Lint overlapping ranges directly from exhaustiveness

Author: Nadrieril

compiler/rustc_pattern_analysis/src/lib.rs

@@ -27,11 +27,9 @@ use rustc_middle::ty::Ty;
 #[cfg(feature = "rustc")]
 use rustc_span::ErrorGuaranteed;
 
-use crate::constructor::{Constructor, ConstructorSet};
+use crate::constructor::{Constructor, ConstructorSet, IntRange};
 #[cfg(feature = "rustc")]
-use crate::lints::{
-    lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints, PatternColumn,
-};
+use crate::lints::{lint_nonexhaustive_missing_variants, PatternColumn};
 use crate::pat::DeconstructedPat;
 #[cfg(feature = "rustc")]
 use crate::rustc::RustcMatchCheckCtxt;
@@ -77,6 +75,17 @@ pub trait TypeCx: Sized + fmt::Debug {
 
     /// Raise a bug.
     fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
+
+    /// Lint that the range `pat` overlapped with all the ranges in `overlaps_with`, where the range
+    /// they overlapped over is `overlaps_on`. We only detect singleton overlaps.
+    /// The default implementation does nothing.
+    fn lint_overlapping_range_endpoints(
+        &self,
+        _pat: &DeconstructedPat<'_, Self>,
+        _overlaps_on: IntRange,
+        _overlaps_with: &[&DeconstructedPat<'_, Self>],
+    ) {
+    }
 }
 
 /// Context that provides information global to a match.
@@ -111,16 +120,10 @@ pub fn analyze_match<'p, 'tcx>(
 
     let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity)?;
 
-    let pat_column = PatternColumn::new(arms);
-
-    // Lint ranges that overlap on their endpoints, which is likely a mistake.
-    if !report.overlapping_range_endpoints.is_empty() {
-        lint_overlapping_range_endpoints(cx, &report.overlapping_range_endpoints);
-    }
-
     // Run the non_exhaustive_omitted_patterns lint. Only run on refutable patterns to avoid hitting
     // `if let`s. Only run if the match is exhaustive otherwise the error is redundant.
     if tycx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
+        let pat_column = PatternColumn::new(arms);
         lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty)?;
     }
 

compiler/rustc_pattern_analysis/src/lints.rs

@@ -1,14 +1,11 @@
-use rustc_session::lint;
 use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::ErrorGuaranteed;
 
-use crate::errors::{
-    self, NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered,
-};
+use crate::errors::{NonExhaustiveOmittedPattern, NonExhaustiveOmittedPatternLintOnArm, Uncovered};
 use crate::pat::PatOrWild;
 use crate::rustc::{
-    self, Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy,
-    RustcMatchCheckCtxt, SplitConstructorSet, WitnessPat,
+    Constructor, DeconstructedPat, MatchArm, MatchCtxt, PlaceCtxt, RevealedTy, RustcMatchCheckCtxt,
+    SplitConstructorSet, WitnessPat,
 };
 
 /// A column of patterns in the matrix, where a column is the intuitive notion of "subpatterns that
@@ -196,26 +193,3 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
     }
     Ok(())
 }
-
-pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
-    cx: MatchCtxt<'a, 'p, 'tcx>,
-    overlapping_range_endpoints: &[rustc::OverlappingRanges<'p, 'tcx>],
-) {
-    let rcx = cx.tycx;
-    for overlap in overlapping_range_endpoints {
-        let overlap_as_pat = rcx.hoist_pat_range(&overlap.overlaps_on, overlap.pat.ty());
-        let overlaps: Vec<_> = overlap
-            .overlaps_with
-            .iter()
-            .map(|pat| pat.data().unwrap().span)
-            .map(|span| errors::Overlap { range: overlap_as_pat.clone(), span })
-            .collect();
-        let pat_span = overlap.pat.data().unwrap().span;
-        rcx.tcx.emit_spanned_lint(
-            lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
-            rcx.match_lint_level,
-            pat_span,
-            errors::OverlappingRangeEndpoints { overlap: overlaps, range: pat_span },
-        );
-    }
-}

