Rollup merge of #118822 - Nadrieril:librarify, r=compiler-errors

Extract exhaustiveness into its own crate

It now makes sense to extract exhaustiveness into its own crate! This was much-requested by rust-analyzer (they currently maintain by hand a copy of the algorithm), and I hope this can serve other projects e.g. clippy.

This is the churny PR: it exclusively moves code around. It's not yet useable outside of rustc but I wanted the churny parts to be out of the way.

r? `@compiler-errors`

compiler/rustc_mir_build/src/errors.rs

@@ -1,15 +1,12 @@
-use crate::{
-    fluent_generated as fluent,
-    thir::pattern::{deconstruct_pat::WitnessPat, MatchCheckCtxt},
-};
+use crate::fluent_generated as fluent;
 use rustc_errors::DiagnosticArgValue;
 use rustc_errors::{
     error_code, AddToDiagnostic, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
     Handler, IntoDiagnostic, MultiSpan, SubdiagnosticMessage,
 };
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
-use rustc_middle::thir::Pat;
 use rustc_middle::ty::{self, Ty};
+use rustc_pattern_analysis::{cx::MatchCheckCtxt, errors::Uncovered};
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 
@@ -812,94 +809,6 @@ pub struct NonPartialEqMatch<'tcx> {
     pub non_peq_ty: Ty<'tcx>,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(mir_build_overlapping_range_endpoints)]
-#[note]
-pub struct OverlappingRangeEndpoints<'tcx> {
-    #[label(mir_build_range)]
-    pub range: Span,
-    #[subdiagnostic]
-    pub overlap: Vec<Overlap<'tcx>>,
-}
-
-pub struct Overlap<'tcx> {
-    pub span: Span,
-    pub range: Pat<'tcx>,
-}
-
-impl<'tcx> AddToDiagnostic for Overlap<'tcx> {
-    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
-    where
-        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
-    {
-        let Overlap { span, range } = self;
-
-        // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
-        // does not support `#[subdiagnostic(eager)]`...
-        let message = format!("this range overlaps on `{range}`...");
-        diag.span_label(span, message);
-    }
-}
-
-#[derive(LintDiagnostic)]
-#[diag(mir_build_non_exhaustive_omitted_pattern)]
-#[help]
-#[note]
-pub(crate) struct NonExhaustiveOmittedPattern<'tcx> {
-    pub scrut_ty: Ty<'tcx>,
-    #[subdiagnostic]
-    pub uncovered: Uncovered<'tcx>,
-}
-
-#[derive(LintDiagnostic)]
-#[diag(mir_build_non_exhaustive_omitted_pattern_lint_on_arm)]
-#[help]
-pub(crate) struct NonExhaustiveOmittedPatternLintOnArm {
-    #[label]
-    pub lint_span: Span,
-    #[suggestion(code = "#[{lint_level}({lint_name})]\n", applicability = "maybe-incorrect")]
-    pub suggest_lint_on_match: Option<Span>,
-    pub lint_level: &'static str,
-    pub lint_name: &'static str,
-}
-
-#[derive(Subdiagnostic)]
-#[label(mir_build_uncovered)]
-pub(crate) struct Uncovered<'tcx> {
-    #[primary_span]
-    span: Span,
-    count: usize,
-    witness_1: Pat<'tcx>,
-    witness_2: Pat<'tcx>,
-    witness_3: Pat<'tcx>,
-    remainder: usize,
-}
-
-impl<'tcx> Uncovered<'tcx> {
-    pub fn new<'p>(
-        span: Span,
-        cx: &MatchCheckCtxt<'p, 'tcx>,
-        witnesses: Vec<WitnessPat<'tcx>>,
-    ) -> Self {
-        let witness_1 = witnesses.get(0).unwrap().to_diagnostic_pat(cx);
-        Self {
-            span,
-            count: witnesses.len(),
-            // Substitute dummy values if witnesses is smaller than 3. These will never be read.
-            witness_2: witnesses
-                .get(1)
-                .map(|w| w.to_diagnostic_pat(cx))
-                .unwrap_or_else(|| witness_1.clone()),
-            witness_3: witnesses
-                .get(2)
-                .map(|w| w.to_diagnostic_pat(cx))
-                .unwrap_or_else(|| witness_1.clone()),
-            witness_1,
-            remainder: witnesses.len().saturating_sub(3),
-        }
-    }
-}
-
 #[derive(Diagnostic)]
 #[diag(mir_build_pattern_not_covered, code = "E0005")]
 pub(crate) struct PatternNotCovered<'s, 'tcx> {

