From 961a4da08e7ec1ed15cce6170566332646bd65cb Mon Sep 17 00:00:00 2001 From: Mazdak Farrokhzad Date: Mon, 29 Jul 2019 23:29:14 +0200 Subject: [PATCH] Stabilize bind_by_move_pattern_guards in 1.39.0. --- src/librustc_mir/hair/pattern/check_match.rs | 90 +------------------- src/libsyntax/feature_gate/accepted.rs | 2 + src/libsyntax/feature_gate/active.rs | 3 - 3 files changed, 6 insertions(+), 89 deletions(-) diff --git a/src/librustc_mir/hair/pattern/check_match.rs b/src/librustc_mir/hair/pattern/check_match.rs index 5352888006c..1b4b56082a6 100644 --- a/src/librustc_mir/hair/pattern/check_match.rs +++ b/src/librustc_mir/hair/pattern/check_match.rs @@ -5,11 +5,6 @@ use super::{Pattern, PatternContext, PatternError, PatternKind}; use rustc::middle::borrowck::SignalledError; -use rustc::middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor}; -use rustc::middle::expr_use_visitor::{LoanCause, MutateMode}; -use rustc::middle::expr_use_visitor as euv; -use rustc::middle::mem_categorization::cmt_; -use rustc::middle::region; use rustc::session::Session; use rustc::ty::{self, Ty, TyCtxt}; use rustc::ty::subst::{InternalSubsts, SubstsRef}; @@ -36,9 +31,7 @@ let mut visitor = MatchVisitor { tcx, - body_owner: def_id, tables: tcx.body_tables(body_id), - region_scope_tree: &tcx.region_scope_tree(def_id), param_env: tcx.param_env(def_id), identity_substs: InternalSubsts::identity_for_item(tcx, def_id), signalled_error: SignalledError::NoErrorsSeen, @@ -53,11 +46,9 @@ fn create_e0004(sess: &Session, sp: Span, error_message: String) -> DiagnosticBu struct MatchVisitor<'a, 'tcx> { tcx: TyCtxt<'tcx>, - body_owner: DefId, tables: &'a ty::TypeckTables<'tcx>, param_env: ty::ParamEnv<'tcx>, identity_substs: SubstsRef<'tcx>, - region_scope_tree: &'a region::ScopeTree, signalled_error: SignalledError, } @@ -151,11 +142,8 @@ fn check_match( // Second, if there is a guard on each arm, make sure it isn't // assigning or borrowing anything mutably. - if let Some(ref guard) = arm.guard { + if arm.guard.is_some() { self.signalled_error = SignalledError::SawSomeError; - if !self.tcx.features().bind_by_move_pattern_guards { - check_for_mutation_in_guard(self, &guard); - } } // Third, perform some lints. @@ -582,19 +570,10 @@ fn check_legality_of_move_bindings( "cannot bind by-move with sub-bindings") .span_label(p.span, "binds an already bound by-move value by moving it") .emit(); - } else if has_guard { - if !cx.tcx.features().bind_by_move_pattern_guards { - let mut err = struct_span_err!(cx.tcx.sess, p.span, E0008, - "cannot bind by-move into a pattern guard"); - err.span_label(p.span, "moves value into pattern guard"); - if cx.tcx.sess.opts.unstable_features.is_nightly_build() { - err.help("add `#![feature(bind_by_move_pattern_guards)]` to the \ - crate attributes to enable"); - } - err.emit(); + } else if !has_guard { + if let Some(_by_ref_span) = by_ref_span { + span_vec.push(p.span); } - } else if let Some(_by_ref_span) = by_ref_span { - span_vec.push(p.span); } }; @@ -636,67 +615,6 @@ fn check_legality_of_move_bindings( } } -/// Ensures that a pattern guard doesn't borrow by mutable reference or assign. -// -// FIXME: this should be done by borrowck. -fn check_for_mutation_in_guard(cx: &MatchVisitor<'_, '_>, guard: &hir::Guard) { - let mut checker = MutationChecker { - cx, - }; - match guard { - hir::Guard::If(expr) => - ExprUseVisitor::new(&mut checker, - cx.tcx, - cx.body_owner, - cx.param_env, - cx.region_scope_tree, - cx.tables, - None).walk_expr(expr), - }; -} - -struct MutationChecker<'a, 'tcx> { - cx: &'a MatchVisitor<'a, 'tcx>, -} - -impl<'a, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'tcx> { - fn matched_pat(&mut self, _: &Pat, _: &cmt_<'_>, _: euv::MatchMode) {} - fn consume(&mut self, _: hir::HirId, _: Span, _: &cmt_<'_>, _: ConsumeMode) {} - fn consume_pat(&mut self, _: &Pat, _: &cmt_<'_>, _: ConsumeMode) {} - fn borrow(&mut self, - _: hir::HirId, - span: Span, - _: &cmt_<'_>, - _: ty::Region<'tcx>, - kind:ty:: BorrowKind, - _: LoanCause) { - match kind { - ty::MutBorrow => { - let mut err = struct_span_err!(self.cx.tcx.sess, span, E0301, - "cannot mutably borrow in a pattern guard"); - err.span_label(span, "borrowed mutably in pattern guard"); - if self.cx.tcx.sess.opts.unstable_features.is_nightly_build() { - err.help("add `#![feature(bind_by_move_pattern_guards)]` to the \ - crate attributes to enable"); - } - err.emit(); - } - ty::ImmBorrow | ty::UniqueImmBorrow => {} - } - } - fn decl_without_init(&mut self, _: hir::HirId, _: Span) {} - fn mutate(&mut self, _: hir::HirId, span: Span, _: &cmt_<'_>, mode: MutateMode) { - match mode { - MutateMode::JustWrite | MutateMode::WriteAndRead => { - struct_span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard") - .span_label(span, "assignment in pattern guard") - .emit(); - } - MutateMode::Init => {} - } - } -} - /// Forbids bindings in `@` patterns. This is necessary for memory safety, /// because of the way rvalues are handled in the borrow check. (See issue /// #14587.) diff --git a/src/libsyntax/feature_gate/accepted.rs b/src/libsyntax/feature_gate/accepted.rs index 6c0b271c6c5..eff9f90a861 100644 --- a/src/libsyntax/feature_gate/accepted.rs +++ b/src/libsyntax/feature_gate/accepted.rs @@ -241,6 +241,8 @@ macro_rules! declare_features { (accepted, underscore_const_names, "1.37.0", Some(54912), None), /// Allows free and inherent `async fn`s, `async` blocks, and `.await` expressions. (accepted, async_await, "1.39.0", Some(50547), None), + /// Allows mixing bind-by-move in patterns and references to those identifiers in guards. + (accepted, bind_by_move_pattern_guards, "1.39.0", Some(15287), None), // ------------------------------------------------------------------------- // feature-group-end: accepted features diff --git a/src/libsyntax/feature_gate/active.rs b/src/libsyntax/feature_gate/active.rs index 5a248df6af2..dd78777b569 100644 --- a/src/libsyntax/feature_gate/active.rs +++ b/src/libsyntax/feature_gate/active.rs @@ -461,9 +461,6 @@ pub fn set(&self, features: &mut Features, span: Span) { /// Allows non-builtin attributes in inner attribute position. (active, custom_inner_attributes, "1.30.0", Some(54726), None), - /// Allows mixing bind-by-move in patterns and references to those identifiers in guards. - (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None), - /// Allows `impl Trait` in bindings (`let`, `const`, `static`). (active, impl_trait_in_bindings, "1.30.0", Some(63065), None),