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carbon-lang/toolchain/check/check_unit.cpp
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Dana JansensandRichard Smith 13da710e94 Poison impl lookup queries with concrete results (#5373) 
Once a concrete result has been found, it's not legal to write an `impl`
that would change the concrete result afterward.

---------

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
2025-04-29 21:55:11 +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/check_unit.h"
#include <string>
#include <utility>
#include "llvm/ADT/IntrusiveRefCntPtr.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/VirtualFileSystem.h"
#include "toolchain/base/kind_switch.h"
#include "toolchain/base/pretty_stack_trace_function.h"
#include "toolchain/check/diagnostic_helpers.h"
#include "toolchain/check/generic.h"
#include "toolchain/check/handle.h"
#include "toolchain/check/impl.h"
#include "toolchain/check/impl_lookup.h"
#include "toolchain/check/import.h"
#include "toolchain/check/import_cpp.h"
#include "toolchain/check/import_ref.h"
#include "toolchain/check/inst.h"
#include "toolchain/check/node_id_traversal.h"
#include "toolchain/check/type.h"
#include "toolchain/diagnostics/diagnostic.h"
#include "toolchain/sem_ir/function.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/import_ir.h"
#include "toolchain/sem_ir/typed_insts.h"
namespace Carbon::Check {
// Returns the number of imported IRs, to assist in Context construction.
static auto GetImportedIRCount(UnitAndImports* unit_and_imports) -> int {
int count = 0;
for (auto& package_imports : unit_and_imports->package_imports) {
count += package_imports.imports.size();
}
if (!unit_and_imports->api_for_impl) {
// Leave an empty slot for `ImportIRId::ApiForImpl`.
++count;
}
if (!unit_and_imports->cpp_import_names.empty()) {
// Leave an empty slot for `ImportIRId::Cpp`.
++count;
}
return count;
}
CheckUnit::CheckUnit(
UnitAndImports* unit_and_imports,
llvm::ArrayRef<Parse::GetTreeAndSubtreesFn> tree_and_subtrees_getters,
llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> fs,
llvm::raw_ostream* vlog_stream)
: unit_and_imports_(unit_and_imports),
total_ir_count_(tree_and_subtrees_getters.size()),
fs_(std::move(fs)),
vlog_stream_(vlog_stream),
emitter_(&unit_and_imports_->err_tracker, tree_and_subtrees_getters,
unit_and_imports_->unit->sem_ir),
context_(&emitter_, unit_and_imports_->unit->tree_and_subtrees_getter,
unit_and_imports_->unit->sem_ir,
GetImportedIRCount(unit_and_imports),
tree_and_subtrees_getters.size(), vlog_stream) {}
auto CheckUnit::Run() -> void {
Timings::ScopedTiming timing(unit_and_imports_->unit->timings, "check");
// We can safely mark this as checked at the start.
unit_and_imports_->is_checked = true;
PrettyStackTraceFunction context_dumper(
[&](llvm::raw_ostream& output) { context_.PrintForStackDump(output); });
// Add a block for the file.
context_.inst_block_stack().Push();
InitPackageScopeAndImports();
// Eagerly import the impls declared in the api file to prepare to redeclare
// them.
ImportImplsFromApiFile(context_);
if (!ProcessNodeIds()) {
context_.sem_ir().set_has_errors(true);
return;
}
FinishRun();
}
auto CheckUnit::InitPackageScopeAndImports() -> void {
// Importing makes many namespaces, so only canonicalize the type once.
auto namespace_type_id =
GetSingletonType(context_, SemIR::NamespaceType::TypeInstId);
// Define the package scope, with an instruction for `package` expressions to
// reference.
