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Add #[loop_match] for improved DFA codegen

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Co-authored-by: Folkert de Vries <folkert@folkertdev.nl>
This commit is contained in:
bjorn3
2025-02-18 14:16:57 +01:00
committed by Folkert de Vries
parent 42245d34d2
commit ba5556d239
57 changed files with 2480 additions and 45 deletions
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1
Cargo.lock
View File

@@ -4117,6 +4117,7 @@ dependencies = [
"rustc_apfloat",
"rustc_arena",
"rustc_ast",
"rustc_attr_data_structures",
"rustc_data_structures",
"rustc_errors",
"rustc_fluent_macro",

6
compiler/rustc_attr_data_structures/src/attributes.rs
View File

@@ -212,6 +212,9 @@ pub enum AttributeKind {
first_span: Span,
},
/// Represents `#[const_continue]`.
ConstContinue(Span),
/// Represents `#[rustc_const_stable]` and `#[rustc_const_unstable]`.
ConstStability {
stability: PartialConstStability,
@@ -231,6 +234,9 @@ pub enum AttributeKind {
/// Represents `#[inline]` and `#[rustc_force_inline]`.
Inline(InlineAttr, Span),
/// Represents `#[loop_match]`.
LoopMatch(Span),
/// Represents `#[rustc_macro_transparency]`.
MacroTransparency(Transparency),

31
compiler/rustc_attr_parsing/src/attributes/loop_match.rs Normal file
View File

@@ -0,0 +1,31 @@
use rustc_attr_data_structures::AttributeKind;
use rustc_feature::{AttributeTemplate, template};
use rustc_span::{Symbol, sym};
use crate::attributes::{AttributeOrder, OnDuplicate, SingleAttributeParser};
use crate::context::{AcceptContext, Stage};
use crate::parser::ArgParser;
pub(crate) struct LoopMatchParser;
impl<S: Stage> SingleAttributeParser<S> for LoopMatchParser {
const PATH: &[Symbol] = &[sym::loop_match];
const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
const TEMPLATE: AttributeTemplate = template!(Word);
fn convert(cx: &mut AcceptContext<'_, '_, S>, _args: &ArgParser<'_>) -> Option<AttributeKind> {
Some(AttributeKind::LoopMatch(cx.attr_span))
}
}
pub(crate) struct ConstContinueParser;
impl<S: Stage> SingleAttributeParser<S> for ConstContinueParser {
const PATH: &[Symbol] = &[sym::const_continue];
const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
const TEMPLATE: AttributeTemplate = template!(Word);
fn convert(cx: &mut AcceptContext<'_, '_, S>, _args: &ArgParser<'_>) -> Option<AttributeKind> {
Some(AttributeKind::ConstContinue(cx.attr_span))
}
}

1
compiler/rustc_attr_parsing/src/attributes/mod.rs
View File

@@ -32,6 +32,7 @@ pub(crate) mod confusables;
pub(crate) mod deprecation;
pub(crate) mod inline;
pub(crate) mod lint_helpers;
pub(crate) mod loop_match;
pub(crate) mod must_use;
pub(crate) mod repr;
pub(crate) mod semantics;

3
compiler/rustc_attr_parsing/src/context.rs
View File

@@ -20,6 +20,7 @@ use crate::attributes::confusables::ConfusablesParser;
use crate::attributes::deprecation::DeprecationParser;
use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
use crate::attributes::lint_helpers::{AsPtrParser, PubTransparentParser};
use crate::attributes::loop_match::{ConstContinueParser, LoopMatchParser};
use crate::attributes::must_use::MustUseParser;
use crate::attributes::repr::{AlignParser, ReprParser};
use crate::attributes::semantics::MayDangleParser;
@@ -110,9 +111,11 @@ attribute_parsers!(
// tidy-alphabetical-start
Single<AsPtrParser>,
Single<ColdParser>,
Single<ConstContinueParser>,
Single<ConstStabilityIndirectParser>,
Single<DeprecationParser>,
Single<InlineParser>,
Single<LoopMatchParser>,
Single<MayDangleParser>,
Single<MustUseParser>,
Single<NoMangleParser>,

13
compiler/rustc_feature/src/builtin_attrs.rs
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@@ -657,6 +657,19 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
EncodeCrossCrate::Yes, min_generic_const_args, experimental!(type_const),
),
// The `#[loop_match]` and `#[const_continue]` attributes are part of the
// lang experiment for RFC 3720 tracked in:
//
// - https://github.com/rust-lang/rust/issues/132306
gated!(
const_continue, Normal, template!(Word), ErrorFollowing,
EncodeCrossCrate::No, loop_match, experimental!(const_continue)
),
gated!(
loop_match, Normal, template!(Word), ErrorFollowing,
EncodeCrossCrate::No, loop_match, experimental!(loop_match)
),
// ==========================================================================
// Internal attributes: Stability, deprecation, and unsafe:
// ==========================================================================

2
compiler/rustc_feature/src/unstable.rs
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@@ -557,6 +557,8 @@ declare_features! (
/// Allows using `#[link(kind = "link-arg", name = "...")]`
/// to pass custom arguments to the linker.
(unstable, link_arg_attribute, "1.76.0", Some(99427)),
/// Allows fused `loop`/`match` for direct intraprocedural jumps.
(incomplete, loop_match, "CURRENT_RUSTC_VERSION", Some(132306)),
/// Give access to additional metadata about declarative macro meta-variables.
(unstable, macro_metavar_expr, "1.61.0", Some(83527)),
/// Provides a way to concatenate identifiers using metavariable expressions.

3
compiler/rustc_hir_typeck/messages.ftl
View File

@@ -79,6 +79,9 @@ hir_typeck_cast_unknown_pointer = cannot cast {$to ->
.note = the type information given here is insufficient to check whether the pointer cast is valid
.label_from = the type information given here is insufficient to check whether the pointer cast is valid
hir_typeck_const_continue_bad_label =
`#[const_continue]` must break to a labeled block that participates in a `#[loop_match]`
hir_typeck_const_select_must_be_const = this argument must be a `const fn`
.help = consult the documentation on `const_eval_select` for more information

7
compiler/rustc_hir_typeck/src/errors.rs
View File

@@ -1167,3 +1167,10 @@ pub(crate) struct AbiCannotBeCalled {
pub span: Span,
pub abi: ExternAbi,
}
#[derive(Diagnostic)]
#[diag(hir_typeck_const_continue_bad_label)]
pub(crate) struct ConstContinueBadLabel {
#[primary_span]
pub span: Span,
}

70
compiler/rustc_hir_typeck/src/loops.rs
View File

@@ -2,6 +2,8 @@ use std::collections::BTreeMap;
use std::fmt;
use Context::*;
use rustc_ast::Label;
use rustc_attr_data_structures::{AttributeKind, find_attr};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::LocalDefId;
@@ -14,8 +16,9 @@ use rustc_span::hygiene::DesugaringKind;
use rustc_span::{BytePos, Span};
use crate::errors::{
BreakInsideClosure, BreakInsideCoroutine, BreakNonLoop, ContinueLabeledBlock, OutsideLoop,
OutsideLoopSuggestion, UnlabeledCfInWhileCondition, UnlabeledInLabeledBlock,
BreakInsideClosure, BreakInsideCoroutine, BreakNonLoop, ConstContinueBadLabel,
ContinueLabeledBlock, OutsideLoop, OutsideLoopSuggestion, UnlabeledCfInWhileCondition,
UnlabeledInLabeledBlock,
};
/// The context in which a block is encountered.
@@ -37,6 +40,11 @@ enum Context {
AnonConst,
/// E.g. `const { ... }`.
ConstBlock,
/// E.g. `#[loop_match] loop { state = 'label: { /* ... */ } }`.
LoopMatch {
/// The label of the labeled block (not of the loop itself).
labeled_block: Label,
},
}
#[derive(Clone)]
@@ -141,7 +149,12 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
}
}
hir::ExprKind::Loop(ref b, _, source, _) => {
self.with_context(Loop(source), |v| v.visit_block(b));
let cx = match self.is_loop_match(e, b) {
Some(labeled_block) => LoopMatch { labeled_block },
None => Loop(source),
};
self.with_context(cx, |v| v.visit_block(b));
}
hir::ExprKind::Closure(&hir::Closure {
ref fn_decl, body, fn_decl_span, kind, ..
@@ -197,6 +210,23 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
Err(hir::LoopIdError::UnresolvedLabel) => None,
};
// A `#[const_continue]` must break to a block in a `#[loop_match]`.
if find_attr!(self.tcx.hir_attrs(e.hir_id), AttributeKind::ConstContinue(_)) {
if let Some(break_label) = break_label.label {
let is_target_label = |cx: &Context| match cx {
Context::LoopMatch { labeled_block } => {
break_label.ident.name == labeled_block.ident.name
}
_ => false,
};
if !self.cx_stack.iter().rev().any(is_target_label) {
let span = break_label.ident.span;
self.tcx.dcx().emit_fatal(ConstContinueBadLabel { span });
}
}
}
if let Some(Node::Block(_)) = loop_id.map(|id| self.tcx.hir_node(id)) {
return;
}
@@ -299,7 +329,7 @@ impl<'hir> CheckLoopVisitor<'hir> {
cx_pos: usize,
) {
match self.cx_stack[cx_pos] {
LabeledBlock | Loop(_) => {}
LabeledBlock | Loop(_) | LoopMatch { .. } => {}
Closure(closure_span) => {
self.tcx.dcx().emit_err(BreakInsideClosure {
span,
@@ -380,4 +410,36 @@ impl<'hir> CheckLoopVisitor<'hir> {
});
}
}
/// Is this a loop annotated with `#[loop_match]` that looks syntactically sound?
fn is_loop_match(
&self,
e: &'hir hir::Expr<'hir>,
body: &'hir hir::Block<'hir>,
) -> Option<Label> {
if !find_attr!(self.tcx.hir_attrs(e.hir_id), AttributeKind::LoopMatch(_)) {
return None;
}
// NOTE: Diagnostics are emitted during MIR construction.
// Accept either `state = expr` or `state = expr;`.
let loop_body_expr = match body.stmts {
[] => match body.expr {
Some(expr) => expr,
None => return None,
},
[single] if body.expr.is_none() => match single.kind {
hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr) => expr,
_ => return None,
},
[..] => return None,
};
let hir::ExprKind::Assign(_, rhs_expr, _) = loop_body_expr.kind else { return None };
let hir::ExprKind::Block(_, label) = rhs_expr.kind else { return None };
label
}
}

