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carbon-lang/toolchain/check/handle_function.cpp
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Jon Ross-Perkins 8738497301 Fix parse support for 'fn F[];' (#5135) 
According to approved syntax at
https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p3848.md#syntax-defined,
`fn F[]` without explicit parameters should be valid. This makes it
work, then adds some validation to prevent `class C[]` in check.

Note that for `fn`, positional parameters are a TODO -- but this allows
me to test validation in `fn destroy[]` which is rejected, not just a
TODO.
2025-03-18 00:31:17 +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/base/kind_switch.h"
#include "toolchain/check/context.h"
#include "toolchain/check/control_flow.h"
#include "toolchain/check/convert.h"
#include "toolchain/check/decl_introducer_state.h"
#include "toolchain/check/decl_name_stack.h"
#include "toolchain/check/function.h"
#include "toolchain/check/generic.h"
#include "toolchain/check/handle.h"
#include "toolchain/check/import.h"
#include "toolchain/check/import_ref.h"
#include "toolchain/check/inst.h"
#include "toolchain/check/interface.h"
#include "toolchain/check/keyword_modifier_set.h"
#include "toolchain/check/literal.h"
#include "toolchain/check/merge.h"
#include "toolchain/check/modifiers.h"
#include "toolchain/check/name_component.h"
#include "toolchain/check/name_lookup.h"
#include "toolchain/check/type.h"
#include "toolchain/check/type_completion.h"
#include "toolchain/lex/token_kind.h"
#include "toolchain/parse/node_ids.h"
#include "toolchain/sem_ir/builtin_function_kind.h"
#include "toolchain/sem_ir/entry_point.h"
#include "toolchain/sem_ir/function.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/pattern.h"
#include "toolchain/sem_ir/typed_insts.h"
namespace Carbon::Check {
auto HandleParseNode(Context& context, Parse::FunctionIntroducerId node_id)
-> bool {
// Create an instruction block to hold the instructions created as part of the
// function signature, such as parameter and return types.
context.inst_block_stack().Push();
// Push the bracketing node.
context.node_stack().Push(node_id);
// Optional modifiers and the name follow.
context.decl_introducer_state_stack().Push<Lex::TokenKind::Fn>();
context.decl_name_stack().PushScopeAndStartName();
// The function is potentially generic.
StartGenericDecl(context);
return true;
}
auto HandleParseNode(Context& context, Parse::ReturnTypeId node_id) -> bool {
// Propagate the type expression.
auto [type_node_id, type_inst_id] = context.node_stack().PopExprWithNodeId();
auto type_id = ExprAsType(context, type_node_id, type_inst_id).type_id;
// If the previous node was `IdentifierNameBeforeParams`, then it would have
// caused these entries to be pushed to the pattern stacks. But it's possible
// to have a fn declaration without any parameters, in which case we find
// `IdentifierNameNotBeforeParams` on the node stack. Then these entries are
// not on the pattern stacks yet. They are only needed in that case if we have
// a return type, which we now know that we do.
if (context.node_stack().PeekNodeKind() ==
Parse::NodeKind::IdentifierNameNotBeforeParams) {
context.pattern_block_stack().Push();
context.full_pattern_stack().PushFullPattern(
FullPatternStack::Kind::ExplicitParamList);
}
auto return_slot_pattern_id = AddPatternInst<SemIR::ReturnSlotPattern>(
context, node_id, {.type_id = type_id, .type_inst_id = type_inst_id});
auto param_pattern_id = AddPatternInst<SemIR::OutParamPattern>(
context, node_id,
{.type_id = type_id,
.subpattern_id = return_slot_pattern_id,
.index = SemIR::CallParamIndex::None});
context.node_stack().Push(node_id, param_pattern_id);
return true;
}
// Returns the ID of the self parameter pattern, or None.
