| use super::deconstruct_pat::{Constructor, DeconstructedPat}; |
| use super::usefulness::{ |
| compute_match_usefulness, MatchArm, MatchCheckCtxt, Reachability, UsefulnessReport, |
| }; |
| |
| use crate::errors::*; |
| |
| use rustc_arena::TypedArena; |
| use rustc_ast::Mutability; |
| use rustc_data_structures::stack::ensure_sufficient_stack; |
| use rustc_errors::{ |
| struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan, |
| }; |
| use rustc_hir as hir; |
| use rustc_hir::def::*; |
| use rustc_hir::def_id::LocalDefId; |
| 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}; |
| use rustc_session::lint::builtin::{ |
| BINDINGS_WITH_VARIANT_NAME, IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS, |
| }; |
| use rustc_session::Session; |
| use rustc_span::hygiene::DesugaringKind; |
| use rustc_span::Span; |
| |
| pub(crate) fn check_match(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> { |
| let (thir, expr) = tcx.thir_body(def_id)?; |
| let thir = thir.borrow(); |
| let pattern_arena = TypedArena::default(); |
| let mut visitor = MatchVisitor { |
| tcx, |
| thir: &*thir, |
| param_env: tcx.param_env(def_id), |
| lint_level: tcx.hir().local_def_id_to_hir_id(def_id), |
| let_source: LetSource::None, |
| pattern_arena: &pattern_arena, |
| error: Ok(()), |
| }; |
| visitor.visit_expr(&thir[expr]); |
| |
| for param in thir.params.iter() { |
| if let Some(box ref pattern) = param.pat { |
| visitor.check_irrefutable(pattern, "function argument", None); |
| } |
| } |
| visitor.error |
| } |
| |
| fn create_e0004( |
| sess: &Session, |
| sp: Span, |
| error_message: String, |
| ) -> DiagnosticBuilder<'_, ErrorGuaranteed> { |
| struct_span_err!(sess, sp, E0004, "{}", &error_message) |
| } |
| |
| #[derive(PartialEq)] |
| enum RefutableFlag { |
| Irrefutable, |
| Refutable, |
| } |
| use RefutableFlag::*; |
| |
| #[derive(Clone, Copy, Debug, PartialEq, Eq)] |
| enum LetSource { |
| None, |
| IfLet, |
| IfLetGuard, |
| LetElse, |
| WhileLet, |
| } |
| |
| struct MatchVisitor<'a, 'p, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| thir: &'a Thir<'tcx>, |
| lint_level: HirId, |
| let_source: LetSource, |
| pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>, |
| error: Result<(), ErrorGuaranteed>, |
| } |
| |
| impl<'a, 'tcx> Visitor<'a, 'tcx> for MatchVisitor<'a, '_, 'tcx> { |
| fn thir(&self) -> &'a Thir<'tcx> { |
| self.thir |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn visit_arm(&mut self, arm: &Arm<'tcx>) { |
| match arm.guard { |
| Some(Guard::If(expr)) => { |
| self.with_let_source(LetSource::IfLetGuard, |this| { |
| this.visit_expr(&this.thir[expr]) |
| }); |
| } |
| Some(Guard::IfLet(ref pat, expr)) => { |
| self.with_let_source(LetSource::IfLetGuard, |this| { |
| this.check_let(pat, expr, LetSource::IfLetGuard, pat.span); |
| this.visit_pat(pat); |
| this.visit_expr(&this.thir[expr]); |
| }); |
| } |
| None => {} |
| } |
| self.visit_pat(&arm.pattern); |
| self.visit_expr(&self.thir[arm.body]); |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn visit_expr(&mut self, ex: &Expr<'tcx>) { |
| match ex.kind { |
| ExprKind::Scope { value, lint_level, .. } => { |
| let old_lint_level = self.lint_level; |
| if let LintLevel::Explicit(hir_id) = lint_level { |
| self.lint_level = hir_id; |
| } |
| self.visit_expr(&self.thir[value]); |
| self.lint_level = old_lint_level; |
| return; |
| } |
| ExprKind::If { cond, then, else_opt, if_then_scope: _ } => { |
| // Give a specific `let_source` for the condition. |
| let let_source = match ex.span.desugaring_kind() { |
| Some(DesugaringKind::WhileLoop) => LetSource::WhileLet, |
| _ => LetSource::IfLet, |
| }; |
| self.with_let_source(let_source, |this| this.visit_expr(&self.thir[cond])); |
| self.with_let_source(LetSource::None, |this| { |
| this.visit_expr(&this.thir[then]); |
| if let Some(else_) = else_opt { |
| this.visit_expr(&this.thir[else_]); |
| } |
| }); |
| return; |
| } |
| ExprKind::Match { scrutinee, box ref arms } => { |
| let source = match ex.span.desugaring_kind() { |
