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carbon-lang/toolchain/check/convert.cpp
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Jon Ross-PerkinsandDana Jansens 42e2280150 Clean up singleton TypeId use (#6300) 
#6289 absentmindedly added fields in more places, and this is undoing
that plus further fixes.

This does some cleanup of types with relation to singletons. For
`TypeType` and `ErrorInst`, they're always complete due to a
`SetComplete` call in `file.cpp`. For `CppVoidType`, it's intended to be
incomplete by construction, and so a `TypeId` should be okay. The intent
though on not generally providing these had been that `GetSingletonType`
needs to be called to get a type to be marked as complete.

In the case of `AutoType`, removing `TypeId`does change a small printing
detail. I think that's old legacy that's just been carried forward.

Otherwise, for both `InstType` and `AutoType`, I've added
`GetSingletonType` calls where they were used in order to ensure
completeness is applied correctly. These calls cause small SemIR
permutations.

This causes `AutoType` to be seen by lowering, so I'm adding a
placeholder for it. Also merging two functions that look like they're
identical in intent -- not sure why they're separate.

---------

Co-authored-by: Dana Jansens <danakj@orodu.net>
2025-10-30 22:50:59 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "toolchain/check/convert.h"
#include <optional>
#include <string>
#include <utility>
#include "common/check.h"
#include "common/map.h"
#include "llvm/ADT/STLExtras.h"
#include "toolchain/base/kind_switch.h"
#include "toolchain/check/action.h"
#include "toolchain/check/context.h"
#include "toolchain/check/control_flow.h"
#include "toolchain/check/diagnostic_helpers.h"
#include "toolchain/check/eval.h"
#include "toolchain/check/impl_lookup.h"
#include "toolchain/check/import_ref.h"
#include "toolchain/check/inst.h"
#include "toolchain/check/operator.h"
#include "toolchain/check/pattern_match.h"
#include "toolchain/check/type.h"
#include "toolchain/check/type_completion.h"
#include "toolchain/diagnostics/format_providers.h"
#include "toolchain/sem_ir/copy_on_write_block.h"
#include "toolchain/sem_ir/expr_info.h"
#include "toolchain/sem_ir/file.h"
#include "toolchain/sem_ir/generic.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/inst.h"
#include "toolchain/sem_ir/type.h"
#include "toolchain/sem_ir/typed_insts.h"
// TODO: This contains a lot of recursion. Consider removing it in order to
// prevent accidents.
// NOLINTBEGIN(misc-no-recursion)
namespace Carbon::Check {
// Marks the initializer `init_id` as initializing `target_id`.
static auto MarkInitializerFor(SemIR::File& sem_ir, SemIR::InstId init_id,
ConversionTarget& target) -> void {
CARBON_CHECK(target.is_initializer());
auto return_slot_arg_id = FindReturnSlotArgForInitializer(sem_ir, init_id);
if (return_slot_arg_id.has_value()) {
// Replace the temporary in the return slot with a reference to our target.
CARBON_CHECK(sem_ir.insts().Get(return_slot_arg_id).kind() ==
SemIR::TemporaryStorage::Kind,
"Return slot for initializer does not contain a temporary; "
"initialized multiple times? Have {0}",
sem_ir.insts().Get(return_slot_arg_id));
target.init_id =
target.init_block->MergeReplacing(return_slot_arg_id, target.init_id);
}
}
// For a value or initializing expression using a copy value representation,
// copy the value into a temporary object.
static auto CopyValueToTemporary(Context& context, SemIR::InstId init_id)
-> SemIR::InstId {
// TODO: Consider using `None` to mean that we immediately materialize and
// initialize a temporary, rather than two separate instructions.
auto init = context.insts().Get(init_id);
auto temporary_id = AddInst<SemIR::TemporaryStorage>(
context, SemIR::LocId(init_id), {.type_id = init.type_id()});
return AddInstWithCleanup<SemIR::Temporary>(context, SemIR::LocId(init_id),
{.type_id = init.type_id(),
.storage_id = temporary_id,
.init_id = init_id});
}
// Commits to using a temporary to store the result of the initializing
// expression described by `init_id`, and returns the location of the
// temporary. If `discarded` is `true`, the result is discarded, and no
// temporary will be created if possible; if no temporary is created, the
// return value will be `SemIR::InstId::None`.
static auto FinalizeTemporary(Context& context, SemIR::InstId init_id,
bool discarded) -> SemIR::InstId {
auto& sem_ir = context.sem_ir();
auto return_slot_arg_id = FindReturnSlotArgForInitializer(sem_ir, init_id);
if (return_slot_arg_id.has_value()) {
// The return slot should already have a materialized temporary in it.
CARBON_CHECK(sem_ir.insts().Get(return_slot_arg_id).kind() ==
SemIR::TemporaryStorage::Kind,
"Return slot for initializer does not contain a temporary; "
"initialized multiple times? Have {0}",
sem_ir.insts().Get(return_slot_arg_id));
auto init = sem_ir.insts().Get(init_id);
return AddInstWithCleanup<SemIR::Temporary>(
context, SemIR::LocId(init_id),
{.type_id = init.type_id(),
.storage_id = return_slot_arg_id,
.init_id = init_id});
}
if (discarded) {
// Don't invent a temporary that we're going to discard.
return SemIR::InstId::None;
}
// The initializer has no return slot, but we want to produce a temporary
// object. Materialize one now.
return CopyValueToTemporary(context, init_id);
}
// Materialize a temporary to hold the result of the given expression if it is
// an initializing expression.
static auto MaterializeIfInitializing(Context& context, SemIR::InstId expr_id)
-> SemIR::InstId {
if (GetExprCategory(context.sem_ir(), expr_id) ==
SemIR::ExprCategory::Initializing) {
return FinalizeTemporary(context, expr_id, /*discarded=*/false);
}
return expr_id;
}
// Helper to allow `MakeElementAccessInst` to call `AddInst` with either a
// `PendingBlock` or `Context` (defined in `inst.h`).
template <typename AccessInstT>
static auto AddInst(PendingBlock& block, SemIR::LocId loc_id, AccessInstT inst)
-> SemIR::InstId {
return block.AddInst<AccessInstT>(loc_id, inst);
}
// Creates and adds an instruction to perform element access into an aggregate.
template <typename AccessInstT, typename InstBlockT>
static auto MakeElementAccessInst(Context& context, SemIR::LocId loc_id,
SemIR::InstId aggregate_id,
SemIR::TypeId elem_type_id, InstBlockT& block,
size_t i) -> SemIR::InstId {
if constexpr (std::is_same_v<AccessInstT, SemIR::ArrayIndex>) {
// TODO: Add a new instruction kind for indexing an array at a constant
// index so that we don't need an integer literal instruction here, and
// remove this special case.
auto index_id = block.template AddInst<SemIR::IntValue>(
loc_id, {.type_id = GetSingletonType(context,
SemIR::IntLiteralType::TypeInstId),
.int_id = context.ints().Add(static_cast<int64_t>(i))});
return AddInst<AccessInstT>(block, loc_id,
{elem_type_id, aggregate_id, index_id});
} else {
return AddInst<AccessInstT>(
block, loc_id, {elem_type_id, aggregate_id, SemIR::ElementIndex(i)});
}
}
// Get the conversion target kind to use when initializing an element of an
// aggregate.
static auto GetAggregateElementConversionTargetKind(SemIR::File& sem_ir,
ConversionTarget target)
-> ConversionTarget::Kind {
// If we're forming an initializer, then we want an initializer for each
// element.
if (target.is_initializer()) {
// Perform a final destination store if we're performing an in-place
// initialization.
auto init_repr = SemIR::InitRepr::ForType(sem_ir, target.type_id);
CARBON_CHECK(init_repr.kind != SemIR::InitRepr::Dependent,
"Aggregate should not have dependent init kind");
if (init_repr.kind == SemIR::InitRepr::InPlace) {
return ConversionTarget::FullInitializer;
}
return ConversionTarget::Initializer;
}
// Otherwise, we want a value representation for each element.
return ConversionTarget::Value;
}
// Converts an element of one aggregate so that it can be used as an element of
// another aggregate.
//
// For the source: `src_id` is the source aggregate, `src_elem_type` is the
// element type, `src_field_index` is the index, and `SourceAccessInstT` is the
// kind of instruction used to access the source element.
//
// For the target: `kind` is the kind of conversion or initialization,
// `target_elem_type` is the element type. For initialization, `target_id` is
// the destination, `target_block` is a pending block for target location
// calculations that will be spliced as the return slot of the initializer if
// necessary, `target_field_index` is the index, and `TargetAccessInstT` is the
// kind of instruction used to access the destination element.
template <typename SourceAccessInstT, typename TargetAccessInstT>
static auto ConvertAggregateElement(
Context& context, SemIR::LocId loc_id, SemIR::InstId src_id,
SemIR::TypeInstId src_elem_type_inst,
llvm::ArrayRef<SemIR::InstId> src_literal_elems,
ConversionTarget::Kind kind, SemIR::InstId target_id,
SemIR::TypeInstId target_elem_type_inst, PendingBlock* target_block,
size_t src_field_index, size_t target_field_index,
SemIR::ClassType* vtable_class_type = nullptr) -> SemIR::InstId {
auto src_elem_type =
context.types().GetTypeIdForTypeInstId(src_elem_type_inst);
auto target_elem_type =
context.types().GetTypeIdForTypeInstId(target_elem_type_inst);
// Compute the location of the source element. This goes into the current code
// block, not into the target block.
