Exhaustiveness: Statically enforce revealing of opaques

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -554,7 +554,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
         let cx = self.new_cx(refutability, None, scrut, pat.span);
         let pat = self.lower_pattern(&cx, pat)?;
         let arms = [MatchArm { pat, arm_data: self.lint_level, has_guard: false }];
-        let report = analyze_match(&cx, &arms, pat.ty());
+        let report = analyze_match(&cx, &arms, pat.ty().inner());
         Ok((cx, report))
     }
 
@@ -972,7 +972,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
                 }
             } else if ty == cx.tcx.types.str_ {
                 err.note("`&str` cannot be matched exhaustively, so a wildcard `_` is necessary");
-            } else if cx.is_foreign_non_exhaustive_enum(ty) {
+            } else if cx.is_foreign_non_exhaustive_enum(cx.reveal_opaque_ty(ty)) {
                 err.note(format!("`{ty}` is marked as non-exhaustive, so a wildcard `_` is necessary to match exhaustively"));
             }
         }
@@ -1112,12 +1112,12 @@ fn collect_non_exhaustive_tys<'tcx>(
     non_exhaustive_tys: &mut FxIndexSet<Ty<'tcx>>,
 ) {
     if matches!(pat.ctor(), Constructor::NonExhaustive) {
-        non_exhaustive_tys.insert(pat.ty());
+        non_exhaustive_tys.insert(pat.ty().inner());
     }
     if let Constructor::IntRange(range) = pat.ctor() {
         if cx.is_range_beyond_boundaries(range, pat.ty()) {
             // The range denotes the values before `isize::MIN` or the values after `usize::MAX`/`isize::MAX`.
-            non_exhaustive_tys.insert(pat.ty());
+            non_exhaustive_tys.insert(pat.ty().inner());
         }
     }
     pat.iter_fields()

compiler/rustc_pattern_analysis/src/lib.rs

@@ -61,8 +61,6 @@ pub trait TypeCx: Sized + fmt::Debug {
     /// Extra data to store in a pattern.
     type PatData: Clone;
 
-    /// FIXME(Nadrieril): `Cx` should only give us revealed types.
-    fn reveal_opaque_ty(&self, ty: Self::Ty) -> Self::Ty;
     fn is_exhaustive_patterns_feature_on(&self) -> bool;
 
     /// The number of fields for this constructor.
@@ -114,6 +112,7 @@ pub fn analyze_match<'p, 'tcx>(
 ) -> rustc::UsefulnessReport<'p, 'tcx> {
     // Arena to store the extra wildcards we construct during analysis.
     let wildcard_arena = tycx.pattern_arena;
+    let scrut_ty = tycx.reveal_opaque_ty(scrut_ty);
     let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
     let cx = MatchCtxt { tycx, wildcard_arena };
 

compiler/rustc_pattern_analysis/src/lints.rs

@@ -1,7 +1,7 @@
 use smallvec::SmallVec;
 
 use rustc_data_structures::captures::Captures;
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::ty;
 use rustc_session::lint;
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::Span;
@@ -12,10 +12,9 @@ use crate::errors::{
     OverlappingRangeEndpoints, Uncovered,
 };
 use crate::rustc::{
-    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RustcMatchCheckCtxt,
+    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy, RustcMatchCheckCtxt,
     SplitConstructorSet, WitnessPat,
 };
-use crate::TypeCx;
 
 /// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
 /// inspect the same subvalue/place".
@@ -48,14 +47,8 @@ impl<'p, 'tcx> PatternColumn<'p, 'tcx> {
     fn is_empty(&self) -> bool {
         self.patterns.is_empty()
     }
-    fn head_ty(&self, cx: MatchCtxt<'_, 'p, 'tcx>) -> Option<Ty<'tcx>> {
-        if self.patterns.len() == 0 {
-            return None;
-        }
-
-        let ty = self.patterns[0].ty();
-        // FIXME(Nadrieril): `Cx` should only give us revealed types.
-        Some(cx.tycx.reveal_opaque_ty(ty))
+    fn head_ty(&self) -> Option<RevealedTy<'tcx>> {
+        self.patterns.first().map(|pat| pat.ty())
     }
 
     /// Do constructor splitting on the constructors of the column.
@@ -117,7 +110,7 @@ fn collect_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
     column: &PatternColumn<'p, 'tcx>,
 ) -> Vec<WitnessPat<'p, 'tcx>> {
-    let Some(ty) = column.head_ty(cx) else {
+    let Some(ty) = column.head_ty() else {
         return Vec::new();
     };
     let pcx = &PlaceCtxt::new_dummy(cx, ty);
@@ -164,7 +157,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
     arms: &[MatchArm<'p, 'tcx>],
     pat_column: &PatternColumn<'p, 'tcx>,
-    scrut_ty: Ty<'tcx>,
+    scrut_ty: RevealedTy<'tcx>,
 ) {
     let rcx: &RustcMatchCheckCtxt<'_, '_> = cx.tycx;
     if !matches!(
@@ -182,7 +175,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
                 rcx.match_lint_level,
                 rcx.scrut_span,
                 NonExhaustiveOmittedPattern {
-                    scrut_ty,
+                    scrut_ty: scrut_ty.inner(),
                     uncovered: Uncovered::new(rcx.scrut_span, rcx, witnesses),
                 },
             );
@@ -218,7 +211,7 @@ pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
     cx: MatchCtxt<'a, 'p, 'tcx>,
     column: &PatternColumn<'p, 'tcx>,
 ) {
-    let Some(ty) = column.head_ty(cx) else {
+    let Some(ty) = column.head_ty() else {
         return;
     };
     let pcx = &PlaceCtxt::new_dummy(cx, ty);