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carbon-lang/executable_semantics/interpreter/interpreter.cpp
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Geoff RomerandJon Meow 17e0a1afb9 Implement static name resolution (#958) 
This doesn't actually use the results of name resolution, but it does verify that they are present.
Also ensures that name resolution and type checking are applied to deduced function parameters and the implicit call to `Main()`.

Co-authored-by: Jon Meow <46229924+jonmeow@users.noreply.github.com>
2021-11-30 13:33:54 -08:00

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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 "executable_semantics/interpreter/interpreter.h"
#include <iterator>
#include <map>
#include <optional>
#include <utility>
#include <variant>
#include <vector>
#include "common/check.h"
#include "executable_semantics/ast/declaration.h"
#include "executable_semantics/ast/expression.h"
#include "executable_semantics/common/arena.h"
#include "executable_semantics/common/error.h"
#include "executable_semantics/interpreter/action.h"
#include "executable_semantics/interpreter/stack.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Casting.h"
using llvm::cast;
using llvm::dyn_cast;
namespace Carbon {
//
// Auxiliary Functions
//
void Interpreter::PrintEnv(Env values, llvm::raw_ostream& out) {
llvm::ListSeparator sep;
for (const auto& [name, allocation] : values) {
out << sep << name << ": ";
heap_.PrintAllocation(allocation, out);
}
}
//
// State Operations
//
auto Interpreter::CurrentEnv() -> Env { return todo_.CurrentScope().values(); }
// Returns the given name from the environment, printing an error if not found.
auto Interpreter::GetFromEnv(SourceLocation source_loc, const std::string& name)
-> Address {
std::optional<AllocationId> pointer = CurrentEnv().Get(name);
if (!pointer) {
FATAL_RUNTIME_ERROR(source_loc) << "could not find `" << name << "`";
}
return Address(*pointer);
}
void Interpreter::PrintState(llvm::raw_ostream& out) {
out << "{\nstack: " << todo_;
out << "\nheap: " << heap_;
if (!todo_.IsEmpty()) {
out << "\nvalues: ";
PrintEnv(CurrentEnv(), out);
}
out << "\n}\n";
}
auto Interpreter::EvalPrim(Operator op,
const std::vector<Nonnull<const Value*>>& args,
SourceLocation source_loc) -> Nonnull<const Value*> {
switch (op) {
case Operator::Neg:
return arena_->New<IntValue>(-cast<IntValue>(*args[0]).value());
case Operator::Add:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() +
cast<IntValue>(*args[1]).value());
case Operator::Sub:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() -
cast<IntValue>(*args[1]).value());
case Operator::Mul:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() *
cast<IntValue>(*args[1]).value());
case Operator::Not:
return arena_->New<BoolValue>(!cast<BoolValue>(*args[0]).value());
case Operator::And:
return arena_->New<BoolValue>(cast<BoolValue>(*args[0]).value() &&
cast<BoolValue>(*args[1]).value());
case Operator::Or:
return arena_->New<BoolValue>(cast<BoolValue>(*args[0]).value() ||
cast<BoolValue>(*args[1]).value());
case Operator::Eq:
return arena_->New<BoolValue>(ValueEqual(args[0], args[1], source_loc));
case Operator::Ptr:
return arena_->New<PointerType>(args[0]);
case Operator::Deref:
FATAL() << "dereference not implemented yet";
}
}
void Interpreter::InitEnv(const Declaration& d, Env* env) {
switch (d.kind()) {
case DeclarationKind::FunctionDeclaration: {
const auto& func_def = cast<FunctionDeclaration>(d);
Env new_env = *env;
// Bring the deduced parameters into scope.