| Some(DesugaringKind::ForLoop) => hir::MatchSource::ForLoopDesugar, |
| Some(DesugaringKind::QuestionMark) => hir::MatchSource::TryDesugar, |
| Some(DesugaringKind::Await) => hir::MatchSource::AwaitDesugar, |
| _ => hir::MatchSource::Normal, |
| }; |
| self.check_match(scrutinee, arms, source, ex.span); |
| } |
| ExprKind::Let { box ref pat, expr } => { |
| self.check_let(pat, expr, self.let_source, ex.span); |
| } |
| ExprKind::LogicalOp { op: LogicalOp::And, lhs, rhs } => { |
| self.check_let_chain(self.let_source, ex.span, lhs, rhs); |
| } |
| _ => {} |
| }; |
| self.with_let_source(LetSource::None, |this| visit::walk_expr(this, ex)); |
| } |
| |
| fn visit_stmt(&mut self, stmt: &Stmt<'tcx>) { |
| let old_lint_level = self.lint_level; |
| match stmt.kind { |
| StmtKind::Let { |
| box ref pattern, initializer, else_block, lint_level, span, .. |
| } => { |
| if let LintLevel::Explicit(lint_level) = lint_level { |
| self.lint_level = lint_level; |
| } |
| |
| if let Some(initializer) = initializer && else_block.is_some() { |
| self.check_let(pattern, initializer, LetSource::LetElse, span); |
| } |
| |
| if else_block.is_none() { |
| self.check_irrefutable(pattern, "local binding", Some(span)); |
| } |
| } |
| _ => {} |
| } |
| visit::walk_stmt(self, stmt); |
| self.lint_level = old_lint_level; |
| } |
| } |
| |
| impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> { |
| #[instrument(level = "trace", skip(self, f))] |
| fn with_let_source(&mut self, let_source: LetSource, f: impl FnOnce(&mut Self)) { |
| let old_let_source = self.let_source; |
| self.let_source = let_source; |
| ensure_sufficient_stack(|| f(self)); |
| self.let_source = old_let_source; |
| } |
| |
| fn check_patterns(&self, pat: &Pat<'tcx>, rf: RefutableFlag) { |
| pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat)); |
| check_for_bindings_named_same_as_variants(self, pat, rf); |
| } |
| |
| fn lower_pattern( |
| &self, |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| pattern: &Pat<'tcx>, |
| ) -> &'p DeconstructedPat<'p, 'tcx> { |
| cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, &pattern)) |
| } |
| |
| fn new_cx(&self, hir_id: HirId, refutable: bool) -> MatchCheckCtxt<'p, 'tcx> { |
| MatchCheckCtxt { |
| tcx: self.tcx, |
| param_env: self.param_env, |
| module: self.tcx.parent_module(hir_id).to_def_id(), |
| pattern_arena: &self.pattern_arena, |
| refutable, |
| } |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn check_let(&mut self, pat: &Pat<'tcx>, scrutinee: ExprId, source: LetSource, span: Span) { |
| if let LetSource::None = source { |
| return; |
| } |
| self.check_patterns(pat, Refutable); |
| let mut cx = self.new_cx(self.lint_level, true); |
| let tpat = self.lower_pattern(&mut cx, pat); |
| self.check_let_reachability(&mut cx, self.lint_level, source, tpat, span); |
| } |
| |
| fn check_match( |
| &mut self, |
| scrut: ExprId, |
| arms: &[ArmId], |
| source: hir::MatchSource, |
| expr_span: Span, |
| ) { |
| let mut cx = self.new_cx(self.lint_level, true); |
| |
| for &arm in arms { |
| // Check the arm for some things unrelated to exhaustiveness. |
| let arm = &self.thir.arms[arm]; |
| self.check_patterns(&arm.pattern, Refutable); |
| } |
| |
| let tarms: Vec<_> = arms |
| .iter() |
| .map(|&arm| { |
| let arm = &self.thir.arms[arm]; |
| let hir_id = match arm.lint_level { |
| LintLevel::Explicit(hir_id) => hir_id, |
| LintLevel::Inherited => self.lint_level, |
| }; |
| let pat = self.lower_pattern(&mut cx, &arm.pattern); |
| MatchArm { pat, hir_id, has_guard: arm.guard.is_some() } |
| }) |
| .collect(); |
| |
| let scrut = &self.thir[scrut]; |
| let scrut_ty = scrut.ty; |
| let report = compute_match_usefulness(&cx, &tarms, self.lint_level, scrut_ty); |
| |
| match source { |
| // Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }` |
| // when the iterator is an uninhabited type. unreachable_code will trigger instead. |
| hir::MatchSource::ForLoopDesugar if arms.len() == 1 => {} |
| hir::MatchSource::ForLoopDesugar |