// TODO: Do this during initial traversal of implicit params.
static auto FindSelfPattern(Context& context,
SemIR::InstBlockId implicit_param_patterns_id)
-> SemIR::InstId {
auto implicit_param_patterns =
context.inst_blocks().GetOrEmpty(implicit_param_patterns_id);
if (const auto* i = llvm::find_if(implicit_param_patterns,
[&](auto implicit_param_id) {
return SemIR::IsSelfPattern(
context.sem_ir(), implicit_param_id);
});
i != implicit_param_patterns.end()) {
return *i;
}
return SemIR::InstId::None;
}
// Diagnoses issues with the modifiers, removing modifiers that shouldn't be
// present.
static auto DiagnoseModifiers(Context& context,
Parse::AnyFunctionDeclId node_id,
DeclIntroducerState& introducer,
bool is_definition,
SemIR::InstId parent_scope_inst_id,
std::optional<SemIR::Inst> parent_scope_inst,
SemIR::InstId self_param_id) -> void {
CheckAccessModifiersOnDecl(context, introducer, parent_scope_inst);
LimitModifiersOnDecl(context, introducer,
KeywordModifierSet::Access | KeywordModifierSet::Extern |
KeywordModifierSet::Method |
KeywordModifierSet::Interface);
RestrictExternModifierOnDecl(context, introducer, parent_scope_inst,
is_definition);
CheckMethodModifiersOnFunction(context, introducer, parent_scope_inst_id,
parent_scope_inst);
RequireDefaultFinalOnlyInInterfaces(context, introducer, parent_scope_inst);
if (introducer.modifier_set.HasAnyOf(KeywordModifierSet::Interface)) {
// TODO: Once we are saving the modifiers for a function, add check that
// the function may only be defined if it is marked `default` or `final`.
context.TODO(introducer.modifier_node_id(ModifierOrder::Decl),
"interface modifier");
}
if (!self_param_id.has_value() &&
introducer.modifier_set.HasAnyOf(KeywordModifierSet::Method)) {
CARBON_DIAGNOSTIC(VirtualWithoutSelf, Error, "virtual class function");
context.emitter().Emit(node_id, VirtualWithoutSelf);
introducer.modifier_set.Remove(KeywordModifierSet::Method);
}
}
// Returns the virtual-family modifier as an enum.
static auto GetVirtualModifier(const KeywordModifierSet& modifier_set)
-> SemIR::Function::VirtualModifier {
return modifier_set.ToEnum<SemIR::Function::VirtualModifier>()
.Case(KeywordModifierSet::Virtual,
SemIR::Function::VirtualModifier::Virtual)
.Case(KeywordModifierSet::Abstract,
SemIR::Function::VirtualModifier::Abstract)
.Case(KeywordModifierSet::Impl, SemIR::Function::VirtualModifier::Impl)
.Default(SemIR::Function::VirtualModifier::None);
}
// Tries to merge new_function into prev_function_id. Since new_function won't
// have a definition even if one is upcoming, set is_definition to indicate the
// planned result.
//
// If merging is successful, returns true and may update the previous function.
// Otherwise, returns false. Prints a diagnostic when appropriate.
static auto MergeFunctionRedecl(Context& context,
Parse::AnyFunctionDeclId node_id,
SemIR::Function& new_function,
bool new_is_definition,
SemIR::FunctionId prev_function_id,
SemIR::ImportIRId prev_import_ir_id) -> bool {
auto& prev_function = context.functions().Get(prev_function_id);
if (!CheckFunctionTypeMatches(context, new_function, prev_function)) {
return false;
}
DiagnoseIfInvalidRedecl(
context, Lex::TokenKind::Fn, prev_function.name_id,
RedeclInfo(new_function, node_id, new_is_definition),
RedeclInfo(prev_function, prev_function.latest_decl_id(),
prev_function.has_definition_started()),
prev_import_ir_id);
if (new_is_definition && prev_function.has_definition_started()) {
return false;
}
if (!prev_function.first_owning_decl_id.has_value()) {
prev_function.first_owning_decl_id = new_function.first_owning_decl_id;
}
if (new_is_definition) {
// Track the signature from the definition, so that IDs in the body
// match IDs in the signature.
prev_function.MergeDefinition(new_function);
prev_function.return_slot_pattern_id = new_function.return_slot_pattern_id;
prev_function.self_param_id = new_function.self_param_id;
}
if (prev_import_ir_id.has_value()) {
ReplacePrevInstForMerge(context, new_function.parent_scope_id,
prev_function.name_id,
new_function.first_owning_decl_id);
}
return true;
}
// Check whether this is a redeclaration, merging if needed.