for (Nonnull<const GenericBinding*> deduced :
func_def.deduced_parameters()) {
AllocationId a =
heap_.AllocateValue(arena_->New<VariableType>(deduced->name()));
new_env.Set(deduced->name(), a);
}
Nonnull<const FunctionValue*> f = arena_->New<FunctionValue>(&func_def);
AllocationId a = heap_.AllocateValue(f);
env->Set(func_def.name(), a);
break;
}
case DeclarationKind::ClassDeclaration: {
const auto& class_decl = cast<ClassDeclaration>(d);
std::vector<NamedValue> fields;
std::vector<NamedValue> methods;
for (Nonnull<const Member*> m : class_decl.members()) {
switch (m->kind()) {
case MemberKind::FieldMember: {
const BindingPattern& binding = cast<FieldMember>(*m).binding();
const Expression& type_expression =
cast<ExpressionPattern>(binding.type()).expression();
auto type = InterpExp(Env(arena_), &type_expression);
fields.push_back({.name = *binding.name(), .value = type});
break;
}
}
}
auto st = arena_->New<NominalClassType>(
class_decl.name(), std::move(fields), std::move(methods));
AllocationId a = heap_.AllocateValue(st);
env->Set(class_decl.name(), a);
break;
}
case DeclarationKind::ChoiceDeclaration: {
const auto& choice = cast<ChoiceDeclaration>(d);
std::vector<NamedValue> alts;
for (Nonnull<const AlternativeSignature*> alternative :
choice.alternatives()) {
auto t = InterpExp(Env(arena_), &alternative->signature());
alts.push_back({.name = alternative->name(), .value = t});
}
auto ct = arena_->New<ChoiceType>(choice.name(), std::move(alts));
AllocationId a = heap_.AllocateValue(ct);
env->Set(choice.name(), a);
break;
}
case DeclarationKind::VariableDeclaration: {
const auto& var = cast<VariableDeclaration>(d);
// Adds an entry in `globals` mapping the variable's name to the
// result of evaluating the initializer.
Nonnull<const Value*> v =
Convert(InterpExp(*env, &var.initializer()), &var.static_type());
AllocationId a = heap_.AllocateValue(v);
env->Set(*var.binding().name(), a);
break;
}
}
}
void Interpreter::InitGlobals(llvm::ArrayRef<Nonnull<Declaration*>> fs) {
for (const auto d : fs) {
InitEnv(*d, &globals_);
}
}
auto Interpreter::CreateStruct(const std::vector<FieldInitializer>& fields,
const std::vector<Nonnull<const Value*>>& values)
-> Nonnull<const Value*> {
CHECK(fields.size() == values.size());
std::vector<NamedValue> elements;
for (size_t i = 0; i < fields.size(); ++i) {
elements.push_back({.name = fields[i].name(), .value = values[i]});
}
return arena_->New<StructValue>(std::move(elements));
}
auto Interpreter::PatternMatch(Nonnull<const Value*> p, Nonnull<const Value*> v,
SourceLocation source_loc)
-> std::optional<Env> {
switch (p->kind()) {
case Value::Kind::BindingPlaceholderValue: {
const auto& placeholder = cast<BindingPlaceholderValue>(*p);
Env values(arena_);
if (placeholder.name().has_value()) {
AllocationId a = heap_.AllocateValue(v);
values.Set(*placeholder.name(), a);
}
return values;
}
case Value::Kind::TupleValue:
switch (v->kind()) {
case Value::Kind::TupleValue: {
const auto& p_tup = cast<TupleValue>(*p);
const auto& v_tup = cast<TupleValue>(*v);
if (p_tup.elements().size() != v_tup.elements().size()) {
FATAL_PROGRAM_ERROR(source_loc)
<< "arity mismatch in tuple pattern match:\n pattern: "
<< p_tup << "\n value: " << v_tup;
}
Env values(arena_);
for (size_t i = 0; i < p_tup.elements().size(); ++i) {
std::optional<Env> matches = PatternMatch(
p_tup.elements()[i], v_tup.elements()[i], source_loc);
if (!matches) {
return std::nullopt;
}
for (const auto& [name, value] : *matches) {
values.Set(name, value);
}
} // for
return values;
}
default:
FATAL() << "expected a tuple value in pattern, not " << *v;
}
case Value::Kind::StructValue: {
const auto& p_struct = cast<StructValue>(*p);
const auto& v_struct = cast<StructValue>(*v);
CHECK(p_struct.elements().size() == v_struct.elements().size());
Env values(arena_);
for (size_t i = 0; i < p_struct.elements().size(); ++i) {
CHECK(p_struct.elements()[i].name == v_struct.elements()[i].name);
std::optional<Env> matches =
PatternMatch(p_struct.elements()[i].value,
v_struct.elements()[i].value, source_loc);
if (!matches) {
return std::nullopt;
}
for (const auto& [name, value] : *matches) {
values.Set(name, value);
}
}
return values;
}
case Value::Kind::AlternativeValue:
switch (v->kind()) {
case Value::Kind::AlternativeValue: {
const auto& p_alt = cast<AlternativeValue>(*p);
const auto& v_alt = cast<AlternativeValue>(*v);
if (p_alt.choice_name() != v_alt.choice_name() ||
p_alt.alt_name() != v_alt.alt_name()) {
return std::nullopt;
}
return PatternMatch(&p_alt.argument(), &v_alt.argument(), source_loc);
}
default:
FATAL() << "expected a choice alternative in pattern, not " << *v;
}
case Value::Kind::FunctionType:
switch (v->kind()) {
case Value::Kind::FunctionType: {
const auto& p_fn = cast<FunctionType>(*p);
const auto& v_fn = cast<FunctionType>(*v);
std::optional<Env> param_matches =
PatternMatch(&p_fn.parameters(), &v_fn.parameters(), source_loc);
if (!param_matches) {
return std::nullopt;
}
std::optional<Env> ret_matches = PatternMatch(
&p_fn.return_type(), &v_fn.return_type(), source_loc);
if (!ret_matches) {
return std::nullopt;
}
Env values = *param_matches;
for (const auto& [name, value] : *ret_matches) {
values.Set(name, value);
}
return values;
}
default:
return std::nullopt;
}
case Value::Kind::AutoType:
// `auto` matches any type, without binding any new names. We rely
// on the typechecker to ensure that `v` is a type.