13
compiler/rustc_middle/src/thir.rs
View File

@@ -378,6 +378,14 @@ pub enum ExprKind<'tcx> {
Loop {
body: ExprId,
},
/// A `#[loop_match] loop { state = 'blk: { match state { ... } } }` expression.
LoopMatch {
/// The state variable that is updated, and also the scrutinee of the match.
state: ExprId,
region_scope: region::Scope,
arms: Box<[ArmId]>,
match_span: Span,
},
/// Special expression representing the `let` part of an `if let` or similar construct
/// (including `if let` guards in match arms, and let-chains formed by `&&`).
///
@@ -454,6 +462,11 @@ pub enum ExprKind<'tcx> {
Continue {
label: region::Scope,
},
/// A `#[const_continue] break` expression.
ConstContinue {
label: region::Scope,
value: ExprId,
},
/// A `return` expression.
Return {
value: Option<ExprId>,

3
compiler/rustc_middle/src/thir/visit.rs
View File

@@ -83,7 +83,7 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
visitor.visit_pat(pat);
}
Loop { body } => visitor.visit_expr(&visitor.thir()[body]),
Match { scrutinee, ref arms, .. } => {
LoopMatch { state: scrutinee, ref arms, .. } | Match { scrutinee, ref arms, .. } => {
visitor.visit_expr(&visitor.thir()[scrutinee]);
for &arm in &**arms {
visitor.visit_arm(&visitor.thir()[arm]);
@@ -108,6 +108,7 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
}
}
Continue { label: _ } => {}
ConstContinue { value, label: _ } => visitor.visit_expr(&visitor.thir()[value]),
Return { value } => {
if let Some(value) = value {
visitor.visit_expr(&visitor.thir()[value])

1
compiler/rustc_mir_build/Cargo.toml
View File

@@ -11,6 +11,7 @@ rustc_abi = { path = "../rustc_abi" }
rustc_apfloat = "0.2.0"
rustc_arena = { path = "../rustc_arena" }
rustc_ast = { path = "../rustc_ast" }
rustc_attr_data_structures = { path = "../rustc_attr_data_structures" }
rustc_data_structures = { path = "../rustc_data_structures" }
rustc_errors = { path = "../rustc_errors" }
rustc_fluent_macro = { path = "../rustc_fluent_macro" }

33
compiler/rustc_mir_build/messages.ftl
View File

@@ -84,6 +84,15 @@ mir_build_call_to_unsafe_fn_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
mir_build_confused = missing patterns are not covered because `{$variable}` is interpreted as a constant pattern, not a new variable
mir_build_const_continue_bad_const = could not determine the target branch for this `#[const_continue]`
.label = this value is too generic
.note = the value must be a literal or a monomorphic const
mir_build_const_continue_missing_value = a `#[const_continue]` must break to a label with a value
mir_build_const_continue_unknown_jump_target = the target of this `#[const_continue]` is not statically known
.label = this value must be a literal or a monomorphic const
mir_build_const_defined_here = constant defined here
mir_build_const_param_in_pattern = constant parameters cannot be referenced in patterns
@@ -212,6 +221,30 @@ mir_build_literal_in_range_out_of_bounds =
literal out of range for `{$ty}`
.label = this value does not fit into the type `{$ty}` whose range is `{$min}..={$max}`
mir_build_loop_match_arm_with_guard =
match arms that are part of a `#[loop_match]` cannot have guards
mir_build_loop_match_bad_rhs =
this expression must be a single `match` wrapped in a labeled block
mir_build_loop_match_bad_statements =
statements are not allowed in this position within a `#[loop_match]`
mir_build_loop_match_invalid_match =
invalid match on `#[loop_match]` state
.note = a local variable must be the scrutinee within a `#[loop_match]`
mir_build_loop_match_invalid_update =
invalid update of the `#[loop_match]` state
.label = the assignment must update this variable
mir_build_loop_match_missing_assignment =
expected a single assignment expression
mir_build_loop_match_unsupported_type =
this `#[loop_match]` state value has type `{$ty}`, which is not supported
.note = only integers, floats, bool, char, and enums without fields are supported
mir_build_lower_range_bound_must_be_less_than_or_equal_to_upper =
lower range bound must be less than or equal to upper
.label = lower bound larger than upper bound

2
compiler/rustc_mir_build/src/builder/expr/as_place.rs
View File

@@ -565,12 +565,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
| ExprKind::Match { .. }
| ExprKind::If { .. }
| ExprKind::Loop { .. }
| ExprKind::LoopMatch { .. }
| ExprKind::Block { .. }
| ExprKind::Let { .. }
| ExprKind::Assign { .. }
| ExprKind::AssignOp { .. }
| ExprKind::Break { .. }
| ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. }
| ExprKind::Literal { .. }

2
compiler/rustc_mir_build/src/builder/expr/as_rvalue.rs
View File

@@ -538,6 +538,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
| ExprKind::RawBorrow { .. }
| ExprKind::Adt { .. }
| ExprKind::Loop { .. }
| ExprKind::LoopMatch { .. }
| ExprKind::LogicalOp { .. }
| ExprKind::Call { .. }
| ExprKind::Field { .. }
@@ -548,6 +549,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
| ExprKind::UpvarRef { .. }
| ExprKind::Break { .. }
| ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. }
| ExprKind::InlineAsm { .. }

2
compiler/rustc_mir_build/src/builder/expr/category.rs
View File

@@ -83,9 +83,11 @@ impl Category {
| ExprKind::NamedConst { .. } => Some(Category::Constant),
ExprKind::Loop { .. }
| ExprKind::LoopMatch { .. }
| ExprKind::Block { .. }
| ExprKind::Break { .. }
| ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. } =>
// FIXME(#27840) these probably want their own

122
compiler/rustc_mir_build/src/builder/expr/into.rs
View File

@@ -8,15 +8,16 @@ use rustc_hir::lang_items::LangItem;
use rustc_middle::mir::*;
use rustc_middle::span_bug;
use rustc_middle::thir::*;
use rustc_middle::ty::{CanonicalUserTypeAnnotation, Ty};
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty};
use rustc_span::DUMMY_SP;
use rustc_span::source_map::Spanned;
use rustc_trait_selection::infer::InferCtxtExt;
use tracing::{debug, instrument};
use crate::builder::expr::category::{Category, RvalueFunc};
use crate::builder::matches::DeclareLetBindings;
use crate::builder::matches::{DeclareLetBindings, HasMatchGuard};
use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, NeedsTemporary};
use crate::errors::{LoopMatchArmWithGuard, LoopMatchUnsupportedType};
impl<'a, 'tcx> Builder<'a, 'tcx> {
/// Compile `expr`, storing the result into `destination`, which
@@ -244,6 +245,122 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
None
})
}
ExprKind::LoopMatch { state, region_scope, match_span, ref arms } => {
// Intuitively, this is a combination of a loop containing a labeled block
// containing a match.
//
// The only new bit here is that the lowering of the match is wrapped in a
// `in_const_continuable_scope`, which makes the match arms and their target basic
// block available to the lowering of `#[const_continue]`.
fn is_supported_loop_match_type(ty: Ty<'_>) -> bool {
match ty.kind() {
ty::Uint(_) | ty::Int(_) | ty::Float(_) | ty::Bool | ty::Char => true,
ty::Adt(adt_def, _) => match adt_def.adt_kind() {
ty::AdtKind::Struct | ty::AdtKind::Union => false,
ty::AdtKind::Enum => {
adt_def.variants().iter().all(|v| v.fields.is_empty())
}
},
_ => false,
}
}
let state_ty = this.thir.exprs[state].ty;
if !is_supported_loop_match_type(state_ty) {
let span = this.thir.exprs[state].span;
this.tcx.dcx().emit_fatal(LoopMatchUnsupportedType { span, ty: state_ty })
}
let loop_block = this.cfg.start_new_block();
// Start the loop.
this.cfg.goto(block, source_info, loop_block);
this.in_breakable_scope(Some(loop_block), destination, expr_span, |this| {
// Logic for `loop`.
let mut body_block = this.cfg.start_new_block();
this.cfg.terminate(
loop_block,
source_info,
TerminatorKind::FalseUnwind {
real_target: body_block,
unwind: UnwindAction::Continue,
},
);
this.diverge_from(loop_block);
// Logic for `match`.
let scrutinee_place_builder =
unpack!(body_block = this.as_place_builder(body_block, state));
let scrutinee_span = this.thir.exprs[state].span;
let match_start_span = match_span.shrink_to_lo().to(scrutinee_span);
let mut patterns = Vec::with_capacity(arms.len());
for &arm_id in arms.iter() {
let arm = &this.thir[arm_id];
if let Some(guard) = arm.guard {
let span = this.thir.exprs[guard].span;
this.tcx.dcx().emit_fatal(LoopMatchArmWithGuard { span })
}
patterns.push((&*arm.pattern, HasMatchGuard::No));
}
// The `built_tree` maps match arms to their basic block (where control flow
// jumps to when a value matches the arm). This structure is stored so that a
// `#[const_continue]` can figure out what basic block to jump to.
let built_tree = this.lower_match_tree(
body_block,
scrutinee_span,
&scrutinee_place_builder,
match_start_span,
patterns,
false,
);
let state_place = scrutinee_place_builder.to_place(this);
// This is logic for the labeled block: a block is a drop scope, hence
// `in_scope`, and a labeled block can be broken out of with a `break 'label`,
// hence the `in_breakable_scope`.
//
// Then `in_const_continuable_scope` stores information for the lowering of
// `#[const_continue]`, and finally the match is lowered in the standard way.
unpack!(
body_block = this.in_scope(
(region_scope, source_info),
LintLevel::Inherited,
move |this| {
this.in_breakable_scope(None, state_place, expr_span, |this| {
Some(this.in_const_continuable_scope(
arms.clone(),
built_tree.clone(),
state_place,
expr_span,
|this| {
this.lower_match_arms(
destination,
scrutinee_place_builder,
scrutinee_span,
arms,
built_tree,
this.source_info(match_span),
)
},
))
})
}
)
);
this.cfg.goto(body_block, source_info, loop_block);
// Loops are only exited by `break` expressions.
None
})
}
ExprKind::Call { ty: _, fun, ref args, from_hir_call, fn_span } => {
let fun = unpack!(block = this.as_local_operand(block, fun));
let args: Box<[_]> = args
@@ -601,6 +718,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Break { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. } => {

3
compiler/rustc_mir_build/src/builder/expr/stmt.rs
View File

@@ -98,6 +98,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
ExprKind::Break { label, value } => {
this.break_scope(block, value, BreakableTarget::Break(label), source_info)
}
ExprKind::ConstContinue { label, value } => {
this.break_const_continuable_scope(block, value, label, source_info)
}
ExprKind::Return { value } => {
this.break_scope(block, value, BreakableTarget::Return, source_info)
}