static auto TryMergeRedecl(Context& context, Parse::AnyFunctionDeclId node_id,
const DeclNameStack::NameContext& name_context,
SemIR::FunctionDecl& function_decl,
SemIR::Function& function_info, bool is_definition)
-> void {
if (name_context.state == DeclNameStack::NameContext::State::Poisoned) {
DiagnosePoisonedName(context, name_context.name_id_for_new_inst(),
name_context.poisoning_loc_id, name_context.loc_id);
return;
}
auto prev_id = name_context.prev_inst_id();
if (!prev_id.has_value()) {
return;
}
auto prev_function_id = SemIR::FunctionId::None;
auto prev_type_id = SemIR::TypeId::None;
auto prev_import_ir_id = SemIR::ImportIRId::None;
CARBON_KIND_SWITCH(context.insts().Get(prev_id)) {
case CARBON_KIND(SemIR::FunctionDecl function_decl): {
prev_function_id = function_decl.function_id;
prev_type_id = function_decl.type_id;
break;
}
case SemIR::ImportRefLoaded::Kind: {
auto import_ir_inst = GetCanonicalImportIRInst(context, prev_id);
// Verify the decl so that things like aliases are name conflicts.
const auto* import_ir =
context.import_irs().Get(import_ir_inst.ir_id).sem_ir;
if (!import_ir->insts().Is<SemIR::FunctionDecl>(import_ir_inst.inst_id)) {
break;
}
// Use the type to get the ID.
if (auto struct_value = context.insts().TryGetAs<SemIR::StructValue>(
context.constant_values().GetConstantInstId(prev_id))) {
if (auto function_type = context.types().TryGetAs<SemIR::FunctionType>(
struct_value->type_id)) {
prev_function_id = function_type->function_id;
prev_type_id = struct_value->type_id;
prev_import_ir_id = import_ir_inst.ir_id;
}
}
break;
}
default:
break;
}
if (!prev_function_id.has_value()) {
DiagnoseDuplicateName(context, name_context.name_id, name_context.loc_id,
prev_id);
return;
}
if (MergeFunctionRedecl(context, node_id, function_info, is_definition,
prev_function_id, prev_import_ir_id)) {
// When merging, use the existing function rather than adding a new one.
function_decl.function_id = prev_function_id;
function_decl.type_id = prev_type_id;
}
}
// Adds the declaration to name lookup when appropriate.
static auto MaybeAddToNameLookup(
Context& context, const DeclNameStack::NameContext& name_context,
const KeywordModifierSet& modifier_set,
const std::optional<SemIR::Inst>& parent_scope_inst, SemIR::InstId decl_id)
-> void {
if (name_context.state == DeclNameStack::NameContext::State::Poisoned ||
name_context.prev_inst_id().has_value()) {
return;
}
// At interface scope, a function declaration introduces an associated
// function.
auto lookup_result_id = decl_id;
if (parent_scope_inst && !name_context.has_qualifiers) {
if (auto interface_scope =
parent_scope_inst->TryAs<SemIR::InterfaceDecl>()) {
lookup_result_id = BuildAssociatedEntity(
context, interface_scope->interface_id, decl_id);
}
}
context.decl_name_stack().AddName(name_context, lookup_result_id,
modifier_set.GetAccessKind());
}
// If the function is the entry point, do corresponding validation.
static auto ValidateForEntryPoint(Context& context,
Parse::AnyFunctionDeclId node_id,
SemIR::FunctionId function_id,
const SemIR::Function& function_info)
-> void {
if (!SemIR::IsEntryPoint(context.sem_ir(), function_id)) {
return;
}
auto return_type_id = function_info.GetDeclaredReturnType(context.sem_ir());
// TODO: Update this once valid signatures for the entry point are decided.
if (function_info.implicit_param_patterns_id.has_value() ||
!function_info.param_patterns_id.has_value() ||
!context.inst_blocks().Get(function_info.param_patterns_id).empty() ||
(return_type_id.has_value() &&
return_type_id != GetTupleType(context, {}) &&
// TODO: Decide on valid return types for `Main.Run`. Perhaps we should
// have an interface for this.
return_type_id != MakeIntType(context, node_id, SemIR::IntKind::Signed,
context.ints().Add(32)))) {
CARBON_DIAGNOSTIC(InvalidMainRunSignature, Error,
"invalid signature for `Main.Run` function; expected "
"`fn ()` or `fn () -> i32`");
context.emitter().Emit(node_id, InvalidMainRunSignature);
}
}
// Requests a vtable be created when processing a virtual function.