// TODO: Ideally we would discard this instruction if it's unused.
auto src_elem_id = !src_literal_elems.empty()
? src_literal_elems[src_field_index]
: MakeElementAccessInst<SourceAccessInstT>(
context, loc_id, src_id, src_elem_type, context,
src_field_index);
// If we're performing a conversion rather than an initialization, we won't
// have or need a target.
ConversionTarget target = {.kind = kind, .type_id = target_elem_type};
if (!target.is_initializer()) {
return Convert(context, loc_id, src_elem_id, target);
}
// Compute the location of the target element and initialize it.
PendingBlock::DiscardUnusedInstsScope scope(target_block);
target.init_block = target_block;
target.init_id = MakeElementAccessInst<TargetAccessInstT>(
context, loc_id, target_id, target_elem_type, *target_block,
target_field_index);
return Convert(context, loc_id, src_elem_id, target, vtable_class_type);
}
// Performs a conversion from a tuple to an array type. This function only
// converts the type, and does not perform a final conversion to the requested
// expression category.
static auto ConvertTupleToArray(Context& context, SemIR::TupleType tuple_type,
SemIR::ArrayType array_type,
SemIR::InstId value_id, ConversionTarget target)
-> SemIR::InstId {
auto& sem_ir = context.sem_ir();
auto tuple_elem_types = sem_ir.inst_blocks().Get(tuple_type.type_elements_id);
auto value = sem_ir.insts().Get(value_id);
SemIR::LocId value_loc_id(value_id);
// If we're initializing from a tuple literal, we will use its elements
// directly. Otherwise, materialize a temporary if needed and index into the
// result.
llvm::ArrayRef<SemIR::InstId> literal_elems;
if (auto tuple_literal = value.TryAs<SemIR::TupleLiteral>()) {
literal_elems = sem_ir.inst_blocks().Get(tuple_literal->elements_id);
} else {
value_id = MaterializeIfInitializing(context, value_id);
}
// Check that the tuple is the right size.
std::optional<uint64_t> array_bound =
sem_ir.GetArrayBoundValue(array_type.bound_id);
if (!array_bound) {
// TODO: Should this fall back to using `ImplicitAs`?
if (target.diagnose) {
CARBON_DIAGNOSTIC(ArrayInitDependentBound, Error,
"cannot initialize array with dependent bound from a "
"list of initializers");
context.emitter().Emit(value_loc_id, ArrayInitDependentBound);
}
return SemIR::ErrorInst::InstId;
}
if (tuple_elem_types.size() != array_bound) {
if (target.diagnose) {
CARBON_DIAGNOSTIC(ArrayInitFromLiteralArgCountMismatch, Error,
"cannot initialize array of {0} element{0:s} from {1} "
"initializer{1:s}",
Diagnostics::IntAsSelect, Diagnostics::IntAsSelect);
CARBON_DIAGNOSTIC(
ArrayInitFromExprArgCountMismatch, Error,
"cannot initialize array of {0} element{0:s} from tuple "
"with {1} element{1:s}",
Diagnostics::IntAsSelect, Diagnostics::IntAsSelect);
context.emitter().Emit(value_loc_id,
literal_elems.empty()
? ArrayInitFromExprArgCountMismatch
: ArrayInitFromLiteralArgCountMismatch,
*array_bound, tuple_elem_types.size());
}
return SemIR::ErrorInst::InstId;
}
PendingBlock target_block_storage(&context);
PendingBlock* target_block =
target.init_block ? target.init_block : &target_block_storage;
// Arrays are always initialized in-place. Allocate a temporary as the
// destination for the array initialization if we weren't given one.
SemIR::InstId return_slot_arg_id = target.init_id;
if (!target.init_id.has_value()) {
return_slot_arg_id = target_block->AddInst<SemIR::TemporaryStorage>(
value_loc_id, {.type_id = target.type_id});
}
// Initialize each element of the array from the corresponding element of the
// tuple.
// TODO: Annotate diagnostics coming from here with the array element index,
// if initializing from a tuple literal.
llvm::SmallVector<SemIR::InstId> inits;
inits.reserve(*array_bound + 1);
for (auto [i, src_type_inst_id] : llvm::enumerate(
context.types().GetBlockAsTypeInstIds(tuple_elem_types))) {
// TODO: This call recurses back into conversion. Switch to an iterative
// approach.
auto init_id =
ConvertAggregateElement<SemIR::TupleAccess, SemIR::ArrayIndex>(
context, value_loc_id, value_id, src_type_inst_id, literal_elems,
ConversionTarget::FullInitializer, return_slot_arg_id,
array_type.element_type_inst_id, target_block, i, i);
if (init_id == SemIR::ErrorInst::InstId) {
return SemIR::ErrorInst::InstId;
}
inits.push_back(init_id);
}
// Flush the temporary here if we didn't insert it earlier, so we can add a
// reference to the return slot.
target_block->InsertHere();
return AddInst<SemIR::ArrayInit>(context, value_loc_id,
{.type_id = target.type_id,
.inits_id = sem_ir.inst_blocks().Add(inits),
.dest_id = return_slot_arg_id});
}
// Performs a conversion from a tuple to a tuple type. This function only
// converts the type, and does not perform a final conversion to the requested
// expression category.
static auto ConvertTupleToTuple(Context& context, SemIR::TupleType src_type,
SemIR::TupleType dest_type,
SemIR::InstId value_id, ConversionTarget target)
-> SemIR::InstId {
auto& sem_ir = context.sem_ir();
auto src_elem_types = sem_ir.inst_blocks().Get(src_type.type_elements_id);
auto dest_elem_types = sem_ir.inst_blocks().Get(dest_type.type_elements_id);
auto value = sem_ir.insts().Get(value_id);
SemIR::LocId value_loc_id(value_id);
// If we're initializing from a tuple literal, we will use its elements
// directly. Otherwise, materialize a temporary if needed and index into the
// result.
llvm::ArrayRef<SemIR::InstId> literal_elems;
auto literal_elems_id = SemIR::InstBlockId::None;
if (auto tuple_literal = value.TryAs<SemIR::TupleLiteral>()) {
literal_elems_id = tuple_literal->elements_id;
literal_elems = sem_ir.inst_blocks().Get(literal_elems_id);
} else {
value_id = MaterializeIfInitializing(context, value_id);
}
// Check that the tuples are the same size.
if (src_elem_types.size() != dest_elem_types.size()) {
if (target.diagnose) {
CARBON_DIAGNOSTIC(
TupleInitElementCountMismatch, Error,
"cannot initialize tuple of {0} element{0:s} from tuple "
"with {1} element{1:s}",
Diagnostics::IntAsSelect, Diagnostics::IntAsSelect);
context.emitter().Emit(value_loc_id, TupleInitElementCountMismatch,
dest_elem_types.size(), src_elem_types.size());
}
return SemIR::ErrorInst::InstId;
}
ConversionTarget::Kind inner_kind =
GetAggregateElementConversionTargetKind(sem_ir, target);
// Initialize each element of the destination from the corresponding element
// of the source.
// TODO: Annotate diagnostics coming from here with the element index.
auto new_block =
literal_elems_id.has_value()
? SemIR::CopyOnWriteInstBlock(&sem_ir, literal_elems_id)
: SemIR::CopyOnWriteInstBlock(
&sem_ir, SemIR::CopyOnWriteInstBlock::UninitializedBlock{
src_elem_types.size()});
for (auto [i, src_type_inst_id, dest_type_inst_id] : llvm::enumerate(
context.types().GetBlockAsTypeInstIds(src_elem_types),
context.types().GetBlockAsTypeInstIds(dest_elem_types))) {
// TODO: This call recurses back into conversion. Switch to an iterative
// approach.
auto init_id =
ConvertAggregateElement<SemIR::TupleAccess, SemIR::TupleAccess>(
context, value_loc_id, value_id, src_type_inst_id, literal_elems,
inner_kind, target.init_id, dest_type_inst_id, target.init_block, i,
i);
if (init_id == SemIR::ErrorInst::InstId) {
return SemIR::ErrorInst::InstId;
}
new_block.Set(i, init_id);
}
if (target.is_initializer()) {
target.init_block->InsertHere();
return AddInst<SemIR::TupleInit>(context, value_loc_id,
{.type_id = target.type_id,
.elements_id = new_block.id(),
.dest_id = target.init_id});
} else {
return AddInst<SemIR::TupleValue>(
context, value_loc_id,
{.type_id = target.type_id, .elements_id = new_block.id()});
}
}
// Common implementation for ConvertStructToStruct and ConvertStructToClass.
