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Fix debugger stepping behavior with match expressions #87832

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Aug 27, 2021
Merged

Fix debugger stepping behavior with match expressions #87832

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0a42dfc
Fix debugger stepping behavior around `match` expressions
wesleywiser Jul 23, 2021
84a2661
Add test for stepping though `match` expressions
wesleywiser Aug 6, 2021
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63 changes: 54 additions & 9 deletions compiler/rustc_mir_build/src/build/matches/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ use rustc_middle::mir::*;
use rustc_middle::thir::{self, *};
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty};
use rustc_span::symbol::Symbol;
use rustc_span::Span;
use rustc_span::{BytePos, Pos, Span};
use rustc_target::abi::VariantIdx;
use smallvec::{smallvec, SmallVec};

Expand Down Expand Up @@ -143,8 +143,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let mut candidates =
arm_candidates.iter_mut().map(|(_, candidate)| candidate).collect::<Vec<_>>();

let fake_borrow_temps =
self.lower_match_tree(block, scrutinee_span, match_has_guard, &mut candidates);
let match_start_span = span.shrink_to_lo().to(scrutinee.span);

let fake_borrow_temps = self.lower_match_tree(
block,
scrutinee_span,
match_start_span,
match_has_guard,
&mut candidates,
);

self.lower_match_arms(
destination,
Expand Down Expand Up @@ -224,6 +231,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
&mut self,
block: BasicBlock,
scrutinee_span: Span,
match_start_span: Span,
match_has_guard: bool,
candidates: &mut [&mut Candidate<'pat, 'tcx>],
) -> Vec<(Place<'tcx>, Local)> {
Expand All @@ -236,7 +244,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {

// This will generate code to test scrutinee_place and
// branch to the appropriate arm block
self.match_candidates(scrutinee_span, block, &mut otherwise, candidates, &mut fake_borrows);
self.match_candidates(
match_start_span,
scrutinee_span,
block,
&mut otherwise,
candidates,
&mut fake_borrows,
);

if let Some(otherwise_block) = otherwise {
// See the doc comment on `match_candidates` for why we may have an
Expand Down Expand Up @@ -339,8 +354,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// all the arm blocks will rejoin here
let end_block = self.cfg.start_new_block();

let end_brace = self.source_info(
outer_source_info.span.with_lo(outer_source_info.span.hi() - BytePos::from_usize(1)),
);
for arm_block in arm_end_blocks {
self.cfg.goto(unpack!(arm_block), outer_source_info, end_block);
let block = &self.cfg.basic_blocks[arm_block.0];
let last_location = block.statements.last().map(|s| s.source_info);

self.cfg.goto(unpack!(arm_block), last_location.unwrap_or(end_brace), end_block);
}

self.source_scope = outer_source_info.scope;
Expand Down Expand Up @@ -533,8 +554,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
set_match_place: bool,
) -> BlockAnd<()> {
let mut candidate = Candidate::new(initializer.clone(), &irrefutable_pat, false);
let fake_borrow_temps =
self.lower_match_tree(block, irrefutable_pat.span, false, &mut [&mut candidate]);
let fake_borrow_temps = self.lower_match_tree(
block,
irrefutable_pat.span,
irrefutable_pat.span,
false,
&mut [&mut candidate],
);
// For matches and function arguments, the place that is being matched
// can be set when creating the variables. But the place for
// let PATTERN = ... might not even exist until we do the assignment.
Expand Down Expand Up @@ -993,6 +1019,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn match_candidates<'pat>(
&mut self,
span: Span,
scrutinee_span: Span,
start_block: BasicBlock,
otherwise_block: &mut Option<BasicBlock>,
candidates: &mut [&mut Candidate<'pat, 'tcx>],
Expand Down Expand Up @@ -1022,6 +1049,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
self.match_simplified_candidates(
span,
scrutinee_span,
start_block,
otherwise_block,
&mut *new_candidates,
Expand All @@ -1030,6 +1058,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
} else {
self.match_simplified_candidates(
span,
scrutinee_span,
start_block,
otherwise_block,
candidates,
Expand All @@ -1042,6 +1071,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn match_simplified_candidates(
&mut self,
span: Span,
scrutinee_span: Span,
start_block: BasicBlock,
otherwise_block: &mut Option<BasicBlock>,
candidates: &mut [&mut Candidate<'_, 'tcx>],
Expand Down Expand Up @@ -1087,6 +1117,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
// Test for the remaining candidates.
self.test_candidates_with_or(
span,
scrutinee_span,
unmatched_candidates,
block,
otherwise_block,
Expand Down Expand Up @@ -1257,6 +1288,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn test_candidates_with_or(
&mut self,
span: Span,
scrutinee_span: Span,
candidates: &mut [&mut Candidate<'_, 'tcx>],
block: BasicBlock,
otherwise_block: &mut Option<BasicBlock>,
Expand All @@ -1269,7 +1301,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
match *first_candidate.match_pairs[0].pattern.kind {
PatKind::Or { .. } => (),
_ => {
self.test_candidates(span, candidates, block, otherwise_block, fake_borrows);
self.test_candidates(
span,
scrutinee_span,
candidates,
block,
otherwise_block,
fake_borrows,
);
return;
}
}
Expand Down Expand Up @@ -1302,6 +1341,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {

self.match_candidates(
span,
scrutinee_span,
remainder_start,
otherwise_block,
remaining_candidates,
Expand Down Expand Up @@ -1330,6 +1370,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
otherwise
};
self.match_candidates(
or_span,
or_span,
candidate.pre_binding_block.unwrap(),
otherwise,
Expand Down Expand Up @@ -1497,6 +1538,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
fn test_candidates<'pat, 'b, 'c>(
&mut self,
span: Span,
scrutinee_span: Span,
mut candidates: &'b mut [&'c mut Candidate<'pat, 'tcx>],
block: BasicBlock,
otherwise_block: &mut Option<BasicBlock>,
Expand Down Expand Up @@ -1591,6 +1633,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let candidate_start = this.cfg.start_new_block();
this.match_candidates(
span,
scrutinee_span,
candidate_start,
remainder_start,
&mut *candidates,
Expand All @@ -1607,6 +1650,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let remainder_start = remainder_start.unwrap_or_else(|| this.cfg.start_new_block());
this.match_candidates(
span,
scrutinee_span,
remainder_start,
otherwise_block,
candidates,
Expand All @@ -1617,7 +1661,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
target_blocks
};

self.perform_test(block, match_place, &test, make_target_blocks);
self.perform_test(span, scrutinee_span, block, match_place, &test, make_target_blocks);
}

/// Determine the fake borrows that are needed from a set of places that
Expand Down Expand Up @@ -1713,6 +1757,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
let fake_borrow_temps = self.lower_match_tree(
block,
pat.span,
pat.span,
false,
&mut [&mut guard_candidate, &mut otherwise_candidate],
);
Expand Down
14 changes: 11 additions & 3 deletions compiler/rustc_mir_build/src/build/matches/test.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ use rustc_middle::ty::util::IntTypeExt;
use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
use rustc_span::def_id::DefId;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::Span;
use rustc_target::abi::VariantIdx;

use std::cmp::Ordering;
Expand Down Expand Up @@ -151,6 +152,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {

pub(super) fn perform_test(
&mut self,
match_start_span: Span,
scrutinee_span: Span,
block: BasicBlock,
place_builder: PlaceBuilder<'tcx>,
test: &Test<'tcx>,
Expand Down Expand Up @@ -206,10 +209,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
debug!("num_enum_variants: {}, variants: {:?}", num_enum_variants, variants);
let discr_ty = adt_def.repr.discr_type().to_ty(tcx);
let discr = self.temp(discr_ty, test.span);
self.cfg.push_assign(block, source_info, discr, Rvalue::Discriminant(place));
self.cfg.push_assign(
block,
self.source_info(scrutinee_span),
discr,
Rvalue::Discriminant(place),
);
self.cfg.terminate(
block,
source_info,
self.source_info(match_start_span),
TerminatorKind::SwitchInt {
discr: Operand::Move(discr),
switch_ty: discr_ty,
Expand Down Expand Up @@ -246,7 +254,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
targets: switch_targets,
}
};
self.cfg.terminate(block, source_info, terminator);
self.cfg.terminate(block, self.source_info(match_start_span), terminator);
}

TestKind::Eq { value, ty } => {
Expand Down
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