static auto RequestVtableIfVirtual(
Context& context, Parse::AnyFunctionDeclId node_id,
SemIR::Function::VirtualModifier virtual_modifier,
const std::optional<SemIR::Inst>& parent_scope_inst, SemIR::InstId decl_id)
-> void {
// In order to request a vtable, the function must be virtual, and in a class
// scope.
if (virtual_modifier == SemIR::Function::VirtualModifier::None ||
!parent_scope_inst) {
return;
}
auto class_decl = parent_scope_inst->TryAs<SemIR::ClassDecl>();
if (!class_decl) {
return;
}
auto& class_info = context.classes().Get(class_decl->class_id);
if (virtual_modifier == SemIR::Function::VirtualModifier::Impl &&
!class_info.base_id.has_value()) {
CARBON_DIAGNOSTIC(ImplWithoutBase, Error, "impl without base class");
context.emitter().Emit(node_id, ImplWithoutBase);
}
// TODO: If this is an `impl` function, check there's a matching base
// function that's impl or virtual.
class_info.is_dynamic = true;
context.vtable_stack().AddInstId(decl_id);
}
// Validates the `destroy` function's signature. May replace invalid values for
// recovery.
static auto ValidateIfDestroy(Context& context, bool is_redecl,
std::optional<SemIR::Inst> parent_scope_inst,
SemIR::Function& function_info) -> void {
if (function_info.name_id != SemIR::NameId::Destroy) {
return;
}
// For recovery, always force explicit parameters to be empty. We do this
// before any of the returns for simplicity.
auto orig_param_patterns_id = function_info.param_patterns_id;
function_info.param_patterns_id = SemIR::InstBlockId::Empty;
// Use differences on merge to diagnose remaining issues.
if (is_redecl) {
return;
}
if (!parent_scope_inst || !parent_scope_inst->Is<SemIR::ClassDecl>()) {
CARBON_DIAGNOSTIC(DestroyFunctionOutsideClass, Error,
"declaring `fn destroy` in non-class scope");
context.emitter().Emit(function_info.latest_decl_id(),
DestroyFunctionOutsideClass);
return;
}
if (!function_info.self_param_id.has_value()) {
CARBON_DIAGNOSTIC(DestroyFunctionMissingSelf, Error,
"missing implicit `self` parameter");
context.emitter().Emit(function_info.latest_decl_id(),
DestroyFunctionMissingSelf);
return;
}
// `self` must be the only implicit parameter.
if (auto block =
context.inst_blocks().Get(function_info.implicit_param_patterns_id);
block.size() > 1) {
// Point at the first non-`self` parameter.
auto param_id = block[function_info.self_param_id == block[0] ? 1 : 0];
CARBON_DIAGNOSTIC(DestroyFunctionUnexpectedImplicitParam, Error,
"unexpected implicit parameter");
context.emitter().Emit(param_id, DestroyFunctionUnexpectedImplicitParam);
return;
}
if (!orig_param_patterns_id.has_value()) {
CARBON_DIAGNOSTIC(DestroyFunctionPositionalParams, Error,
"missing empty explicit parameter list");
context.emitter().Emit(function_info.latest_decl_id(),
DestroyFunctionPositionalParams);
return;
}
if (orig_param_patterns_id != SemIR::InstBlockId::Empty) {
CARBON_DIAGNOSTIC(DestroyFunctionNonEmptyExplicitParams, Error,
"unexpected parameter");
context.emitter().Emit(context.inst_blocks().Get(orig_param_patterns_id)[0],
DestroyFunctionNonEmptyExplicitParams);
return;
}
if (auto return_type_id =
function_info.GetDeclaredReturnType(context.sem_ir());
return_type_id.has_value() &&
return_type_id != GetTupleType(context, {})) {
CARBON_DIAGNOSTIC(DestroyFunctionIncorrectReturnType, Error,
"incorrect return type; must be unspecified or `()`");
context.emitter().Emit(function_info.return_slot_pattern_id,
DestroyFunctionIncorrectReturnType);
return;
}
}
// Diagnoses when positional params aren't supported. Reassigns the pattern
// block if needed.