template <typename TargetAccessInstT>
static auto ConvertStructToStructOrClass(
Context& context, SemIR::StructType src_type, SemIR::StructType dest_type,
SemIR::InstId value_id, ConversionTarget target,
SemIR::ClassType* vtable_class_type = nullptr) -> SemIR::InstId {
static_assert(std::is_same_v<SemIR::ClassElementAccess, TargetAccessInstT> ||
std::is_same_v<SemIR::StructAccess, TargetAccessInstT>);
constexpr bool ToClass =
std::is_same_v<SemIR::ClassElementAccess, TargetAccessInstT>;
auto& sem_ir = context.sem_ir();
auto src_elem_fields = sem_ir.struct_type_fields().Get(src_type.fields_id);
auto dest_elem_fields = sem_ir.struct_type_fields().Get(dest_type.fields_id);
bool dest_has_vptr = !dest_elem_fields.empty() &&
dest_elem_fields.front().name_id == SemIR::NameId::Vptr;
int dest_vptr_offset = (dest_has_vptr ? 1 : 0);
auto dest_elem_fields_size = dest_elem_fields.size() - dest_vptr_offset;
auto value = sem_ir.insts().Get(value_id);
SemIR::LocId value_loc_id(value_id);
// If we're initializing from a struct literal, we will use its elements
// directly. Otherwise, materialize a temporary if needed and index into the
// result.
llvm::ArrayRef<SemIR::InstId> literal_elems;
auto literal_elems_id = SemIR::InstBlockId::None;
if (auto struct_literal = value.TryAs<SemIR::StructLiteral>()) {
literal_elems_id = struct_literal->elements_id;
literal_elems = sem_ir.inst_blocks().Get(literal_elems_id);
} else {
value_id = MaterializeIfInitializing(context, value_id);
}
// Check that the structs are the same size.
// TODO: If not, include the name of the first source field that doesn't
// exist in the destination or vice versa in the diagnostic.
if (src_elem_fields.size() != dest_elem_fields_size) {
if (target.diagnose) {
CARBON_DIAGNOSTIC(
StructInitElementCountMismatch, Error,
"cannot initialize {0:class|struct} with {1} field{1:s} from struct "
"with {2} field{2:s}",
Diagnostics::BoolAsSelect, Diagnostics::IntAsSelect,
Diagnostics::IntAsSelect);
context.emitter().Emit(value_loc_id, StructInitElementCountMismatch,
ToClass, dest_elem_fields_size,
src_elem_fields.size());
}
return SemIR::ErrorInst::InstId;
}
// Prepare to look up fields in the source by index.
Map<SemIR::NameId, int32_t> src_field_indexes;
if (src_type.fields_id != dest_type.fields_id) {
for (auto [i, field] : llvm::enumerate(src_elem_fields)) {
auto result = src_field_indexes.Insert(field.name_id, i);
CARBON_CHECK(result.is_inserted(), "Duplicate field in source structure");
}
}
ConversionTarget::Kind inner_kind =
GetAggregateElementConversionTargetKind(sem_ir, target);
// Initialize each element of the destination from the corresponding element
// of the source.
// TODO: Annotate diagnostics coming from here with the element index.
auto new_block =
literal_elems_id.has_value() && !dest_has_vptr
? SemIR::CopyOnWriteInstBlock(&sem_ir, literal_elems_id)
: SemIR::CopyOnWriteInstBlock(
&sem_ir, SemIR::CopyOnWriteInstBlock::UninitializedBlock{
dest_elem_fields.size()});
for (auto [i, dest_field] : llvm::enumerate(dest_elem_fields)) {
if (dest_field.name_id == SemIR::NameId::Vptr) {
if constexpr (!ToClass) {
CARBON_FATAL("Only classes should have vptrs.");
}
target.init_block->InsertHere();
auto vptr_type_id =
context.types().GetTypeIdForTypeInstId(dest_field.type_inst_id);
auto dest_id =
AddInst<SemIR::ClassElementAccess>(context, value_loc_id,
{.type_id = vptr_type_id,
.base_id = target.init_id,
.index = SemIR::ElementIndex(i)});
auto vtable_decl_id =
context.classes().Get(vtable_class_type->class_id).vtable_decl_id;
LoadImportRef(context, vtable_decl_id);
auto canonical_vtable_decl_id =
context.constant_values().GetConstantInstId(vtable_decl_id);
auto vtable_ptr_id = AddInst<SemIR::VtablePtr>(
context, value_loc_id,
{.type_id = GetPointerType(context, SemIR::VtableType::TypeInstId),
.vtable_id = context.insts()
.GetAs<SemIR::VtableDecl>(canonical_vtable_decl_id)
.vtable_id,
.specific_id = vtable_class_type->specific_id});
auto init_id = AddInst<SemIR::InitializeFrom>(context, value_loc_id,
{.type_id = vptr_type_id,
.src_id = vtable_ptr_id,
.dest_id = dest_id});
new_block.Set(i, init_id);
continue;
}
// Find the matching source field.
auto src_field_index = i;
if (src_type.fields_id != dest_type.fields_id) {
if (auto lookup = src_field_indexes.Lookup(dest_field.name_id)) {
src_field_index = lookup.value();
} else {
if (target.diagnose) {
if (literal_elems_id.has_value()) {
CARBON_DIAGNOSTIC(
StructInitMissingFieldInLiteral, Error,
"missing value for field `{0}` in struct initialization",
SemIR::NameId);
context.emitter().Emit(value_loc_id,
StructInitMissingFieldInLiteral,
dest_field.name_id);
} else {
CARBON_DIAGNOSTIC(StructInitMissingFieldInConversion, Error,
"cannot convert from struct type {0} to {1}: "
"missing field `{2}` in source type",
TypeOfInstId, SemIR::TypeId, SemIR::NameId);
context.emitter().Emit(value_loc_id,
StructInitMissingFieldInConversion, value_id,
target.type_id, dest_field.name_id);
}
}
return SemIR::ErrorInst::InstId;
}
}
auto src_field = src_elem_fields[src_field_index];
// TODO: This call recurses back into conversion. Switch to an iterative
// approach.
auto init_id =
ConvertAggregateElement<SemIR::StructAccess, TargetAccessInstT>(
context, value_loc_id, value_id, src_field.type_inst_id,
literal_elems, inner_kind, target.init_id, dest_field.type_inst_id,
target.init_block, src_field_index,
src_field_index + dest_vptr_offset, vtable_class_type);
if (init_id == SemIR::ErrorInst::InstId) {
return SemIR::ErrorInst::InstId;
}
new_block.Set(i, init_id);
}
bool is_init = target.is_initializer();
if (ToClass) {
target.init_block->InsertHere();
CARBON_CHECK(is_init,
"Converting directly to a class value is not supported");
return AddInst<SemIR::ClassInit>(context, value_loc_id,
{.type_id = target.type_id,
.elements_id = new_block.id(),
.dest_id = target.init_id});
} else if (is_init) {
target.init_block->InsertHere();
return AddInst<SemIR::StructInit>(context, value_loc_id,
{.type_id = target.type_id,
.elements_id = new_block.id(),
.dest_id = target.init_id});
} else {
return AddInst<SemIR::StructValue>(
context, value_loc_id,
{.type_id = target.type_id, .elements_id = new_block.id()});
}
}
// Performs a conversion from a struct to a struct type. This function only
// converts the type, and does not perform a final conversion to the requested
// expression category.
static auto ConvertStructToStruct(Context& context, SemIR::StructType src_type,
SemIR::StructType dest_type,
SemIR::InstId value_id,
ConversionTarget target) -> SemIR::InstId {
return ConvertStructToStructOrClass<SemIR::StructAccess>(
context, src_type, dest_type, value_id, target);
}
// Performs a conversion from a struct to a class type. This function only
// converts the type, and does not perform a final conversion to the requested
// expression category.
static auto ConvertStructToClass(Context& context, SemIR::StructType src_type,
SemIR::ClassType dest_type,
SemIR::InstId value_id,
ConversionTarget target,
SemIR::ClassType* vtable_class_type)
-> SemIR::InstId {
PendingBlock target_block(&context);
auto& dest_class_info = context.classes().Get(dest_type.class_id);
CARBON_CHECK(dest_class_info.inheritance_kind != SemIR::Class::Abstract);
auto object_repr_id =
dest_class_info.GetObjectRepr(context.sem_ir(), dest_type.specific_id);
if (object_repr_id == SemIR::ErrorInst::TypeId) {
return SemIR::ErrorInst::InstId;
}
if (context.types().Is<SemIR::CustomLayoutType>(object_repr_id)) {
// Builtin conversion does not apply.
return value_id;
}
auto dest_struct_type =
context.types().GetAs<SemIR::StructType>(object_repr_id);
// If we're trying to create a class value, form a temporary for the value to
// point to.
bool need_temporary = !target.is_initializer();
if (need_temporary) {
target.kind = ConversionTarget::Initializer;
target.init_block = &target_block;
target.init_id = target_block.AddInst<SemIR::TemporaryStorage>(
SemIR::LocId(value_id), {.type_id = target.type_id});
}
auto result_id = ConvertStructToStructOrClass<SemIR::ClassElementAccess>(
context, src_type, dest_struct_type, value_id, target,
vtable_class_type ? vtable_class_type : &dest_type);
if (need_temporary) {
target_block.InsertHere();
result_id =
AddInstWithCleanup<SemIR::Temporary>(context, SemIR::LocId(value_id),
{.type_id = target.type_id,
.storage_id = target.init_id,
.init_id = result_id});
}
return result_id;
}
// An inheritance path is a sequence of `BaseDecl`s and corresponding base types
// in order from derived to base.
using InheritancePath =
llvm::SmallVector<std::pair<SemIR::InstId, SemIR::TypeId>>;
// Computes the inheritance path from class `derived_id` to class `base_id`.
