Propagate pattern errors via a new `PatKind::Error` variant

Instead of via `Const::new_error`

11 files changed, 55 insertions, 28 deletions

diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index 08f7434a4a9..67804998a32 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -19,11 +19,12 @@ use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
 use rustc_middle::ty::adjustment::PointerCoercion;
-use rustc_middle::ty::GenericArgsRef;
-use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarArgs};
-use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
+use rustc_middle::ty::{
+    self, AdtDef, CanonicalUserType, CanonicalUserTypeAnnotation, FnSig, GenericArgsRef, List, Ty,
+    UpvarArgs,
+};
 use rustc_span::def_id::LocalDefId;
-use rustc_span::{sym, Span, Symbol, DUMMY_SP};
+use rustc_span::{sym, ErrorGuaranteed, Span, Symbol, DUMMY_SP};
 use rustc_target::abi::{FieldIdx, VariantIdx};
 use rustc_target::asm::InlineAsmRegOrRegClass;
 use std::fmt;
@@ -632,7 +633,7 @@ impl<'tcx> Pat<'tcx> {
 
         use PatKind::*;
         match &self.kind {
-            Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } => {}
+            Wild | Range(..) | Binding { subpattern: None, .. } | Constant { .. } | Error(_) => {}
             AscribeUserType { subpattern, .. }
             | Binding { subpattern: Some(subpattern), .. }
             | Deref { subpattern } => subpattern.walk_(it),
@@ -647,6 +648,21 @@ impl<'tcx> Pat<'tcx> {
         }
     }
 
+    /// Whether the pattern has a `PatKind::Error` nested within.
+    pub fn pat_error_reported(&self) -> Result<(), ErrorGuaranteed> {
+        let mut error = None;
+        self.walk(|pat| {
+            if let PatKind::Error(e) = pat.kind && error.is_none() {
+                error = Some(e);
+            }
+            error.is_none()
+        });
+        match error {
+            None => Ok(()),
+            Some(e) => Err(e),
+        }
+    }
+
     /// Walk the pattern in left-to-right order.
     ///
     /// If you always want to recurse, prefer this method over `walk`.
@@ -771,6 +787,10 @@ pub enum PatKind<'tcx> {
     Or {
         pats: Box<[Box<Pat<'tcx>>]>,
     },
+
+    /// An error has been encountered during lowering. We probably shouldn't report more lints
+    /// related to this pattern.
+    Error(ErrorGuaranteed),
 }
 
 #[derive(Clone, Debug, PartialEq, HashStable, TypeVisitable)]
@@ -934,6 +954,7 @@ impl<'tcx> fmt::Display for Pat<'tcx> {
                 }
                 Ok(())
             }
+            PatKind::Error(_) => write!(f, "<error>"),
         }
     }
 }
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index b84e1568884..afb58438519 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -226,7 +226,7 @@ pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'
             is_primary: _,
             name: _,
         } => visitor.visit_pat(&subpattern),
-        Binding { .. } | Wild => {}
+        Binding { .. } | Wild | Error(_) => {}
         Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {
             for subpattern in subpatterns {
                 visitor.visit_pat(&subpattern.pattern);
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index eb1c6a9824a..ab3ffabe297 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -814,7 +814,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
             }
 
-            PatKind::Constant { .. } | PatKind::Range { .. } | PatKind::Wild => {}
+            PatKind::Constant { .. }
+            | PatKind::Range { .. }
+            | PatKind::Wild
+            | PatKind::Error(_) => {}
 
             PatKind::Deref { ref subpattern } => {
                 self.visit_primary_bindings(subpattern, pattern_user_ty.deref(), f);
diff --git a/compiler/rustc_mir_build/src/build/matches/simplify.rs b/compiler/rustc_mir_build/src/build/matches/simplify.rs
index 17ac1f4e0ce..f340feb40d4 100644
--- a/compiler/rustc_mir_build/src/build/matches/simplify.rs
+++ b/compiler/rustc_mir_build/src/build/matches/simplify.rs
@@ -168,7 +168,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 Ok(())
             }
 
-            PatKind::Wild => {
+            PatKind::Wild | PatKind::Error(_) => {
                 // nothing left to do
                 Ok(())
             }
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 795d1db8eec..dde3702ca63 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -77,7 +77,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | PatKind::Wild
             | PatKind::Binding { .. }
             | PatKind::Leaf { .. }
-            | PatKind::Deref { .. } => self.error_simplifiable(match_pair),
+            | PatKind::Deref { .. }
+            | PatKind::Error(_) => self.error_simplifiable(match_pair),
         }
     }
 
