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carbon-lang/toolchain/check/handle_function.cpp
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Geoff RomerandJon Ross-Perkins dc32aa2690 Initial support for binding patterns in SemIR (#4221) 
Introduces the `BindingPattern` and `SymbolicBindingPattern` insts, and
a separate stack of pattern blocks that they are emitted into. The
intent is to generate the corresponding pattern-matching insts (like
`BindName`) from them in a separate pass, but that is deferred to future
PRs.

See
[here](https://docs.google.com/document/d/1U_vQH17V893J9aF1LJXUnFYBNSs2MjKl4bJPaWCB2zo/edit?usp=sharing&resourcekey=0-w0xGYZ0An31Kpz-wvzSXwQ)
for the design this is based on, but note that during review we have
chosen to deviate from that design by putting the patterns in separate
blocks, and omitting the "forward references" from a `BindingPattern` to
its corresponding `BindName`. This in turn necessitates having separate
inst kinds for symbolic and non-symbolic binding patterns.

---------

Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
2024-09-25 19:12:58 +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/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_ref.h"
#include "toolchain/check/interface.h"
#include "toolchain/check/merge.h"
#include "toolchain/check/modifiers.h"
#include "toolchain/check/name_component.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/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);
// Start a new pattern block for the signature.
context.pattern_block_stack().Push();
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);
// TODO: Use a dedicated instruction rather than VarStorage here.
context.AddInstAndPush<SemIR::VarStorage>(
node_id, {.type_id = type_id, .name_id = SemIR::NameId::ReturnSlot});
return true;
}
static auto DiagnoseModifiers(Context& context, DeclIntroducerState& introducer,
bool is_definition,
SemIR::InstId parent_scope_inst_id,
std::optional<SemIR::Inst> parent_scope_inst)
-> 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);
}
// Checks that the parameter lists specified in a function declaration are
// valid for a function declaration, and numbers the parameters.
static auto CheckFunctionSignature(Context& context,
const NameComponent& name_and_params)
-> void {
SemIR::RuntimeParamIndex next_index(0);
for (auto param_id : llvm::concat<const SemIR::InstId>(
context.inst_blocks().GetOrEmpty(name_and_params.implicit_params_id),
context.inst_blocks().GetOrEmpty(name_and_params.params_id))) {
auto param = context.insts().Get(param_id);
// Find the parameter in the pattern.
// TODO: This duplicates work done by Function::GetParamFromParamRefId.
if (auto addr_pattern = param.TryAs<SemIR::AddrPattern>()) {
param_id = addr_pattern->inner_id;
param = context.insts().Get(param_id);
}
auto bind_name = param.TryAs<SemIR::AnyBindName>();
if (bind_name) {
param_id = bind_name->value_id;
param = context.insts().Get(param_id);
}
auto param_inst = param.TryAs<SemIR::Param>();
if (!param_inst) {
// Once we support more generalized patterns we will need to diagnose
// parameters with unsupported patterns.
context.TODO(param_id, "unexpected syntax for parameter");
// TODO: Also repair the param ID so downstream code doesn't need to deal
// with this.
continue;
}
// If this is a runtime parameter, number it.
if (bind_name && bind_name->kind == SemIR::BindName::Kind) {
param_inst->runtime_index = next_index;
context.ReplaceInstBeforeConstantUse(param_id, *param_inst);
++next_index.index;
}
}
// TODO: Also assign a parameter index to the return storage, if present.
}
// 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, SemIRLoc new_loc,
SemIR::Function& new_function,
bool new_is_import, 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;
}
CheckIsAllowedRedecl(context, Lex::TokenKind::Fn, prev_function.name_id,
RedeclInfo(new_function, new_loc, new_is_definition),
RedeclInfo(prev_function, prev_function.latest_decl_id(),
prev_function.definition_id.is_valid()),
prev_import_ir_id);
if (!prev_function.first_owning_decl_id.is_valid()) {
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_storage_id = new_function.return_storage_id;
}
if ((prev_import_ir_id.is_valid() && !new_is_import)) {
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,
SemIR::InstId prev_id,
SemIR::FunctionDecl& function_decl,
SemIR::Function& function_info, bool is_definition)
-> void {
if (!prev_id.is_valid()) {
return;
}
auto prev_function_id = SemIR::FunctionId::Invalid;
auto prev_import_ir_id = SemIR::ImportIRId::Invalid;
CARBON_KIND_SWITCH(context.insts().Get(prev_id)) {
case CARBON_KIND(SemIR::FunctionDecl function_decl): {
prev_function_id = function_decl.function_id;
break;
}
case SemIR::ImportRefLoaded::Kind: {
auto import_ir_inst =
GetCanonicalImportIRInst(context, &context.sem_ir(), 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_import_ir_id = import_ir_inst.ir_id;
}
}
break;
}
default:
break;
}
if (!prev_function_id.is_valid()) {
context.DiagnoseDuplicateName(function_info.latest_decl_id(), prev_id);
return;
}
if (MergeFunctionRedecl(context, node_id, function_info,
/*new_is_import=*/false, 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;
}
}
// 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_storage_id = SemIR::InstId::Invalid;
if (auto [return_node, maybe_return_storage_id] =
context.node_stack().PopWithNodeIdIf<Parse::NodeKind::ReturnType>();
maybe_return_storage_id) {
return_storage_id = *maybe_return_storage_id;
}