// Returns nullopt if `derived_id` is not a class derived from `base_id`.
static auto ComputeInheritancePath(Context& context, SemIR::LocId loc_id,
SemIR::TypeId derived_id,
SemIR::TypeId base_id)
-> std::optional<InheritancePath> {
// We intend for NRVO to be applied to `result`. All `return` statements in
// this function should `return result;`.
std::optional<InheritancePath> result(std::in_place);
if (!TryToCompleteType(context, derived_id, loc_id)) {
// TODO: Should we give an error here? If we don't, and there is an
// inheritance path when the class is defined, we may have a coherence
// problem.
result = std::nullopt;
return result;
}
while (derived_id != base_id) {
auto derived_class_type =
context.types().TryGetAs<SemIR::ClassType>(derived_id);
if (!derived_class_type) {
result = std::nullopt;
break;
}
auto& derived_class = context.classes().Get(derived_class_type->class_id);
auto base_type_id = derived_class.GetBaseType(
context.sem_ir(), derived_class_type->specific_id);
if (!base_type_id.has_value()) {
result = std::nullopt;
break;
}
result->push_back({derived_class.base_id, base_type_id});
derived_id = base_type_id;
}
return result;
}
// Performs a conversion from a derived class value or reference to a base class
// value or reference.
static auto ConvertDerivedToBase(Context& context, SemIR::LocId loc_id,
SemIR::InstId value_id,
const InheritancePath& path) -> SemIR::InstId {
// Materialize a temporary if necessary.
value_id = ConvertToValueOrRefExpr(context, value_id);
// Preserve type qualifiers.
auto quals = context.types()
.GetUnqualifiedTypeAndQualifiers(
context.insts().Get(value_id).type_id())
.second;
// Add a series of `.base` accesses.
for (auto [base_id, base_type_id] : path) {
auto base_decl = context.insts().GetAs<SemIR::BaseDecl>(base_id);
value_id = AddInst<SemIR::ClassElementAccess>(
context, loc_id,
{.type_id = GetQualifiedType(context, base_type_id, quals),
.base_id = value_id,
.index = base_decl.index});
}
return value_id;
}
// Performs a conversion from a derived class pointer to a base class pointer.
static auto ConvertDerivedPointerToBasePointer(
Context& context, SemIR::LocId loc_id, SemIR::PointerType src_ptr_type,
SemIR::TypeId dest_ptr_type_id, SemIR::InstId ptr_id,
const InheritancePath& path) -> SemIR::InstId {
auto pointee_type_id =
context.types().GetTypeIdForTypeInstId(src_ptr_type.pointee_id);
// Form `*p`.
ptr_id = ConvertToValueExpr(context, ptr_id);
auto ref_id = AddInst<SemIR::Deref>(
context, loc_id, {.type_id = pointee_type_id, .pointer_id = ptr_id});
// Convert as a reference expression.
ref_id = ConvertDerivedToBase(context, loc_id, ref_id, path);
// Take the address.
return AddInst<SemIR::AddrOf>(
context, loc_id, {.type_id = dest_ptr_type_id, .lvalue_id = ref_id});
}
// Returns whether `category` is a valid expression category to produce as a
// result of a conversion with kind `target_kind`, or at most needs a temporary
// to be materialized.
static auto IsValidExprCategoryForConversionTarget(
SemIR::ExprCategory category, ConversionTarget::Kind target_kind) -> bool {
switch (target_kind) {
case ConversionTarget::Value:
return category == SemIR::ExprCategory::Value;
case ConversionTarget::ValueOrRef:
case ConversionTarget::Discarded:
return category == SemIR::ExprCategory::Value ||
category == SemIR::ExprCategory::DurableRef ||
category == SemIR::ExprCategory::EphemeralRef ||
category == SemIR::ExprCategory::Initializing;
case ConversionTarget::DurableRef:
return category == SemIR::ExprCategory::DurableRef;
case ConversionTarget::CppThunkRef:
return category == SemIR::ExprCategory::EphemeralRef;
case ConversionTarget::ExplicitAs:
case ConversionTarget::ExplicitUnsafeAs:
return true;
case ConversionTarget::Initializer:
case ConversionTarget::FullInitializer:
return category == SemIR::ExprCategory::Initializing;
}
}
// Determines whether the initialization representation of the type is a copy of
// the value representation.
static auto InitReprIsCopyOfValueRepr(const SemIR::File& sem_ir,
SemIR::TypeId type_id) -> bool {
// The initializing representation is a copy of the value representation if
// they're both copies of the object representation.
return SemIR::InitRepr::ForType(sem_ir, type_id).IsCopyOfObjectRepr() &&
SemIR::ValueRepr::ForType(sem_ir, type_id)
.IsCopyOfObjectRepr(sem_ir, type_id);
}
// Determines whether we can pull a value directly out of an initializing
// expression of type `type_id` to initialize a target of type `type_id` and
// kind `target_kind`.
static auto CanUseValueOfInitializer(const SemIR::File& sem_ir,
SemIR::TypeId type_id,
ConversionTarget::Kind target_kind)
-> bool {
if (!IsValidExprCategoryForConversionTarget(SemIR::ExprCategory::Value,
target_kind)) {
// We don't want a value expression.
return false;
}
// We can pull a value out of an initializing expression if it holds one.
return InitReprIsCopyOfValueRepr(sem_ir, type_id);
}
// Determine whether the given set of qualifiers can be added by a conversion
// of an expression of the given category.
static auto CanAddQualifiers(SemIR::TypeQualifiers quals,
SemIR::ExprCategory cat) -> bool {
if (quals.HasAnyOf(SemIR::TypeQualifiers::MaybeUnformed) &&
!SemIR::IsRefCategory(cat)) {
// `MaybeUnformed(T)` may have a different value representation or
// initializing representation from `T`, so only allow it to be added for a
// reference expression.
// TODO: We should allow converting an initializing expression of type `T`
// to `MaybeUnformed(T)`. `PerformBuiltinConversion` will need to generate
// an `InPlaceInit` instruction when needed.
// NOLINTNEXTLINE(readability-simplify-boolean-expr)
return false;
}
// `const` and `partial` can always be added.
return true;
}
// Determine whether the given set of qualifiers can be removed by a conversion
// of an expression of the given category.
static auto CanRemoveQualifiers(SemIR::TypeQualifiers quals,
SemIR::ExprCategory cat,
ConversionTarget::Kind kind) -> bool {
bool allow_unsafe = kind == ConversionTarget::ExplicitUnsafeAs;
if (quals.HasAnyOf(SemIR::TypeQualifiers::Const) && !allow_unsafe &&
SemIR::IsRefCategory(cat) &&
IsValidExprCategoryForConversionTarget(cat, kind)) {
// Removing `const` is an unsafe conversion for a reference expression. But
// it's OK if we will be converting to a different category as part of this
// overall conversion anyway.
return false;
}
if (quals.HasAnyOf(SemIR::TypeQualifiers::Partial) &&
(!allow_unsafe || cat == SemIR::ExprCategory::Initializing)) {
// TODO: Allow removing `partial` for initializing expressions as a safe
// conversion. `PerformBuiltinConversion` will need to initialize the vptr
// as part of the conversion.
return false;
}
if (quals.HasAnyOf(SemIR::TypeQualifiers::MaybeUnformed) &&
(!allow_unsafe || cat == SemIR::ExprCategory::Initializing)) {
// As an unsafe conversion, `MaybeUnformed` can be removed from a value or
// reference expression.
return false;
}
return true;
}
static auto DiagnoseConversionFailureToConstraintValue(
Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
SemIR::TypeId target_type_id) -> void {
CARBON_CHECK(context.types().IsFacetType(target_type_id));
// If the source type is/has a facet value (converted with `as type` or
// otherwise), then we can include its `FacetType` in the diagnostic to help
// explain what interfaces the source type implements.
auto const_expr_id = GetCanonicalFacetOrTypeValue(context, expr_id);
auto const_expr_type_id = context.insts().Get(const_expr_id).type_id();
if (context.types().Is<SemIR::FacetType>(const_expr_type_id)) {
CARBON_DIAGNOSTIC(ConversionFailureFacetToFacet, Error,
"cannot convert type {0} that implements {1} into type "
"implementing {2}",
InstIdAsType, SemIR::TypeId, SemIR::TypeId);
context.emitter().Emit(loc_id, ConversionFailureFacetToFacet, expr_id,
const_expr_type_id, target_type_id);
} else {
CARBON_DIAGNOSTIC(ConversionFailureTypeToFacet, Error,
"cannot convert type {0} into type implementing {1}",
InstIdAsType, SemIR::TypeId);
context.emitter().Emit(loc_id, ConversionFailureTypeToFacet, expr_id,
target_type_id);
}
}
static auto PerformBuiltinConversion(
Context& context, SemIR::LocId loc_id, SemIR::InstId value_id,
ConversionTarget target, SemIR::ClassType* vtable_class_type = nullptr)
-> SemIR::InstId {
auto& sem_ir = context.sem_ir();
auto value = sem_ir.insts().Get(value_id);
auto value_type_id = value.type_id();
auto target_type_inst = sem_ir.types().GetAsInst(target.type_id);
// Various forms of implicit conversion are supported as builtin conversions,
// either in addition to or instead of `impl`s of `ImplicitAs` in the Carbon
// prelude. There are a few reasons we need to perform some of these
// conversions as builtins:
//
// 1) Conversions from struct and tuple *literals* have special rules that
// cannot be implemented by invoking `ImplicitAs`. Specifically, we must
// recurse into the elements of the literal before performing
// initialization in order to avoid unnecessary conversions between
// expression categories that would be performed by `ImplicitAs.Convert`.
