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Model thunk call as a pattern match (#6988)

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This makes the thunk-call logic more general and more supportable by
reusing the existing pattern-matching logic.

---------

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This commit is contained in:
Geoff Romer
2026-03-31 21:50:06 +00:00
committed by GitHub
co-authored by Richard Smith
parent f4260feee4
commit 47e9d62fd5
3 changed files with 105 additions and 75 deletions
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toolchain/check/pattern_match.cpp
+64 -3
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@@ -46,7 +46,14 @@ struct CalleeState {
// State for local pattern matching.
struct LocalState {};
using State = std::variant<CallerState*, CalleeState*, LocalState*>;
// State for thunk pattern matching.
struct ThunkState {
// The not-yet-processed `Call` arguments for the outer call.
llvm::ArrayRef<SemIR::InstId> outer_call_args;
};
using State =
std::variant<CallerState*, CalleeState*, LocalState*, ThunkState*>;
// The worklist and state machine for a pattern-matching operation.
//
@@ -356,9 +363,13 @@ auto MatchContext::DoPreWork(State state,
}
}
auto MatchContext::DoPostWork(State /*state*/,
auto MatchContext::DoPostWork(State state,
SemIR::AnyBindingPattern binding_pattern,
WorkItem entry) -> void {
if (std::holds_alternative<ThunkState*>(state)) {
// Pass through the result from the subpattern.
return;
}
// We're logically consuming this map entry, so we invalidate it in order
// to avoid accidentally consuming it twice.
auto [bind_name_id, type_expr_region_id] =
@@ -517,6 +528,19 @@ auto MatchContext::DoPreWork(State state, SemIR::AnyParamPattern param_pattern,
callee_state->call_param_patterns.push_back(entry.pattern_id);
break;
}
case CARBON_KIND(ThunkState* thunk_state): {
auto param_id = thunk_state->outer_call_args.consume_front();
if (auto var_param_pattern =
context_.insts().TryGetAs<SemIR::VarParamPattern>(
entry.pattern_id)) {
AddWork({.pattern_id = var_param_pattern->subpattern_id,
.work = PreWork{.scrutinee_id = param_id},
.allow_unmarked_ref = entry.allow_unmarked_ref});
} else {
results_stack_.AppendToTop(param_id);
}
break;
}
case CARBON_KIND(LocalState* _): {
CARBON_FATAL("Found ValueParamPattern during local pattern match");
}
@@ -600,6 +624,9 @@ auto MatchContext::DoVarPreWorkImpl(State state, SemIR::TypeId pattern_type_id,
// insts.
return scrutinee_id;
}
case CARBON_KIND(ThunkState* _): {
return scrutinee_id;
}
case CARBON_KIND(LocalState* _): {
// In a `var`/`let` declaration, the `VarStorage` inst is created before
// we start pattern matching.
@@ -676,7 +703,8 @@ auto MatchContext::DoPreWork(State state, SemIR::TuplePattern tuple_pattern,
}
};
if (!scrutinee_id.has_value()) {
CARBON_CHECK(std::holds_alternative<CalleeState*>(state));
CARBON_CHECK(std::holds_alternative<CalleeState*>(state) ||
std::holds_alternative<ThunkState*>(state));
// If we don't have a scrutinee yet, we're still on the caller side of the
// pattern, so the subpatterns don't have a scrutinee either.
for (auto subpattern_id : llvm::reverse(subpattern_ids)) {
@@ -745,6 +773,9 @@ auto MatchContext::DoPostWork(State /*state*/,
auto MatchContext::Dispatch(State state, WorkItem entry) -> void {
if (entry.pattern_id == SemIR::ErrorInst::InstId) {
if (need_subpattern_results()) {
results_stack_.AppendToTop(SemIR::ErrorInst::InstId);
}
return;
}
Diagnostics::AnnotationScope annotate_diagnostics(
@@ -881,6 +912,36 @@ auto CalleePatternMatch(Context& context,
.param_ranges = {implicit_end, explicit_end, return_end}};
}
auto ThunkPatternMatch(Context& context, SemIR::InstId self_pattern_id,
SemIR::InstBlockId param_patterns_id,
llvm::ArrayRef<SemIR::InstId> outer_call_args)
-> ThunkPatternMatchResults {
ThunkState state = {.outer_call_args = outer_call_args};
MatchContext match(context);
llvm::SmallVector<SemIR::InstId> inner_args;
inner_args.reserve(outer_call_args.size() + 1);
if (self_pattern_id.has_value()) {
inner_args.push_back(match.MatchWithResult(
&state,
{.pattern_id = self_pattern_id,
.work = MatchContext::PreWork{.scrutinee_id = SemIR::InstId::None}}));
}
if (param_patterns_id.has_value()) {
for (SemIR::InstId inst_id : context.inst_blocks().Get(param_patterns_id)) {
inner_args.push_back(match.MatchWithResult(
&state, {.pattern_id = inst_id,
.work = MatchContext::PreWork{.scrutinee_id =
SemIR::InstId::None}}));
}
}
return {.syntactic_args = std::move(inner_args),
.ignored_call_args = state.outer_call_args};
}
auto CallerPatternMatch(Context& context, SemIR::SpecificId specific_id,
SemIR::InstId self_pattern_id,
SemIR::InstBlockId param_patterns_id,