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Auto merge of #59114 - matthewjasper:enable-migate-2015, r=<try>
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Enable NLL migrate mode on the 2015 edition

Blocked on #58739

## What is in this PR?

* Remove the `-Zborrowck=ast` flag option from rustc.
* The default in the 2015 edition is now `-Zborrowck=migrate`.
* The 2018 edition default is unchanged: it's still `-Zborrowck=migrate`.
* Enable the `-Ztwo-phase-borrows` flag on all editions.
* Remove most dead code that handled these options.
* Update tests for the above changes.

## What is *not* in this PR?

These are left for future PRs

* Use `-Zborrowck=mir` in NLL compare mode tests
* Remove the `-Zborrowck=compare` option
* Remove the `-Ztwo-phase-borrows` flag. It's kept so that perf.rlo has time to stop using it (cc @Mark-Simulacrum)
* Remove MIR typeck as its own MIR pass - it's now run by NLL.
* Enabling `-Zborrowck=mir` by default

Soundness issues that are fixed by NLL will stay open until full NLL is emitting hard errors. However, these diagnostics and completeness issues can now be closed:

Closes #18330
Closes #22323
Closes #23591
Closes #26736
Closes #27487
Closes #28092
Closes #28970
Closes #29733
Closes #30104
Closes #38915
Closes #39908
Closes #43407
Closes #47524
Closes #48540
Closes #49073
Closes #52614
Closes #55085
Closes #56093
Closes #56496
Closes #57804

cc #43234

r? @pnkfelix
cc @rust-lang/lang
cc @rust-lang/wg-compiler-nll
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bors committed Mar 11, 2019
2 parents e68bf8a + 4eebb5e commit 65cb35a
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2 changes: 1 addition & 1 deletion src/librustc/infer/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -93,7 +93,7 @@ impl SuppressRegionErrors {
pub fn when_nll_is_enabled(tcx: TyCtxt<'_, '_, '_>) -> Self {
match tcx.borrowck_mode() {
// If we're on AST or Migrate mode, report AST region errors
BorrowckMode::Ast | BorrowckMode::Migrate => SuppressRegionErrors { suppressed: false },
BorrowckMode::Migrate => SuppressRegionErrors { suppressed: false },

// If we're on MIR or Compare mode, don't report AST region errors as they should
// be reported by NLL
Expand Down
17 changes: 2 additions & 15 deletions src/librustc/session/config.rs
Original file line number Diff line number Diff line change
Expand Up @@ -437,7 +437,6 @@ pub enum PrintRequest {

#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum BorrowckMode {
Ast,
Mir,
Compare,
Migrate,
Expand All @@ -448,7 +447,6 @@ impl BorrowckMode {
/// on the AST borrow check if the MIR-based one errors.
pub fn migrate(self) -> bool {
match self {
BorrowckMode::Ast => false,
BorrowckMode::Compare => false,
BorrowckMode::Mir => false,
BorrowckMode::Migrate => true,
Expand All @@ -458,21 +456,11 @@ impl BorrowckMode {
/// Should we emit the AST-based borrow checker errors?
pub fn use_ast(self) -> bool {
match self {
BorrowckMode::Ast => true,
BorrowckMode::Compare => true,
BorrowckMode::Mir => false,
BorrowckMode::Migrate => false,
}
}
/// Should we emit the MIR-based borrow checker errors?
pub fn use_mir(self) -> bool {
match self {
BorrowckMode::Ast => false,
BorrowckMode::Compare => true,
BorrowckMode::Mir => true,
BorrowckMode::Migrate => true,
}
}
}

pub enum Input {
Expand Down Expand Up @@ -604,7 +592,7 @@ impl Default for Options {
incremental: None,
debugging_opts: basic_debugging_options(),
prints: Vec::new(),
borrowck_mode: BorrowckMode::Ast,
borrowck_mode: BorrowckMode::Migrate,
cg: basic_codegen_options(),
error_format: ErrorOutputType::default(),
externs: Externs(BTreeMap::new()),
Expand Down Expand Up @@ -2250,10 +2238,9 @@ pub fn build_session_options_and_crate_config(
}));

let borrowck_mode = match debugging_opts.borrowck.as_ref().map(|s| &s[..]) {
None | Some("ast") => BorrowckMode::Ast,
None | Some("migrate") => BorrowckMode::Migrate,
Some("mir") => BorrowckMode::Mir,
Some("compare") => BorrowckMode::Compare,
Some("migrate") => BorrowckMode::Migrate,
Some(m) => early_error(error_format, &format!("unknown borrowck mode `{}`", m)),
};

Expand Down
60 changes: 7 additions & 53 deletions src/librustc/ty/context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,6 @@ use rustc_target::spec::abi;
use syntax::ast;
use syntax::attr;
use syntax::source_map::MultiSpan;
use syntax::edition::Edition;
use syntax::feature_gate;
use syntax::symbol::{Symbol, keywords, InternedString};
use syntax_pos::Span;
Expand Down Expand Up @@ -1472,21 +1471,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
/// because that method has a narrower effect that can be toggled
/// off via a separate `-Z` flag, at least for the short term.
pub fn allow_bind_by_move_patterns_with_guards(self) -> bool {
self.features().bind_by_move_pattern_guards && self.use_mir_borrowck()
self.features().bind_by_move_pattern_guards
}