// 2) (Not implemented yet) Conversion of a facet to a facet type depends on
// the value of the facet, not only its type, and therefore cannot be
// modeled by `ImplicitAs`.
// 3) Some of these conversions are used while checking the library
// definition of `ImplicitAs` itself or implementations of it.
//
// We also expect to see better performance by avoiding an `impl` lookup for
// common conversions.
//
// TODO: We should provide a debugging flag to turn off as many of these
// builtin conversions as we can so that we can test that they do the same
// thing as the library implementations.
//
// The builtin conversions that correspond to `impl`s in the library all
// correspond to `final impl`s, so we don't need to worry about `ImplicitAs`
// being specialized in any of these cases.
// If the value is already of the right kind and expression category, there's
// nothing to do. Performing a conversion would decompose and rebuild tuples
// and structs, so it's important that we bail out early in this case.
if (value_type_id == target.type_id) {
auto value_cat = SemIR::GetExprCategory(sem_ir, value_id);
if (IsValidExprCategoryForConversionTarget(value_cat, target.kind)) {
return value_id;
}
// If the source is an initializing expression, we may be able to pull a
// value right out of it.
if (value_cat == SemIR::ExprCategory::Initializing &&
CanUseValueOfInitializer(sem_ir, value_type_id, target.kind)) {
return AddInst<SemIR::ValueOfInitializer>(
context, loc_id, {.type_id = value_type_id, .init_id = value_id});
}
// PerformBuiltinConversion converts each part of a tuple or struct, even
// when the types are the same. This is not done for classes since they have
// to define their conversions as part of their api.
//
// If a class adapts a tuple or struct, we convert each of its parts when
// there's no other conversion going on (the source and target types are the
// same). To do so, we have to insert a conversion of the value up to the
// foundation and back down, and a conversion of the initializing object if
// there is one.
//
// Implementation note: We do the conversion through a call to
// PerformBuiltinConversion() call rather than a Convert() call to avoid
// extraneous `converted` semir instructions on the adapted types, and as a
// shortcut to doing the explicit calls to walk the parts of the
// tuple/struct which happens inside PerformBuiltinConversion().
if (auto foundation_type_id =
context.types().GetTransitiveAdaptedType(value_type_id);
foundation_type_id != value_type_id &&
(context.types().Is<SemIR::TupleType>(foundation_type_id) ||
context.types().Is<SemIR::StructType>(foundation_type_id))) {
auto foundation_value_id = AddInst<SemIR::AsCompatible>(
context, loc_id,
{.type_id = foundation_type_id, .source_id = value_id});
auto foundation_init_id = target.init_id;
if (foundation_init_id != SemIR::InstId::None) {
foundation_init_id = target.init_block->AddInst<SemIR::AsCompatible>(
loc_id,
{.type_id = foundation_type_id, .source_id = target.init_id});
}
{
// While the types are the same, the conversion can still fail if it
// performs a copy while converting the value to another category, and
// the type (or some part of it) is not copyable.
Diagnostics::AnnotationScope annotate_diagnostics(
&context.emitter(), [&](auto& builder) {
CARBON_DIAGNOSTIC(InCopy, Note, "in copy of {0}", TypeOfInstId);
builder.Note(value_id, InCopy, value_id);
});
foundation_value_id =
PerformBuiltinConversion(context, loc_id, foundation_value_id,
{.kind = target.kind,
.type_id = foundation_type_id,
.init_id = foundation_init_id,
.init_block = target.init_block,
.diagnose = target.diagnose});
if (foundation_value_id == SemIR::ErrorInst::InstId) {
return SemIR::ErrorInst::InstId;
}
}
return AddInst<SemIR::AsCompatible>(
context, loc_id,
{.type_id = target.type_id, .source_id = foundation_value_id});
}
}
// T implicitly converts to U if T and U are the same ignoring qualifiers, and
// we're allowed to remove / add any qualifiers that differ. Similarly, T
// explicitly converts to U if T is compatible with U, and we're allowed to
// remove / add any qualifiers that differ.
if (target.type_id != value_type_id) {
auto [target_foundation_id, target_quals] =
target.is_explicit_as()
? context.types().GetTransitiveUnqualifiedAdaptedType(
target.type_id)
: context.types().GetUnqualifiedTypeAndQualifiers(target.type_id);
auto [value_foundation_id, value_quals] =
target.is_explicit_as()
? context.types().GetTransitiveUnqualifiedAdaptedType(value_type_id)
: context.types().GetUnqualifiedTypeAndQualifiers(value_type_id);
if (target_foundation_id == value_foundation_id) {
auto category = SemIR::GetExprCategory(context.sem_ir(), value_id);
auto added_quals = target_quals & ~value_quals;
auto removed_quals = value_quals & ~target_quals;
if (CanAddQualifiers(added_quals, category) &&
CanRemoveQualifiers(removed_quals, category, target.kind)) {
// For a struct or tuple literal, perform a category conversion if
// necessary.
if (category == SemIR::ExprCategory::Mixed) {
value_id = PerformBuiltinConversion(context, loc_id, value_id,
{.kind = ConversionTarget::Value,
.type_id = value_type_id,
.diagnose = target.diagnose});
}
// `MaybeUnformed(T)` has a pointer value representation, and `T` might
// not, so convert as needed when removing `MaybeUnformed`.
bool need_value_binding = false;
if ((removed_quals & SemIR::TypeQualifiers::MaybeUnformed) !=
SemIR::TypeQualifiers::None &&
category == SemIR::ExprCategory::Value) {
value_id = AddInst<SemIR::ValueAsRef>(
context, loc_id,
{.type_id = value_type_id, .value_id = value_id});
need_value_binding = true;
}
value_id = AddInst<SemIR::AsCompatible>(
context, loc_id,
{.type_id = target.type_id, .source_id = value_id});
if (need_value_binding) {
value_id = AddInst<SemIR::AcquireValue>(
context, loc_id,
{.type_id = target.type_id, .value_id = value_id});
}
return value_id;
} else {
// TODO: Produce a custom diagnostic explaining that we can't perform
// this conversion due to the change in qualifiers and/or the expression
// category.
}
}
}
// A tuple (T1, T2, ..., Tn) converts to (U1, U2, ..., Un) if each Ti
// converts to Ui.
if (auto target_tuple_type = target_type_inst.TryAs<SemIR::TupleType>()) {
if (auto src_tuple_type =
sem_ir.types().TryGetAs<SemIR::TupleType>(value_type_id)) {
return ConvertTupleToTuple(context, *src_tuple_type, *target_tuple_type,
value_id, target);
}
}
// A struct {.f_1: T_1, .f_2: T_2, ..., .f_n: T_n} converts to
// {.f_p(1): U_p(1), .f_p(2): U_p(2), ..., .f_p(n): U_p(n)} if
// (p(1), ..., p(n)) is a permutation of (1, ..., n) and each Ti converts
// to Ui.
if (auto target_struct_type = target_type_inst.TryAs<SemIR::StructType>()) {
if (auto src_struct_type =
sem_ir.types().TryGetAs<SemIR::StructType>(value_type_id)) {
return ConvertStructToStruct(context, *src_struct_type,
*target_struct_type, value_id, target);
}
}
// No other conversions apply when the source and destination types are the
// same.
if (value_type_id == target.type_id) {
return value_id;
}
// A tuple (T1, T2, ..., Tn) converts to array(T, n) if each Ti converts to T.
if (auto target_array_type = target_type_inst.TryAs<SemIR::ArrayType>()) {
if (auto src_tuple_type =
sem_ir.types().TryGetAs<SemIR::TupleType>(value_type_id)) {
return ConvertTupleToArray(context, *src_tuple_type, *target_array_type,
value_id, target);
}
}
// A struct {.f_1: T_1, .f_2: T_2, ..., .f_n: T_n} converts to a class type
// if it converts to the struct type that is the class's representation type
// (a struct with the same fields as the class, plus a base field where
// relevant).
if (auto target_class_type = target_type_inst.TryAs<SemIR::ClassType>()) {
if (auto src_struct_type =
sem_ir.types().TryGetAs<SemIR::StructType>(value_type_id)) {
if (!context.classes()
.Get(target_class_type->class_id)
.adapt_id.has_value()) {
return ConvertStructToClass(context, *src_struct_type,
*target_class_type, value_id, target,
vtable_class_type);
}
}
// An expression of type T converts to U if T is a class derived from U.