144
compiler/rustc_mir_build/src/builder/matches/mod.rs
View File

@@ -18,7 +18,9 @@ use rustc_middle::bug;
use rustc_middle::middle::region;
use rustc_middle::mir::{self, *};
use rustc_middle::thir::{self, *};
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty};
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, Ty, ValTree, ValTreeKind};
use rustc_pattern_analysis::constructor::RangeEnd;
use rustc_pattern_analysis::rustc::{DeconstructedPat, RustcPatCtxt};
use rustc_span::{BytePos, Pos, Span, Symbol, sym};
use tracing::{debug, instrument};
@@ -426,7 +428,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
/// (by [Builder::lower_match_tree]).
///
/// `outer_source_info` is the SourceInfo for the whole match.
fn lower_match_arms(
pub(crate) fn lower_match_arms(
&mut self,
destination: Place<'tcx>,
scrutinee_place_builder: PlaceBuilder<'tcx>,
@@ -1395,7 +1397,7 @@ pub(crate) struct ArmHasGuard(pub(crate) bool);
/// A sub-branch in the output of match lowering. Match lowering has generated MIR code that will
/// branch to `success_block` when the matched value matches the corresponding pattern. If there is
/// a guard, its failure must continue to `otherwise_block`, which will resume testing patterns.
#[derive(Debug)]
#[derive(Debug, Clone)]
struct MatchTreeSubBranch<'tcx> {
span: Span,
/// The block that is branched to if the corresponding subpattern matches.
@@ -1411,7 +1413,7 @@ struct MatchTreeSubBranch<'tcx> {
}
/// A branch in the output of match lowering.
#[derive(Debug)]
#[derive(Debug, Clone)]
struct MatchTreeBranch<'tcx> {
sub_branches: Vec<MatchTreeSubBranch<'tcx>>,
}
@@ -1430,8 +1432,8 @@ struct MatchTreeBranch<'tcx> {
/// Here the first arm gives the first `MatchTreeBranch`, which has two sub-branches, one for each
/// alternative of the or-pattern. They are kept separate because each needs to bind `x` to a
/// different place.
#[derive(Debug)]
struct BuiltMatchTree<'tcx> {
#[derive(Debug, Clone)]
pub(crate) struct BuiltMatchTree<'tcx> {
branches: Vec<MatchTreeBranch<'tcx>>,
otherwise_block: BasicBlock,
/// If any of the branches had a guard, we collect here the places and locals to fakely borrow
@@ -1489,7 +1491,7 @@ impl<'tcx> MatchTreeBranch<'tcx> {
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum HasMatchGuard {
pub(crate) enum HasMatchGuard {
Yes,
No,
}
@@ -1504,7 +1506,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
/// `refutable` indicates whether the candidate list is refutable (for `if let` and `let else`)
/// or not (for `let` and `match`). In the refutable case we return the block to which we branch
/// on failure.
fn lower_match_tree(
pub(crate) fn lower_match_tree(
&mut self,
block: BasicBlock,
scrutinee_span: Span,
@@ -1890,7 +1892,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
debug!("expanding or-pattern: candidate={:#?}\npats={:#?}", candidate, pats);
candidate.or_span = Some(match_pair.pattern_span);
candidate.subcandidates = pats
.into_vec()
.into_iter()
.map(|flat_pat| Candidate::from_flat_pat(flat_pat, candidate.has_guard))
.collect();
@@ -2864,4 +2865,129 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
true
}
/// Attempt to statically pick the `BasicBlock` that a value would resolve to at runtime.
pub(crate) fn static_pattern_match(
&self,
cx: &RustcPatCtxt<'_, 'tcx>,
valtree: ValTree<'tcx>,
arms: &[ArmId],
built_match_tree: &BuiltMatchTree<'tcx>,
) -> Option<BasicBlock> {
let it = arms.iter().zip(built_match_tree.branches.iter());
for (&arm_id, branch) in it {
let pat = cx.lower_pat(&*self.thir.arms[arm_id].pattern);
// Peel off or-patterns if they exist.
if let rustc_pattern_analysis::rustc::Constructor::Or = pat.ctor() {
for pat in pat.iter_fields() {
// For top-level or-patterns (the only ones we accept right now), when the
// bindings are the same (e.g. there are none), the sub_branch is stored just
// once.
let sub_branch = branch
.sub_branches
.get(pat.idx)
.or_else(|| branch.sub_branches.last())
.unwrap();
match self.static_pattern_match_inner(valtree, &pat.pat) {
true => return Some(sub_branch.success_block),
false => continue,
}
}
} else if self.static_pattern_match_inner(valtree, &pat) {
return Some(branch.sub_branches[0].success_block);
}
}
None
}
/// Helper for [`Self::static_pattern_match`], checking whether the value represented by the
/// `ValTree` matches the given pattern. This function does not recurse, meaning that it does
/// not handle or-patterns, or patterns for types with fields.
fn static_pattern_match_inner(
&self,
valtree: ty::ValTree<'tcx>,
pat: &DeconstructedPat<'_, 'tcx>,
) -> bool {
use rustc_pattern_analysis::constructor::{IntRange, MaybeInfiniteInt};
use rustc_pattern_analysis::rustc::Constructor;
match pat.ctor() {
Constructor::Variant(variant_index) => {
let ValTreeKind::Branch(box [actual_variant_idx]) = *valtree else {
bug!("malformed valtree for an enum")
};
let ValTreeKind::Leaf(actual_variant_idx) = ***actual_variant_idx else {
bug!("malformed valtree for an enum")
};
*variant_index == VariantIdx::from_u32(actual_variant_idx.to_u32())
}
Constructor::IntRange(int_range) => {
let size = pat.ty().primitive_size(self.tcx);
let actual_int = valtree.unwrap_leaf().to_bits(size);
let actual_int = if pat.ty().is_signed() {
MaybeInfiniteInt::new_finite_int(actual_int, size.bits())
} else {
MaybeInfiniteInt::new_finite_uint(actual_int)
};
IntRange::from_singleton(actual_int).is_subrange(int_range)
}
Constructor::Bool(pattern_value) => match valtree.unwrap_leaf().try_to_bool() {
Ok(actual_value) => *pattern_value == actual_value,
Err(()) => bug!("bool value with invalid bits"),
},
Constructor::F16Range(l, h, end) => {
let actual = valtree.unwrap_leaf().to_f16();
match end {
RangeEnd::Included => (*l..=*h).contains(&actual),
RangeEnd::Excluded => (*l..*h).contains(&actual),
}
}
Constructor::F32Range(l, h, end) => {
let actual = valtree.unwrap_leaf().to_f32();
match end {
RangeEnd::Included => (*l..=*h).contains(&actual),
RangeEnd::Excluded => (*l..*h).contains(&actual),
}
}
Constructor::F64Range(l, h, end) => {
let actual = valtree.unwrap_leaf().to_f64();
match end {
RangeEnd::Included => (*l..=*h).contains(&actual),
RangeEnd::Excluded => (*l..*h).contains(&actual),
}
}
Constructor::F128Range(l, h, end) => {
let actual = valtree.unwrap_leaf().to_f128();
match end {
RangeEnd::Included => (*l..=*h).contains(&actual),
RangeEnd::Excluded => (*l..*h).contains(&actual),
}
}
Constructor::Wildcard => true,
// These we may eventually support:
Constructor::Struct
| Constructor::Ref
| Constructor::DerefPattern(_)
| Constructor::Slice(_)
| Constructor::UnionField
| Constructor::Or
| Constructor::Str(_) => bug!("unsupported pattern constructor {:?}", pat.ctor()),
// These should never occur here:
Constructor::Opaque(_)
| Constructor::Never
| Constructor::NonExhaustive
| Constructor::Hidden
| Constructor::Missing
| Constructor::PrivateUninhabited => {
bug!("unsupported pattern constructor {:?}", pat.ctor())
}
}
}
}