auto package_scope_id = context_.name_scopes().Add(
SemIR::Namespace::PackageInstId, SemIR::NameId::PackageNamespace,
SemIR::NameScopeId::None);
CARBON_CHECK(package_scope_id == SemIR::NameScopeId::Package);
auto package_inst_id =
AddInst<SemIR::Namespace>(context_, Parse::NodeId::None,
{.type_id = namespace_type_id,
.name_scope_id = SemIR::NameScopeId::Package,
.import_id = SemIR::InstId::None});
CARBON_CHECK(package_inst_id == SemIR::Namespace::PackageInstId);
// Call `SetSpecialImportIRs()` to set `ImportIRId::ApiForImpl` and
// `ImportIRId::Cpp` first, as required.
if (unit_and_imports_->api_for_impl) {
const auto& names = context_.parse_tree().packaging_decl()->names;
auto import_decl_id = AddInst<SemIR::ImportDecl>(
context_, names.node_id,
{.package_id = SemIR::NameId::ForPackageName(names.package_id)});
SetSpecialImportIRs(
context_, {.decl_id = import_decl_id,
.is_export = false,
.sem_ir = unit_and_imports_->api_for_impl->unit->sem_ir});
} else {
SetSpecialImportIRs(context_,
{.decl_id = SemIR::InstId::None, .sem_ir = nullptr});
}
// Add import instructions for everything directly imported. Implicit imports
// are handled separately.
for (auto& package_imports : unit_and_imports_->package_imports) {
CARBON_CHECK(!package_imports.import_decl_id.has_value());
package_imports.import_decl_id = AddInst<SemIR::ImportDecl>(
context_, package_imports.node_id,
{.package_id =
SemIR::NameId::ForPackageName(package_imports.package_id)});
}
// Process the imports.
if (unit_and_imports_->api_for_impl) {
ImportApiFile(context_, namespace_type_id,
*unit_and_imports_->api_for_impl->unit->sem_ir);
}
ImportCurrentPackage(package_inst_id, namespace_type_id);
CARBON_CHECK(context_.scope_stack().PeekIndex() == ScopeIndex::Package);
ImportOtherPackages(namespace_type_id);
const auto& cpp_import_names = unit_and_imports_->cpp_import_names;
if (!cpp_import_names.empty()) {
auto* cpp_ast = unit_and_imports_->unit->cpp_ast;
CARBON_CHECK(cpp_ast);
CARBON_CHECK(!cpp_ast->get());
*cpp_ast =
ImportCppFiles(context_, unit_and_imports_->unit->sem_ir->filename(),
cpp_import_names, fs_);
}
}
auto CheckUnit::CollectDirectImports(
llvm::SmallVector<SemIR::ImportIR>& results,
llvm::MutableArrayRef<int> ir_to_result_index, SemIR::InstId import_decl_id,
const PackageImports& imports, bool is_local) -> void {
for (const auto& import : imports.imports) {
const auto& direct_ir = *import.unit_info->unit->sem_ir;
auto& index = ir_to_result_index[direct_ir.check_ir_id().index];
if (index != -1) {
// This should only happen when doing API imports for an implementation
// file. Don't change the entry; is_export doesn't matter.
continue;
}
index = results.size();
results.push_back({.decl_id = import_decl_id,
// Only tag exports in API files, ignoring the value in
// implementation files.
.is_export = is_local && import.names.is_export,
.sem_ir = &direct_ir});
}
}
auto CheckUnit::CollectTransitiveImports(SemIR::InstId import_decl_id,
const PackageImports* local_imports,
const PackageImports* api_imports)
-> llvm::SmallVector<SemIR::ImportIR> {
llvm::SmallVector<SemIR::ImportIR> results;
// Track whether an IR was imported in full, including `export import`. This
// distinguishes from IRs that are indirectly added without all names being
// exported to this IR.
llvm::SmallVector<int> ir_to_result_index(total_ir_count_, -1);
// First add direct imports. This means that if an entity is imported both
// directly and indirectly, the import path will reflect the direct import.