return Env(arena_);
default:
if (ValueEqual(p, v, source_loc)) {
return Env(arena_);
} else {
return std::nullopt;
}
}
}
void Interpreter::StepLvalue() {
Action& act = todo_.CurrentAction();
const Expression& exp = cast<LValAction>(act).expression();
if (trace_) {
llvm::outs() << "--- step lvalue " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case ExpressionKind::IdentifierExpression: {
// { {x :: C, E, F} :: S, H}
// -> { {E(x) :: C, E, F} :: S, H}
CHECK(cast<IdentifierExpression>(exp).has_named_entity())
<< "Identifier '" << exp << "' at " << exp.source_loc()
<< " was not resolved";
Address pointer =
GetFromEnv(exp.source_loc(), cast<IdentifierExpression>(exp).name());
Nonnull<const Value*> v = arena_->New<LValue>(pointer);
return todo_.FinishAction(v);
}
case ExpressionKind::FieldAccessExpression: {
if (act.pos() == 0) {
// { {e.f :: C, E, F} :: S, H}
// -> { e :: [].f :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<LValAction>(
&cast<FieldAccessExpression>(exp).aggregate()));
} else {
// { v :: [].f :: C, E, F} :: S, H}
// -> { { &v.f :: C, E, F} :: S, H }
Address aggregate = cast<LValue>(*act.results()[0]).address();
Address field = aggregate.SubobjectAddress(
cast<FieldAccessExpression>(exp).field());
return todo_.FinishAction(arena_->New<LValue>(field));
}
}
case ExpressionKind::IndexExpression: {
if (act.pos() == 0) {
// { {e[i] :: C, E, F} :: S, H}
// -> { e :: [][i] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<LValAction>(
&cast<IndexExpression>(exp).aggregate()));
} else if (act.pos() == 1) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<IndexExpression>(exp).offset()));
} else {
// { v :: [][i] :: C, E, F} :: S, H}
// -> { { &v[i] :: C, E, F} :: S, H }
Address aggregate = cast<LValue>(*act.results()[0]).address();
std::string f =
std::to_string(cast<IntValue>(*act.results()[1]).value());
Address field = aggregate.SubobjectAddress(f);
return todo_.FinishAction(arena_->New<LValue>(field));
}
}
case ExpressionKind::TupleLiteral:
case ExpressionKind::StructLiteral:
case ExpressionKind::StructTypeLiteral:
case ExpressionKind::IntLiteral:
case ExpressionKind::BoolLiteral:
case ExpressionKind::CallExpression:
case ExpressionKind::PrimitiveOperatorExpression:
case ExpressionKind::IntTypeLiteral:
case ExpressionKind::BoolTypeLiteral:
case ExpressionKind::TypeTypeLiteral:
case ExpressionKind::FunctionTypeLiteral:
case ExpressionKind::ContinuationTypeLiteral:
case ExpressionKind::StringLiteral:
case ExpressionKind::StringTypeLiteral:
case ExpressionKind::IntrinsicExpression:
FATAL() << "Can't treat expression as lvalue: " << exp;
case ExpressionKind::UnimplementedExpression:
FATAL() << "Unimplemented: " << exp;
}
}
auto Interpreter::Convert(Nonnull<const Value*> value,
Nonnull<const Value*> destination_type) const
-> Nonnull<const Value*> {
switch (value->kind()) {
case Value::Kind::IntValue:
case Value::Kind::FunctionValue:
case Value::Kind::LValue:
case Value::Kind::BoolValue:
case Value::Kind::NominalClassValue:
case Value::Kind::AlternativeValue:
case Value::Kind::IntType:
case Value::Kind::BoolType:
case Value::Kind::TypeType:
case Value::Kind::FunctionType:
case Value::Kind::PointerType:
case Value::Kind::AutoType:
case Value::Kind::StructType:
case Value::Kind::NominalClassType:
case Value::Kind::ChoiceType:
case Value::Kind::ContinuationType:
case Value::Kind::VariableType:
case Value::Kind::BindingPlaceholderValue:
case Value::Kind::AlternativeConstructorValue:
case Value::Kind::ContinuationValue:
case Value::Kind::StringType:
case Value::Kind::StringValue:
// TODO: add `CHECK(TypeEqual(type, value->dynamic_type()))`, once we
// have Value::dynamic_type.