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -1,28 +1,26 @@
+use smallvec::SmallVec;
 use std::fmt;
 use std::iter::once;
 
 use rustc_arena::{DroplessArena, TypedArena};
 use rustc_data_structures::captures::Captures;
 use rustc_hir::def_id::DefId;
 use rustc_hir::HirId;
-use rustc_index::Idx;
-use rustc_index::IndexVec;
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::{self, Const};
 use rustc_middle::thir::{FieldPat, Pat, PatKind, PatRange, PatRangeBoundary};
 use rustc_middle::ty::layout::IntegerExt;
-use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, VariantDef};
-use rustc_span::ErrorGuaranteed;
-use rustc_span::{Span, DUMMY_SP};
+use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeVisitableExt, VariantDef};
+use rustc_session::lint;
+use rustc_span::{ErrorGuaranteed, Span, DUMMY_SP};
 use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
-use smallvec::SmallVec;
 
 use crate::constructor::{
     IntRange, MaybeInfiniteInt, OpaqueId, RangeEnd, Slice, SliceKind, VariantVisibility,
 };
-use crate::TypeCx;
+use crate::{errors, TypeCx};
 
 use crate::constructor::Constructor::*;
 
@@ -991,6 +989,27 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
     fn bug(&self, fmt: fmt::Arguments<'_>) -> ! {
         span_bug!(self.scrut_span, "{}", fmt)
     }
+
+    fn lint_overlapping_range_endpoints(
+        &self,
+        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        overlaps_on: IntRange,
+        overlaps_with: &[&crate::pat::DeconstructedPat<'_, Self>],
+    ) {
+        let overlap_as_pat = self.hoist_pat_range(&overlaps_on, pat.ty());
+        let overlaps: Vec<_> = overlaps_with
+            .iter()
+            .map(|pat| pat.data().unwrap().span)
+            .map(|span| errors::Overlap { range: overlap_as_pat.clone(), span })
+            .collect();
+        let pat_span = pat.data().unwrap().span;
+        self.tcx.emit_spanned_lint(
+            lint::builtin::OVERLAPPING_RANGE_ENDPOINTS,
+            self.match_lint_level,
+            pat_span,
+            errors::OverlappingRangeEndpoints { overlap: overlaps, range: pat_span },
+        );
+    }
 }
 
 /// Recursively expand this pattern into its subpatterns. Only useful for or-patterns.

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -1340,10 +1340,11 @@ impl<Cx: TypeCx> WitnessMatrix<Cx> {
 /// We can however get false negatives because exhaustiveness does not explore all cases. See the
 /// section on relevancy at the top of the file.
 fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
+    mcx: MatchCtxt<'_, Cx>,
     overlap_range: IntRange,
     matrix: &Matrix<'p, Cx>,
     specialized_matrix: &Matrix<'p, Cx>,
-    overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
+    _overlapping_range_endpoints: &mut Vec<OverlappingRanges<'p, Cx>>,
 ) {
     let overlap = overlap_range.lo;
     // Ranges that look like `lo..=overlap`.
@@ -1373,11 +1374,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
                     .map(|&(_, pat)| pat)
                     .collect();
                 if !overlaps_with.is_empty() {
-                    overlapping_range_endpoints.push(OverlappingRanges {
-                        pat,
-                        overlaps_on: overlap_range,
-                        overlaps_with,
-                    });
+                    mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
                 }
             }
             suffixes.push((child_row_id, pat))
@@ -1393,11 +1390,7 @@ fn collect_overlapping_range_endpoints<'p, Cx: TypeCx>(
                     .map(|&(_, pat)| pat)
                     .collect();
                 if !overlaps_with.is_empty() {
-                    overlapping_range_endpoints.push(OverlappingRanges {
-                        pat,
-                        overlaps_on: overlap_range,
-                        overlaps_with,
-                    });
+                    mcx.tycx.lint_overlapping_range_endpoints(pat, overlap_range, &overlaps_with);
                 }
             }
             prefixes.push((child_row_id, pat))
@@ -1538,6 +1531,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>(
                 && spec_matrix.rows.iter().any(|row| !row.intersects.is_empty())
             {
                 collect_overlapping_range_endpoints(
+                    mcx,
                     overlap_range,
                     matrix,
                     &spec_matrix,