if (local_imports) {
CollectDirectImports(results, ir_to_result_index, import_decl_id,
*local_imports,
/*is_local=*/true);
}
if (api_imports) {
CollectDirectImports(results, ir_to_result_index, import_decl_id,
*api_imports,
/*is_local=*/false);
}
// Loop through direct imports for any indirect exports. The underlying vector
// is appended during iteration, so take the size first.
const int direct_imports = results.size();
for (int direct_index : llvm::seq(direct_imports)) {
bool is_export = results[direct_index].is_export;
for (const auto& indirect_ir :
results[direct_index].sem_ir->import_irs().array_ref()) {
if (!indirect_ir.is_export) {
continue;
}
auto& indirect_index =
ir_to_result_index[indirect_ir.sem_ir->check_ir_id().index];
if (indirect_index == -1) {
indirect_index = results.size();
// TODO: In the case of a recursive `export import`, this only points at
// the outermost import. May want something that better reflects the
// recursion.
results.push_back({.decl_id = results[direct_index].decl_id,
.is_export = is_export,
.sem_ir = indirect_ir.sem_ir});
} else if (is_export) {
results[indirect_index].is_export = true;
}
}
}
return results;
}
auto CheckUnit::ImportCurrentPackage(SemIR::InstId package_inst_id,
SemIR::TypeId namespace_type_id) -> void {
// Add imports from the current package.
auto import_map_lookup =
unit_and_imports_->package_imports_map.Lookup(PackageNameId::None);
if (!import_map_lookup) {
// Push the scope; there are no names to add.
context_.scope_stack().PushForEntity(
package_inst_id, SemIR::NameScopeId::Package, SemIR::SpecificId::None,
/*lexical_lookup_has_load_error=*/false);
return;
}
PackageImports& self_import =
unit_and_imports_->package_imports[import_map_lookup.value()];
if (self_import.has_load_error) {
context_.name_scopes().Get(SemIR::NameScopeId::Package).set_has_error();
}
ImportLibrariesFromCurrentPackage(
context_, namespace_type_id,
CollectTransitiveImports(self_import.import_decl_id, &self_import,
/*api_imports=*/nullptr));
context_.scope_stack().PushForEntity(
package_inst_id, SemIR::NameScopeId::Package, SemIR::SpecificId::None,
context_.name_scopes().Get(SemIR::NameScopeId::Package).has_error());
}
auto CheckUnit::ImportOtherPackages(SemIR::TypeId namespace_type_id) -> void {
// api_imports_list is initially the size of the current file's imports,
// including for API files, for simplicity in iteration. It's only really used
// when processing an implementation file, in order to combine the API file
// imports.
//
// For packages imported by the API file, the PackageNameId is the package
// name and the index is into the API's import list. Otherwise, the initial
// {None, -1} state remains.
llvm::SmallVector<std::pair<PackageNameId, int32_t>> api_imports_list;
api_imports_list.resize(unit_and_imports_->package_imports.size(),
{PackageNameId::None, -1});
// When there's an API file, add the mapping to api_imports_list.
if (unit_and_imports_->api_for_impl) {
const auto& api_identifiers =
unit_and_imports_->api_for_impl->unit->value_stores->identifiers();
auto& impl_identifiers =
unit_and_imports_->unit->value_stores->identifiers();
for (auto [api_imports_index, api_imports] :
llvm::enumerate(unit_and_imports_->api_for_impl->package_imports)) {
// Skip the current package.
if (!api_imports.package_id.has_value()) {
continue;
}
// Translate the package ID from the API file to the implementation file.
auto impl_package_id = api_imports.package_id;
if (auto package_identifier_id = impl_package_id.AsIdentifierId();
package_identifier_id.has_value()) {
impl_package_id = PackageNameId::ForIdentifier(
impl_identifiers.Add(api_identifiers.Get(package_identifier_id)));
}
if (auto lookup =
unit_and_imports_->package_imports_map.Lookup(impl_package_id)) {
// On a hit, replace the entry to unify the API and implementation
// imports.
api_imports_list[lookup.value()] = {impl_package_id, api_imports_index};
} else {
// On a miss, add the package as API-only.
api_imports_list.push_back({impl_package_id, api_imports_index});
}
}
}
for (auto [i, api_imports_entry] : llvm::enumerate(api_imports_list)) {
// These variables are updated after figuring out which imports are present.
auto import_decl_id = SemIR::InstId::None;
PackageNameId package_id = PackageNameId::None;
bool has_load_error = false;
// Identify the local package imports if present.