| | hir::MatchSource::Normal |
| | hir::MatchSource::FormatArgs => report_arm_reachability(&cx, &report), |
| // Unreachable patterns in try and await expressions occur when one of |
| // the arms are an uninhabited type. Which is OK. |
| hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {} |
| } |
| |
| // Check if the match is exhaustive. |
| let witnesses = report.non_exhaustiveness_witnesses; |
| if !witnesses.is_empty() { |
| if source == hir::MatchSource::ForLoopDesugar && arms.len() == 2 { |
| // the for loop pattern is not irrefutable |
| let pat = &self.thir[arms[1]].pattern; |
| // `pat` should be `Some(<pat_field>)` from a desugared for loop. |
| debug_assert_eq!(pat.span.desugaring_kind(), Some(DesugaringKind::ForLoop)); |
| let PatKind::Variant { ref subpatterns, .. } = pat.kind else { bug!() }; |
| let [pat_field] = &subpatterns[..] else { bug!() }; |
| self.check_irrefutable(&pat_field.pattern, "`for` loop binding", None); |
| } else { |
| self.error = Err(non_exhaustive_match( |
| &cx, self.thir, scrut_ty, scrut.span, witnesses, arms, expr_span, |
| )); |
| } |
| } |
| } |
| |
| fn check_let_reachability( |
| &mut self, |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| pat_id: HirId, |
| source: LetSource, |
| pat: &'p DeconstructedPat<'p, 'tcx>, |
| span: Span, |
| ) { |
| if is_let_irrefutable(cx, pat_id, pat) { |
| irrefutable_let_patterns(cx.tcx, pat_id, source, 1, span); |
| } |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn check_let_chain( |
| &mut self, |
| let_source: LetSource, |
| top_expr_span: Span, |
| mut lhs: ExprId, |
| rhs: ExprId, |
| ) { |
| if let LetSource::None = let_source { |
| return; |
| } |
| |
| // Lint level enclosing the next `lhs`. |
| let mut cur_lint_level = self.lint_level; |
| |
| // Obtain the refutabilities of all exprs in the chain, |
| // and record chain members that aren't let exprs. |
| let mut chain_refutabilities = Vec::new(); |
| |
| let add = |expr: ExprId, mut local_lint_level| { |
| // `local_lint_level` is the lint level enclosing the pattern inside `expr`. |
| let mut expr = &self.thir[expr]; |
| debug!(?expr, ?local_lint_level, "add"); |
| // Fast-forward through scopes. |
| while let ExprKind::Scope { value, lint_level, .. } = expr.kind { |
| if let LintLevel::Explicit(hir_id) = lint_level { |
| local_lint_level = hir_id |
| } |
| expr = &self.thir[value]; |
| } |
| debug!(?expr, ?local_lint_level, "after scopes"); |
| match expr.kind { |
| ExprKind::Let { box ref pat, expr: _ } => { |
| let mut ncx = self.new_cx(local_lint_level, true); |
| let tpat = self.lower_pattern(&mut ncx, pat); |
| let refutable = !is_let_irrefutable(&mut ncx, local_lint_level, tpat); |
| Some((expr.span, refutable)) |
| } |
| _ => None, |
| } |
| }; |
| |
| // Let chains recurse on the left, so we start by adding the rightmost. |
| chain_refutabilities.push(add(rhs, cur_lint_level)); |
| |
| loop { |
| while let ExprKind::Scope { value, lint_level, .. } = self.thir[lhs].kind { |
| if let LintLevel::Explicit(hir_id) = lint_level { |
| cur_lint_level = hir_id |
| } |
| lhs = value; |
| } |
| if let ExprKind::LogicalOp { op: LogicalOp::And, lhs: new_lhs, rhs: expr } = |
| self.thir[lhs].kind |
| { |
| chain_refutabilities.push(add(expr, cur_lint_level)); |
| lhs = new_lhs; |
| } else { |
| chain_refutabilities.push(add(lhs, cur_lint_level)); |
| break; |
| } |
| } |
| debug!(?chain_refutabilities); |
| chain_refutabilities.reverse(); |
| |
| // Third, emit the actual warnings. |
| if chain_refutabilities.iter().all(|r| matches!(*r, Some((_, false)))) { |
| // The entire chain is made up of irrefutable `let` statements |
| irrefutable_let_patterns( |
| self.tcx, |
| self.lint_level, |
| let_source, |
| chain_refutabilities.len(), |
| top_expr_span, |
| ); |
| return; |
| } |
| |
| if let Some(until) = chain_refutabilities.iter().position(|r| !matches!(*r, Some((_, false)))) && until > 0 { |
| // The chain has a non-zero prefix of irrefutable `let` statements. |
| |