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

@@ -1,7 +1,9 @@
-use super::deconstruct_pat::{Constructor, DeconstructedPat, WitnessPat};
-use super::usefulness::{
-    compute_match_usefulness, MatchArm, MatchCheckCtxt, Usefulness, UsefulnessReport,
-};
+use rustc_pattern_analysis::constructor::Constructor;
+use rustc_pattern_analysis::cx::MatchCheckCtxt;
+use rustc_pattern_analysis::errors::Uncovered;
+use rustc_pattern_analysis::pat::{DeconstructedPat, WitnessPat};
+use rustc_pattern_analysis::usefulness::{Usefulness, UsefulnessReport};
+use rustc_pattern_analysis::{analyze_match, MatchArm};
 
 use crate::errors::*;
 
@@ -284,7 +286,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
                 check_borrow_conflicts_in_at_patterns(self, pat);
                 check_for_bindings_named_same_as_variants(self, pat, refutable);
             });
-            Ok(cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, pat)))
+            Ok(cx.pattern_arena.alloc(cx.lower_pat(pat)))
         }
     }
 
@@ -433,7 +435,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
         }
 
         let scrut_ty = scrut.ty;
-        let report = compute_match_usefulness(&cx, &tarms, scrut_ty);
+        let report = analyze_match(&cx, &tarms, scrut_ty);
 
         match source {
             // Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }`
@@ -547,7 +549,7 @@ impl<'thir, 'p, 'tcx> MatchVisitor<'thir, 'p, 'tcx> {
         let cx = self.new_cx(refutability, None, scrut, pat.span);
         let pat = self.lower_pattern(&cx, pat)?;
         let arms = [MatchArm { pat, hir_id: self.lint_level, has_guard: false }];
-        let report = compute_match_usefulness(&cx, &arms, pat.ty());
+        let report = analyze_match(&cx, &arms, pat.ty());
         Ok((cx, report))
     }
 
@@ -924,7 +926,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
         pattern = if witnesses.len() < 4 {
             witnesses
                 .iter()
-                .map(|witness| witness.to_diagnostic_pat(cx).to_string())
+                .map(|witness| cx.hoist_witness_pat(witness).to_string())
                 .collect::<Vec<String>>()
                 .join(" | ")
         } else {
@@ -948,7 +950,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
     if !is_empty_match {
         let mut non_exhaustive_tys = FxHashSet::default();
         // Look at the first witness.
-        collect_non_exhaustive_tys(cx.tcx, &witnesses[0], &mut non_exhaustive_tys);
+        collect_non_exhaustive_tys(cx, &witnesses[0], &mut non_exhaustive_tys);
 
         for ty in non_exhaustive_tys {
             if ty.is_ptr_sized_integral() {
@@ -1083,13 +1085,13 @@ fn joined_uncovered_patterns<'p, 'tcx>(
     witnesses: &[WitnessPat<'tcx>],
 ) -> String {
     const LIMIT: usize = 3;
-    let pat_to_str = |pat: &WitnessPat<'tcx>| pat.to_diagnostic_pat(cx).to_string();
+    let pat_to_str = |pat: &WitnessPat<'tcx>| cx.hoist_witness_pat(pat).to_string();
     match witnesses {
         [] => bug!(),
-        [witness] => format!("`{}`", witness.to_diagnostic_pat(cx)),
+        [witness] => format!("`{}`", cx.hoist_witness_pat(witness)),
         [head @ .., tail] if head.len() < LIMIT => {
             let head: Vec<_> = head.iter().map(pat_to_str).collect();
-            format!("`{}` and `{}`", head.join("`, `"), tail.to_diagnostic_pat(cx))
+            format!("`{}` and `{}`", head.join("`, `"), cx.hoist_witness_pat(tail))
         }
         _ => {
             let (head, tail) = witnesses.split_at(LIMIT);
@@ -1100,7 +1102,7 @@ fn joined_uncovered_patterns<'p, 'tcx>(
 }
 
 fn collect_non_exhaustive_tys<'tcx>(
-    tcx: TyCtxt<'tcx>,
+    cx: &MatchCheckCtxt<'_, 'tcx>,
     pat: &WitnessPat<'tcx>,
     non_exhaustive_tys: &mut FxHashSet<Ty<'tcx>>,
 ) {
@@ -1108,13 +1110,13 @@ fn collect_non_exhaustive_tys<'tcx>(
         non_exhaustive_tys.insert(pat.ty());
     }
     if let Constructor::IntRange(range) = pat.ctor() {
-        if range.is_beyond_boundaries(pat.ty(), tcx) {
+        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());
         }
     }
     pat.iter_fields()
-        .for_each(|field_pat| collect_non_exhaustive_tys(tcx, field_pat, non_exhaustive_tys))
+        .for_each(|field_pat| collect_non_exhaustive_tys(cx, field_pat, non_exhaustive_tys))
 }
 
 fn report_adt_defined_here<'tcx>(

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

@@ -2,11 +2,8 @@
 
 mod check_match;
 mod const_to_pat;
-pub(crate) mod deconstruct_pat;
-mod usefulness;
 
 pub(crate) use self::check_match::check_match;
-pub(crate) use self::usefulness::MatchCheckCtxt;
 
 use crate::errors::*;
 use crate::thir::util::UserAnnotatedTyHelpers;