auto name = PopNameComponent(context);
if (!name.params_id.is_valid()) {
context.TODO(node_id, "function with positional parameters");
name.params_id = SemIR::InstBlockId::Empty;
}
// Check that the function signature is valid and number the parameters.
CheckFunctionSignature(context, name);
auto name_context = context.decl_name_stack().FinishName(name);
context.node_stack()
.PopAndDiscardSoloNodeId<Parse::NodeKind::FunctionIntroducer>();
// 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, introducer, is_definition, parent_scope_inst_id,
parent_scope_inst);
bool is_extern = introducer.modifier_set.HasAnyOf(KeywordModifierSet::Extern);
auto virtual_modifier =
introducer.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);
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");
}
// Add the function declaration.
auto decl_block_id = context.inst_block_stack().Pop();
auto function_decl = SemIR::FunctionDecl{
SemIR::TypeId::Invalid, SemIR::FunctionId::Invalid, decl_block_id};
auto decl_id =
context.AddPlaceholderInst(SemIR::LocIdAndInst(node_id, function_decl));
// 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_storage_id = return_storage_id,
.virtual_modifier = virtual_modifier}};
if (is_definition) {
function_info.definition_id = decl_id;
}
TryMergeRedecl(context, node_id, name_context.prev_inst_id(), function_decl,
function_info, is_definition);
// Create a new function if this isn't a valid redeclaration.
if (!function_decl.function_id.is_valid()) {
if (function_info.is_extern && context.IsImplFile()) {
DiagnoseExternRequiresDeclInApiFile(context, node_id);
}
function_info.generic_id = FinishGenericDecl(context, decl_id);
function_decl.function_id = context.functions().Add(function_info);
} else {
FinishGenericRedecl(context, decl_id, function_info.generic_id);
// TODO: Validate that the redeclaration doesn't set an access modifier.
}
function_decl.type_id = context.GetFunctionType(
function_decl.function_id, context.scope_stack().PeekSpecificId());
// Write the function ID into the FunctionDecl.
context.ReplaceInstBeforeConstantUse(decl_id, function_decl);
// Check if we need to add this to name lookup, now that the function decl is
// done.
if (!name_context.prev_inst_id().is_valid()) {
// 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,
introducer.modifier_set.GetAccessKind());
}
if (SemIR::IsEntryPoint(context.sem_ir(), function_decl.function_id)) {
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_refs_id.is_valid() ||
!function_info.param_refs_id.is_valid() ||
!context.inst_blocks().Get(function_info.param_refs_id).empty() ||
(return_type_id.is_valid() &&
return_type_id !=
context.GetBuiltinType(SemIR::BuiltinInstKind::IntType) &&
return_type_id != context.GetTupleType({}))) {
CARBON_DIAGNOSTIC(InvalidMainRunSignature, Error,
"invalid signature for `Main.Run` function; expected "
"`fn ()` or `fn () -> i32`");
context.emitter().Emit(node_id, InvalidMainRunSignature);
}
}
if (!is_definition && context.IsImplFile() && !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;
}
// 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.scope_stack().Push(decl_id);
StartGenericDefinition(context);
context.AddCurrentCodeBlockToFunction();
// Check the return type is complete.
CheckFunctionReturnType(context, function.return_storage_id, function,
SemIR::SpecificId::Invalid);
// Check the parameter types are complete.
for (auto param_ref_id : llvm::concat<const SemIR::InstId>(
context.inst_blocks().GetOrEmpty(function.implicit_param_refs_id),
context.inst_blocks().GetOrEmpty(function.param_refs_id))) {
auto [param_id, param] =
SemIR::Function::GetParamFromParamRefId(context.sem_ir(), param_ref_id);
// The parameter types need to be complete.
context.TryToCompleteType(param.type_id, [&] {
CARBON_DIAGNOSTIC(
IncompleteTypeInFunctionParam, Error,
"parameter has incomplete type `{0}` in function definition",
SemIR::TypeId);
return context.emitter().Build(param_id, IncompleteTypeInFunctionParam,
param.type_id);
});
}
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 (context.is_current_position_reachable()) {
if (context.functions().Get(function_id).return_storage_id.is_valid()) {
CARBON_DIAGNOSTIC(
MissingReturnStatement, Error,
"missing `return` at end of function with declared return type");
context.emitter().Emit(TokenOnly(node_id), MissingReturnStatement);
} else {
context.AddInst<SemIR::Return>(node_id, {});
}
}
context.scope_stack().Pop();
context.inst_block_stack().Pop();
context.return_scope_stack().pop_back();
context.decl_name_stack().PopScope();
// If this is a generic function, collect information about the definition.
auto& function = context.functions().Get(function_id);
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 the builtin
// `builtin_inst_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_refs =
context.inst_blocks().GetOrEmpty(function.implicit_param_refs_id);
auto param_refs = context.inst_blocks().GetOrEmpty(function.param_refs_id);
param_type_ids.reserve(implicit_param_refs.size() + param_refs.size());
for (auto param_id :
llvm::concat<const SemIR::InstId>(implicit_param_refs, param_refs)) {
// 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.is_valid()) {
return_type_id = context.GetTupleType({});
}
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);
if (IsValidBuiltinDeclaration(context, function, builtin_kind)) {
function.builtin_function_kind = builtin_kind;
} 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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