264
compiler/rustc_mir_build/src/builder/scope.rs
View File

@@ -83,20 +83,24 @@ that contains only loops and breakable blocks. It tracks where a `break`,
use std::mem;
use interpret::ErrorHandled;
use rustc_data_structures::fx::FxHashMap;
use rustc_hir::HirId;
use rustc_index::{IndexSlice, IndexVec};
use rustc_middle::middle::region;
use rustc_middle::mir::*;
use rustc_middle::thir::{ExprId, LintLevel};
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::mir::{self, *};
use rustc_middle::thir::{AdtExpr, AdtExprBase, ArmId, ExprId, ExprKind, LintLevel};
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt, ValTree};
use rustc_middle::{bug, span_bug};
use rustc_pattern_analysis::rustc::RustcPatCtxt;
use rustc_session::lint::Level;
use rustc_span::source_map::Spanned;
use rustc_span::{DUMMY_SP, Span};
use tracing::{debug, instrument};
use super::matches::BuiltMatchTree;
use crate::builder::{BlockAnd, BlockAndExtension, BlockFrame, Builder, CFG};
use crate::errors::{ConstContinueBadConst, ConstContinueUnknownJumpTarget};
#[derive(Debug)]
pub(crate) struct Scopes<'tcx> {
@@ -105,6 +109,8 @@ pub(crate) struct Scopes<'tcx> {
/// The current set of breakable scopes. See module comment for more details.
breakable_scopes: Vec<BreakableScope<'tcx>>,
const_continuable_scopes: Vec<ConstContinuableScope<'tcx>>,
/// The scope of the innermost if-then currently being lowered.
if_then_scope: Option<IfThenScope>,
@@ -174,6 +180,20 @@ struct BreakableScope<'tcx> {
continue_drops: Option<DropTree>,
}
#[derive(Debug)]
struct ConstContinuableScope<'tcx> {
/// The scope for the `#[loop_match]` which its `#[const_continue]`s will jump to.
region_scope: region::Scope,
/// The place of the state of a `#[loop_match]`, which a `#[const_continue]` must update.
state_place: Place<'tcx>,
arms: Box<[ArmId]>,
built_match_tree: BuiltMatchTree<'tcx>,
/// Drops that happen on a `#[const_continue]`
const_continue_drops: DropTree,
}
#[derive(Debug)]
struct IfThenScope {
/// The if-then scope or arm scope
@@ -461,6 +481,7 @@ impl<'tcx> Scopes<'tcx> {
Self {
scopes: Vec::new(),
breakable_scopes: Vec::new(),
const_continuable_scopes: Vec::new(),
if_then_scope: None,
unwind_drops: DropTree::new(),
coroutine_drops: DropTree::new(),
@@ -552,6 +573,59 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
}
}
/// Start a const-continuable scope, which tracks where `#[const_continue] break` should
/// branch to.
pub(crate) fn in_const_continuable_scope<F>(
&mut self,
arms: Box<[ArmId]>,
built_match_tree: BuiltMatchTree<'tcx>,
state_place: Place<'tcx>,
span: Span,
f: F,
) -> BlockAnd<()>
where
F: FnOnce(&mut Builder<'a, 'tcx>) -> BlockAnd<()>,
{
let region_scope = self.scopes.topmost();
let scope = ConstContinuableScope {
region_scope,
state_place,
const_continue_drops: DropTree::new(),
arms,
built_match_tree,
};
self.scopes.const_continuable_scopes.push(scope);
let normal_exit_block = f(self);
let const_continue_scope = self.scopes.const_continuable_scopes.pop().unwrap();
assert!(const_continue_scope.region_scope == region_scope);
let break_block = self.build_exit_tree(
const_continue_scope.const_continue_drops,
region_scope,
span,
None,
);
match (normal_exit_block, break_block) {
(block, None) => block,
(normal_block, Some(exit_block)) => {
let target = self.cfg.start_new_block();
let source_info = self.source_info(span);
self.cfg.terminate(
normal_block.into_block(),
source_info,
TerminatorKind::Goto { target },
);
self.cfg.terminate(
exit_block.into_block(),
source_info,
TerminatorKind::Goto { target },
);
target.unit()
}
}
}
/// Start an if-then scope which tracks drop for `if` expressions and `if`
/// guards.
///
@@ -742,6 +816,190 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
self.cfg.start_new_block().unit()
}
/// Based on `FunctionCx::eval_unevaluated_mir_constant_to_valtree`.
fn eval_unevaluated_mir_constant_to_valtree(
&self,
constant: ConstOperand<'tcx>,
) -> Result<(ty::ValTree<'tcx>, Ty<'tcx>), interpret::ErrorHandled> {
assert!(!constant.const_.ty().has_param());
let (uv, ty) = match constant.const_ {
mir::Const::Unevaluated(uv, ty) => (uv.shrink(), ty),
mir::Const::Ty(_, c) => match c.kind() {
// A constant that came from a const generic but was then used as an argument to
// old-style simd_shuffle (passing as argument instead of as a generic param).
ty::ConstKind::Value(cv) => return Ok((cv.valtree, cv.ty)),
other => span_bug!(constant.span, "{other:#?}"),
},
mir::Const::Val(mir::ConstValue::Scalar(mir::interpret::Scalar::Int(val)), ty) => {
return Ok((ValTree::from_scalar_int(self.tcx, val), ty));
}
// We should never encounter `Const::Val` unless MIR opts (like const prop) evaluate
// a constant and write that value back into `Operand`s. This could happen, but is
// unlikely. Also: all users of `simd_shuffle` are on unstable and already need to take
// a lot of care around intrinsics. For an issue to happen here, it would require a
// macro expanding to a `simd_shuffle` call without wrapping the constant argument in a
// `const {}` block, but the user pass through arbitrary expressions.
// FIXME(oli-obk): Replace the magic const generic argument of `simd_shuffle` with a
// real const generic, and get rid of this entire function.
other => span_bug!(constant.span, "{other:#?}"),
};
match self.tcx.const_eval_resolve_for_typeck(self.typing_env(), uv, constant.span) {
Ok(Ok(valtree)) => Ok((valtree, ty)),
Ok(Err(ty)) => span_bug!(constant.span, "could not convert {ty:?} to a valtree"),
Err(e) => Err(e),
}
}
/// Sets up the drops for jumping from `block` to `scope`.
pub(crate) fn break_const_continuable_scope(
&mut self,
mut block: BasicBlock,
value: ExprId,
scope: region::Scope,
source_info: SourceInfo,
) -> BlockAnd<()> {
let span = source_info.span;
// A break can only break out of a scope, so the value should be a scope.
let rustc_middle::thir::ExprKind::Scope { value, .. } = self.thir[value].kind else {
span_bug!(span, "break value must be a scope")
};
let constant = match &self.thir[value].kind {
ExprKind::Adt(box AdtExpr { variant_index, fields, base, .. }) => {
assert!(matches!(base, AdtExprBase::None));
assert!(fields.is_empty());
ConstOperand {
span: self.thir[value].span,
user_ty: None,
const_: Const::Ty(
self.thir[value].ty,
ty::Const::new_value(
self.tcx,
ValTree::from_branches(
self.tcx,
[ValTree::from_scalar_int(self.tcx, variant_index.as_u32().into())],
),
self.thir[value].ty,
),
),
}
}
_ => self.as_constant(&self.thir[value]),
};
let break_index = self
.scopes
.const_continuable_scopes
.iter()
.rposition(|const_continuable_scope| const_continuable_scope.region_scope == scope)
.unwrap_or_else(|| span_bug!(span, "no enclosing const-continuable scope found"));
let scope = &self.scopes.const_continuable_scopes[break_index];
let state_decl = &self.local_decls[scope.state_place.as_local().unwrap()];
let state_ty = state_decl.ty;
let (discriminant_ty, rvalue) = match state_ty.kind() {
ty::Adt(adt_def, _) if adt_def.is_enum() => {
(state_ty.discriminant_ty(self.tcx), Rvalue::Discriminant(scope.state_place))
}
ty::Uint(_) | ty::Int(_) | ty::Float(_) | ty::Bool | ty::Char => {
(state_ty, Rvalue::Use(Operand::Copy(scope.state_place)))
}
_ => span_bug!(state_decl.source_info.span, "unsupported #[loop_match] state"),
};
// The `PatCtxt` is normally used in pattern exhaustiveness checking, but reused
// here because it performs normalization and const evaluation.
let dropless_arena = rustc_arena::DroplessArena::default();
let typeck_results = self.tcx.typeck(self.def_id);
let cx = RustcPatCtxt {
tcx: self.tcx,
typeck_results,
module: self.tcx.parent_module(self.hir_id).to_def_id(),
// FIXME(#132279): We're in a body, should handle opaques.
typing_env: rustc_middle::ty::TypingEnv::non_body_analysis(self.tcx, self.def_id),
dropless_arena: &dropless_arena,
match_lint_level: self.hir_id,
whole_match_span: Some(rustc_span::Span::default()),
scrut_span: rustc_span::Span::default(),
refutable: true,
known_valid_scrutinee: true,
};
let valtree = match self.eval_unevaluated_mir_constant_to_valtree(constant) {
Ok((valtree, ty)) => {
// Defensively check that the type is monomorphic.
assert!(!ty.has_param());
valtree
}
Err(ErrorHandled::Reported(..)) => return self.cfg.start_new_block().unit(),
Err(ErrorHandled::TooGeneric(_)) => {
self.tcx.dcx().emit_fatal(ConstContinueBadConst { span: constant.span });
}
};
let Some(real_target) =
self.static_pattern_match(&cx, valtree, &*scope.arms, &scope.built_match_tree)
else {
self.tcx.dcx().emit_fatal(ConstContinueUnknownJumpTarget { span })
};
self.block_context.push(BlockFrame::SubExpr);
let state_place = scope.state_place;
block = self.expr_into_dest(state_place, block, value).into_block();
self.block_context.pop();
let discr = self.temp(discriminant_ty, source_info.span);
let scope_index = self
.scopes
.scope_index(self.scopes.const_continuable_scopes[break_index].region_scope, span);
let scope = &mut self.scopes.const_continuable_scopes[break_index];
self.cfg.push_assign(block, source_info, discr, rvalue);
let drop_and_continue_block = self.cfg.start_new_block();
let imaginary_target = self.cfg.start_new_block();
self.cfg.terminate(
block,
source_info,
TerminatorKind::FalseEdge { real_target: drop_and_continue_block, imaginary_target },
);
let drops = &mut scope.const_continue_drops;
let drop_idx = self.scopes.scopes[scope_index + 1..]
.iter()
.flat_map(|scope| &scope.drops)
.fold(ROOT_NODE, |drop_idx, &drop| drops.add_drop(drop, drop_idx));
drops.add_entry_point(imaginary_target, drop_idx);
self.cfg.terminate(imaginary_target, source_info, TerminatorKind::UnwindResume);
let region_scope = scope.region_scope;
let scope_index = self.scopes.scope_index(region_scope, span);
let mut drops = DropTree::new();
let drop_idx = self.scopes.scopes[scope_index + 1..]
.iter()
.flat_map(|scope| &scope.drops)
.fold(ROOT_NODE, |drop_idx, &drop| drops.add_drop(drop, drop_idx));
drops.add_entry_point(drop_and_continue_block, drop_idx);
// `build_drop_trees` doesn't have access to our source_info, so we
// create a dummy terminator now. `TerminatorKind::UnwindResume` is used
// because MIR type checking will panic if it hasn't been overwritten.
// (See `<ExitScopes as DropTreeBuilder>::link_entry_point`.)
self.cfg.terminate(drop_and_continue_block, source_info, TerminatorKind::UnwindResume);
self.build_exit_tree(drops, region_scope, span, Some(real_target));
return self.cfg.start_new_block().unit();
}
/// Sets up the drops for breaking from `block` due to an `if` condition
/// that turned out to be false.
///

2
compiler/rustc_mir_build/src/check_unsafety.rs
View File

@@ -465,10 +465,12 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
| ExprKind::Break { .. }
| ExprKind::Closure { .. }
| ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Return { .. }
| ExprKind::Become { .. }
| ExprKind::Yield { .. }
| ExprKind::Loop { .. }
| ExprKind::LoopMatch { .. }
| ExprKind::Let { .. }
| ExprKind::Match { .. }
| ExprKind::Box { .. }

77
compiler/rustc_mir_build/src/errors.rs
View File

@@ -1149,3 +1149,80 @@ impl Subdiagnostic for Rust2024IncompatiblePatSugg {
}
}
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_invalid_update)]
pub(crate) struct LoopMatchInvalidUpdate {
#[primary_span]
pub lhs: Span,
#[label]
pub scrutinee: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_invalid_match)]
#[note]
pub(crate) struct LoopMatchInvalidMatch {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_unsupported_type)]
#[note]
pub(crate) struct LoopMatchUnsupportedType<'tcx> {
#[primary_span]
pub span: Span,
pub ty: Ty<'tcx>,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_bad_statements)]
pub(crate) struct LoopMatchBadStatements {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_bad_rhs)]
pub(crate) struct LoopMatchBadRhs {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_missing_assignment)]
pub(crate) struct LoopMatchMissingAssignment {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_loop_match_arm_with_guard)]
pub(crate) struct LoopMatchArmWithGuard {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_const_continue_bad_const)]
pub(crate) struct ConstContinueBadConst {
#[primary_span]
#[label]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_const_continue_missing_value)]
pub(crate) struct ConstContinueMissingValue {
#[primary_span]
pub span: Span,
}
#[derive(Diagnostic)]
#[diag(mir_build_const_continue_unknown_jump_target)]
#[note]
pub(crate) struct ConstContinueUnknownJumpTarget {
#[primary_span]
pub span: Span,
}

