITH_VARIANT_NAME,
BINDINGS_WITH_VARIANT_NAME,
p.hir_id,
p.span,
&format!(
Expand All @@ -310,79 +310,63 @@ fn check_for_bindings_named_same_as_variants(cx: &MatchVisitor<'_, '_>, pat: &Pa
}

/// Checks for common cases of "catchall" patterns that may not be intended as such.
fn pat_is_catchall(pat: &Pat<'_>) -> bool {
match pat.kind {
hir::PatKind::Binding(.., None) => true,
hir::PatKind::Binding(.., Some(ref s)) => pat_is_catchall(s),
hir::PatKind::Ref(ref s, _) => pat_is_catchall(s),
hir::PatKind::Tuple(ref v, _) => v.iter().all(|p| pat_is_catchall(&p)),
fn pat_is_catchall(pat: &super::Pat<'_>) -> bool {
use super::PatKind::*;
match &*pat.kind {
Binding { subpattern: None, .. } => true,
Binding { subpattern: Some(s), .. } | Deref { subpattern: s } => pat_is_catchall(s),
Leaf { subpatterns: s } => s.iter().all(|p| pat_is_catchall(&p.pattern)),
_ => false,
}
}

fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) {
let mut err = tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, "unreachable pattern");
if let Some(catchall) = catchall {
// We had a catchall pattern, hint at that.
err.span_label(span, "unreachable pattern");
err.span_label(catchall, "matches any value");
}
err.emit();
}

fn irrefutable_let_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, source: hir::MatchSource) {
let msg = match source {
hir::MatchSource::IfLetDesugar { .. } => "irrefutable if-let pattern",
hir::MatchSource::WhileLetDesugar => "irrefutable while-let pattern",
_ => bug!(),
};
tcx.lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, msg);
}

/// Check for unreachable patterns.
fn check_arms<'p, 'tcx>(
cx: &mut MatchCheckCtxt<'p, 'tcx>,
arms: &[(&'p super::Pat<'tcx>, &hir::Pat<'_>, bool)],
arms: &[(&'p super::Pat<'tcx>, HirId, bool)],
source: hir::MatchSource,
) -> Matrix<'p, 'tcx> {
let mut seen = Matrix::empty();
let mut catchall = None;
for (arm_index, (pat, hir_pat, has_guard)) in arms.iter().enumerate() {
for (arm_index, (pat, id, has_guard)) in arms.iter().copied().enumerate() {
let v = PatStack::from_pattern(pat);

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

hir::MatchSource::IfLetDesugar { .. } | hir::MatchSource::WhileLetDesugar => {
// check which arm we're on.
// 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",
);
}
0 => unreachable_pattern(cx.tcx, pat.span, id, None),
// 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,
);
}
1 => irrefutable_let_pattern(cx.tcx, pat.span, id, source),
_ => bug!(),
}
}

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_pattern(cx.tcx, pat.span, id, catchall);
}

// Unreachable patterns in try and await expressions occur when one of
Expand All @@ -392,19 +376,14 @@ fn check_arms<'p, 'tcx>(
}
Useful(unreachable_subpatterns) => {
for pat in unreachable_subpatterns {
cx.tcx.lint_hir(
lint::builtin::UNREACHABLE_PATTERNS,
hir_pat.hir_id,
pat.span,
"unreachable pattern",
);
unreachable_pattern(cx.tcx, pat.span, id, None);
}
}
UsefulWithWitness(_) => bug!(),
}
if !has_guard {
seen.push(v);
if catchall.is_none() && pat_is_catchall(hir_pat) {
if catchall.is_none() && pat_is_catchall(pat) {
catchall = Some(pat.span);
}
}
Expand Down
4 changes: 3 additions & 1 deletion src/test/ui/pattern/usefulness/struct-pattern-match-useless.stderr
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
error: unreachable pattern
--> $DIR/struct-pattern-match-useless.rs:12:9
|
LL | Foo { x: _x, y: _y } => (),
| -------------------- matches any value
LL | Foo { .. } => ()
| ^^^^^^^^^^
| ^^^^^^^^^^ unreachable pattern
|
note: lint level defined here
--> $DIR/struct-pattern-match-useless.rs:1:9
Expand Down

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