PackageImports* local_imports = nullptr;
if (i < unit_and_imports_->package_imports.size()) {
local_imports = &unit_and_imports_->package_imports[i];
if (!local_imports->package_id.has_value()) {
// Skip the current package.
continue;
}
import_decl_id = local_imports->import_decl_id;
package_id = local_imports->package_id;
has_load_error |= local_imports->has_load_error;
}
// Identify the API package imports if present.
PackageImports* api_imports = nullptr;
if (api_imports_entry.second != -1) {
api_imports = &unit_and_imports_->api_for_impl
->package_imports[api_imports_entry.second];
if (local_imports) {
CARBON_CHECK(package_id == api_imports_entry.first);
} else {
auto import_ir_inst_id =
context_.import_ir_insts().Add(SemIR::ImportIRInst(
SemIR::ImportIRId::ApiForImpl, api_imports->import_decl_id));
import_decl_id =
AddInst(context_, MakeImportedLocIdAndInst<SemIR::ImportDecl>(
context_, import_ir_inst_id,
{.package_id = SemIR::NameId::ForPackageName(
api_imports_entry.first)}));
package_id = api_imports_entry.first;
}
has_load_error |= api_imports->has_load_error;
}
// Do the actual import.
ImportLibrariesFromOtherPackage(
context_, namespace_type_id, import_decl_id, package_id,
CollectTransitiveImports(import_decl_id, local_imports, api_imports),
has_load_error);
}
}
// Loops over all nodes in the tree. On some errors, this may return early,
// for example if an unrecoverable state is encountered.
// NOLINTNEXTLINE(readability-function-size)
auto CheckUnit::ProcessNodeIds() -> bool {
NodeIdTraversal traversal(&context_, vlog_stream_);
Parse::NodeId node_id = Parse::NodeId::None;
// On crash, report which token we were handling.
PrettyStackTraceFunction node_dumper([&](llvm::raw_ostream& output) {
const auto& tree = unit_and_imports_->unit->tree_and_subtrees_getter();
auto converted = tree.NodeToDiagnosticLoc(node_id, /*token_only=*/false);
converted.loc.FormatLocation(output);
output << "checking " << context_.parse_tree().node_kind(node_id) << "\n";
// Crash output has a tab indent; try to indent slightly past that.