103
compiler/rustc_mir_build/src/thir/cx/expr.rs
View File

@@ -1,6 +1,7 @@
use itertools::Itertools;
use rustc_abi::{FIRST_VARIANT, FieldIdx};
use rustc_ast::UnsafeBinderCastKind;
use rustc_attr_data_structures::{AttributeKind, find_attr};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir as hir;
use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
@@ -21,6 +22,7 @@ use rustc_middle::{bug, span_bug};
use rustc_span::{Span, sym};
use tracing::{debug, info, instrument, trace};
use crate::errors::*;
use crate::thir::cx::ThirBuildCx;
impl<'tcx> ThirBuildCx<'tcx> {
@@ -796,7 +798,27 @@ impl<'tcx> ThirBuildCx<'tcx> {
}
hir::ExprKind::Ret(v) => ExprKind::Return { value: v.map(|v| self.mirror_expr(v)) },
hir::ExprKind::Become(call) => ExprKind::Become { value: self.mirror_expr(call) },
hir::ExprKind::Break(dest, ref value) => match dest.target_id {
hir::ExprKind::Break(dest, ref value) => {
if find_attr!(self.tcx.hir_attrs(expr.hir_id), AttributeKind::ConstContinue(_)) {
match dest.target_id {
Ok(target_id) => {
let Some(value) = value else {
let span = expr.span;
self.tcx.dcx().emit_fatal(ConstContinueMissingValue { span })
};
ExprKind::ConstContinue {
label: region::Scope {
local_id: target_id.local_id,
data: region::ScopeData::Node,
},
value: self.mirror_expr(value),
}
}
Err(err) => bug!("invalid loop id for break: {}", err),
}
} else {
match dest.target_id {
Ok(target_id) => ExprKind::Break {
label: region::Scope {
local_id: target_id.local_id,
@@ -805,7 +827,9 @@ impl<'tcx> ThirBuildCx<'tcx> {
value: value.map(|value| self.mirror_expr(value)),
},
Err(err) => bug!("invalid loop id for break: {}", err),
},
}
}
}
hir::ExprKind::Continue(dest) => match dest.target_id {
Ok(loop_id) => ExprKind::Continue {
label: region::Scope {
@@ -840,6 +864,80 @@ impl<'tcx> ThirBuildCx<'tcx> {
match_source,
},
hir::ExprKind::Loop(body, ..) => {
if find_attr!(self.tcx.hir_attrs(expr.hir_id), AttributeKind::LoopMatch(_)) {
let dcx = self.tcx.dcx();
// Accept either `state = expr` or `state = expr;`.
let loop_body_expr = match body.stmts {
[] => match body.expr {
Some(expr) => expr,
None => dcx.emit_fatal(LoopMatchMissingAssignment { span: body.span }),
},
[single] if body.expr.is_none() => match single.kind {
hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr) => expr,
_ => dcx.emit_fatal(LoopMatchMissingAssignment { span: body.span }),
},
[first @ last] | [first, .., last] => dcx
.emit_fatal(LoopMatchBadStatements { span: first.span.to(last.span) }),
};
let hir::ExprKind::Assign(state, rhs_expr, _) = loop_body_expr.kind else {
dcx.emit_fatal(LoopMatchMissingAssignment { span: loop_body_expr.span })
};
let hir::ExprKind::Block(block_body, _) = rhs_expr.kind else {
dcx.emit_fatal(LoopMatchBadRhs { span: rhs_expr.span })
};
// The labeled block should contain one match expression, but defining items is
// allowed.
for stmt in block_body.stmts {
if !matches!(stmt.kind, rustc_hir::StmtKind::Item(_)) {
dcx.emit_fatal(LoopMatchBadStatements { span: stmt.span })
}
}
let Some(block_body_expr) = block_body.expr else {
dcx.emit_fatal(LoopMatchBadRhs { span: block_body.span })
};
let hir::ExprKind::Match(scrutinee, arms, _match_source) = block_body_expr.kind
else {
dcx.emit_fatal(LoopMatchBadRhs { span: block_body_expr.span })
};
fn local(expr: &rustc_hir::Expr<'_>) -> Option<hir::HirId> {
if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind {
if let Res::Local(hir_id) = path.res {
return Some(hir_id);
}
}
None
}
let Some(scrutinee_hir_id) = local(scrutinee) else {
dcx.emit_fatal(LoopMatchInvalidMatch { span: scrutinee.span })
};
if local(state) != Some(scrutinee_hir_id) {
dcx.emit_fatal(LoopMatchInvalidUpdate {
scrutinee: scrutinee.span,
lhs: state.span,
})
}
ExprKind::LoopMatch {
state: self.mirror_expr(state),
region_scope: region::Scope {
local_id: block_body.hir_id.local_id,
data: region::ScopeData::Node,
},
arms: arms.iter().map(|a| self.convert_arm(a)).collect(),
match_span: block_body_expr.span,
}
} else {
let block_ty = self.typeck_results.node_type(body.hir_id);
let (temp_lifetime, backwards_incompatible) = self
.rvalue_scopes
@@ -853,6 +951,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
});
ExprKind::Loop { body }
}
}
hir::ExprKind::Field(source, ..) => ExprKind::Field {
lhs: self.mirror_expr(source),
variant_index: FIRST_VARIANT,

7
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View File

@@ -331,7 +331,11 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
| WrapUnsafeBinder { source } => self.is_known_valid_scrutinee(&self.thir()[*source]),
// These diverge.
Become { .. } | Break { .. } | Continue { .. } | Return { .. } => true,
Become { .. }
| Break { .. }
| Continue { .. }
| ConstContinue { .. }
| Return { .. } => true,
// These are statements that evaluate to `()`.
Assign { .. } | AssignOp { .. } | InlineAsm { .. } | Let { .. } => true,
@@ -353,6 +357,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
| Literal { .. }
| LogicalOp { .. }
| Loop { .. }
| LoopMatch { .. }
| Match { .. }
| NamedConst { .. }
| NonHirLiteral { .. }

21
compiler/rustc_mir_build/src/thir/print.rs
View File

@@ -318,6 +318,20 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
self.print_expr(*body, depth_lvl + 2);
print_indented!(self, ")", depth_lvl);
}
LoopMatch { state, region_scope, match_span, arms } => {
print_indented!(self, "LoopMatch {", depth_lvl);
print_indented!(self, "state:", depth_lvl + 1);
self.print_expr(*state, depth_lvl + 2);
print_indented!(self, format!("region_scope: {:?}", region_scope), depth_lvl + 1);
print_indented!(self, format!("match_span: {:?}", match_span), depth_lvl + 1);
print_indented!(self, "arms: [", depth_lvl + 1);
for arm_id in arms.iter() {
self.print_arm(*arm_id, depth_lvl + 2);
}
print_indented!(self, "]", depth_lvl + 1);
print_indented!(self, "}", depth_lvl);
}
Let { expr, pat } => {
print_indented!(self, "Let {", depth_lvl);
print_indented!(self, "expr:", depth_lvl + 1);
@@ -415,6 +429,13 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
print_indented!(self, format!("label: {:?}", label), depth_lvl + 1);
print_indented!(self, "}", depth_lvl);
}
ConstContinue { label, value } => {
print_indented!(self, "ConstContinue (", depth_lvl);
print_indented!(self, format!("label: {:?}", label), depth_lvl + 1);
print_indented!(self, "value:", depth_lvl + 1);
self.print_expr(*value, depth_lvl + 2);
print_indented!(self, ")", depth_lvl);
}
Return { value } => {
print_indented!(self, "Return {", depth_lvl);
print_indented!(self, "value:", depth_lvl + 1);

9
compiler/rustc_passes/messages.ftl
View File

@@ -82,11 +82,14 @@ passes_collapse_debuginfo =
passes_confusables = attribute should be applied to an inherent method
.label = not an inherent method
passes_const_continue_attr =
`#[const_continue]` should be applied to a break expression
.label = not a break expression
passes_const_stable_not_stable =
attribute `#[rustc_const_stable]` can only be applied to functions that are declared `#[stable]`
.label = attribute specified here
passes_coroutine_on_non_closure =
attribute should be applied to closures
.label = not a closure
@@ -446,6 +449,10 @@ passes_linkage =
attribute should be applied to a function or static
.label = not a function definition or static
passes_loop_match_attr =
`#[loop_match]` should be applied to a loop
.label = not a loop
passes_macro_export =
`#[macro_export]` only has an effect on macro definitions

32
compiler/rustc_passes/src/check_attr.rs
View File

@@ -132,6 +132,12 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
Attribute::Parsed(AttributeKind::Optimize(_, attr_span)) => {
self.check_optimize(hir_id, *attr_span, span, target)
}
Attribute::Parsed(AttributeKind::LoopMatch(attr_span)) => {
self.check_loop_match(hir_id, *attr_span, target)
}
Attribute::Parsed(AttributeKind::ConstContinue(attr_span)) => {
self.check_const_continue(hir_id, *attr_span, target)
}
Attribute::Parsed(AttributeKind::AllowInternalUnstable(syms)) => self
.check_allow_internal_unstable(
hir_id,
@@ -2630,6 +2636,32 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
}
}
}
fn check_loop_match(&self, hir_id: HirId, attr_span: Span, target: Target) {
let node_span = self.tcx.hir_span(hir_id);
if !matches!(target, Target::Expression) {
self.dcx().emit_err(errors::LoopMatchAttr { attr_span, node_span });
return;
}
if !matches!(self.tcx.hir_expect_expr(hir_id).kind, hir::ExprKind::Loop(..)) {
self.dcx().emit_err(errors::LoopMatchAttr { attr_span, node_span });
};
}
fn check_const_continue(&self, hir_id: HirId, attr_span: Span, target: Target) {
let node_span = self.tcx.hir_span(hir_id);
if !matches!(target, Target::Expression) {
self.dcx().emit_err(errors::ConstContinueAttr { attr_span, node_span });
return;
}
if !matches!(self.tcx.hir_expect_expr(hir_id).kind, hir::ExprKind::Break(..)) {
self.dcx().emit_err(errors::ConstContinueAttr { attr_span, node_span });
};
}
}
impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {

18
compiler/rustc_passes/src/errors.rs
View File

@@ -31,6 +31,24 @@ pub(crate) struct AutoDiffAttr {
pub attr_span: Span,
}
#[derive(Diagnostic)]
#[diag(passes_loop_match_attr)]
pub(crate) struct LoopMatchAttr {
#[primary_span]
pub attr_span: Span,
#[label]
pub node_span: Span,
}
#[derive(Diagnostic)]
#[diag(passes_const_continue_attr)]
pub(crate) struct ConstContinueAttr {
#[primary_span]
pub attr_span: Span,
#[label]
pub node_span: Span,
}
#[derive(LintDiagnostic)]
#[diag(passes_outer_crate_level_attr)]
pub(crate) struct OuterCrateLevelAttr;

3
compiler/rustc_pattern_analysis/src/constructor.rs
View File

@@ -314,7 +314,8 @@ impl IntRange {
IntRange { lo, hi }
}
fn is_subrange(&self, other: &Self) -> bool {
#[inline]
pub fn is_subrange(&self, other: &Self) -> bool {
other.lo <= self.lo && self.hi <= other.hi
}

2
compiler/rustc_span/src/symbol.rs
View File

@@ -692,6 +692,7 @@ symbols! {
const_closures,
const_compare_raw_pointers,
const_constructor,
const_continue,
const_deallocate,
const_destruct,
const_eval_limit,
@@ -1304,6 +1305,7 @@ symbols! {
logf64,
loongarch_target_feature,
loop_break_value,
loop_match,
lt,
m68k_target_feature,
macro_at_most_once_rep,

8
compiler/rustc_ty_utils/src/consts.rs
View File

@@ -226,7 +226,11 @@ fn recurse_build<'tcx>(
ExprKind::Yield { .. } => {
error(GenericConstantTooComplexSub::YieldNotSupported(node.span))?
}
ExprKind::Continue { .. } | ExprKind::Break { .. } | ExprKind::Loop { .. } => {
ExprKind::Continue { .. }
| ExprKind::ConstContinue { .. }
| ExprKind::Break { .. }
| ExprKind::Loop { .. }
| ExprKind::LoopMatch { .. } => {
error(GenericConstantTooComplexSub::LoopNotSupported(node.span))?
}
ExprKind::Box { .. } => error(GenericConstantTooComplexSub::BoxNotSupported(node.span))?,
@@ -329,6 +333,7 @@ impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
| thir::ExprKind::NeverToAny { .. }
| thir::ExprKind::PointerCoercion { .. }
| thir::ExprKind::Loop { .. }
| thir::ExprKind::LoopMatch { .. }
| thir::ExprKind::Let { .. }
| thir::ExprKind::Match { .. }
| thir::ExprKind::Block { .. }
@@ -342,6 +347,7 @@ impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
| thir::ExprKind::RawBorrow { .. }
| thir::ExprKind::Break { .. }
| thir::ExprKind::Continue { .. }
| thir::ExprKind::ConstContinue { .. }
| thir::ExprKind::Return { .. }
| thir::ExprKind::Become { .. }
| thir::ExprKind::Array { .. }

52
src/doc/unstable-book/src/language-features/loop-match.md Normal file
View File

@@ -0,0 +1,52 @@
# `loop_match`
The tracking issue for this feature is: [#132306]
[#132306]: https://github.com/rust-lang/rust/issues/132306
------
The `#[loop_match]` and `#[const_continue]` attributes can be used to improve the code
generation of logic that fits this shape:
```ignore (pseudo-rust)
loop {
state = 'blk: {
match state {
State::A => {
break 'blk State::B
}
State::B => { /* ... */ }
/* ... */
}
}
}
```
Here the loop itself can be annotated with `#[loop_match]`, and any `break 'blk` with
`#[const_continue]` if the value is know at compile time:
```ignore (pseudo-rust)
#[loop_match]
loop {
state = 'blk: {
match state {
State::A => {
#[const_continue]
break 'blk State::B
}
State::B => { /* ... */ }
/* ... */
}
}
}
```
The observable behavior of this loop is exactly the same as without the extra attributes.
The difference is in the generated output: normally, when the state is `A`, control flow
moves from the `A` branch, back to the top of the loop, then to the `B` branch. With the
attributes, The `A` branch will immediately jump to the `B` branch.
Removing the indirection can be beneficial for stack usage and branch prediction, and
enables other optimizations by clearly splitting out the control flow paths that your
program will actually use.

30
tests/ui/feature-gates/feature-gate-loop-match.rs Normal file
View File

@@ -0,0 +1,30 @@
// Test that `#[loop_match]` and `#[const_continue]` cannot be used without
// `#![feature(loop_match)]`.
enum State {
A,
B,
C,
}
fn main() {
let mut state = State::A;
#[loop_match] //~ ERROR the `#[loop_match]` attribute is an experimental feature
'a: loop {
state = 'blk: {
match state {
State::A => {
#[const_continue]
//~^ ERROR the `#[const_continue]` attribute is an experimental feature
break 'blk State::B;
}
State::B => {
#[const_continue]
//~^ ERROR the `#[const_continue]` attribute is an experimental feature
break 'blk State::C;
}
State::C => break 'a,
}
};
}
}

33
tests/ui/feature-gates/feature-gate-loop-match.stderr Normal file
View File

@@ -0,0 +1,33 @@
error[E0658]: the `#[loop_match]` attribute is an experimental feature
--> $DIR/feature-gate-loop-match.rs:12:5
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
|
= note: see issue #132306 <https://github.com/rust-lang/rust/issues/132306> for more information
= help: add `#![feature(loop_match)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: the `#[const_continue]` attribute is an experimental feature
--> $DIR/feature-gate-loop-match.rs:17:21
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #132306 <https://github.com/rust-lang/rust/issues/132306> for more information
= help: add `#![feature(loop_match)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error[E0658]: the `#[const_continue]` attribute is an experimental feature
--> $DIR/feature-gate-loop-match.rs:22:21
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #132306 <https://github.com/rust-lang/rust/issues/132306> for more information
= help: add `#![feature(loop_match)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0658`.

23
tests/ui/loop-match/break-to-block.rs Normal file
View File

@@ -0,0 +1,23 @@
// Test that a `break` without `#[const_continue]` still works as expected.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
fn main() {
assert_eq!(helper(), 1);
}
fn helper() -> u8 {
let mut state = 0u8;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
0 => break 'blk 1,
_ => break 'a state,
}
}
}
}

26
tests/ui/loop-match/const-continue-to-block.rs Normal file
View File

@@ -0,0 +1,26 @@
// Test that a `#[const_continue]` that breaks to a normal labeled block (that
// is not part of a `#[loop_match]`) produces an error.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![crate_type = "lib"]
fn const_continue_to_block() -> u8 {
let state = 0;
#[loop_match]
loop {
state = 'blk: {
match state {
0 => {
#[const_continue]
break 'blk 1;
}
_ => 'b: {
#[const_continue]
break 'b 2;
//~^ ERROR `#[const_continue]` must break to a labeled block that participates in a `#[loop_match]`
}
}
}
}
}

8
tests/ui/loop-match/const-continue-to-block.stderr Normal file
View File

@@ -0,0 +1,8 @@
error: `#[const_continue]` must break to a labeled block that participates in a `#[loop_match]`
--> $DIR/const-continue-to-block.rs:20:27
|
LL | break 'b 2;
| ^^
error: aborting due to 1 previous error

27
tests/ui/loop-match/const-continue-to-loop.rs Normal file
View File

@@ -0,0 +1,27 @@
// Test that a `#[const_continue]` that breaks to the label of the loop itself
// rather than to the label of the block within the `#[loop_match]` produces an
// error.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![crate_type = "lib"]
fn const_continue_to_loop() -> u8 {
let mut state = 0;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
0 => {
#[const_continue]
break 'blk 1;
}
_ => {
#[const_continue]
break 'a 2;
//~^ ERROR `#[const_continue]` must break to a labeled block that participates in a `#[loop_match]`
}
}
}
}
}

8
tests/ui/loop-match/const-continue-to-loop.stderr Normal file
View File

@@ -0,0 +1,8 @@
error: `#[const_continue]` must break to a labeled block that participates in a `#[loop_match]`
--> $DIR/const-continue-to-loop.rs:21:27
|
LL | break 'a 2;
| ^^
error: aborting due to 1 previous error

29
tests/ui/loop-match/const-continue-to-polymorphic-const.rs Normal file
View File

@@ -0,0 +1,29 @@
// Test that a `#[const_continue]` that breaks on a polymorphic constant produces an error.
// A polymorphic constant does not have a concrete value at MIR building time, and therefore the
// `#[loop_match]~ desugaring can't handle such values.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![crate_type = "lib"]
trait Foo {
const TARGET: u8;
fn test_u8(mut state: u8) -> &'static str {
#[loop_match]
loop {
state = 'blk: {
match state {
0 => {
#[const_continue]
break 'blk Self::TARGET;
//~^ ERROR could not determine the target branch for this `#[const_continue]`
}
1 => return "bar",
2 => return "baz",
_ => unreachable!(),
}
}
}
}
}

8
tests/ui/loop-match/const-continue-to-polymorphic-const.stderr Normal file
View File

@@ -0,0 +1,8 @@
error: could not determine the target branch for this `#[const_continue]`
--> $DIR/const-continue-to-polymorphic-const.rs:18:36
|
LL | break 'blk Self::TARGET;
| ^^^^^^^^^^^^ this value is too generic
error: aborting due to 1 previous error

47
tests/ui/loop-match/drop-in-match-arm.rs Normal file
View File

@@ -0,0 +1,47 @@
// Test that dropping values works in match arms, which is nontrivial
// because each match arm needs its own scope.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
use std::sync::atomic::{AtomicBool, Ordering};
fn main() {
assert_eq!(helper(), 1);
assert!(DROPPED.load(Ordering::Relaxed));
}
static DROPPED: AtomicBool = AtomicBool::new(false);
struct X;
impl Drop for X {
fn drop(&mut self) {
DROPPED.store(true, Ordering::Relaxed);
}
}
#[no_mangle]
#[inline(never)]
fn helper() -> i32 {
let mut state = 0;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
0 => match X {
_ => {
assert!(!DROPPED.load(Ordering::Relaxed));
break 'blk 1;
}
},
_ => {
assert!(DROPPED.load(Ordering::Relaxed));
break 'a state;
}
}
};
}
}