//
// TODO: Combine this with the qualifiers and adapter conversion logic above
// to allow qualifiers and inheritance conversions to be performed together.
if (auto path = ComputeInheritancePath(context, loc_id, value_type_id,
target.type_id);
path && !path->empty()) {
return ConvertDerivedToBase(context, loc_id, value_id, *path);
}
}
// A pointer T* converts to [qualified] U* if T is the same as U, or is a
// class derived from U.
if (auto target_pointer_type = target_type_inst.TryAs<SemIR::PointerType>()) {
if (auto src_pointer_type =
sem_ir.types().TryGetAs<SemIR::PointerType>(value_type_id)) {
auto target_pointee_id = context.types().GetTypeIdForTypeInstId(
target_pointer_type->pointee_id);
auto src_pointee_id =
context.types().GetTypeIdForTypeInstId(src_pointer_type->pointee_id);
// Try to complete the pointee types so that we can walk through adapters
// to their adapted types.
TryToCompleteType(context, target_pointee_id, loc_id);
TryToCompleteType(context, src_pointee_id, loc_id);
auto [unqual_target_pointee_type_id, target_quals] =
sem_ir.types().GetTransitiveUnqualifiedAdaptedType(target_pointee_id);
auto [unqual_src_pointee_type_id, src_quals] =
sem_ir.types().GetTransitiveUnqualifiedAdaptedType(src_pointee_id);
// If the qualifiers are incompatible, we can't perform a conversion,
// except with `unsafe as`.
if ((src_quals & ~target_quals) != SemIR::TypeQualifiers::None &&
target.kind != ConversionTarget::ExplicitUnsafeAs) {
// TODO: Consider producing a custom diagnostic here for a cast that
// discards constness.
return value_id;
}
if (unqual_target_pointee_type_id != unqual_src_pointee_type_id) {
// If there's an inheritance path from target to source, this is a
// derived to base conversion.
if (auto path = ComputeInheritancePath(context, loc_id,
unqual_src_pointee_type_id,
unqual_target_pointee_type_id);
path && !path->empty()) {
value_id = ConvertDerivedPointerToBasePointer(
context, loc_id, *src_pointer_type, target.type_id, value_id,
*path);
} else {
// No conversion was possible.
return value_id;
}
}
// Perform a compatible conversion to add any new qualifiers.
if (src_quals != target_quals) {
return AddInst<SemIR::AsCompatible>(
context, loc_id,
{.type_id = target.type_id, .source_id = value_id});
}
return value_id;
}
}
if (target.type_id == SemIR::TypeType::TypeId ||
sem_ir.types().Is<SemIR::FacetType>(target.type_id)) {
auto type_value_id = SemIR::InstId::None;
// A tuple of types converts to type `type`.
// TODO: This should apply even for non-literal tuples.
if (auto tuple_literal = value.TryAs<SemIR::TupleLiteral>()) {
llvm::SmallVector<SemIR::InstId> type_inst_ids;
for (auto tuple_inst_id :
sem_ir.inst_blocks().Get(tuple_literal->elements_id)) {
// TODO: This call recurses back into conversion. Switch to an
// iterative approach.
type_inst_ids.push_back(
ExprAsType(context, loc_id, tuple_inst_id, target.diagnose)
.inst_id);
}
// TODO: Should we add this as an instruction? It will contain references
// to local InstIds.
auto tuple_type_id = GetTupleType(context, type_inst_ids);
type_value_id = sem_ir.types().GetInstId(tuple_type_id);
}
// `{}` converts to `{} as type`.
// TODO: This conversion should also be performed for a non-literal value
// of type `{}`.
if (auto struct_literal = value.TryAs<SemIR::StructLiteral>();
struct_literal &&
struct_literal->elements_id == SemIR::InstBlockId::Empty) {
type_value_id = sem_ir.types().GetInstId(value_type_id);
}
if (type_value_id != SemIR::InstId::None) {
if (sem_ir.types().Is<SemIR::FacetType>(target.type_id)) {
// Use the converted `TypeType` value for converting to a facet.
value_id = type_value_id;
value_type_id = SemIR::TypeType::TypeId;
} else {
// We wanted a `TypeType`, and we've done that.
return type_value_id;
}
}
}
// FacetType converts to Type by wrapping the facet value in
// FacetAccessType.
if (target.type_id == SemIR::TypeType::TypeId &&
sem_ir.types().Is<SemIR::FacetType>(value_type_id)) {
return AddInst<SemIR::FacetAccessType>(
context, loc_id,
{.type_id = target.type_id, .facet_value_inst_id = value_id});
}
// Type values can convert to facet values, and facet values can convert to
// other facet values, as long as they satisfy the required interfaces of the
// target `FacetType`.
if (sem_ir.types().Is<SemIR::FacetType>(target.type_id) &&
(sem_ir.types().Is<SemIR::TypeType>(value_type_id) ||
sem_ir.types().Is<SemIR::FacetType>(value_type_id))) {
// TODO: Runtime facet values should be allowed to convert based on their
// FacetTypes, but we assume constant values for impl lookup at the moment.
if (!context.constant_values().Get(value_id).is_constant()) {
context.TODO(loc_id, "conversion of runtime facet value");
return SemIR::ErrorInst::InstId;
}
// Get the canonical type for which we want to attach a new set of witnesses
// to match the requirements of the target FacetType.
auto type_inst_id = SemIR::TypeInstId::None;
if (sem_ir.types().Is<SemIR::FacetType>(value_type_id)) {
type_inst_id = AddTypeInst<SemIR::FacetAccessType>(
context, loc_id,
{.type_id = SemIR::TypeType::TypeId,
.facet_value_inst_id = value_id});
} else {
type_inst_id = context.types().GetAsTypeInstId(value_id);
// Shortcut for lossless round trips through a FacetAccessType (which
// evaluates to SymbolicBindingType when wrapping a symbolic binding) when
// converting back to the type of the original symbolic binding facet
// value.
//
// In the case where the FacetAccessType wraps a SymbolicBinding with the
// exact facet type that we are converting to, the resulting FacetValue
// would evaluate back to the original SymbolicBinding as its canonical
// form. We can skip past the whole impl lookup step then and do that
// here.
//
// TODO: This instruction is going to become a `SymbolicBindingType`, so
// we'll need to handle that instead.
auto facet_value_inst_id =
GetCanonicalFacetOrTypeValue(context, type_inst_id);
if (sem_ir.insts().Get(facet_value_inst_id).type_id() == target.type_id) {
return facet_value_inst_id;
}
}
// Conversion from a facet value (which has type `FacetType`) or a type
// value (which has type `TypeType`) to a facet value. We can do this if the
// type satisfies the requirements of the target `FacetType`, as determined
// by finding impl witnesses for the target FacetType.
auto lookup_result = LookupImplWitness(
context, loc_id, sem_ir.constant_values().Get(type_inst_id),
sem_ir.types().GetConstantId(target.type_id));
if (lookup_result.has_value()) {
if (lookup_result.has_error_value()) {
return SemIR::ErrorInst::InstId;
} else {
// Note that `FacetValue`'s type is the same `FacetType` that was used
// to construct the set of witnesses, ie. the query to
// `LookupImplWitness()`. This ensures that the witnesses are in the
// same order as the `required_interfaces()` in the `FacetValue`'s type.
return AddInst<SemIR::FacetValue>(
context, loc_id,
{.type_id = target.type_id,
.type_inst_id = type_inst_id,
.witnesses_block_id = lookup_result.inst_block_id()});
}
} else {
// If impl lookup fails, don't keep looking for another way to convert.
// See https://github.com/carbon-language/carbon-lang/issues/5122.
// TODO: Pass this function into `LookupImplWitness` so it can construct
// the error add notes explaining failure.
if (target.diagnose) {
DiagnoseConversionFailureToConstraintValue(context, loc_id, value_id,
target.type_id);
}
return SemIR::ErrorInst::InstId;
}
}
// No builtin conversion applies.
return value_id;
}
// Determine whether this is a C++ enum type.