/// If true, we should use a naive AST walk to determine if match
/// guard could perform bad mutations (or mutable-borrows).
pub fn check_for_mutation_in_guard_via_ast_walk(self) -> bool {
// If someone requests the feature, then be a little more
// careful and ensure that MIR-borrowck is enabled (which can
// happen via edition selection, via `feature(nll)`, or via an
// appropriate `-Z` flag) before disabling the mutation check.
if self.allow_bind_by_move_patterns_with_guards() {
return false;
}

return true;
!self.allow_bind_by_move_patterns_with_guards()
}

/// If true, we should use the AST-based borrowck (we may *also* use
Expand All @@ -1495,12 +1486,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
self.borrowck_mode().use_ast()
}

/// If true, we should use the MIR-based borrowck (we may *also* use
/// the AST-based borrowck).
pub fn use_mir_borrowck(self) -> bool {
self.borrowck_mode().use_mir()
}

/// If true, we should use the MIR-based borrow check, but also
/// fall back on the AST borrow check if the MIR-based one errors.
pub fn migrate_borrowck(self) -> bool {
Expand All @@ -1517,38 +1502,18 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
/// statements (which simulate the maximal effect of executing the
/// patterns in a match arm).
pub fn emit_read_for_match(&self) -> bool {
self.use_mir_borrowck() && !self.sess.opts.debugging_opts.nll_dont_emit_read_for_match
}

/// If true, pattern variables for use in guards on match arms
/// will be bound as references to the data, and occurrences of
/// those variables in the guard expression will implicitly
/// dereference those bindings. (See rust-lang/rust#27282.)
pub fn all_pat_vars_are_implicit_refs_within_guards(self) -> bool {
self.borrowck_mode().use_mir()
}

/// If true, we should enable two-phase borrows checks. This is
/// done with either: `-Ztwo-phase-borrows`, `#![feature(nll)]`,
/// or by opting into an edition after 2015.
pub fn two_phase_borrows(self) -> bool {
self.sess.rust_2018() || self.features().nll ||
self.sess.opts.debugging_opts.two_phase_borrows
!self.sess.opts.debugging_opts.nll_dont_emit_read_for_match
}

/// What mode(s) of borrowck should we run? AST? MIR? both?
/// (Also considers the `#![feature(nll)]` setting.)
pub fn borrowck_mode(&self) -> BorrowckMode {
// Here are the main constraints we need to deal with:
//
// 1. An opts.borrowck_mode of `BorrowckMode::Ast` is
// 1. An opts.borrowck_mode of `BorrowckMode::Migrate` is
// synonymous with no `-Z borrowck=...` flag at all.
// (This is arguably a historical accident.)
//
// 2. `BorrowckMode::Migrate` is the limited migration to
// NLL that we are deploying with the 2018 edition.
//
// 3. We want to allow developers on the Nightly channel
// 2. We want to allow developers on the Nightly channel
// to opt back into the "hard error" mode for NLL,
// (which they can do via specifying `#![feature(nll)]`
// explicitly in their crate).
Expand All @@ -1561,24 +1526,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
// a user's attempt to specify `-Z borrowck=compare`, which
// we arguably do not need anymore and should remove.)
//
// * Otherwise, if no `-Z borrowck=...` flag was given (or
// if `borrowck=ast` was specified), then use the default
// as required by the edition.
// * Otherwise, if no `-Z borrowck=...` then use migrate mode
//
// * Otherwise, use the behavior requested via `-Z borrowck=...`

if self.features().nll { return BorrowckMode::Mir; }

match self.sess.opts.borrowck_mode {
mode @ BorrowckMode::Mir |
mode @ BorrowckMode::Compare |
mode @ BorrowckMode::Migrate => mode,

BorrowckMode::Ast => match self.sess.edition() {
Edition::Edition2015 => BorrowckMode::Ast,
Edition::Edition2018 => BorrowckMode::Migrate,
},
}
self.sess.opts.borrowck_mode
}

#[inline]
Expand Down
6 changes: 0 additions & 6 deletions src/librustc_borrowck/borrowck/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,6 @@ pub mod gather_loans;

pub mod move_data;

mod unused;

#[derive(Clone, Copy)]
pub struct LoanDataFlowOperator;

Expand Down Expand Up @@ -139,10 +137,6 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
check_loans::check_loans(&mut bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
}

if !tcx.use_mir_borrowck() {
unused::check(&mut bccx, body);
}

Lrc::new(BorrowCheckResult {
used_mut_nodes: bccx.used_mut_nodes.into_inner(),
signalled_any_error: bccx.signalled_any_error.into_inner(),
Expand Down
116 changes: 0 additions & 116 deletions src/librustc_borrowck/borrowck/unused.rs

This file was deleted.

5 changes: 2 additions & 3 deletions src/librustc_mir/borrow_check/borrow_set.rs
Original file line number Diff line number Diff line change
Expand Up @@ -303,9 +303,8 @@ impl<'a, 'gcx, 'tcx> GatherBorrows<'a, 'gcx, 'tcx> {
/// allowed to be split into separate Reservation and
/// Activation phases.
fn allow_two_phase_borrow(&self, kind: mir::BorrowKind) -> bool {
self.tcx.two_phase_borrows()
&& (kind.allows_two_phase_borrow()
|| self.tcx.sess.opts.debugging_opts.two_phase_beyond_autoref)
kind.allows_two_phase_borrow()
|| self.tcx.sess.opts.debugging_opts.two_phase_beyond_autoref
}

/// If this is a two-phase borrow, then we will record it
Expand Down
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