43
tests/ui/loop-match/invalid-attribute.rs Normal file
View File

@@ -0,0 +1,43 @@
// Test that the `#[loop_match]` and `#[const_continue]` attributes can only be
// placed on expressions.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![loop_match] //~ ERROR should be applied to a loop
#![const_continue] //~ ERROR should be applied to a break expression
extern "C" {
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
fn f();
}
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
#[repr(C)]
struct S {
a: u32,
b: u32,
}
trait Invoke {
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
extern "C" fn invoke(&self);
}
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
extern "C" fn ok() {}
fn main() {
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
|| {};
{
#[loop_match] //~ ERROR should be applied to a loop
#[const_continue] //~ ERROR should be applied to a break expression
5
};
}

131
tests/ui/loop-match/invalid-attribute.stderr Normal file
View File

@@ -0,0 +1,131 @@
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:16:1
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | #[repr(C)]
LL | struct S {
| -------- not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:15:1
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
...
LL | struct S {
| -------- not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:30:1
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | extern "C" fn ok() {}
| ------------------ not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:29:1
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
LL | #[const_continue]
LL | extern "C" fn ok() {}
| ------------------ not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:35:5
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | || {};
| -- not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:34:5
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
LL | #[const_continue]
LL | || {};
| -- not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:40:9
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | 5
| - not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:39:9
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
LL | #[const_continue]
LL | 5
| - not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:25:5
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | extern "C" fn invoke(&self);
| ---------------------------- not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:24:5
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
LL | #[const_continue]
LL | extern "C" fn invoke(&self);
| ---------------------------- not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:11:5
|
LL | #[const_continue]
| ^^^^^^^^^^^^^^^^^
LL | fn f();
| ------- not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:10:5
|
LL | #[loop_match]
| ^^^^^^^^^^^^^
LL | #[const_continue]
LL | fn f();
| ------- not a loop
error: `#[const_continue]` should be applied to a break expression
--> $DIR/invalid-attribute.rs:7:1
|
LL | / #![allow(incomplete_features)]
LL | | #![feature(loop_match)]
LL | | #![loop_match]
LL | | #![const_continue]
| | ^^^^^^^^^^^^^^^^^^
... |
LL | | };
LL | | }
| |_- not a break expression
error: `#[loop_match]` should be applied to a loop
--> $DIR/invalid-attribute.rs:6:1
|
LL | / #![allow(incomplete_features)]
LL | | #![feature(loop_match)]
LL | | #![loop_match]
| | ^^^^^^^^^^^^^^
LL | | #![const_continue]
... |
LL | | };
LL | | }
| |_- not a loop
error: aborting due to 14 previous errors

161
tests/ui/loop-match/invalid.rs Normal file
View File

@@ -0,0 +1,161 @@
// Test that the correct error is emitted when `#[loop_match]` is applied to
// syntax it does not support.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![crate_type = "lib"]
enum State {
A,
B,
C,
}
fn invalid_update() {
let mut fake = State::A;
let state = State::A;
#[loop_match]
loop {
fake = 'blk: {
//~^ ERROR invalid update of the `#[loop_match]` state
match state {
_ => State::B,
}
}
}
}
fn invalid_scrutinee() {
let mut state = State::A;
#[loop_match]
loop {
state = 'blk: {
match State::A {
//~^ ERROR invalid match on `#[loop_match]` state
_ => State::B,
}
}
}
}
fn bad_statements_1() {
let mut state = State::A;
#[loop_match]
loop {
1;
//~^ ERROR statements are not allowed in this position within a `#[loop_match]`
state = 'blk: {
match State::A {
_ => State::B,
}
}
}
}
fn bad_statements_2() {
let mut state = State::A;
#[loop_match]
loop {
state = 'blk: {
1;
//~^ ERROR statements are not allowed in this position within a `#[loop_match]`
match State::A {
_ => State::B,
}
}
}
}
fn bad_rhs_1() {
let mut state = State::A;
#[loop_match]
loop {
state = State::B
//~^ ERROR this expression must be a single `match` wrapped in a labeled block
}
}
fn bad_rhs_2() {
let mut state = State::A;
#[loop_match]
loop {
state = 'blk: {
State::B
//~^ ERROR this expression must be a single `match` wrapped in a labeled block
}
}
}
fn bad_rhs_3() {
let mut state = ();
#[loop_match]
loop {
state = 'blk: {
//~^ ERROR this expression must be a single `match` wrapped in a labeled block
}
}
}
fn missing_assignment() {
#[loop_match]
loop {
() //~ ERROR expected a single assignment expression
}
}
fn empty_loop_body() {
#[loop_match]
loop {
//~^ ERROR expected a single assignment expression
}
}
fn break_without_value() {
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
State::A => {
#[const_continue]
break 'blk;
//~^ ERROR mismatched types
}
_ => break 'a,
}
}
}
}
fn break_without_value_unit() {
let mut state = ();
#[loop_match]
'a: loop {
state = 'blk: {
match state {
() => {
#[const_continue]
break 'blk;
//~^ ERROR a `#[const_continue]` must break to a label with a value
}
}
}
}
}
fn arm_has_guard(cond: bool) {
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
State::A => {
#[const_continue]
break 'blk State::B;
}
State::B if cond => break 'a,
//~^ ERROR match arms that are part of a `#[loop_match]` cannot have guards
_ => break 'a,
}
}
}
}

91
tests/ui/loop-match/invalid.stderr Normal file
View File

@@ -0,0 +1,91 @@
error[E0308]: mismatched types
--> $DIR/invalid.rs:120:21
|
LL | break 'blk;
| ^^^^^^^^^^ expected `State`, found `()`
|
help: give the `break` a value of the expected type
|
LL | break 'blk /* value */;
| +++++++++++
error: invalid update of the `#[loop_match]` state
--> $DIR/invalid.rs:18:9
|
LL | fake = 'blk: {
| ^^^^
LL |
LL | match state {
| ----- the assignment must update this variable
error: invalid match on `#[loop_match]` state
--> $DIR/invalid.rs:32:19
|
LL | match State::A {
| ^^^^^^^^
|
= note: a local variable must be the scrutinee within a `#[loop_match]`
error: statements are not allowed in this position within a `#[loop_match]`
--> $DIR/invalid.rs:44:9
|
LL | 1;
| ^^
error: statements are not allowed in this position within a `#[loop_match]`
--> $DIR/invalid.rs:59:13
|
LL | 1;
| ^^
error: this expression must be a single `match` wrapped in a labeled block
--> $DIR/invalid.rs:72:17
|
LL | state = State::B
| ^^^^^^^^
error: this expression must be a single `match` wrapped in a labeled block
--> $DIR/invalid.rs:82:13
|
LL | State::B
| ^^^^^^^^
error: this expression must be a single `match` wrapped in a labeled block
--> $DIR/invalid.rs:92:17
|
LL | state = 'blk: {
| _________________^
LL | |
LL | | }
| |_________^
error: expected a single assignment expression
--> $DIR/invalid.rs:101:9
|
LL | ()
| ^^
error: expected a single assignment expression
--> $DIR/invalid.rs:107:10
|
LL | loop {
| __________^
LL | |
LL | | }
| |_____^
error: a `#[const_continue]` must break to a label with a value
--> $DIR/invalid.rs:137:21
|
LL | break 'blk;
| ^^^^^^^^^^
error: match arms that are part of a `#[loop_match]` cannot have guards
--> $DIR/invalid.rs:155:29
|
LL | State::B if cond => break 'a,
| ^^^^
error: aborting due to 12 previous errors
For more information about this error, try `rustc --explain E0308`.

45
tests/ui/loop-match/loop-match.rs Normal file
View File

@@ -0,0 +1,45 @@
// Test that a basic correct example of `#[loop_match]` with `#[const_continue]`
// works correctly.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
enum State {
A,
B,
C,
}
fn main() {
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
State::A => {
#[const_continue]
break 'blk State::B;
}
State::B => {
// Without special logic, the compiler believes this is a
// reassignment to an immutable variable because of the
// `loop`. So this tests that local variables work.
let _a = 0;
if true {
#[const_continue]
break 'blk State::C;
} else {
#[const_continue]
break 'blk State::A;
}
}
State::C => break 'a,
}
};
}
assert!(matches!(state, State::C))
}

48
tests/ui/loop-match/macro.rs Normal file
View File

@@ -0,0 +1,48 @@
// Test that macros can be defined in the labeled block. This should not trigger an error about
// statements not being allowed in that position, and should of course work as expected.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
enum State {
A,
B,
C,
}
fn main() {
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
macro_rules! const_continue {
($e:expr) => {
#[const_continue]
break 'blk $e;
};
}
match state {
State::A => {
const_continue!(State::B);
}
State::B => {
// Without special logic, the compiler believes this is a
// reassignment to an immutable variable because of the
// `loop`. So this tests that local variables work.
let _a = 0;
if true {
const_continue!(State::C);
} else {
const_continue!(State::A);
}
}
State::C => break 'a,
}
};
}
assert!(matches!(state, State::C))
}

83
tests/ui/loop-match/nested.rs Normal file
View File

@@ -0,0 +1,83 @@
// Test that a nested `#[loop_match]` works as expected, and that e.g. a
// `#[const_continue]` of the inner `#[loop_match]` does not interact with the
// outer `#[loop_match]`.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
enum State1 {
A,
B,
C,
}
enum State2 {
X,
Y,
Z,
}
fn main() {
assert_eq!(run(), concat!("ab", "xyz", "xyz", "c"))
}
fn run() -> String {
let mut accum = String::new();
let mut state1 = State1::A;
let mut state2 = State2::X;
let mut first = true;
#[loop_match]
'a: loop {
state1 = 'blk1: {
match state1 {
State1::A => {
accum.push('a');
#[const_continue]
break 'blk1 State1::B;
}
State1::B => {
accum.push('b');
#[loop_match]
loop {
state2 = 'blk2: {
match state2 {
State2::X => {
accum.push('x');
#[const_continue]
break 'blk2 State2::Y;
}
State2::Y => {
accum.push('y');
#[const_continue]
break 'blk2 State2::Z;
}
State2::Z => {
accum.push('z');
if first {
first = false;
#[const_continue]
break 'blk2 State2::X;
} else {
#[const_continue]
break 'blk1 State1::C;
}
}
}
}
}
}
State1::C => {
accum.push('c');
break 'a;
}
}
}
}
accum
}