| // Check if the let source is while, for there is no alternative place to put a prefix, |
| // and we shouldn't lint. |
| // For let guards inside a match, prefixes might use bindings of the match pattern, |
| // so can't always be moved out. |
| // FIXME: Add checking whether the bindings are actually used in the prefix, |
| // and lint if they are not. |
| if !matches!(let_source, LetSource::WhileLet | LetSource::IfLetGuard) { |
| // Emit the lint |
| let prefix = &chain_refutabilities[..until]; |
| let span_start = prefix[0].unwrap().0; |
| let span_end = prefix.last().unwrap().unwrap().0; |
| let span = span_start.to(span_end); |
| let count = prefix.len(); |
| self.tcx.emit_spanned_lint(IRREFUTABLE_LET_PATTERNS, self.lint_level, span, LeadingIrrefutableLetPatterns { count }); |
| } |
| } |
| |
| if let Some(from) = chain_refutabilities.iter().rposition(|r| !matches!(*r, Some((_, false)))) && from != (chain_refutabilities.len() - 1) { |
| // The chain has a non-empty suffix of irrefutable `let` statements |
| let suffix = &chain_refutabilities[from + 1..]; |
| let span_start = suffix[0].unwrap().0; |
| let span_end = suffix.last().unwrap().unwrap().0; |
| let span = span_start.to(span_end); |
| let count = suffix.len(); |
| self.tcx.emit_spanned_lint(IRREFUTABLE_LET_PATTERNS, self.lint_level, span, TrailingIrrefutableLetPatterns { count }); |
| } |
| } |
| |
| #[instrument(level = "trace", skip(self))] |
| fn check_irrefutable(&mut self, pat: &Pat<'tcx>, origin: &str, sp: Option<Span>) { |
| let mut cx = self.new_cx(self.lint_level, false); |
| |
| let pattern = self.lower_pattern(&mut cx, pat); |
| let pattern_ty = pattern.ty(); |
| let arm = MatchArm { pat: pattern, hir_id: self.lint_level, has_guard: false }; |
| let report = compute_match_usefulness(&cx, &[arm], self.lint_level, pattern_ty); |
| |
| // Note: we ignore whether the pattern is unreachable (i.e. whether the type is empty). We |
| // only care about exhaustiveness here. |
| let witnesses = report.non_exhaustiveness_witnesses; |
| if witnesses.is_empty() { |
| // The pattern is irrefutable. |
| self.check_patterns(pat, Irrefutable); |
| return; |
| } |
| |
| let inform = sp.is_some().then_some(Inform); |
| let mut let_suggestion = None; |
| let mut misc_suggestion = None; |
| let mut interpreted_as_const = None; |
| if let PatKind::Constant { .. } = pat.kind |
| && let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(pat.span) |
| { |
| // If the pattern to match is an integer literal: |
| if snippet.chars().all(|c| c.is_digit(10)) { |
| // Then give a suggestion, the user might've meant to create a binding instead. |
| misc_suggestion = Some(MiscPatternSuggestion::AttemptedIntegerLiteral { |
| start_span: pat.span.shrink_to_lo() |
| }); |
| } else if snippet.chars().all(|c| c.is_alphanumeric() || c == '_') { |
| interpreted_as_const = Some(InterpretedAsConst { |
| span: pat.span, |
| variable: snippet, |
| }); |
| } |
| } |
| |
| if let Some(span) = sp |
| && self.tcx.sess.source_map().is_span_accessible(span) |
| && interpreted_as_const.is_none() |
| { |
| let mut bindings = vec![]; |
| pat.each_binding(|name, _, _, _| bindings.push(name)); |
| |
| let semi_span = span.shrink_to_hi(); |
| let start_span = span.shrink_to_lo(); |
| let end_span = semi_span.shrink_to_lo(); |
| let count = witnesses.len(); |
| |
| let_suggestion = Some(if bindings.is_empty() { |
| SuggestLet::If { start_span, semi_span, count } |
| } else { |
| SuggestLet::Else { end_span, count } |
| }); |
| }; |
| |
| let adt_defined_here = try { |
| let ty = pattern_ty.peel_refs(); |
| let ty::Adt(def, _) = ty.kind() else { None? }; |
| let adt_def_span = cx.tcx.hir().get_if_local(def.did())?.ident()?.span; |
| let mut variants = vec![]; |
| |
| for span in maybe_point_at_variant(&cx, *def, witnesses.iter().take(5)) { |
| variants.push(Variant { span }); |
| } |
| AdtDefinedHere { adt_def_span, ty, variants } |
| }; |
| |
| self.error = Err(self.tcx.sess.emit_err(PatternNotCovered { |
| span: pat.span, |
| origin, |
| uncovered: Uncovered::new(pat.span, &cx, witnesses), |