@@ -111,7 +112,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | PatKind::Binding { .. }
             | PatKind::AscribeUserType { .. }
             | PatKind::Leaf { .. }
-            | PatKind::Deref { .. } => {
+            | PatKind::Deref { .. }
+            | PatKind::Error(_) => {
                 // don't know how to add these patterns to a switch
                 false
             }
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index 192bd4a83e3..6cf2ecc51e9 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -224,7 +224,8 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 PatKind::Wild |
                 // these just wrap other patterns
                 PatKind::Or { .. } |
-                PatKind::AscribeUserType { .. } => {}
+                PatKind::AscribeUserType { .. } |
+                PatKind::Error(_) => {}
             }
         };
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 93434dd3cc2..5caf37f5b06 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -19,7 +19,7 @@ use rustc_hir::HirId;
 use rustc_middle::thir::visit::{self, Visitor};
 use rustc_middle::thir::*;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
 use rustc_session::lint::builtin::{
     BINDINGS_WITH_VARIANT_NAME, IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS,
 };
@@ -683,7 +683,7 @@ fn non_exhaustive_match<'p, 'tcx>(
     expr_span: Span,
 ) -> ErrorGuaranteed {
     for &arm in arms {
-        if let Err(err) = thir[arm].pattern.error_reported() {
+        if let Err(err) = thir[arm].pattern.pat_error_reported() {
             return err;
         }
     }
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 fde6defd87f..32d389c4354 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
@@ -196,9 +196,7 @@ impl<'tcx> ConstToPat<'tcx> {
                     };
                     // All branches above emitted an error. Don't print any more lints.
                     // We errored. Signal that in the pattern, so that follow up errors can be silenced.
-                    let kind = PatKind::Constant {
-                        value: mir::Const::Ty(ty::Const::new_error(self.tcx(), e, cv.ty())),
-                    };
+                    let kind = PatKind::Error(e);
                     return Box::new(Pat { span: self.span, ty: cv.ty(), kind });
                 } else if !self.saw_const_match_lint.get() {
                     if let Some(mir_structural_match_violation) = mir_structural_match_violation {
@@ -351,7 +349,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 let e = tcx.sess.emit_err(InvalidPattern { span, non_sm_ty: ty });
                 self.saw_const_match_error.set(Some(e));
                 // We errored. Signal that in the pattern, so that follow up errors can be silenced.
-                PatKind::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
+                PatKind::Error(e)
             }
             ty::Adt(adt_def, _) if !self.type_marked_structural(ty) => {
                 debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, ty,);
@@ -359,7 +357,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 let e = tcx.sess.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::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
+                PatKind::Error(e)
             }
             ty::Adt(adt_def, args) if adt_def.is_enum() => {
                 let (&variant_index, fields) = cv.unwrap_branch().split_first().unwrap();
@@ -434,17 +432,13 @@ impl<'tcx> ConstToPat<'tcx> {
                     } else {
                         if let Some(e) = self.saw_const_match_error.get() {
                             // We already errored. Signal that in the pattern, so that follow up errors can be silenced.
-                            PatKind::Constant {
-                                value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
-                            }
+                            PatKind::Error(e)
                         } else {
                             let err = TypeNotStructural { span, non_sm_ty: *pointee_ty };
                             let e = tcx.sess.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::Constant {
-                                value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
-                            }
+                            PatKind::Error(e)
                         }
                     }
                 }
@@ -456,9 +450,7 @@ impl<'tcx> ConstToPat<'tcx> {
                         let err = UnsizedPattern { span, non_sm_ty: *pointee_ty };
                         let e = tcx.sess.emit_err(err);
                         // We errored. Signal that in the pattern, so that follow up errors can be silenced.
-                        PatKind::Constant {
-                            value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
-                        }
+                        PatKind::Error(e)
                     } else {
                         let old = self.behind_reference.replace(true);
                         // `b"foo"` produces a `&[u8; 3]`, but you can't use constants of array type when
@@ -489,7 +481,7 @@ impl<'tcx> ConstToPat<'tcx> {
                 let e = tcx.sess.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::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
+                PatKind::Error(e)
             }
         };
 
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index a7a000ba31c..bbc0aeb66cf 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -1525,6 +1525,10 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                 let pats = expand_or_pat(pat);
                 fields = Fields::from_iter(cx, pats.into_iter().map(mkpat));
             }
+            PatKind::Error(_) => {
+                ctor = Opaque;
+                fields = Fields::empty();
+            }
         }
         DeconstructedPat::new(ctor, fields, pat.ty, pat.span)
     }
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 25726c5a872..400ff16acce 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -791,6 +791,7 @@ impl<'tcx> PatternFoldable<'tcx> for PatKind<'tcx> {
     fn super_fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
         match *self {
             PatKind::Wild => PatKind::Wild,
+            PatKind::Error(e) => PatKind::Error(e),
             PatKind::AscribeUserType {
                 ref subpattern,
                 ascription: Ascription { ref annotation, variance },
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index 3b6276cfeb0..c957611b975 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -757,6 +757,9 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 print_indented!(self, "]", depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl + 1);
             }
+            PatKind::Error(_) => {
+                print_indented!(self, "Error", depth_lvl + 1);
+            }
         }
 
         print_indented!(self, "}", depth_lvl);