54
tests/ui/loop-match/or-patterns.rs Normal file
View File

@@ -0,0 +1,54 @@
// Test that `#[loop_match]` supports or-patterns.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum State {
A,
B,
C,
D,
}
fn main() {
let mut states = vec![];
let mut first = true;
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
State::A => {
states.push(state);
if first {
#[const_continue]
break 'blk State::B;
} else {
#[const_continue]
break 'blk State::D;
}
}
State::B | State::D => {
states.push(state);
if first {
first = false;
#[const_continue]
break 'blk State::A;
} else {
#[const_continue]
break 'blk State::C;
}
}
State::C => {
states.push(state);
break 'a;
}
}
}
}
assert_eq!(states, [State::A, State::B, State::A, State::D, State::C]);
}

27
tests/ui/loop-match/unsupported-type.rs Normal file
View File

@@ -0,0 +1,27 @@
// Test that the right error is emitted when the `#[loop_match]` state is an
// unsupported type.
#![allow(incomplete_features)]
#![feature(loop_match)]
#![crate_type = "lib"]
fn unsupported_type() {
let mut state = Some(false);
#[loop_match]
'a: loop {
state = 'blk: {
//~^ ERROR this `#[loop_match]` state value has type `Option<bool>`, which is not supported
match state {
Some(false) => {
#[const_continue]
break 'blk Some(true);
}
Some(true) => {
#[const_continue]
break 'blk None;
}
None => break 'a,
}
}
}
}

10
tests/ui/loop-match/unsupported-type.stderr Normal file
View File

@@ -0,0 +1,10 @@
error: this `#[loop_match]` state value has type `Option<bool>`, which is not supported
--> $DIR/unsupported-type.rs:12:9
|
LL | state = 'blk: {
| ^^^^^
|
= note: only integers, floats, bool, char, and enums without fields are supported
error: aborting due to 1 previous error

53
tests/ui/loop-match/unwind.rs Normal file
View File

@@ -0,0 +1,53 @@
// Test that `#[const_continue]` correctly emits cleanup paths for drops.
//
// Here, we first drop `DropBomb`, causing an unwind. Then `ExitOnDrop` should
// be dropped, causing us to exit with `0` rather than with some non-zero value
// due to the panic, which is what causes the test to pass.
//@ run-pass
//@ needs-unwind
#![allow(incomplete_features)]
#![feature(loop_match)]
enum State {
A,
B,
}
struct ExitOnDrop;
impl Drop for ExitOnDrop {
fn drop(&mut self) {
std::process::exit(0);
}
}
struct DropBomb;
impl Drop for DropBomb {
fn drop(&mut self) {
panic!("this must unwind");
}
}
fn main() {
let mut state = State::A;
#[loop_match]
'a: loop {
state = 'blk: {
match state {
State::A => {
let _exit = ExitOnDrop;
let _bomb = DropBomb;
#[const_continue]
break 'blk State::B;
}
State::B => break 'a,
}
};
}
unreachable!();
}

117
tests/ui/loop-match/valid-patterns.rs Normal file
View File

@@ -0,0 +1,117 @@
// Test that signed and unsigned integer patterns work with `#[loop_match]`.
//@ run-pass
#![allow(incomplete_features)]
#![feature(loop_match)]
fn main() {
assert_eq!(integer(0), 2);
assert_eq!(integer(-1), 2);
assert_eq!(integer(2), 2);
assert_eq!(boolean(true), false);
assert_eq!(boolean(false), false);
assert_eq!(character('a'), 'b');
assert_eq!(character('b'), 'b');
assert_eq!(character('c'), 'd');
assert_eq!(character('d'), 'd');
assert_eq!(test_f32(1.0), core::f32::consts::PI);
assert_eq!(test_f32(2.5), core::f32::consts::PI);
assert_eq!(test_f32(4.0), 4.0);
assert_eq!(test_f64(1.0), core::f64::consts::PI);
assert_eq!(test_f64(2.5), core::f64::consts::PI);
assert_eq!(test_f64(4.0), 4.0);
}
fn integer(mut state: i32) -> i32 {
#[loop_match]
'a: loop {
state = 'blk: {
match state {
-1 => {
#[const_continue]
break 'blk 2;
}
0 => {
#[const_continue]
break 'blk -1;
}
2 => break 'a,
_ => unreachable!("weird value {:?}", state),
}
}
}
state
}
fn boolean(mut state: bool) -> bool {
#[loop_match]
loop {
state = 'blk: {
match state {
true => {
#[const_continue]
break 'blk false;
}
false => return state,
}
}
}
}
fn character(mut state: char) -> char {
#[loop_match]
loop {
state = 'blk: {
match state {
'a' => {
#[const_continue]
break 'blk 'b';
}
'b' => return state,
'c' => {
#[const_continue]
break 'blk 'd';
}
_ => return state,
}
}
}
}
fn test_f32(mut state: f32) -> f32 {
#[loop_match]
loop {
state = 'blk: {
match state {
1.0 => {
#[const_continue]
break 'blk 2.5;
}
2.0..3.0 => return core::f32::consts::PI,
_ => return state,
}
}
}
}
fn test_f64(mut state: f64) -> f64 {
#[loop_match]
loop {
state = 'blk: {
match state {
1.0 => {
#[const_continue]
break 'blk 2.5;
}
2.0..3.0 => return core::f64::consts::PI,
_ => return state,
}
}
}
}

22
tests/ui/thir-print/thir-tree-loop-match.rs Normal file
View File

@@ -0,0 +1,22 @@
//@ check-pass
//@ compile-flags: -Zunpretty=thir-tree
#![allow(incomplete_features)]
#![feature(loop_match)]
fn boolean(mut state: bool) -> bool {
#[loop_match]
loop {
state = 'blk: {
match state {
true => {
#[const_continue]
break 'blk false;
}
false => return state,
}
}
}
}
fn main() {}

301
tests/ui/thir-print/thir-tree-loop-match.stdout Normal file
View File

@@ -0,0 +1,301 @@
DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean):
params: [
Param {
ty: bool
ty_span: Some($DIR/thir-tree-loop-match.rs:7:23: 7:27 (#0))
self_kind: None
hir_id: Some(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).1))
param: Some(
Pat: {
ty: bool
span: $DIR/thir-tree-loop-match.rs:7:12: 7:21 (#0)
kind: PatKind {
Binding {
name: "state"
mode: BindingMode(No, Mut)
var: LocalVarId(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).2))
ty: bool
is_primary: true
subpattern: None
}
}
}
)
}
]
body:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(28)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:7:37: 20:2 (#0)
kind:
Scope {
region_scope: Node(28)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).28))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(28)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:7:37: 20:2 (#0)
kind:
Block {
targeted_by_break: false
span: $DIR/thir-tree-loop-match.rs:7:37: 20:2 (#0)
region_scope: Node(3)
safety_mode: Safe
stmts: []
expr:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(28)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:9:5: 19:6 (#0)
kind:
Scope {
region_scope: Node(4)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).4))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(28)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:9:5: 19:6 (#0)
kind:
NeverToAny {
source:
Expr {
ty: !
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(28)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:9:5: 19:6 (#0)
kind:
LoopMatch {
state:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(5)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:10:9: 10:14 (#0)
kind:
Scope {
region_scope: Node(7)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).7))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(5)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:10:9: 10:14 (#0)
kind:
VarRef {
id: LocalVarId(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).2))
}
}
}
}
region_scope: Node(10)
match_span: $DIR/thir-tree-loop-match.rs:11:13: 17:14 (#0)
arms: [
Arm {
pattern:
Pat: {
ty: bool
span: $DIR/thir-tree-loop-match.rs:12:17: 12:21 (#0)
kind: PatKind {
Constant {
value: Ty(bool, true)
}
}
}
guard: None
body:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(16)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:12:25: 15:18 (#0)
kind:
Scope {
region_scope: Node(17)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).17))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(16)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:12:25: 15:18 (#0)
kind:
NeverToAny {
source:
Expr {
ty: !
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(16)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:12:25: 15:18 (#0)
kind:
Block {
targeted_by_break: false
span: $DIR/thir-tree-loop-match.rs:12:25: 15:18 (#0)
region_scope: Node(18)
safety_mode: Safe
stmts: [
Stmt {
kind: Expr {
scope: Node(21)
expr:
Expr {
ty: !
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(21)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:14:21: 14:37 (#0)
kind:
Scope {
region_scope: Node(19)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).19))
value:
Expr {
ty: !
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(21)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:14:21: 14:37 (#0)
kind:
ConstContinue (
label: Node(10)
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(21)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:14:32: 14:37 (#0)
kind:
Scope {
region_scope: Node(20)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).20))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(21)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:14:32: 14:37 (#0)
kind:
Literal( lit: Spanned { node: Bool(false), span: $DIR/thir-tree-loop-match.rs:14:32: 14:37 (#0) }, neg: false)
}
}
}
)
}
}
}
}
}
]
expr: []
}
}
}
}
}
}
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).16))
scope: Node(16)
span: $DIR/thir-tree-loop-match.rs:12:17: 15:18 (#0)
}
Arm {
pattern:
Pat: {
ty: bool
span: $DIR/thir-tree-loop-match.rs:16:17: 16:22 (#0)
kind: PatKind {
Constant {
value: Ty(bool, false)
}
}
}
guard: None
body:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(24)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:16:26: 16:38 (#0)
kind:
Scope {
region_scope: Node(25)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).25))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(24)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:16:26: 16:38 (#0)
kind:
NeverToAny {
source:
Expr {
ty: !
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(24)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:16:26: 16:38 (#0)
kind:
Return {
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(24)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:16:33: 16:38 (#0)
kind:
Scope {
region_scope: Node(26)
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).26))
value:
Expr {
ty: bool
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(24)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:16:33: 16:38 (#0)
kind:
VarRef {
id: LocalVarId(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).2))
}
}
}
}
}
}
}
}
}
}
lint_level: Explicit(HirId(DefId(0:3 ~ thir_tree_loop_match[3c53]::boolean).24))
scope: Node(24)
span: $DIR/thir-tree-loop-match.rs:16:17: 16:38 (#0)
}
]
}
}
}
}
}
}
}
}
}
}
DefId(0:4 ~ thir_tree_loop_match[3c53]::main):
params: [
]
body:
Expr {
ty: ()
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(2)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:22:11: 22:13 (#0)
kind:
Scope {
region_scope: Node(2)
lint_level: Explicit(HirId(DefId(0:4 ~ thir_tree_loop_match[3c53]::main).2))
value:
Expr {
ty: ()
temp_lifetime: TempLifetime { temp_lifetime: Some(Node(2)), backwards_incompatible: None }
span: $DIR/thir-tree-loop-match.rs:22:11: 22:13 (#0)
kind:
Block {
targeted_by_break: false
span: $DIR/thir-tree-loop-match.rs:22:11: 22:13 (#0)
region_scope: Node(1)
safety_mode: Safe
stmts: []
expr: []
}
}
}
}