return value;
case Value::Kind::StructValue: {
const auto& struct_val = cast<StructValue>(*value);
switch (destination_type->kind()) {
case Value::Kind::StructType: {
const auto& destination_struct_type =
cast<StructType>(*destination_type);
std::vector<NamedValue> new_elements;
for (const auto& [field_name, field_type] :
destination_struct_type.fields()) {
std::optional<Nonnull<const Value*>> old_value =
struct_val.FindField(field_name);
new_elements.push_back(
{.name = field_name, .value = Convert(*old_value, field_type)});
}
return arena_->New<StructValue>(std::move(new_elements));
}
case Value::Kind::NominalClassType:
return arena_->New<NominalClassValue>(destination_type, value);
default:
FATAL() << "Can't convert value " << *value << " to type "
<< *destination_type;
}
}
case Value::Kind::TupleValue: {
const auto& tuple = cast<TupleValue>(value);
const auto& destination_tuple_type = cast<TupleValue>(destination_type);
CHECK(tuple->elements().size() ==
destination_tuple_type->elements().size());
std::vector<Nonnull<const Value*>> new_elements;
for (size_t i = 0; i < tuple->elements().size(); ++i) {
new_elements.push_back(Convert(tuple->elements()[i],
destination_tuple_type->elements()[i]));
}
return arena_->New<TupleValue>(std::move(new_elements));
}
}
}
void Interpreter::StepExp() {
Action& act = todo_.CurrentAction();
const Expression& exp = cast<ExpressionAction>(act).expression();
if (trace_) {
llvm::outs() << "--- step exp " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case ExpressionKind::IndexExpression: {
if (act.pos() == 0) {
// { { e[i] :: C, E, F} :: S, H}
// -> { { e :: [][i] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<IndexExpression>(exp).aggregate()));
} else if (act.pos() == 1) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<IndexExpression>(exp).offset()));
} else {
// { { v :: [][i] :: C, E, F} :: S, H}
// -> { { v_i :: C, E, F} : S, H}
const auto& tuple = cast<TupleValue>(*act.results()[0]);
int i = cast<IntValue>(*act.results()[1]).value();
if (i < 0 || i >= static_cast<int>(tuple.elements().size())) {
FATAL_RUNTIME_ERROR_NO_LINE()
<< "index " << i << " out of range in " << tuple;
}
return todo_.FinishAction(tuple.elements()[i]);
}
}
case ExpressionKind::TupleLiteral: {
if (act.pos() <
static_cast<int>(cast<TupleLiteral>(exp).fields().size())) {
// { { vk :: (f1=v1,..., fk=[],fk+1=ek+1,...) :: C, E, F} :: S,
// H}
// -> { { ek+1 :: (f1=v1,..., fk=vk, fk+1=[],...) :: C, E, F} :: S,
// H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
cast<TupleLiteral>(exp).fields()[act.pos()]));
} else {
return todo_.FinishAction(arena_->New<TupleValue>(act.results()));
}
}
case ExpressionKind::StructLiteral: {
const auto& literal = cast<StructLiteral>(exp);
if (act.pos() < static_cast<int>(literal.fields().size())) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&literal.fields()[act.pos()].expression()));
} else {
return todo_.FinishAction(
CreateStruct(literal.fields(), act.results()));
}
}
case ExpressionKind::StructTypeLiteral: {
const auto& struct_type = cast<StructTypeLiteral>(exp);
if (act.pos() < static_cast<int>(struct_type.fields().size())) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&struct_type.fields()[act.pos()].expression()));
} else {
std::vector<NamedValue> fields;
for (size_t i = 0; i < struct_type.fields().size(); ++i) {
fields.push_back({struct_type.fields()[i].name(), act.results()[i]});
}
return todo_.FinishAction(arena_->New<StructType>(std::move(fields)));
