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Support constexpr pointers (#6907)

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This moves the LValue path code from macros.cpp to constant.cpp, so that
it can be called from `MapAPValueToConstant`. TODO messages are updated
accordingly to avoid referring to macros. Added a constexpr pointer test
to `constexpr.carbon` to show the result of this change.
This commit is contained in:
Nicholas Bishop
2026-03-16 19:19:20 +00:00
committed by GitHub
parent c006013e0c
commit 943cd41924
7 changed files with 185 additions and 123 deletions
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toolchain/check/cpp/macros.cpp
+10 -82
View File
@@ -12,8 +12,6 @@
#include "toolchain/check/cpp/constant.h"
#include "toolchain/check/cpp/import.h"
#include "toolchain/check/literal.h"
#include "toolchain/check/member_access.h"
#include "toolchain/check/type_completion.h"
namespace Carbon::Check {
@@ -109,87 +107,17 @@ auto TryEvaluateMacro(Context& context, SemIR::LocId loc_id,
CARBON_FATAL("failed to evaluate macro as constant expression");
}
clang::APValue ap_value = evaluated_result.Val;
// TODO: Add support for other types.
if (result_expr->isGLValue()) {
const auto* value_decl =
ap_value.getLValueBase().get<const clang::ValueDecl*>();
if (!ap_value.hasLValuePath()) {
context.TODO(loc_id, "Macro expanded to lvalue with no path");
return SemIR::ErrorInst::InstId;
}
if (ap_value.isLValueOnePastTheEnd()) {
context.TODO(loc_id, "Macro expanded to a one-past-the-end lvalue");
return SemIR::ErrorInst::InstId;
}
auto key = SemIR::ClangDeclKey::ForNonFunctionDecl(
// TODO: can this const_cast be avoided?
const_cast<clang::ValueDecl*>(value_decl));
auto inst_id = ImportCppDecl(context, loc_id, key);
if (ap_value.getLValuePath().size() == 0) {
return inst_id;
}
// Import the base type so that its fields can be accessed.
auto var_storage = context.insts().GetAs<SemIR::VarStorage>(inst_id);
// TODO: currently an error isn't reachable here because incomplete
// array types can't be imported. Once that changes, switch to
// `RequireCompleteType` and handle the error.
CompleteTypeOrCheckFail(context, var_storage.type_id);
clang::QualType qual_type = ap_value.getLValueBase().getType();
for (const auto& entry : ap_value.getLValuePath()) {
if (qual_type->isArrayType()) {
context.TODO(loc_id, "Macro expanded to array type");
} else {
const auto* decl =
cast<clang::Decl>(entry.getAsBaseOrMember().getPointer());
const auto* field_decl = dyn_cast<clang::FieldDecl>(decl);
if (!field_decl) {
context.TODO(loc_id, "Macro expanded to a base class subobject");
return SemIR::ErrorInst::InstId;
}
auto field_inst_id =
ImportCppDecl(context, loc_id,
SemIR::ClangDeclKey::ForNonFunctionDecl(
const_cast<clang::FieldDecl*>(field_decl)));
if (field_inst_id == SemIR::ErrorInst::InstId) {
context.TODO(loc_id,
"Unsupported field in macro expansion: " +
ap_value.getAsString(context.ast_context(),
result_expr->getType()));
return SemIR::ErrorInst::InstId;
}
const SemIR::FieldDecl& field_decl_inst =
context.insts().GetAs<SemIR::FieldDecl>(field_inst_id);
qual_type = field_decl->getType();
inst_id = PerformMemberAccess(context, loc_id, inst_id,
field_decl_inst.name_id);
}
}
return inst_id;
} else {
auto const_id =
MapAPValueToConstant(context, loc_id, ap_value, result_expr->getType());
if (const_id == SemIR::ConstantId::NotConstant) {
context.TODO(loc_id,
"Unsupported: macro evaluated to a constant of type: " +
result_expr->getType().getAsString());
return SemIR::ErrorInst::InstId;
}
return context.constant_values().GetInstId(const_id);
auto const_id = MapAPValueToConstant(context, loc_id, evaluated_result.Val,
result_expr->getType(),
/*is_lvalue=*/result_expr->isGLValue());
if (const_id == SemIR::ConstantId::NotConstant) {
context.TODO(loc_id,
"Unsupported: macro evaluated to a constant of type: " +
result_expr->getType().getAsString());
return SemIR::ErrorInst::InstId;
}
return context.constant_values().GetInstId(const_id);
}
} // namespace Carbon::Check