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Allow abstract types to be used in Convert (#7388)

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Notably this allows accessing fields in an abstract base class via a
derived class without going through `base`. E.g.
`my_obj.field_in_base_class` rather than
`my_obj.base.field_in_base_class`.
This commit is contained in:
Nicholas Bishop
2026-06-19 00:18:48 +00:00
committed by GitHub
parent 833e0c418e
commit 2ebc7cdb40
5 changed files with 198 additions and 228 deletions
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toolchain/check/convert.cpp
+28 -49
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@@ -868,8 +868,12 @@ static auto ConvertStructToClass(Context& context, SemIR::StructType src_type,
target.storage_id.has_value());
PendingBlock target_block(&context);
auto& dest_class_info = context.classes().Get(dest_type.class_id);
CARBON_CHECK(is_partial ||
dest_class_info.inheritance_kind != SemIR::Class::Abstract);
if (!is_partial &&
dest_class_info.inheritance_kind == SemIR::Class::Abstract) {
CARBON_DIAGNOSTIC(AbstractTypeInInit, Error,
"initialization of abstract class {0}", SemIR::TypeId);
context.emitter().Emit(value_id, AbstractTypeInInit, target.type_id);
}
auto object_repr_id =
dest_class_info.GetObjectRepr(context.sem_ir(), dest_type.specific_id);
if (object_repr_id == SemIR::ErrorInst::TypeId) {
@@ -1957,58 +1961,33 @@ auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
}
auto original_inner_expr_id = expr_id;
auto incomplete_diagnostic = [&](auto& builder) {
CARBON_CHECK(!target.is_initializer(),
"Initialization of incomplete types is expected to be "
"caught elsewhere.");
CARBON_DIAGNOSTIC(IncompleteTypeInValueConversion, Context,
"forming value of incomplete type {0}", SemIR::TypeId);
CARBON_DIAGNOSTIC(IncompleteTypeInConversion, Context,
"invalid use of incomplete type {0}", SemIR::TypeId);
builder.Context(loc_id,
target.kind == ConversionTarget::Value
? IncompleteTypeInValueConversion
: IncompleteTypeInConversion,
target.type_id);
};
// Allow forming a value or reference of abstract class type, but not
// an initializer.
bool require_concrete =
target.is_initializer() ||
// TODO: relax this restriction.
!context.insts().Is<SemIR::ClassElementAccess>(expr_id);
// TODO: Push this check down to the points where we perform operations that
// need the type to be complete.
if (ConversionNeedsCompleteTarget(context, expr_id, target)) {
if (require_concrete) {
if (target.diagnose) {
if (!RequireConcreteType(
context, target.type_id, loc_id, incomplete_diagnostic,
[&](auto& builder) {
CARBON_DIAGNOSTIC(AbstractTypeInInit, Context,
"initialization of abstract type {0}",
SemIR::TypeId);
builder.Context(loc_id, AbstractTypeInInit, target.type_id);
})) {
return SemIR::ErrorInst::InstId;
}
} else {
if (!TryIsConcreteType(context, target.type_id, loc_id)) {
return SemIR::ErrorInst::InstId;
}
if (target.diagnose) {
if (!RequireCompleteType(
context, target.type_id, loc_id, [&](auto& builder) {
CARBON_CHECK(
!target.is_initializer(),
"Initialization of incomplete types is expected to be "
"caught elsewhere.");
CARBON_DIAGNOSTIC(IncompleteTypeInValueConversion, Context,
"forming value of incomplete type {0}",
SemIR::TypeId);
CARBON_DIAGNOSTIC(IncompleteTypeInConversion, Context,
"invalid use of incomplete type {0}",
SemIR::TypeId);
builder.Context(loc_id,
target.kind == ConversionTarget::Value
? IncompleteTypeInValueConversion
: IncompleteTypeInConversion,
target.type_id);
})) {
return SemIR::ErrorInst::InstId;
}
} else {
if (target.diagnose) {
if (!RequireCompleteType(context, target.type_id, loc_id,
incomplete_diagnostic)) {
return SemIR::ErrorInst::InstId;
}
} else {
if (!TryToCompleteType(context, target.type_id, loc_id)) {
return SemIR::ErrorInst::InstId;
}
if (!TryToCompleteType(context, target.type_id, loc_id)) {
return SemIR::ErrorInst::InstId;
}
}
}