}
}
case ExpressionKind::FieldAccessExpression: {
const auto& access = cast<FieldAccessExpression>(exp);
if (act.pos() == 0) {
// { { e.f :: C, E, F} :: S, H}
// -> { { e :: [].f :: C, E, F} :: S, H}
return todo_.Spawn(
std::make_unique<ExpressionAction>(&access.aggregate()));
} else {
// { { v :: [].f :: C, E, F} :: S, H}
// -> { { v_f :: C, E, F} : S, H}
return todo_.FinishAction(act.results()[0]->GetField(
arena_, FieldPath(access.field()), exp.source_loc()));
}
}
case ExpressionKind::IdentifierExpression: {
CHECK(act.pos() == 0);
const auto& ident = cast<IdentifierExpression>(exp);
CHECK(ident.has_named_entity())
<< "Identifier '" << exp << "' at " << exp.source_loc()
<< " was not resolved";
// { {x :: C, E, F} :: S, H} -> { {H(E(x)) :: C, E, F} :: S, H}
Address pointer = GetFromEnv(exp.source_loc(), ident.name());
return todo_.FinishAction(heap_.Read(pointer, exp.source_loc()));
}
case ExpressionKind::IntLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<IntValue>(cast<IntLiteral>(exp).value()));
case ExpressionKind::BoolLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<BoolValue>(cast<BoolLiteral>(exp).value()));
case ExpressionKind::PrimitiveOperatorExpression: {
const auto& op = cast<PrimitiveOperatorExpression>(exp);
if (act.pos() != static_cast<int>(op.arguments().size())) {
// { {v :: op(vs,[],e,es) :: C, E, F} :: S, H}
// -> { {e :: op(vs,v,[],es) :: C, E, F} :: S, H}
Nonnull<const Expression*> arg = op.arguments()[act.pos()];
return todo_.Spawn(std::make_unique<ExpressionAction>(arg));
} else {
// { {v :: op(vs,[]) :: C, E, F} :: S, H}
// -> { {eval_prim(op, (vs,v)) :: C, E, F} :: S, H}
return todo_.FinishAction(
EvalPrim(op.op(), act.results(), exp.source_loc()));
}
}
case ExpressionKind::CallExpression:
if (act.pos() == 0) {
// { {e1(e2) :: C, E, F} :: S, H}
// -> { {e1 :: [](e2) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<CallExpression>(exp).function()));
} else if (act.pos() == 1) {
// { { v :: [](e) :: C, E, F} :: S, H}
// -> { { e :: v([]) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<CallExpression>(exp).argument()));
} else if (act.pos() == 2) {
// { { v2 :: v1([]) :: C, E, F} :: S, H}
// -> { {C',E',F'} :: {C, E, F} :: S, H}
switch (act.results()[0]->kind()) {
case Value::Kind::AlternativeConstructorValue: {
const auto& alt =
cast<AlternativeConstructorValue>(*act.results()[0]);
return todo_.FinishAction(arena_->New<AlternativeValue>(
alt.alt_name(), alt.choice_name(), act.results()[1]));
}
case Value::Kind::FunctionValue: {
const FunctionDeclaration& function =
cast<FunctionValue>(*act.results()[0]).declaration();
Nonnull<const Value*> converted_args = Convert(
act.results()[1], &function.param_pattern().static_type());
std::optional<Env> matches =
PatternMatch(&function.param_pattern().value(), converted_args,
exp.source_loc());
CHECK(matches.has_value())
<< "internal error in call_function, pattern match failed";
Scope new_scope(globals_, &heap_);
for (const auto& [name, value] : *matches) {
new_scope.AddLocal(name, value);
}
CHECK(function.body().has_value())
<< "Calling a function that's missing a body";
return todo_.Spawn(
std::make_unique<StatementAction>(*function.body()),
std::move(new_scope));
}
default:
FATAL_RUNTIME_ERROR(exp.source_loc())
<< "in call, expected a function, not " << *act.results()[0];
}
} else if (act.pos() == 3) {
if (act.results().size() < 3) {
// Control fell through without explicit return.