| inform, |
| interpreted_as_const, |
| _p: (), |
| pattern_ty, |
| let_suggestion, |
| misc_suggestion, |
| adt_defined_here, |
| })); |
| } |
| } |
| |
| fn check_for_bindings_named_same_as_variants( |
| cx: &MatchVisitor<'_, '_, '_>, |
| pat: &Pat<'_>, |
| rf: RefutableFlag, |
| ) { |
| pat.walk_always(|p| { |
| if let PatKind::Binding { |
| name, |
| mode: BindingMode::ByValue, |
| mutability: Mutability::Not, |
| subpattern: None, |
| ty, |
| .. |
| } = p.kind |
| && let ty::Adt(edef, _) = ty.peel_refs().kind() |
| && edef.is_enum() |
| && edef.variants().iter().any(|variant| { |
| variant.name == name && variant.ctor_kind() == Some(CtorKind::Const) |
| }) |
| { |
| let variant_count = edef.variants().len(); |
| let ty_path = with_no_trimmed_paths!({ |
| cx.tcx.def_path_str(edef.did()) |
| }); |
| cx.tcx.emit_spanned_lint( |
| BINDINGS_WITH_VARIANT_NAME, |
| cx.lint_level, |
| p.span, |
| BindingsWithVariantName { |
| // If this is an irrefutable pattern, and there's > 1 variant, |
| // then we can't actually match on this. Applying the below |
| // suggestion would produce code that breaks on `check_irrefutable`. |
| suggestion: if rf == Refutable || variant_count == 1 { |
| Some(p.span) |
| } else { None }, |
| ty_path, |
| name, |
| }, |
| ) |
| } |
| }); |
| } |
| |
| /// Checks for common cases of "catchall" patterns that may not be intended as such. |
| fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool { |
| use Constructor::*; |
| match pat.ctor() { |
| Wildcard => true, |
| Single => pat.iter_fields().all(|pat| pat_is_catchall(pat)), |
| _ => false, |
| } |
| } |
| |
| fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) { |
| tcx.emit_spanned_lint( |
| UNREACHABLE_PATTERNS, |
| id, |
| span, |
| UnreachablePattern { span: if catchall.is_some() { Some(span) } else { None }, catchall }, |
| ); |
| } |
| |
| fn irrefutable_let_patterns( |
| tcx: TyCtxt<'_>, |
| id: HirId, |
| source: LetSource, |
| count: usize, |
| span: Span, |
| ) { |
| macro_rules! emit_diag { |
| ($lint:tt) => {{ |
| tcx.emit_spanned_lint(IRREFUTABLE_LET_PATTERNS, id, span, $lint { count }); |
| }}; |
| } |
| |
| match source { |
| LetSource::None => bug!(), |
| LetSource::IfLet => emit_diag!(IrrefutableLetPatternsIfLet), |
| LetSource::IfLetGuard => emit_diag!(IrrefutableLetPatternsIfLetGuard), |
| LetSource::LetElse => emit_diag!(IrrefutableLetPatternsLetElse), |
| LetSource::WhileLet => emit_diag!(IrrefutableLetPatternsWhileLet), |
| } |
| } |
| |
| fn is_let_irrefutable<'p, 'tcx>( |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| pat_id: HirId, |
| pat: &'p DeconstructedPat<'p, 'tcx>, |
| ) -> bool { |
| let arms = [MatchArm { pat, hir_id: pat_id, has_guard: false }]; |
| let report = compute_match_usefulness(&cx, &arms, pat_id, pat.ty()); |
| |
| // Report if the pattern is unreachable, which can only occur when the type is uninhabited. |
| // This also reports unreachable sub-patterns though, so we can't just replace it with an |
| // `is_uninhabited` check. |
| report_arm_reachability(&cx, &report); |
| |
| // If the list of witnesses is empty, the match is exhaustive, |
| // i.e. the `if let` pattern is irrefutable. |
| report.non_exhaustiveness_witnesses.is_empty() |
| } |
| |
| /// Report unreachable arms, if any. |
| fn report_arm_reachability<'p, 'tcx>( |
| cx: &MatchCheckCtxt<'p, 'tcx>, |
| report: &UsefulnessReport<'p, 'tcx>, |
| ) { |
| use Reachability::*; |
| let mut catchall = None; |
| for (arm, is_useful) in report.arm_usefulness.iter() { |
| match is_useful { |
| Unreachable => unreachable_pattern(cx.tcx, arm.pat.span(), arm.hir_id, catchall), |
| Reachable(unreachables) if unreachables.is_empty() => {} |
| // The arm is reachable, but contains unreachable subpatterns (from or-patterns). |
| Reachable(unreachables) => { |
| let mut unreachables = unreachables.clone(); |
| // Emit lints in the order in which they occur in the file. |
| unreachables.sort_unstable(); |
| for span in unreachables { |