converted.loc.FormatSnippet(output, /*indent=*/10);
});
while (auto maybe_node_id = traversal.Next()) {
node_id = *maybe_node_id;
emitter_.AdvanceToken(context_.parse_tree().node_token(node_id));
if (context_.parse_tree().node_has_error(node_id)) {
context_.TODO(node_id, "handle invalid parse trees in `check`");
return false;
}
bool result;
auto parse_kind = context_.parse_tree().node_kind(node_id);
switch (parse_kind) {
#define CARBON_PARSE_NODE_KIND(Name) \
case Parse::NodeKind::Name: { \
result = HandleParseNode( \
context_, context_.parse_tree().As<Parse::Name##Id>(node_id)); \
break; \
}
#include "toolchain/parse/node_kind.def"
}
if (!result) {
CARBON_CHECK(
unit_and_imports_->err_tracker.seen_error(),
"HandleParseNode for `{0}` returned false without diagnosing.",
parse_kind);
return false;
}
traversal.Handle(parse_kind);
}
return true;
}
auto CheckUnit::CheckRequiredDeclarations() -> void {
for (const auto& function : context_.functions().array_ref()) {
if (!function.first_owning_decl_id.has_value() &&
function.extern_library_id == context_.sem_ir().library_id()) {
auto function_loc_id =
context_.insts().GetCanonicalLocId(function.non_owning_decl_id);
CARBON_CHECK(function_loc_id.kind() ==
SemIR::LocId::Kind::ImportIRInstId);
auto import_ir_id = context_.sem_ir()
.import_ir_insts()
.Get(function_loc_id.import_ir_inst_id())
.ir_id();
auto& import_ir = context_.import_irs().Get(import_ir_id);
if (import_ir.sem_ir->package_id().has_value() !=
context_.sem_ir().package_id().has_value()) {
continue;
}
CARBON_DIAGNOSTIC(
MissingOwningDeclarationInApi, Error,
"owning declaration required for non-owning declaration");
if (!import_ir.sem_ir->package_id().has_value() &&
!context_.sem_ir().package_id().has_value()) {
emitter_.Emit(function.non_owning_decl_id,
MissingOwningDeclarationInApi);
continue;
}
if (import_ir.sem_ir->identifiers().Get(
import_ir.sem_ir->package_id().AsIdentifierId()) ==
context_.sem_ir().identifiers().Get(
context_.sem_ir().package_id().AsIdentifierId())) {
emitter_.Emit(function.non_owning_decl_id,
MissingOwningDeclarationInApi);
}
}
}
}
auto CheckUnit::CheckRequiredDefinitions() -> void {
CARBON_DIAGNOSTIC(MissingDefinitionInImpl, Error,
"no definition found for declaration in impl file");
// Note that more required definitions can be added during this loop.
// NOLINTNEXTLINE(modernize-loop-convert)
for (size_t i = 0; i != context_.definitions_required_by_decl().size(); ++i) {
SemIR::InstId decl_inst_id = context_.definitions_required_by_decl()[i];
SemIR::Inst decl_inst = context_.insts().Get(decl_inst_id);
CARBON_KIND_SWITCH(context_.insts().Get(decl_inst_id)) {
case CARBON_KIND(SemIR::ClassDecl class_decl): {
if (!context_.classes().Get(class_decl.class_id).is_complete()) {
emitter_.Emit(decl_inst_id, MissingDefinitionInImpl);
}
break;
}
case CARBON_KIND(SemIR::FunctionDecl function_decl): {
if (context_.functions().Get(function_decl.function_id).definition_id ==
SemIR::InstId::None) {
emitter_.Emit(decl_inst_id, MissingDefinitionInImpl);
}
break;
}
case CARBON_KIND(SemIR::ImplDecl impl_decl): {
auto& impl = context_.impls().Get(impl_decl.impl_id);
if (!impl.is_complete()) {
FillImplWitnessWithErrors(context_, impl);
CARBON_DIAGNOSTIC(ImplMissingDefinition, Error,
"impl declared but not defined");
emitter_.Emit(decl_inst_id, ImplMissingDefinition);
}
break;
}
case SemIR::InterfaceDecl::Kind: {
// TODO: Handle `interface` as well, once we can test it without
// triggering
// https://github.com/carbon-language/carbon-lang/issues/4071.
CARBON_FATAL("TODO: Support interfaces in DiagnoseMissingDefinitions");
}
default: {
CARBON_FATAL("Unexpected inst in definitions_required_by_decl: {0}",
decl_inst);
}
}
}
// Note that more required definitions can be added during this loop.