return todo_.FinishAction(TupleValue::Empty());
} else {
return todo_.FinishAction(act.results()[2]);
}
} else {
FATAL() << "in handle_value with Call pos " << act.pos();
}
case ExpressionKind::IntrinsicExpression: {
const auto& intrinsic = cast<IntrinsicExpression>(exp);
if (act.pos() == 0) {
return todo_.Spawn(
std::make_unique<ExpressionAction>(&intrinsic.args()));
}
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
switch (cast<IntrinsicExpression>(exp).intrinsic()) {
case IntrinsicExpression::Intrinsic::Print: {
const auto& args = cast<TupleValue>(*act.results()[0]);
// TODO: This could eventually use something like llvm::formatv.
llvm::outs() << cast<StringValue>(*args.elements()[0]).value();
return todo_.FinishAction(TupleValue::Empty());
}
}
}
case ExpressionKind::IntTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<IntType>());
}
case ExpressionKind::BoolTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<BoolType>());
}
case ExpressionKind::TypeTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<TypeType>());
}
case ExpressionKind::FunctionTypeLiteral: {
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<FunctionTypeLiteral>(exp).parameter()));
} else if (act.pos() == 1) {
// { { pt :: fn [] -> e :: C, E, F} :: S, H}
// -> { { e :: fn pt -> []) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<FunctionTypeLiteral>(exp).return_type()));
} else {
// { { rt :: fn pt -> [] :: C, E, F} :: S, H}
// -> { fn pt -> rt :: {C, E, F} :: S, H}
return todo_.FinishAction(arena_->New<FunctionType>(
std::vector<Nonnull<const GenericBinding*>>(), act.results()[0],
act.results()[1]));
}
}
case ExpressionKind::ContinuationTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<ContinuationType>());
}
case ExpressionKind::StringLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<StringValue>(cast<StringLiteral>(exp).value()));
case ExpressionKind::StringTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<StringType>());
}
case ExpressionKind::UnimplementedExpression:
FATAL() << "Unimplemented: " << exp;
} // switch (exp->kind)
}
void Interpreter::StepPattern() {
Action& act = todo_.CurrentAction();
const Pattern& pattern = cast<PatternAction>(act).pattern();
if (trace_) {
llvm::outs() << "--- step pattern " << pattern << " ("
<< pattern.source_loc() << ") --->\n";
}
switch (pattern.kind()) {
case PatternKind::AutoPattern: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<AutoType>());
}
case PatternKind::BindingPattern: {
const auto& binding = cast<BindingPattern>(pattern);
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<PatternAction>(&binding.type()));
} else {
return todo_.FinishAction(arena_->New<BindingPlaceholderValue>(
binding.name(), act.results()[0]));
}
}
case PatternKind::TuplePattern: {
const auto& tuple = cast<TuplePattern>(pattern);
if (act.pos() < static_cast<int>(tuple.fields().size())) {
// { { vk :: (f1=v1,..., fk=[],fk+1=ek+1,...) :: C, E, F} :: S,
// H}
// -> { { ek+1 :: (f1=v1,..., fk=vk, fk+1=[],...) :: C, E, F} :: S,
// H}
return todo_.Spawn(
std::make_unique<PatternAction>(tuple.fields()[act.pos()]));
} else {
return todo_.FinishAction(arena_->New<TupleValue>(act.results()));
}
}
case PatternKind::AlternativePattern: {
const auto& alternative = cast<AlternativePattern>(pattern);
if (act.pos() == 0) {
return todo_.Spawn(
std::make_unique<ExpressionAction>(&alternative.choice_type()));
} else if (act.pos() == 1) {
return todo_.Spawn(
std::make_unique<PatternAction>(&alternative.arguments()));
} else {
CHECK(act.pos() == 2);
const auto& choice_type = cast<ChoiceType>(*act.results()[0]);
return todo_.FinishAction(arena_->New<AlternativeValue>(
alternative.alternative_name(), choice_type.name(),
act.results()[1]));
}
}
case PatternKind::ExpressionPattern:
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<ExpressionPattern>(pattern).expression()));
} else {
return todo_.FinishAction(act.results()[0]);
}
}
}
void Interpreter::StepStmt() {
Action& act = todo_.CurrentAction();
const Statement& stmt = cast<StatementAction>(act).statement();
if (trace_) {
llvm::outs() << "--- step stmt ";
stmt.PrintDepth(1, llvm::outs());
llvm::outs() << " (" << stmt.source_loc() << ") --->\n";
}
switch (stmt.kind()) {
case StatementKind::Match: {
const auto& match_stmt = cast<Match>(stmt);
if (act.pos() == 0) {
// { { (match (e) ...) :: C, E, F} :: S, H}
// -> { { e :: (match ([]) ...) :: C, E, F} :: S, H}
act.StartScope(Scope(CurrentEnv(), &heap_));
return todo_.Spawn(
std::make_unique<ExpressionAction>(&match_stmt.expression()));
} else {
int clause_num = act.pos() - 1;
if (clause_num >= static_cast<int>(match_stmt.clauses().size())) {
return todo_.FinishAction();
}
auto c = match_stmt.clauses()[clause_num];
std::optional<Env> matches =
PatternMatch(&c.pattern().value(),
Convert(act.results()[0], &c.pattern().static_type()),
stmt.source_loc());
if (matches) { // We have a match, start the body.