static auto DiagnosePositionalParams(Context& context,
SemIR::Function& function_info) -> void {
if (function_info.param_patterns_id.has_value()) {
return;
}
context.TODO(function_info.latest_decl_id(),
"function with positional parameters");
function_info.param_patterns_id = SemIR::InstBlockId::Empty;
}
// Build a FunctionDecl describing the signature of a function. This
// handles the common logic shared by function declaration syntax and function
// definition syntax.
static auto BuildFunctionDecl(Context& context,
Parse::AnyFunctionDeclId node_id,
bool is_definition)
-> std::pair<SemIR::FunctionId, SemIR::InstId> {
auto return_slot_pattern_id = SemIR::InstId::None;
if (auto [return_node, maybe_return_slot_pattern_id] =
context.node_stack().PopWithNodeIdIf<Parse::NodeKind::ReturnType>();
maybe_return_slot_pattern_id) {
return_slot_pattern_id = *maybe_return_slot_pattern_id;
}
auto name = PopNameComponent(context, return_slot_pattern_id);
auto name_context = context.decl_name_stack().FinishName(name);
context.node_stack()
.PopAndDiscardSoloNodeId<Parse::NodeKind::FunctionIntroducer>();
auto self_param_id =
FindSelfPattern(context, name.implicit_param_patterns_id);
// Process modifiers.
auto [parent_scope_inst_id, parent_scope_inst] =
context.name_scopes().GetInstIfValid(name_context.parent_scope_id);
auto introducer =
context.decl_introducer_state_stack().Pop<Lex::TokenKind::Fn>();
DiagnoseModifiers(context, node_id, introducer, is_definition,
parent_scope_inst_id, parent_scope_inst, self_param_id);
bool is_extern = introducer.modifier_set.HasAnyOf(KeywordModifierSet::Extern);
auto virtual_modifier = GetVirtualModifier(introducer.modifier_set);
// Add the function declaration.
SemIR::FunctionDecl function_decl = {SemIR::TypeId::None,
SemIR::FunctionId::None,
context.inst_block_stack().Pop()};
auto decl_id =
AddPlaceholderInst(context, SemIR::LocIdAndInst(node_id, function_decl));
RequestVtableIfVirtual(context, node_id, virtual_modifier, parent_scope_inst,
decl_id);
// Build the function entity. This will be merged into an existing function if
// there is one, or otherwise added to the function store.
auto function_info =
SemIR::Function{name_context.MakeEntityWithParamsBase(
name, decl_id, is_extern, introducer.extern_library),
{.return_slot_pattern_id = name.return_slot_pattern_id,
.virtual_modifier = virtual_modifier,
.self_param_id = self_param_id}};
if (is_definition) {
function_info.definition_id = decl_id;
}
// Analyze standard function signatures before positional parameters, so that
// we can have more specific diagnostics and recovery.
bool is_redecl =
name_context.state == DeclNameStack::NameContext::State::Resolved;
ValidateIfDestroy(context, is_redecl, parent_scope_inst, function_info);
DiagnosePositionalParams(context, function_info);
TryMergeRedecl(context, node_id, name_context, function_decl, function_info,
is_definition);
// Create a new function if this isn't a valid redeclaration.
if (!function_decl.function_id.has_value()) {
if (function_info.is_extern && context.sem_ir().is_impl()) {
DiagnoseExternRequiresDeclInApiFile(context, node_id);
}
function_info.generic_id = BuildGenericDecl(context, decl_id);
function_decl.function_id = context.functions().Add(function_info);
function_decl.type_id =
GetFunctionType(context, function_decl.function_id,
context.scope_stack().PeekSpecificId());
} else {
FinishGenericRedecl(context, decl_id, function_info.generic_id);
// TODO: Validate that the redeclaration doesn't set an access modifier.
}
// Write the function ID into the FunctionDecl.
ReplaceInstBeforeConstantUse(context, decl_id, function_decl);
// Diagnose 'definition of `abstract` function' using the canonical Function's
// modifiers.
if (is_definition &&
context.functions().Get(function_decl.function_id).virtual_modifier ==
SemIR::Function::VirtualModifier::Abstract) {
CARBON_DIAGNOSTIC(DefinedAbstractFunction, Error,
"definition of `abstract` function");
context.emitter().Emit(TokenOnly(node_id), DefinedAbstractFunction);
}
// Add to name lookup if needed, now that the decl is built.