| unreachable_pattern(cx.tcx, span, arm.hir_id, None); |
| } |
| } |
| } |
| if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) { |
| catchall = Some(arm.pat.span()); |
| } |
| } |
| } |
| |
| /// Report that a match is not exhaustive. |
| fn non_exhaustive_match<'p, 'tcx>( |
| cx: &MatchCheckCtxt<'p, 'tcx>, |
| thir: &Thir<'tcx>, |
| scrut_ty: Ty<'tcx>, |
| sp: Span, |
| witnesses: Vec<DeconstructedPat<'p, 'tcx>>, |
| arms: &[ArmId], |
| expr_span: Span, |
| ) -> ErrorGuaranteed { |
| let is_empty_match = arms.is_empty(); |
| let non_empty_enum = match scrut_ty.kind() { |
| ty::Adt(def, _) => def.is_enum() && !def.variants().is_empty(), |
| _ => false, |
| }; |
| // In the case of an empty match, replace the '`_` not covered' diagnostic with something more |
| // informative. |
| let mut err; |
| let pattern; |
| let patterns_len; |
| if is_empty_match && !non_empty_enum { |
| return cx.tcx.sess.emit_err(NonExhaustivePatternsTypeNotEmpty { |
| cx, |
| expr_span, |
| span: sp, |
| ty: scrut_ty, |
| }); |
| } else { |
| // FIXME: migration of this diagnostic will require list support |
| let joined_patterns = joined_uncovered_patterns(cx, &witnesses); |
| err = create_e0004( |
| cx.tcx.sess, |
| sp, |
| format!("non-exhaustive patterns: {} not covered", joined_patterns), |
| ); |
| err.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns)); |
| patterns_len = witnesses.len(); |
| pattern = if witnesses.len() < 4 { |
| witnesses |
| .iter() |
| .map(|witness| witness.to_pat(cx).to_string()) |
| .collect::<Vec<String>>() |
| .join(" | ") |
| } else { |
| "_".to_string() |
| }; |
| }; |
| |
| let is_variant_list_non_exhaustive = matches!(scrut_ty.kind(), |
| ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local()); |
| |
| adt_defined_here(cx, &mut err, scrut_ty, &witnesses); |
| err.note(format!( |
| "the matched value is of type `{}`{}", |
| scrut_ty, |
| if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" } |
| )); |
| if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize) |
| && !is_empty_match |
| && witnesses.len() == 1 |
| && matches!(witnesses[0].ctor(), Constructor::NonExhaustive) |
| { |
| err.note(format!( |
| "`{}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \ |
| exhaustively", |
| scrut_ty, |
| )); |
| if cx.tcx.sess.is_nightly_build() { |
| err.help(format!( |
| "add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \ |
| enable precise `{}` matching", |
| scrut_ty, |
| )); |
| } |
| } |
| if let ty::Ref(_, sub_ty, _) = scrut_ty.kind() { |
| if !sub_ty.is_inhabited_from(cx.tcx, cx.module, cx.param_env) { |
| err.note("references are always considered inhabited"); |
| } |
| } |
| |
| let mut suggestion = None; |
| let sm = cx.tcx.sess.source_map(); |
| match arms { |
| [] if sp.eq_ctxt(expr_span) => { |
| // Get the span for the empty match body `{}`. |
| let (indentation, more) = if let Some(snippet) = sm.indentation_before(sp) { |
| (format!("\n{}", snippet), " ") |
| } else { |
| (" ".to_string(), "") |
| }; |
| suggestion = Some(( |
| sp.shrink_to_hi().with_hi(expr_span.hi()), |
| format!( |
| " {{{indentation}{more}{pattern} => todo!(),{indentation}}}", |
| indentation = indentation, |
| more = more, |
| pattern = pattern, |
| ), |
| )); |
| } |
| [only] => { |
| let only = &thir[*only]; |
| let (pre_indentation, is_multiline) = if let Some(snippet) = sm.indentation_before(only.span) |
| && let Ok(with_trailing) = sm.span_extend_while(only.span, |c| c.is_whitespace() || c == ',') |
| && sm.is_multiline(with_trailing) |
| { |
| (format!("\n{}", snippet), true) |
| } else { |
| (" ".to_string(), false) |
| }; |
| let only_body = &thir[only.body]; |
| let comma = if matches!(only_body.kind, ExprKind::Block { .. }) |
| && only.span.eq_ctxt(only_body.span) |
| && is_multiline |
| { |
| "" |
| } else { |
| "," |
| }; |
| suggestion = Some(( |
| only.span.shrink_to_hi(), |
| format!("{}{}{} => todo!()", comma, pre_indentation, pattern), |
| )); |
| } |
| [.., prev, last] => { |
| let prev = &thir[*prev]; |
| let last = &thir[*last]; |
