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Rollup merge of #68422 - Centril:diverges-simplify, r=eddyb

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typeck: simplify the handling of `diverges`

Some drive-by cleanup while working on `hir::ExprKind::Let`.
Ostensibly, this has some perf benefits due to reduced allocation and whatnot as well.

r? @eddyb
This commit is contained in:
Mazdak Farrokhzad 2020-01-22 01:50:10 +01:00 committed by GitHub
commit 4ce792ded6
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 22 additions and 46 deletions
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55
src/librustc_typeck/check/_match.rs
View File

@ -50,30 +50,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
self.warn_arms_when_scrutinee_diverges(arms, match_src);
// Otherwise, we have to union together the types that the
// arms produce and so forth.
let scrut_diverges = self.diverges.get();
self.diverges.set(Diverges::Maybe);
// Otherwise, we have to union together the types that the arms produce and so forth.
let scrut_diverges = self.diverges.replace(Diverges::Maybe);
// rust-lang/rust#55810: Typecheck patterns first (via eager
// collection into `Vec`), so we get types for all bindings.
let all_arm_pats_diverge: Vec<_> = arms
.iter()
.map(|arm| {
let mut all_pats_diverge = Diverges::WarnedAlways;
self.diverges.set(Diverges::Maybe);
self.check_pat_top(&arm.pat, scrut_ty, Some(scrut.span), true);
all_pats_diverge &= self.diverges.get();
// As discussed with @eddyb, this is for disabling unreachable_code
// warnings on patterns (they're now subsumed by unreachable_patterns
// warnings).
match all_pats_diverge {
Diverges::Maybe => Diverges::Maybe,
Diverges::Always { .. } | Diverges::WarnedAlways => Diverges::WarnedAlways,
}
})
.collect();
// #55810: Type check patterns first so we get types for all bindings.
for arm in arms {
self.check_pat_top(&arm.pat, scrut_ty, Some(scrut.span), true);
}
// Now typecheck the blocks.
//
@ -104,11 +87,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
CoerceMany::with_coercion_sites(coerce_first, arms)
};
let mut other_arms = vec![]; // used only for diagnostics
let mut other_arms = vec![]; // Used only for diagnostics.
let mut prior_arm_ty = None;
for (i, (arm, pats_diverge)) in arms.iter().zip(all_arm_pats_diverge).enumerate() {
for (i, arm) in arms.iter().enumerate() {
if let Some(g) = &arm.guard {
self.diverges.set(pats_diverge);
self.diverges.set(Diverges::Maybe);
match g {
hir::Guard::If(e) => {
self.check_expr_has_type_or_error(e, tcx.types.bool, |_| {})
@ -116,7 +99,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
};
}
self.diverges.set(pats_diverge);
self.diverges.set(Diverges::Maybe);
let arm_ty = if source_if
&& if_no_else
&& i != 0
@ -200,16 +183,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
arms: &'tcx [hir::Arm<'tcx>],
source: hir::MatchSource,
) {
if self.diverges.get().is_always() {
use hir::MatchSource::*;
let msg = match source {
IfDesugar { .. } | IfLetDesugar { .. } => "block in `if` expression",
WhileDesugar { .. } | WhileLetDesugar { .. } => "block in `while` expression",
_ => "arm",
};
for arm in arms {
self.warn_if_unreachable(arm.body.hir_id, arm.body.span, msg);
}
use hir::MatchSource::*;
let msg = match source {
IfDesugar { .. } | IfLetDesugar { .. } => "block in `if` expression",
WhileDesugar { .. } | WhileLetDesugar { .. } => "block in `while` expression",
_ => "arm",
};
for arm in arms {
self.warn_if_unreachable(arm.body.hir_id, arm.body.span, msg);
}
}

6
src/librustc_typeck/check/expr.rs
View File

@ -165,10 +165,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
// Hide the outer diverging and has_errors flags.
let old_diverges = self.diverges.get();
let old_has_errors = self.has_errors.get();
self.diverges.set(Diverges::Maybe);
self.has_errors.set(false);
let old_diverges = self.diverges.replace(Diverges::Maybe);
let old_has_errors = self.has_errors.replace(false);
let ty = self.check_expr_kind(expr, expected, needs);

7
src/librustc_typeck/check/mod.rs
View File

@ -4429,10 +4429,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
self.warn_if_unreachable(stmt.hir_id, stmt.span, "statement");
// Hide the outer diverging and `has_errors` flags.
let old_diverges = self.diverges.get();
let old_has_errors = self.has_errors.get();
self.diverges.set(Diverges::Maybe);
self.has_errors.set(false);
let old_diverges = self.diverges.replace(Diverges::Maybe);
let old_has_errors = self.has_errors.replace(false);
match stmt.kind {
hir::StmtKind::Local(ref l) => {
@ -4442,7 +4440,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
hir::StmtKind::Item(_) => {}
hir::StmtKind::Expr(ref expr) => {
// Check with expected type of `()`.
self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit(), |err| {
self.suggest_semicolon_at_end(expr.span, err);
});