MaybeAddToNameLookup(context, name_context, introducer.modifier_set,
parent_scope_inst, decl_id);
ValidateForEntryPoint(context, node_id, function_decl.function_id,
function_info);
if (!is_definition && context.sem_ir().is_impl() && !is_extern) {
context.definitions_required().push_back(decl_id);
}
return {function_decl.function_id, decl_id};
}
auto HandleParseNode(Context& context, Parse::FunctionDeclId node_id) -> bool {
BuildFunctionDecl(context, node_id, /*is_definition=*/false);
context.decl_name_stack().PopScope();
return true;
}
static auto CheckFunctionDefinitionSignature(Context& context,
SemIR::Function& function)
-> void {
auto params_to_complete =
context.inst_blocks().GetOrEmpty(function.call_params_id);
// Check the return type is complete.
if (function.return_slot_pattern_id.has_value()) {
CheckFunctionReturnType(
context, context.insts().GetLocId(function.return_slot_pattern_id),
function, SemIR::SpecificId::None);
params_to_complete = params_to_complete.drop_back();
}
// Check the parameter types are complete.
for (auto param_ref_id : params_to_complete) {
if (param_ref_id == SemIR::ErrorInst::SingletonInstId) {
continue;
}
// The parameter types need to be complete.
RequireCompleteType(
context, context.insts().GetAs<SemIR::AnyParam>(param_ref_id).type_id,
context.insts().GetLocId(param_ref_id), [&] {
CARBON_DIAGNOSTIC(
IncompleteTypeInFunctionParam, Error,
"parameter has incomplete type {0} in function definition",
TypeOfInstId);
return context.emitter().Build(
param_ref_id, IncompleteTypeInFunctionParam, param_ref_id);
});
}
}
// Processes a function definition after a signature for which we have already
// built a function ID. This logic is shared between processing regular function
// definitions and delayed parsing of inline method definitions.
static auto HandleFunctionDefinitionAfterSignature(
Context& context, Parse::FunctionDefinitionStartId node_id,
SemIR::FunctionId function_id, SemIR::InstId decl_id) -> void {
auto& function = context.functions().Get(function_id);
// Create the function scope and the entry block.
context.return_scope_stack().push_back({.decl_id = decl_id});
context.inst_block_stack().Push();
context.region_stack().PushRegion(context.inst_block_stack().PeekOrAdd());
context.scope_stack().Push(decl_id);
StartGenericDefinition(context);
CheckFunctionDefinitionSignature(context, function);
context.node_stack().Push(node_id, function_id);
}
auto HandleFunctionDefinitionSuspend(Context& context,
Parse::FunctionDefinitionStartId node_id)
-> SuspendedFunction {
// Process the declaration portion of the function.
auto [function_id, decl_id] =
BuildFunctionDecl(context, node_id, /*is_definition=*/true);
return {.function_id = function_id,
.decl_id = decl_id,
.saved_name_state = context.decl_name_stack().Suspend()};
}
auto HandleFunctionDefinitionResume(Context& context,
Parse::FunctionDefinitionStartId node_id,
SuspendedFunction suspended_fn) -> void {
context.decl_name_stack().Restore(suspended_fn.saved_name_state);
HandleFunctionDefinitionAfterSignature(
context, node_id, suspended_fn.function_id, suspended_fn.decl_id);
}
auto HandleParseNode(Context& context, Parse::FunctionDefinitionStartId node_id)
-> bool {
// Process the declaration portion of the function.
auto [function_id, decl_id] =
BuildFunctionDecl(context, node_id, /*is_definition=*/true);
HandleFunctionDefinitionAfterSignature(context, node_id, function_id,
decl_id);
return true;
}
auto HandleParseNode(Context& context, Parse::FunctionDefinitionId node_id)
-> bool {
SemIR::FunctionId function_id =
context.node_stack().Pop<Parse::NodeKind::FunctionDefinitionStart>();
// If the `}` of the function is reachable, reject if we need a return value
// and otherwise add an implicit `return;`.
if (IsCurrentPositionReachable(context)) {
if (context.functions()
.Get(function_id)
.return_slot_pattern_id.has_value()) {
CARBON_DIAGNOSTIC(
MissingReturnStatement, Error,
"missing `return` at end of function with declared return type");
context.emitter().Emit(TokenOnly(node_id), MissingReturnStatement);
} else {
AddInst<SemIR::Return>(context, node_id, {});
}
}
context.scope_stack().Pop();
context.inst_block_stack().Pop();
context.return_scope_stack().pop_back();
context.decl_name_stack().PopScope();
auto& function = context.functions().Get(function_id);
function.body_block_ids = context.region_stack().PopRegion();
// If this is a generic function, collect information about the definition.