// Ensure we don't process any more clauses.
act.set_pos(match_stmt.clauses().size() + 1);
for (const auto& [name, value] : *matches) {
act.scope()->AddLocal(name, value);
}
return todo_.Spawn(std::make_unique<StatementAction>(&c.statement()));
} else {
return todo_.RunAgain();
}
}
}
case StatementKind::While:
if (act.pos() % 2 == 0) {
// { { (while (e) s) :: C, E, F} :: S, H}
// -> { { e :: (while ([]) s) :: C, E, F} :: S, H}
act.Clear();
return todo_.Spawn(
std::make_unique<ExpressionAction>(&cast<While>(stmt).condition()));
} else {
Nonnull<const Value*> condition =
Convert(act.results().back(), arena_->New<BoolType>());
if (cast<BoolValue>(*condition).value()) {
// { {true :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { s :: (while (e) s) :: C, E, F } :: S, H}
return todo_.Spawn(
std::make_unique<StatementAction>(&cast<While>(stmt).body()));
} else {
// { {false :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { C, E, F } :: S, H}
return todo_.FinishAction();
}
}
case StatementKind::Break: {
CHECK(act.pos() == 0);
// { { break; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { C, E', F} :: S, H}
return todo_.UnwindPast(&cast<Break>(stmt).loop());
}
case StatementKind::Continue: {
CHECK(act.pos() == 0);
// { { continue; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { (while (e) s) :: C, E', F} :: S, H}
return todo_.UnwindTo(&cast<Continue>(stmt).loop());
}
case StatementKind::Block: {
const auto& block = cast<Block>(stmt);
if (act.pos() >= static_cast<int>(block.statements().size())) {
// If the position is past the end of the block, end processing. Note
// that empty blocks immediately end.
return todo_.FinishAction();
}
// Initialize a scope when starting a block.
if (act.pos() == 0) {
act.StartScope(Scope(CurrentEnv(), &heap_));
}
// Process the next statement in the block. The position will be
// incremented as part of Spawn.
