Handle irrufutable or unreachable let-else · rust-lang/rust@df9a2e0 (original) (raw)
`@@ -17,7 +17,7 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
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`use rustc_session::lint::builtin::BINDINGS_WITH_VARIANT_NAME;
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`use rustc_session::lint::builtin::{IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS};
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`use rustc_session::Session;
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``
`-
use rustc_span::Span;
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``
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`+
use rustc_span::{DesugaringKind, ExpnKind, Span};
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`use std::slice;
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``
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`crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) {
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`@@ -381,6 +381,10 @@ fn irrefutable_let_pattern(tcx: TyCtxt<'_>, id: HirId, span: Span) {
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`}
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``
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`let source = let_source(tcx, id);
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let span = match source {
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LetSource::LetElse(span) => span,
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_ => span,
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};
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` tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
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`LetSource::GenericLet => {
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`` emit_diag!(lint, "let", "let is useless", "removing let");
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`@@ -401,6 +405,14 @@ fn irrefutable_let_pattern(tcx: TyCtxt<'_>, id: HirId, span: Span) {
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`` "removing the guard and adding a let inside the match arm"
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`);
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`}
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LetSource::LetElse(..) => {
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emit_diag!(
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lint,
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"let...else",
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"else clause is useless",
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`` +
"removing the else clause"
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);
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}
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`LetSource::WhileLet => {
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`emit_diag!(
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` lint,
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`@@ -755,6 +767,7 @@ pub enum LetSource {
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`GenericLet,
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`IfLet,
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`IfLetGuard,
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LetElse(Span),
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`WhileLet,
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`}
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``
`@@ -768,6 +781,12 @@ fn let_source(tcx: TyCtxt<'_>, pat_id: HirId) -> LetSource {
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`}) if hir_id == pat_id => {
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`return LetSource::IfLetGuard;
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`}
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hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Let(..), span, .. }) => {
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let expn_data = span.ctxt().outer_expn_data();
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if let ExpnKind::Desugaring(DesugaringKind::LetElse) = expn_data.kind {
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return LetSource::LetElse(expn_data.call_site);
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}
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}
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` _ => {}
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`}
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`let parent_parent = hir.get_parent_node(parent);
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