// TODO: This should be removed once we can properly add a `Copy` impl for C++
// enum types.
static auto IsCppEnum(Context& context, SemIR::TypeId type_id) -> bool {
auto class_type = context.types().TryGetAs<SemIR::ClassType>(type_id);
if (!class_type) {
return false;
}
// A C++-imported class type that is an adapter is an enum.
auto& class_info = context.classes().Get(class_type->class_id);
return class_info.adapt_id.has_value() &&
context.name_scopes().Get(class_info.scope_id).is_cpp_scope();
}
// Given a value expression, form a corresponding initializer that copies from
// that value to the specified target, if it is possible to do so.
static auto PerformCopy(Context& context, SemIR::InstId expr_id,
ConversionTarget& target) -> SemIR::InstId {
// TODO: We don't have a mechanism yet to generate `Copy` impls for each enum
// type imported from C++. For now we fake it by providing a direct copy.
auto type_id = context.insts().Get(expr_id).type_id();
if (IsCppEnum(context, type_id)) {
return expr_id;
}
auto copy_id = BuildUnaryOperator(
context, SemIR::LocId(expr_id), {"Copy"}, expr_id, [&] {
if (!target.diagnose) {
return context.emitter().BuildSuppressed();
}
CARBON_DIAGNOSTIC(CopyOfUncopyableType, Error,
"cannot copy value of type {0}", TypeOfInstId);
return context.emitter().Build(expr_id, CopyOfUncopyableType, expr_id);
});
MarkInitializerFor(context.sem_ir(), copy_id, target);
return copy_id;
}
// Convert a value expression so that it can be used to initialize a C++ thunk
// parameter.
static auto ConvertValueForCppThunkRef(Context& context, SemIR::InstId expr_id)
-> SemIR::InstId {
auto expr = context.insts().Get(expr_id);
// If the expression has a pointer value representation, extract that and use
// it directly.
if (SemIR::ValueRepr::ForType(context.sem_ir(), expr.type_id()).kind ==
SemIR::ValueRepr::Pointer) {
return AddInst<SemIR::ValueAsRef>(
context, SemIR::LocId(expr_id),
{.type_id = expr.type_id(), .value_id = expr_id});
}
// Otherwise, we need a temporary to pass as the thunk argument. Create a copy
// and initialize a temporary from it.
auto temporary_id = AddInst<SemIR::TemporaryStorage>(
context, SemIR::LocId(expr_id), {.type_id = expr.type_id()});
expr_id = Initialize(context, SemIR::LocId(expr_id), temporary_id, expr_id);
return AddInstWithCleanup<SemIR::Temporary>(context, SemIR::LocId(expr_id),
{.type_id = expr.type_id(),
.storage_id = temporary_id,
.init_id = expr_id});
}
// Returns the Core interface name to use for a given kind of conversion.
static auto GetConversionInterfaceName(ConversionTarget::Kind kind)
-> llvm::StringLiteral {
switch (kind) {
case ConversionTarget::ExplicitAs:
return "As";
case ConversionTarget::ExplicitUnsafeAs:
return "UnsafeAs";
default:
return "ImplicitAs";
}
}
auto PerformAction(Context& context, SemIR::LocId loc_id,
SemIR::ConvertToValueAction action) -> SemIR::InstId {
return Convert(context, loc_id, action.inst_id,
{.kind = ConversionTarget::Value,
.type_id = context.types().GetTypeIdForTypeInstId(
action.target_type_inst_id)});
}
auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
ConversionTarget target, SemIR::ClassType* vtable_class_type)
-> SemIR::InstId {
auto& sem_ir = context.sem_ir();
auto orig_expr_id = expr_id;
// Start by making sure both sides are non-errors. If any part is an error,
// the result is an error and we shouldn't diagnose.
if (sem_ir.insts().Get(expr_id).type_id() == SemIR::ErrorInst::TypeId ||
target.type_id == SemIR::ErrorInst::TypeId) {
return SemIR::ErrorInst::InstId;
}
if (SemIR::GetExprCategory(sem_ir, expr_id) == SemIR::ExprCategory::NotExpr) {
// TODO: We currently encounter this for use of namespaces and functions.
// We should provide a better diagnostic for inappropriate use of
// namespace names, and allow use of functions as values.
if (target.diagnose) {
CARBON_DIAGNOSTIC(UseOfNonExprAsValue, Error,
"expression cannot be used as a value");
context.emitter().Emit(expr_id, UseOfNonExprAsValue);
}
return SemIR::ErrorInst::InstId;
}
// We can only perform initialization for complete, non-abstract types. Note
// that `RequireConcreteType` returns true for facet types, since their
// representation is fixed. This allows us to support using the `Self` of an
// interface inside its definition.
if (!RequireConcreteType(
context, target.type_id, loc_id,
[&] {
CARBON_CHECK(!target.is_initializer(),
"Initialization of incomplete types is expected to be "
"caught elsewhere.");
if (!target.diagnose) {
return context.emitter().BuildSuppressed();
}
CARBON_DIAGNOSTIC(IncompleteTypeInValueConversion, Error,
"forming value of incomplete type {0}",
SemIR::TypeId);
CARBON_DIAGNOSTIC(IncompleteTypeInConversion, Error,
"invalid use of incomplete type {0}",
SemIR::TypeId);
return context.emitter().Build(
loc_id,
target.kind == ConversionTarget::Value
? IncompleteTypeInValueConversion
: IncompleteTypeInConversion,
target.type_id);
},
[&] {
if (!target.diagnose || !target.is_initializer()) {
return context.emitter().BuildSuppressed();
}
CARBON_DIAGNOSTIC(AbstractTypeInInit, Error,
"initialization of abstract type {0}",
SemIR::TypeId);
return context.emitter().Build(loc_id, AbstractTypeInInit,
target.type_id);
})) {
return SemIR::ErrorInst::InstId;
}
// The source type doesn't need to be complete, but its completeness can
// affect the result. For example, we don't know what type it adapts or
// derives from unless it's complete.
// TODO: Is there a risk of coherence problems if the source type is
// incomplete, but a conversion would have been possible or would have behaved
// differently if it were complete?
TryToCompleteType(context, context.insts().Get(expr_id).type_id(), loc_id);
// Check whether any builtin conversion applies.
expr_id = PerformBuiltinConversion(context, loc_id, expr_id, target,
vtable_class_type);
if (expr_id == SemIR::ErrorInst::InstId) {
return expr_id;
}
// Defer the action if it's dependent. We do this now rather than before
// attempting any conversion so that we can still perform builtin conversions
// on dependent arguments. This matters for things like converting a
// `template T:! SomeInterface` to `type`, where it's important to form a
// `FacetAccessType` when checking the template. But when running the action
// later, we need to try builtin conversions again, because one may apply that
// didn't apply in the template definition.
// TODO: Support this for targets other than `Value`.
if (sem_ir.insts().Get(expr_id).type_id() != target.type_id &&
target.kind == ConversionTarget::Value &&
(OperandIsDependent(context, expr_id) ||
OperandIsDependent(context, target.type_id))) {
auto target_type_inst_id = context.types().GetInstId(target.type_id);
return AddDependentActionSplice(
context, loc_id,
SemIR::ConvertToValueAction{
.type_id = GetSingletonType(context, SemIR::InstType::TypeInstId),
.inst_id = expr_id,
.target_type_inst_id = target_type_inst_id},
target_type_inst_id);
}
// If this is not a builtin conversion, try an `ImplicitAs` conversion.
if (sem_ir.insts().Get(expr_id).type_id() != target.type_id) {
SemIR::InstId interface_args[] = {
context.types().GetInstId(target.type_id)};
Operator op = {
.interface_name = GetConversionInterfaceName(target.kind),
.interface_args_ref = interface_args,
.op_name = "Convert",
};
expr_id = BuildUnaryOperator(context, loc_id, op, expr_id, [&] {
if (!target.diagnose) {
return context.emitter().BuildSuppressed();
}
int target_kind_for_diag =
target.kind == ConversionTarget::ExplicitAs ? 1
: target.kind == ConversionTarget::ExplicitUnsafeAs ? 2
: 0;
if (target.type_id == SemIR::TypeType::TypeId ||
sem_ir.types().Is<SemIR::FacetType>(target.type_id)) {
CARBON_DIAGNOSTIC(
ConversionFailureNonTypeToFacet, Error,
"cannot{0:=0: implicitly|:} convert non-type value of type {1} "
"{2:to|into type implementing} {3}"
"{0:=1: with `as`|=2: with `unsafe as`|:}",
Diagnostics::IntAsSelect, TypeOfInstId, Diagnostics::BoolAsSelect,
SemIR::TypeId);
return context.emitter().Build(
loc_id, ConversionFailureNonTypeToFacet, target_kind_for_diag,
expr_id, target.type_id == SemIR::TypeType::TypeId, target.type_id);
} else {
CARBON_DIAGNOSTIC(
ConversionFailure, Error,
"cannot{0:=0: implicitly|:} convert expression of type "
"{1} to {2}{0:=1: with `as`|=2: with `unsafe as`|:}",
Diagnostics::IntAsSelect, TypeOfInstId, SemIR::TypeId);
return context.emitter().Build(loc_id, ConversionFailure,
target_kind_for_diag, expr_id,
target.type_id);
}
});
// Pull a value directly out of the initializer if possible and wanted.
if (expr_id != SemIR::ErrorInst::InstId &&
CanUseValueOfInitializer(sem_ir, target.type_id, target.kind)) {
expr_id = AddInst<SemIR::ValueOfInitializer>(
context, loc_id, {.type_id = target.type_id, .init_id = expr_id});
}
}
// Track that we performed a type conversion, if we did so.
if (orig_expr_id != expr_id) {
expr_id = AddInst<SemIR::Converted>(context, loc_id,
{.type_id = target.type_id,
.original_id = orig_expr_id,
.result_id = expr_id});
}
// For `as`, don't perform any value category conversions. In particular, an
// identity conversion shouldn't change the expression category.
if (target.is_explicit_as()) {
return expr_id;
}
// Now perform any necessary value category conversions.