FinishGenericDefinition(context, function.generic_id);
return true;
}
auto HandleParseNode(Context& context,
Parse::BuiltinFunctionDefinitionStartId node_id) -> bool {
// Process the declaration portion of the function.
auto [function_id, _] =
BuildFunctionDecl(context, node_id, /*is_definition=*/true);
context.node_stack().Push(node_id, function_id);
return true;
}
auto HandleParseNode(Context& context, Parse::BuiltinNameId node_id) -> bool {
context.node_stack().Push(node_id);
return true;
}
// Looks up a builtin function kind given its name as a string.
// TODO: Move this out to another file.
static auto LookupBuiltinFunctionKind(Context& context,
Parse::BuiltinNameId name_id)
-> SemIR::BuiltinFunctionKind {
auto builtin_name = context.string_literal_values().Get(
context.tokens().GetStringLiteralValue(
context.parse_tree().node_token(name_id)));
auto kind = SemIR::BuiltinFunctionKind::ForBuiltinName(builtin_name);
if (kind == SemIR::BuiltinFunctionKind::None) {
CARBON_DIAGNOSTIC(UnknownBuiltinFunctionName, Error,
"unknown builtin function name \"{0}\"", std::string);
context.emitter().Emit(name_id, UnknownBuiltinFunctionName,
builtin_name.str());
}
return kind;
}
// Returns whether `function` is a valid declaration of `builtin_kind`.
static auto IsValidBuiltinDeclaration(Context& context,
const SemIR::Function& function,
SemIR::BuiltinFunctionKind builtin_kind)
-> bool {
// Form the list of parameter types for the declaration.
llvm::SmallVector<SemIR::TypeId> param_type_ids;
auto implicit_param_patterns =
context.inst_blocks().GetOrEmpty(function.implicit_param_patterns_id);
auto param_patterns =
context.inst_blocks().GetOrEmpty(function.param_patterns_id);
param_type_ids.reserve(implicit_param_patterns.size() +
param_patterns.size());
for (auto param_id : llvm::concat<const SemIR::InstId>(
implicit_param_patterns, param_patterns)) {
// TODO: We also need to track whether the parameter is declared with
// `var`.
param_type_ids.push_back(context.insts().Get(param_id).type_id());
}
// Get the return type. This is `()` if none was specified.
auto return_type_id = function.GetDeclaredReturnType(context.sem_ir());
if (!return_type_id.has_value()) {
return_type_id = GetTupleType(context, {});
}
return builtin_kind.IsValidType(context.sem_ir(), param_type_ids,
return_type_id);
}
auto HandleParseNode(Context& context,
Parse::BuiltinFunctionDefinitionId /*node_id*/) -> bool {
auto name_id =
context.node_stack().PopForSoloNodeId<Parse::NodeKind::BuiltinName>();
auto [fn_node_id, function_id] =
context.node_stack()
.PopWithNodeId<Parse::NodeKind::BuiltinFunctionDefinitionStart>();
auto builtin_kind = LookupBuiltinFunctionKind(context, name_id);
if (builtin_kind != SemIR::BuiltinFunctionKind::None) {
auto& function = context.functions().Get(function_id);
CheckFunctionDefinitionSignature(context, function);
if (IsValidBuiltinDeclaration(context, function, builtin_kind)) {
function.builtin_function_kind = builtin_kind;
// Build an empty generic definition if this is a generic builtin.
StartGenericDefinition(context);
FinishGenericDefinition(context, function.generic_id);
} else {
CARBON_DIAGNOSTIC(InvalidBuiltinSignature, Error,
"invalid signature for builtin function \"{0}\"",
std::string);
context.emitter().Emit(fn_node_id, InvalidBuiltinSignature,
builtin_kind.name().str());
}
}
context.decl_name_stack().PopScope();
return true;
}
} // namespace Carbon::Check
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