diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs index f33e270c357..327b2736aab 100644 --- a/compiler/rustc_hir_typeck/src/pat.rs +++ b/compiler/rustc_hir_typeck/src/pat.rs @@ -34,7 +34,7 @@ use ty::adjustment::{PatAdjust, PatAdjustment}; use super::report_unexpected_variant_res; use crate::expectation::Expectation; use crate::gather_locals::DeclOrigin; -use crate::{FnCtxt, LoweredTy, errors}; +use crate::{FnCtxt, errors}; const CANNOT_IMPLICITLY_DEREF_POINTER_TRAIT_OBJ: &str = "\ This error indicates that a pointer to a trait type cannot be implicitly dereferenced by a \ @@ -258,6 +258,44 @@ enum InheritedRefMatchRule { }, } +/// When checking patterns containing paths, we need to know the path's resolution to determine +/// whether to apply match ergonomics and implicitly dereference the scrutinee. For instance, when +/// the `deref_patterns` feature is enabled and we're matching against a scrutinee of type +/// `Cow<'a, Option>`, we insert an implicit dereference to allow the pattern `Some(_)` to type, +/// but we must not dereference it when checking the pattern `Cow::Borrowed(_)`. +/// +/// `ResolvedPat` contains the information from resolution needed to determine match ergonomics +/// adjustments, and to finish checking the pattern once we know its adjusted type. +#[derive(Clone, Copy, Debug)] +struct ResolvedPat<'tcx> { + /// The type of the pattern, to be checked against the type of the scrutinee after peeling. This + /// is also used to avoid peeling the scrutinee's constructors (see the `Cow` example above). + ty: Ty<'tcx>, + kind: ResolvedPatKind<'tcx>, +} + +#[derive(Clone, Copy, Debug)] +enum ResolvedPatKind<'tcx> { + Path { res: Res, pat_res: Res, segments: &'tcx [hir::PathSegment<'tcx>] }, +} + +impl<'tcx> ResolvedPat<'tcx> { + fn adjust_mode(&self) -> AdjustMode { + let ResolvedPatKind::Path { res, .. } = self.kind; + if matches!(res, Res::Def(DefKind::Const | DefKind::AssocConst, _)) { + // These constants can be of a reference type, e.g. `const X: &u8 = &0;`. + // Peeling the reference types too early will cause type checking failures. + // Although it would be possible to *also* peel the types of the constants too. + AdjustMode::Pass + } else { + // The remaining possible resolutions for path, struct, and tuple struct patterns are + // ADT constructors. As such, we may peel references freely, but we must not peel the + // ADT itself from the scrutinee if it's a smart pointer. + AdjustMode::Peel { kind: PeelKind::Implicit } + } + } +} + impl<'a, 'tcx> FnCtxt<'a, 'tcx> { /// Experimental pattern feature: after matching against a shared reference, do we limit the /// default binding mode in subpatterns to be `ref` when it would otherwise be `ref mut`? @@ -334,13 +372,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { /// Conversely, inside this module, `check_pat_top` should never be used. #[instrument(level = "debug", skip(self, pat_info))] fn check_pat(&self, pat: &'tcx Pat<'tcx>, expected: Ty<'tcx>, pat_info: PatInfo<'tcx>) { + // For patterns containing paths, we need the path's resolution to determine whether to + // implicitly dereference the scrutinee before matching. let opt_path_res = match pat.kind { PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => { - Some(self.resolve_ty_and_res_fully_qualified_call(qpath, *hir_id, *span)) + Some(self.resolve_pat_path(*hir_id, *span, qpath)) } _ => None, }; - let adjust_mode = self.calc_adjust_mode(pat, opt_path_res.map(|(res, ..)| res)); + let adjust_mode = self.calc_adjust_mode(pat, opt_path_res); let ty = self.check_pat_inner(pat, opt_path_res, adjust_mode, expected, pat_info); self.write_ty(pat.hir_id, ty); @@ -406,7 +446,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { fn check_pat_inner( &self, pat: &'tcx Pat<'tcx>, - opt_path_res: Option<(Res, Option>, &'tcx [hir::PathSegment<'tcx>])>, + opt_path_res: Option, ErrorGuaranteed>>, adjust_mode: AdjustMode, expected: Ty<'tcx>, pat_info: PatInfo<'tcx>, @@ -515,16 +555,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { PatKind::Missing | PatKind::Wild | PatKind::Err(_) => expected, // We allow any type here; we ensure that the type is uninhabited during match checking. PatKind::Never => expected, - PatKind::Expr(PatExpr { kind: PatExprKind::Path(qpath), hir_id, span }) => { - let ty = self.check_pat_path( - *hir_id, - pat.hir_id, - *span, - qpath, - opt_path_res.unwrap(), - expected, - &pat_info.top_info, - ); + PatKind::Expr(PatExpr { kind: PatExprKind::Path(_), hir_id, .. }) => { + let ty = match opt_path_res.unwrap() { + Ok(ref pr) => { + self.check_pat_path(pat.hir_id, pat.span, pr, expected, &pat_info.top_info) + } + Err(guar) => Ty::new_error(self.tcx, guar), + }; self.write_ty(*hir_id, ty); ty } @@ -566,8 +603,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { /// How should the binding mode and expected type be adjusted? /// - /// When the pattern is a path pattern, `opt_path_res` must be `Some(res)`. - fn calc_adjust_mode(&self, pat: &'tcx Pat<'tcx>, opt_path_res: Option) -> AdjustMode { + /// When the pattern contains a path, `opt_path_res` must be `Some(path_res)`. + fn calc_adjust_mode( + &self, + pat: &'tcx Pat<'tcx>, + opt_path_res: Option, ErrorGuaranteed>>, + ) -> AdjustMode { match &pat.kind { // Type checking these product-like types successfully always require // that the expected type be of those types and not reference types. @@ -583,17 +624,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { | PatKind::Deref(_) => AdjustMode::Peel { kind: PeelKind::ExplicitDerefPat }, // A never pattern behaves somewhat like a literal or unit variant. PatKind::Never => AdjustMode::Peel { kind: PeelKind::Implicit }, - PatKind::Expr(PatExpr { kind: PatExprKind::Path(_), .. }) => match opt_path_res.unwrap() { - // These constants can be of a reference type, e.g. `const X: &u8 = &0;`. - // Peeling the reference types too early will cause type checking failures. - // Although it would be possible to *also* peel the types of the constants too. - Res::Def(DefKind::Const | DefKind::AssocConst, _) => AdjustMode::Pass, - // In the `ValueNS`, we have `SelfCtor(..) | Ctor(_, Const), _)` remaining which - // could successfully compile. The former being `Self` requires a unit struct. - // In either case, and unlike constants, the pattern itself cannot be - // a reference type wherefore peeling doesn't give up any expressiveness. - _ => AdjustMode::Peel { kind: PeelKind::Implicit }, - }, + // For patterns with paths, how we peel the scrutinee depends on the path's resolution. + PatKind::Expr(PatExpr { kind: PatExprKind::Path(_), .. }) => { + // If there was an error resolving the path, default to peeling everything. + opt_path_res.unwrap().map_or(AdjustMode::Peel { kind: PeelKind::Implicit }, |pr| pr.adjust_mode()) + } // String and byte-string literals result in types `&str` and `&[u8]` respectively. // All other literals result in non-reference types. @@ -1216,31 +1251,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } - fn check_pat_path( + fn resolve_pat_path( &self, path_id: HirId, - pat_id_for_diag: HirId, span: Span, - qpath: &hir::QPath<'_>, - path_resolution: (Res, Option>, &'tcx [hir::PathSegment<'tcx>]), - expected: Ty<'tcx>, - ti: &TopInfo<'tcx>, - ) -> Ty<'tcx> { + qpath: &'tcx hir::QPath<'_>, + ) -> Result, ErrorGuaranteed> { let tcx = self.tcx; - // We have already resolved the path. - let (res, opt_ty, segments) = path_resolution; + let (res, opt_ty, segments) = + self.resolve_ty_and_res_fully_qualified_call(qpath, path_id, span); match res { Res::Err => { let e = self.dcx().span_delayed_bug(qpath.span(), "`Res::Err` but no error emitted"); self.set_tainted_by_errors(e); - return Ty::new_error(tcx, e); + return Err(e); } Res::Def(DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::Variant, _) => { let expected = "unit struct, unit variant or constant"; let e = report_unexpected_variant_res(tcx, res, None, qpath, span, E0533, expected); - return Ty::new_error(tcx, e); + return Err(e); } Res::SelfCtor(def_id) => { if let ty::Adt(adt_def, _) = *tcx.type_of(def_id).skip_binder().kind() @@ -1258,7 +1289,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { E0533, "unit struct", ); - return Ty::new_error(tcx, e); + return Err(e); } } Res::Def( @@ -1271,15 +1302,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { _ => bug!("unexpected pattern resolution: {:?}", res), } - // Type-check the path. + // Find the type of the path pattern, for later checking. let (pat_ty, pat_res) = self.instantiate_value_path(segments, opt_ty, res, span, span, path_id); + Ok(ResolvedPat { ty: pat_ty, kind: ResolvedPatKind::Path { res, pat_res, segments } }) + } + + fn check_pat_path( + &self, + pat_id_for_diag: HirId, + span: Span, + resolved: &ResolvedPat<'tcx>, + expected: Ty<'tcx>, + ti: &TopInfo<'tcx>, + ) -> Ty<'tcx> { if let Err(err) = - self.demand_suptype_with_origin(&self.pattern_cause(ti, span), expected, pat_ty) + self.demand_suptype_with_origin(&self.pattern_cause(ti, span), expected, resolved.ty) { - self.emit_bad_pat_path(err, pat_id_for_diag, span, res, pat_res, pat_ty, segments); + self.emit_bad_pat_path(err, pat_id_for_diag, span, resolved); } - pat_ty + resolved.ty } fn maybe_suggest_range_literal( @@ -1322,11 +1364,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { mut e: Diag<'_>, hir_id: HirId, pat_span: Span, - res: Res, - pat_res: Res, - pat_ty: Ty<'tcx>, - segments: &'tcx [hir::PathSegment<'tcx>], + resolved_pat: &ResolvedPat<'tcx>, ) { + let ResolvedPatKind::Path { res, pat_res, segments } = resolved_pat.kind; + if let Some(span) = self.tcx.hir_res_span(pat_res) { e.span_label(span, format!("{} defined here", res.descr())); if let [hir::PathSegment { ident, .. }] = &*segments { @@ -1349,7 +1390,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ); } _ => { - let (type_def_id, item_def_id) = match pat_ty.kind() { + let (type_def_id, item_def_id) = match resolved_pat.ty.kind() { ty::Adt(def, _) => match res { Res::Def(DefKind::Const, def_id) => (Some(def.did()), Some(def_id)), _ => (None, None),