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Add explanations and suggestions to irrefutable_let_patterns lint

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This commit is contained in:
Camelid 2020-12-05 13:12:39 -08:00
parent 0148b971c9
commit 5d2a2a1caa
8 changed files with 83 additions and 19 deletions
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35
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
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@ -366,14 +366,31 @@ fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<
}
fn irrefutable_let_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, source: hir::MatchSource) {
tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| {
let msg = match source {
hir::MatchSource::IfLetDesugar { .. } => "irrefutable `if let` pattern",
hir::MatchSource::WhileLetDesugar => "irrefutable `while let` pattern",
hir::MatchSource::IfLetGuardDesugar => "irrefutable `if let` guard",
_ => bug!(),
};
lint.build(msg).emit()
tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
hir::MatchSource::IfLetDesugar { .. } => {
let mut diag = lint.build("irrefutable `if let` pattern");
diag.note("this pattern will always match, so the `if let` is useless");
diag.help("consider replacing the `if let` with a `let`");
diag.emit()
}
hir::MatchSource::WhileLetDesugar => {
let mut diag = lint.build("irrefutable `while let` pattern");
diag.note("this pattern will always match, so the loop will never exit");
diag.help("consider instead using a `loop { ... }` with a `let` inside it");
diag.emit()
}
hir::MatchSource::IfLetGuardDesugar => {
let mut diag = lint.build("irrefutable `if let` guard pattern");
diag.note("this pattern will always match, so the guard is useless");
diag.help("consider removing the guard and adding a `let` inside the match arm");
diag.emit()
}
_ => {
bug!(
"expected `if let`, `while let`, or `if let` guard HIR match source, found {:?}",
source,
)
}
});
}
@ -387,7 +404,7 @@ fn check_if_let_guard<'p, 'tcx>(
report_arm_reachability(&cx, &report, hir::MatchSource::IfLetGuardDesugar);
if report.non_exhaustiveness_witnesses.is_empty() {
// The match is exhaustive, i.e. the if let pattern is irrefutable.
// The match is exhaustive, i.e. the `if let` pattern is irrefutable.
irrefutable_let_pattern(cx.tcx, pat.span, pat_id, hir::MatchSource::IfLetGuardDesugar)
}
}