| if prev.span.eq_ctxt(last.span) { |
| let last_body = &thir[last.body]; |
| let comma = if matches!(last_body.kind, ExprKind::Block { .. }) |
| && last.span.eq_ctxt(last_body.span) |
| { |
| "" |
| } else { |
| "," |
| }; |
| let spacing = if sm.is_multiline(prev.span.between(last.span)) { |
| sm.indentation_before(last.span).map(|indent| format!("\n{indent}")) |
| } else { |
| Some(" ".to_string()) |
| }; |
| if let Some(spacing) = spacing { |
| suggestion = Some(( |
| last.span.shrink_to_hi(), |
| format!("{}{}{} => todo!()", comma, spacing, pattern), |
| )); |
| } |
| } |
| } |
| _ => {} |
| } |
| |
| let msg = format!( |
| "ensure that all possible cases are being handled by adding a match arm with a wildcard \ |
| pattern{}{}", |
| if patterns_len > 1 && patterns_len < 4 && suggestion.is_some() { |
| ", a match arm with multiple or-patterns" |
| } else { |
| // we are either not suggesting anything, or suggesting `_` |
| "" |
| }, |
| match patterns_len { |
| // non-exhaustive enum case |
| 0 if suggestion.is_some() => " as shown", |
| 0 => "", |
| 1 if suggestion.is_some() => " or an explicit pattern as shown", |
| 1 => " or an explicit pattern", |
| _ if suggestion.is_some() => " as shown, or multiple match arms", |
| _ => " or multiple match arms", |
| }, |
| ); |
| if let Some((span, sugg)) = suggestion { |
| err.span_suggestion_verbose(span, msg, sugg, Applicability::HasPlaceholders); |
| } else { |
| err.help(msg); |
| } |
| err.emit() |
| } |
| |
| pub(crate) fn joined_uncovered_patterns<'p, 'tcx>( |
| cx: &MatchCheckCtxt<'p, 'tcx>, |
| witnesses: &[DeconstructedPat<'p, 'tcx>], |
| ) -> String { |
| const LIMIT: usize = 3; |
| let pat_to_str = |pat: &DeconstructedPat<'p, 'tcx>| pat.to_pat(cx).to_string(); |
| match witnesses { |
| [] => bug!(), |
| [witness] => format!("`{}`", witness.to_pat(cx)), |
| [head @ .., tail] if head.len() < LIMIT => { |
| let head: Vec<_> = head.iter().map(pat_to_str).collect(); |
| format!("`{}` and `{}`", head.join("`, `"), tail.to_pat(cx)) |
| } |
| _ => { |
| let (head, tail) = witnesses.split_at(LIMIT); |
| let head: Vec<_> = head.iter().map(pat_to_str).collect(); |
| format!("`{}` and {} more", head.join("`, `"), tail.len()) |
| } |
| } |
| } |
| |
| pub(crate) fn pattern_not_covered_label( |
| witnesses: &[DeconstructedPat<'_, '_>], |
| joined_patterns: &str, |
| ) -> String { |
| format!("pattern{} {} not covered", rustc_errors::pluralize!(witnesses.len()), joined_patterns) |
| } |
| |
| /// Point at the definition of non-covered `enum` variants. |
| fn adt_defined_here<'p, 'tcx>( |
| cx: &MatchCheckCtxt<'p, 'tcx>, |
| err: &mut Diagnostic, |
| ty: Ty<'tcx>, |
| witnesses: &[DeconstructedPat<'p, 'tcx>], |
| ) { |
| let ty = ty.peel_refs(); |
| if let ty::Adt(def, _) = ty.kind() { |
| let mut spans = vec![]; |
| if witnesses.len() < 5 { |
| for sp in maybe_point_at_variant(cx, *def, witnesses.iter()) { |
| spans.push(sp); |
| } |
| } |
| let def_span = cx |
| .tcx |
| .hir() |
| .get_if_local(def.did()) |
| .and_then(|node| node.ident()) |
| .map(|ident| ident.span) |
| .unwrap_or_else(|| cx.tcx.def_span(def.did())); |
| let mut span: MultiSpan = |
| if spans.is_empty() { def_span.into() } else { spans.clone().into() }; |
| |
| span.push_span_label(def_span, ""); |
| for pat in spans { |
| span.push_span_label(pat, "not covered"); |
| } |
| err.span_note(span, format!("`{}` defined here", ty)); |
| } |
| } |
| |
| fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'a>( |
| cx: &MatchCheckCtxt<'p, 'tcx>, |
| def: AdtDef<'tcx>, |
| patterns: impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>>, |
| ) -> Vec<Span> { |
| use Constructor::*; |
| let mut covered = vec![]; |
| for pattern in patterns { |
| if let Variant(variant_index) = pattern.ctor() { |
| if let ty::Adt(this_def, _) = pattern.ty().kind() && this_def.did() != def.did() { |
| continue; |
| } |
| let sp = def.variant(*variant_index).ident(cx.tcx).span; |
| if covered.contains(&sp) { |
| // Don't point at variants that have already been covered due to other patterns to avoid |