// NOLINTNEXTLINE(modernize-loop-convert)
for (size_t i = 0; i != context_.definitions_required_by_use().size(); ++i) {
// This is using the location for the use. We could track the
// list of enclosing locations if this was used from a generic.
auto [loc, specific_id] = context_.definitions_required_by_use()[i];
if (!ResolveSpecificDefinition(context_, loc, specific_id)) {
CARBON_DIAGNOSTIC(MissingGenericFunctionDefinition, Error,
"use of undefined generic function");
CARBON_DIAGNOSTIC(MissingGenericFunctionDefinitionHere, Note,
"generic function declared here");
auto generic_decl_id =
context_.generics()
.Get(context_.specifics().Get(specific_id).generic_id)
.decl_id;
emitter_.Build(loc, MissingGenericFunctionDefinition)
.Note(generic_decl_id, MissingGenericFunctionDefinitionHere)
.Emit();
}
}
}
auto CheckUnit::CheckPoisonedConcreteImplLookupQueries() -> void {
// Impl lookup can generate instructions (via deduce) which we don't use, as
// we're only generating diagnostics here, so we catch and discard them.
context_.inst_block_stack().Push();
auto poisoned_queries =
std::exchange(context_.poisoned_concrete_impl_lookup_queries(), {});
for (const auto& poison : poisoned_queries) {
auto witness_result =
EvalLookupSingleImplWitness(context_, poison.loc_id, poison.query,
poison.non_canonical_query_self_inst_id,
/*poison_concrete_results=*/false);
CARBON_CHECK(witness_result.has_concrete_value());
auto found_witness_id = witness_result.concrete_witness();
if (found_witness_id != poison.impl_witness) {
auto witness_to_impl_id = [&](SemIR::InstId witness_id) {
auto table_id = context_.insts()
.GetAs<SemIR::ImplWitness>(witness_id)
.witness_table_id;
return context_.insts()
.GetAs<SemIR::ImplWitnessTable>(table_id)
.impl_id;
};
// We can get the `Impl` from the resulting witness here, which is the
// `Impl` that conflicts with the previous poison query.
auto bad_impl_id = witness_to_impl_id(found_witness_id);
const auto& bad_impl = context_.impls().Get(bad_impl_id);
auto prev_impl_id = witness_to_impl_id(poison.impl_witness);
const auto& prev_impl = context_.impls().Get(prev_impl_id);
CARBON_DIAGNOSTIC(
PoisonedImplLookupConcreteResult, Error,
"found `impl` that would change the result of an earlier "
"use of `{0} as {1}`",
InstIdAsRawType, SpecificInterfaceIdAsRawType);
auto builder =
emitter_.Build(poison.loc_id, PoisonedImplLookupConcreteResult,
poison.query.query_self_inst_id,
poison.query.query_specific_interface_id);
CARBON_DIAGNOSTIC(
PoisonedImplLookupConcreteResultNoteBadImpl, Note,
"the use would select the `impl` here but it was not found yet");
builder.Note(bad_impl.first_decl_id(),
PoisonedImplLookupConcreteResultNoteBadImpl);
CARBON_DIAGNOSTIC(PoisonedImplLookupConcreteResultNotePreviousImpl, Note,
"the use had selected the `impl` here");
builder.Note(prev_impl.first_decl_id(),
PoisonedImplLookupConcreteResultNotePreviousImpl);
builder.Emit();
}
}
context_.inst_block_stack().PopAndDiscard();
}
auto CheckUnit::FinishRun() -> void {
CheckRequiredDeclarations();
CheckRequiredDefinitions();
CheckPoisonedConcreteImplLookupQueries();
// Pop information for the file-level scope.
context_.sem_ir().set_top_inst_block_id(context_.inst_block_stack().Pop());
context_.scope_stack().Pop();
// Finalizes the list of exports on the IR.
context_.inst_blocks().ReplacePlaceholder(SemIR::InstBlockId::Exports,
context_.exports());
// Finalizes the ImportRef inst block.
context_.inst_blocks().ReplacePlaceholder(SemIR::InstBlockId::ImportRefs,
context_.import_ref_ids());
// Finalizes __global_init.
context_.global_init().Finalize();
context_.sem_ir().set_has_errors(unit_and_imports_->err_tracker.seen_error());
// Verify that Context cleanly finished.
context_.VerifyOnFinish();
}
} // namespace Carbon::Check
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