// This uses fallthrough to implement a very simple state machine over the
// category of expr_id, which is tracked by current_category.
switch (auto current_category = SemIR::GetExprCategory(sem_ir, expr_id);
current_category) {
case SemIR::ExprCategory::NotExpr:
case SemIR::ExprCategory::Mixed:
CARBON_FATAL("Unexpected expression {0} after builtin conversions",
sem_ir.insts().Get(expr_id));
case SemIR::ExprCategory::Error:
return SemIR::ErrorInst::InstId;
case SemIR::ExprCategory::Initializing:
if (target.is_initializer()) {
if (orig_expr_id == expr_id) {
// Don't fill in the return slot if we created the expression through
// a conversion. In that case, we will have created it with the
// target already set.
// TODO: Find a better way to track whether we need to do this.
MarkInitializerFor(sem_ir, expr_id, target);
}
break;
}
// Commit to using a temporary for this initializing expression.
// TODO: Don't create a temporary if the initializing representation
// is already a value representation.
// TODO: If the target is DurableRef, materialize a VarStorage instead of
// a TemporaryStorage to lifetime-extend.
expr_id = FinalizeTemporary(context, expr_id,
target.kind == ConversionTarget::Discarded);
// We now have an ephemeral reference.
current_category = SemIR::ExprCategory::EphemeralRef;
[[fallthrough]];
case SemIR::ExprCategory::DurableRef:
case SemIR::ExprCategory::EphemeralRef:
if (current_category == SemIR::ExprCategory::DurableRef &&
target.kind == ConversionTarget::DurableRef) {
break;
}
// If a reference expression is an acceptable result, we're done.
if (target.kind == ConversionTarget::ValueOrRef ||
target.kind == ConversionTarget::Discarded ||
target.kind == ConversionTarget::CppThunkRef) {
break;
}
// If we have a reference and don't want one, form a value binding.
// TODO: Support types with custom value representations.
expr_id = AddInst<SemIR::AcquireValue>(
context, SemIR::LocId(expr_id),
{.type_id = target.type_id, .value_id = expr_id});
// We now have a value expression.
current_category = SemIR::ExprCategory::Value;
[[fallthrough]];
case SemIR::ExprCategory::Value:
if (target.kind == ConversionTarget::DurableRef) {
if (target.diagnose) {
CARBON_DIAGNOSTIC(ConversionFailureNonRefToRef, Error,
"cannot bind durable reference to non-reference "
"value of type {0}",
SemIR::TypeId);
context.emitter().Emit(loc_id, ConversionFailureNonRefToRef,
target.type_id);
}
return SemIR::ErrorInst::InstId;
}
// When initializing from a value, perform a copy.
if (target.is_initializer()) {
expr_id = PerformCopy(context, expr_id, target);
current_category = SemIR::ExprCategory::Initializing;
}
// When initializing a C++ thunk parameter, form a reference, creating a
// temporary if needed.
if (target.kind == ConversionTarget::CppThunkRef) {
expr_id = ConvertValueForCppThunkRef(context, expr_id);
current_category = SemIR::ExprCategory::EphemeralRef;
}
break;
}
// Perform a final destination store, if necessary.
if (target.kind == ConversionTarget::FullInitializer) {
if (auto init_rep = SemIR::InitRepr::ForType(sem_ir, target.type_id);
init_rep.MightBeByCopy()) {
target.init_block->InsertHere();
expr_id = AddInst<SemIR::InitializeFrom>(context, loc_id,
{.type_id = target.type_id,
.src_id = expr_id,
.dest_id = target.init_id});
}
}
return expr_id;
}
auto Initialize(Context& context, SemIR::LocId loc_id, SemIR::InstId target_id,
SemIR::InstId value_id) -> SemIR::InstId {
PendingBlock target_block(&context);
return Convert(context, loc_id, value_id,
{.kind = ConversionTarget::Initializer,
.type_id = context.insts().Get(target_id).type_id(),
.init_id = target_id,
.init_block = &target_block});
}
auto ConvertToValueExpr(Context& context, SemIR::InstId expr_id)
-> SemIR::InstId {
return Convert(context, SemIR::LocId(expr_id), expr_id,
{.kind = ConversionTarget::Value,
.type_id = context.insts().Get(expr_id).type_id()});
}
auto ConvertToValueOrRefExpr(Context& context, SemIR::InstId expr_id)
-> SemIR::InstId {
return Convert(context, SemIR::LocId(expr_id), expr_id,
{.kind = ConversionTarget::ValueOrRef,
.type_id = context.insts().Get(expr_id).type_id()});
}
auto ConvertToValueOfType(Context& context, SemIR::LocId loc_id,
SemIR::InstId expr_id, SemIR::TypeId type_id)
-> SemIR::InstId {
return Convert(context, loc_id, expr_id,
{.kind = ConversionTarget::Value, .type_id = type_id});
}
auto ConvertToValueOrRefOfType(Context& context, SemIR::LocId loc_id,
SemIR::InstId expr_id, SemIR::TypeId type_id)
-> SemIR::InstId {
return Convert(context, loc_id, expr_id,
{.kind = ConversionTarget::ValueOrRef, .type_id = type_id});
}
// Like ConvertToValueOfType but failure to convert does not result in
// diagnostics. An ErrorInst instruction is still returned on failure.
auto TryConvertToValueOfType(Context& context, SemIR::LocId loc_id,
SemIR::InstId expr_id, SemIR::TypeId type_id)
-> SemIR::InstId {
return Convert(
context, loc_id, expr_id,
{.kind = ConversionTarget::Value, .type_id = type_id, .diagnose = false});
}
auto ConvertToBoolValue(Context& context, SemIR::LocId loc_id,
SemIR::InstId value_id) -> SemIR::InstId {
return ConvertToValueOfType(
context, loc_id, value_id,
GetSingletonType(context, SemIR::BoolType::TypeInstId));
}
auto ConvertForExplicitAs(Context& context, Parse::NodeId as_node,
SemIR::InstId value_id, SemIR::TypeId type_id,
bool unsafe) -> SemIR::InstId {
return Convert(context, as_node, value_id,
{.kind = unsafe ? ConversionTarget::ExplicitUnsafeAs
: ConversionTarget::ExplicitAs,
.type_id = type_id});
}
// TODO: Consider moving this to pattern_match.h.
auto ConvertCallArgs(Context& context, SemIR::LocId call_loc_id,
SemIR::InstId self_id,
llvm::ArrayRef<SemIR::InstId> arg_refs,
SemIR::InstId return_slot_arg_id,
const SemIR::Function& callee,
SemIR::SpecificId callee_specific_id)
-> SemIR::InstBlockId {
auto param_patterns =
context.inst_blocks().GetOrEmpty(callee.param_patterns_id);
auto return_slot_pattern_id = callee.return_slot_pattern_id;
// The caller should have ensured this callee has the right arity.
CARBON_CHECK(arg_refs.size() == param_patterns.size());
if (callee.self_param_id.has_value() && !self_id.has_value()) {
CARBON_DIAGNOSTIC(MissingObjectInMethodCall, Error,
"missing object argument in method call");
CARBON_DIAGNOSTIC(InCallToFunction, Note, "calling function declared here");
context.emitter()
.Build(call_loc_id, MissingObjectInMethodCall)
.Note(callee.latest_decl_id(), InCallToFunction)
.Emit();
self_id = SemIR::ErrorInst::InstId;
}
return CallerPatternMatch(context, callee_specific_id, callee.self_param_id,
callee.param_patterns_id, return_slot_pattern_id,
self_id, arg_refs, return_slot_arg_id);
}
auto TypeExpr::ForUnsugared(Context& context, SemIR::TypeId type_id)
-> TypeExpr {
return {.inst_id = context.types().GetInstId(type_id), .type_id = type_id};
}
auto ExprAsType(Context& context, SemIR::LocId loc_id, SemIR::InstId value_id,
bool diagnose) -> TypeExpr {
auto type_inst_id =
ConvertToValueOfType(context, loc_id, value_id, SemIR::TypeType::TypeId);
if (type_inst_id == SemIR::ErrorInst::TypeInstId) {
return {.inst_id = SemIR::ErrorInst::TypeInstId,
.type_id = SemIR::ErrorInst::TypeId};
}
auto type_const_id = context.constant_values().Get(type_inst_id);
if (!type_const_id.is_constant()) {
if (diagnose) {
CARBON_DIAGNOSTIC(TypeExprEvaluationFailure, Error,
"cannot evaluate type expression");
context.emitter().Emit(loc_id, TypeExprEvaluationFailure);
}
return {.inst_id = SemIR::ErrorInst::TypeInstId,
.type_id = SemIR::ErrorInst::TypeId};
}
return {.inst_id = context.types().GetAsTypeInstId(type_inst_id),
.type_id = context.types().GetTypeIdForTypeConstantId(type_const_id)};
}
auto DiscardExpr(Context& context, SemIR::InstId expr_id) -> void {
// If we discard an initializing expression, convert it to a value or
// reference so that it has something to initialize.
auto expr = context.insts().Get(expr_id);
Convert(context, SemIR::LocId(expr_id), expr_id,
{.kind = ConversionTarget::Discarded, .type_id = expr.type_id()});
// TODO: This will eventually need to do some "do not discard" analysis.
}
} // namespace Carbon::Check
// NOLINTEND(misc-no-recursion)
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