| // visual clutter. |
| continue; |
| } |
| covered.push(sp); |
| } |
| covered.extend(maybe_point_at_variant(cx, def, pattern.iter_fields())); |
| } |
| covered |
| } |
| |
| /// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`. |
| /// Check that there are no borrow or move conflicts in `binding @ subpat` patterns. |
| /// |
| /// For example, this would reject: |
| /// - `ref x @ Some(ref mut y)`, |
| /// - `ref mut x @ Some(ref y)`, |
| /// - `ref mut x @ Some(ref mut y)`, |
| /// - `ref mut? x @ Some(y)`, and |
| /// - `x @ Some(ref mut? y)`. |
| /// |
| /// This analysis is *not* subsumed by NLL. |
| fn check_borrow_conflicts_in_at_patterns<'tcx>(cx: &MatchVisitor<'_, '_, 'tcx>, pat: &Pat<'tcx>) { |
| // Extract `sub` in `binding @ sub`. |
| let PatKind::Binding { name, mode, ty, subpattern: Some(box ref sub), .. } = pat.kind else { return }; |
| |
| let is_binding_by_move = |ty: Ty<'tcx>| !ty.is_copy_modulo_regions(cx.tcx, cx.param_env); |
| |
| let sess = cx.tcx.sess; |
| |
| // Get the binding move, extract the mutability if by-ref. |
| let mut_outer = match mode { |
| BindingMode::ByValue if is_binding_by_move(ty) => { |
| // We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`. |
| let mut conflicts_ref = Vec::new(); |
| sub.each_binding(|_, mode, _, span| match mode { |
| BindingMode::ByValue => {} |
| BindingMode::ByRef(_) => conflicts_ref.push(span), |
| }); |
| if !conflicts_ref.is_empty() { |
| sess.emit_err(BorrowOfMovedValue { |
| binding_span: pat.span, |
| conflicts_ref, |
| name, |
| ty, |
| suggest_borrowing: Some(pat.span.shrink_to_lo()), |
| }); |
| } |
| return; |
| } |
| BindingMode::ByValue => return, |
| BindingMode::ByRef(m) => m.mutability(), |
| }; |
| |
| // We now have `ref $mut_outer binding @ sub` (semantically). |
| // Recurse into each binding in `sub` and find mutability or move conflicts. |
| let mut conflicts_move = Vec::new(); |
| let mut conflicts_mut_mut = Vec::new(); |
| let mut conflicts_mut_ref = Vec::new(); |
| sub.each_binding(|name, mode, ty, span| { |
| match mode { |
| BindingMode::ByRef(mut_inner) => match (mut_outer, mut_inner.mutability()) { |
| // Both sides are `ref`. |
| (Mutability::Not, Mutability::Not) => {} |
| // 2x `ref mut`. |
| (Mutability::Mut, Mutability::Mut) => { |
| conflicts_mut_mut.push(Conflict::Mut { span, name }) |
| } |
| (Mutability::Not, Mutability::Mut) => { |
| conflicts_mut_ref.push(Conflict::Mut { span, name }) |
| } |
| (Mutability::Mut, Mutability::Not) => { |
| conflicts_mut_ref.push(Conflict::Ref { span, name }) |
| } |
| }, |
| BindingMode::ByValue if is_binding_by_move(ty) => { |
| conflicts_move.push(Conflict::Moved { span, name }) // `ref mut?` + by-move conflict. |
| } |
| BindingMode::ByValue => {} // `ref mut?` + by-copy is fine. |
| } |
| }); |
| |
| let report_mut_mut = !conflicts_mut_mut.is_empty(); |
| let report_mut_ref = !conflicts_mut_ref.is_empty(); |
| let report_move_conflict = !conflicts_move.is_empty(); |
| |
| let mut occurrences = match mut_outer { |
| Mutability::Mut => vec![Conflict::Mut { span: pat.span, name }], |
| Mutability::Not => vec![Conflict::Ref { span: pat.span, name }], |
| }; |
| occurrences.extend(conflicts_mut_mut); |
| occurrences.extend(conflicts_mut_ref); |
| occurrences.extend(conflicts_move); |
| |
| // Report errors if any. |
| if report_mut_mut { |
| // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`. |
| sess.emit_err(MultipleMutBorrows { span: pat.span, occurrences }); |
| } else if report_mut_ref { |
| // Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse. |
| match mut_outer { |
| Mutability::Mut => { |
| sess.emit_err(AlreadyMutBorrowed { span: pat.span, occurrences }); |
| } |
| Mutability::Not => { |
| sess.emit_err(AlreadyBorrowed { span: pat.span, occurrences }); |
| } |
| }; |
| } else if report_move_conflict { |
| // Report by-ref and by-move conflicts, e.g. `ref x @ y`. |
| sess.emit_err(MovedWhileBorrowed { span: pat.span, occurrences }); |
| } |
| } |
