From 303a2db2360e332a29a66de94fa65cdb52b0d51c Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 15 Jul 2024 22:11:21 +0200
Subject: [PATCH] remove saw_const_match_error; check if pattern contains an
 Error instead

---
 .../src/thir/pattern/const_to_pat.rs            | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 76efb6574e1..0d54f332585 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -7,15 +7,14 @@
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::thir::{FieldPat, Pat, PatKind};
+use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt, ValTree};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::Span;
 use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::ObligationCause;
 use tracing::{debug, instrument, trace};
 
-use std::cell::Cell;
-
 use super::PatCtxt;
 use crate::errors::{
     ConstPatternDependsOnGenericParameter, CouldNotEvalConstPattern, InvalidPattern, NaNPattern,
@@ -49,11 +48,6 @@ struct ConstToPat<'tcx> {
     span: Span,
     param_env: ty::ParamEnv<'tcx>,
 
-    // This tracks if we emitted some hard error for a given const value, so that
-    // we will not subsequently issue an irrelevant lint for the same const
-    // value.
-    saw_const_match_error: Cell<Option<ErrorGuaranteed>>,
-
     // inference context used for checking `T: Structural` bounds.
     infcx: InferCtxt<'tcx>,
 
@@ -73,7 +67,6 @@ fn new(
             span,
             infcx,
             param_env: pat_ctxt.param_env,
-            saw_const_match_error: Cell::new(None),
             treat_byte_string_as_slice: pat_ctxt
                 .typeck_results
                 .treat_byte_string_as_slice
@@ -131,7 +124,7 @@ fn to_pat(&mut self, c: ty::Const<'tcx>, ty: Ty<'tcx>) -> Box<Pat<'tcx>> {
         // Convert the valtree to a const.
         let inlined_const_as_pat = self.valtree_to_pat(valtree, ty);
 
-        if self.saw_const_match_error.get().is_none() {
+        if !inlined_const_as_pat.references_error() {
             // Always check for `PartialEq` if we had no other errors yet.
             if !self.type_has_partial_eq_impl(ty) {
                 let err = TypeNotPartialEq { span: self.span, non_peq_ty: ty };
@@ -205,7 +198,6 @@ fn valtree_to_pat(&self, cv: ValTree<'tcx>, ty: Ty<'tcx>) -> Box<Pat<'tcx>> {
                 debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, ty,);
                 let err = TypeNotStructural { span, non_sm_ty: ty };
                 let e = tcx.dcx().emit_err(err);
-                self.saw_const_match_error.set(Some(e));
                 // We errored. Signal that in the pattern, so that follow up errors can be silenced.
                 PatKind::Error(e)
             }
@@ -273,7 +265,6 @@ fn valtree_to_pat(&self, cv: ValTree<'tcx>, ty: Ty<'tcx>) -> Box<Pat<'tcx>> {
                     if !pointee_ty.is_sized(tcx, param_env) && !pointee_ty.is_slice() {
                         let err = UnsizedPattern { span, non_sm_ty: *pointee_ty };
                         let e = tcx.dcx().emit_err(err);
-                        self.saw_const_match_error.set(Some(e));
                         // We errored. Signal that in the pattern, so that follow up errors can be silenced.
                         PatKind::Error(e)
                     } else {
@@ -307,7 +298,6 @@ fn valtree_to_pat(&self, cv: ValTree<'tcx>, ty: Ty<'tcx>) -> Box<Pat<'tcx>> {
                     // NaNs are not ever equal to anything so they make no sense as patterns.
                     // Also see <https://github.com/rust-lang/rfcs/pull/3535>.
                     let e = tcx.dcx().emit_err(NaNPattern { span });
-                    self.saw_const_match_error.set(Some(e));
                     PatKind::Error(e)
                 } else {
                     PatKind::Constant {
@@ -328,7 +318,6 @@ fn valtree_to_pat(&self, cv: ValTree<'tcx>, ty: Ty<'tcx>) -> Box<Pat<'tcx>> {
             _ => {
                 let err = InvalidPattern { span, non_sm_ty: ty };
                 let e = tcx.dcx().emit_err(err);
-                self.saw_const_match_error.set(Some(e));
                 // We errored. Signal that in the pattern, so that follow up errors can be silenced.
                 PatKind::Error(e)
             }