return todo_.Spawn(
std::make_unique<StatementAction>(block.statements()[act.pos()]));
}
case StatementKind::VariableDefinition: {
const auto& definition = cast<VariableDefinition>(stmt);
if (act.pos() == 0) {
// { {(var x = e) :: C, E, F} :: S, H}
// -> { {e :: (var x = []) :: C, E, F} :: S, H}
return todo_.Spawn(
std::make_unique<ExpressionAction>(&definition.init()));
} else {
// { { v :: (x = []) :: C, E, F} :: S, H}
// -> { { C, E(x := a), F} :: S, H(a := copy(v))}
Nonnull<const Value*> v =
Convert(act.results()[0], &definition.pattern().static_type());
Nonnull<const Value*> p =
&cast<VariableDefinition>(stmt).pattern().value();
std::optional<Env> matches = PatternMatch(p, v, stmt.source_loc());
CHECK(matches)
<< stmt.source_loc()
<< ": internal error in variable definition, match failed";
for (const auto& [name, value] : *matches) {
Scope& current_scope = todo_.CurrentScope();
current_scope.AddLocal(name, value);
}
return todo_.FinishAction();
}
}
case StatementKind::ExpressionStatement:
if (act.pos() == 0) {
// { {e :: C, E, F} :: S, H}
// -> { {e :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<ExpressionStatement>(stmt).expression()));
} else {
return todo_.FinishAction();
}
case StatementKind::Assign: {
const auto& assign = cast<Assign>(stmt);
if (act.pos() == 0) {
// { {(lv = e) :: C, E, F} :: S, H}
// -> { {lv :: ([] = e) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<LValAction>(&assign.lhs()));
} else if (act.pos() == 1) {
// { { a :: ([] = e) :: C, E, F} :: S, H}
// -> { { e :: (a = []) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(&assign.rhs()));
} else {
// { { v :: (a = []) :: C, E, F} :: S, H}
// -> { { C, E, F} :: S, H(a := v)}
const auto& lval = cast<LValue>(*act.results()[0]);
Nonnull<const Value*> rval =
Convert(act.results()[1], &assign.lhs().static_type());
heap_.Write(lval.address(), rval, stmt.source_loc());
return todo_.FinishAction();
}
}
case StatementKind::If:
if (act.pos() == 0) {
// { {(if (e) then_stmt else else_stmt) :: C, E, F} :: S, H}
// -> { { e :: (if ([]) then_stmt else else_stmt) :: C, E, F} :: S, H}
return todo_.Spawn(
std::make_unique<ExpressionAction>(&cast<If>(stmt).condition()));
} else if (act.pos() == 1) {
Nonnull<const Value*> condition =
Convert(act.results()[0], arena_->New<BoolType>());
if (cast<BoolValue>(*condition).value()) {
// { {true :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { then_stmt :: C, E, F } :: S, H}
return todo_.Spawn(
std::make_unique<StatementAction>(&cast<If>(stmt).then_block()));
} else if (cast<If>(stmt).else_block()) {
// { {false :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { else_stmt :: C, E, F } :: S, H}
return todo_.Spawn(
std::make_unique<StatementAction>(*cast<If>(stmt).else_block()));
} else {
return todo_.FinishAction();
}
} else {
return todo_.FinishAction();
}
case StatementKind::Return:
if (act.pos() == 0) {
// { {return e :: C, E, F} :: S, H}
// -> { {e :: return [] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<Return>(stmt).expression()));
} else {
// { {v :: return [] :: C, E, F} :: {C', E', F'} :: S, H}
// -> { {v :: C', E', F'} :: S, H}
const FunctionDeclaration& function = cast<Return>(stmt).function();
return todo_.UnwindPast(
*function.body(),
Convert(act.results()[0], &function.return_term().static_type()));
}
case StatementKind::Continuation: {
CHECK(act.pos() == 0);
// Create a continuation object by creating a frame similar the
// way one is created in a function call.
auto fragment = arena_->New<ContinuationValue::StackFragment>();
stack_fragments_.push_back(fragment);
std::vector<std::unique_ptr<Action>> reversed_todo;
reversed_todo.push_back(
std::make_unique<StatementAction>(&cast<Continuation>(stmt).body()));
reversed_todo.push_back(
std::make_unique<ScopeAction>(Scope(CurrentEnv(), &heap_)));
fragment->StoreReversed(std::move(reversed_todo));
AllocationId continuation_address =
heap_.AllocateValue(arena_->New<ContinuationValue>(fragment));
// Bind the continuation object to the continuation variable
todo_.CurrentScope().AddLocal(
cast<Continuation>(stmt).continuation_variable(),
continuation_address);
return todo_.FinishAction();
}
case StatementKind::Run: {
auto& run = cast<Run>(stmt);
if (act.pos() == 0) {
// Evaluate the argument of the run statement.
return todo_.Spawn(std::make_unique<ExpressionAction>(&run.argument()));
} else if (act.pos() == 1) {
// Push the continuation onto the current stack.
return todo_.Resume(cast<const ContinuationValue>(act.results()[0]));
} else {
return todo_.FinishAction();
}
}
case StatementKind::Await:
CHECK(act.pos() == 0);
return todo_.Suspend();
}
}
// State transition.
void Interpreter::Step() {
Action& act = todo_.CurrentAction();
switch (act.kind()) {
case Action::Kind::LValAction:
StepLvalue();
break;
case Action::Kind::ExpressionAction:
StepExp();
break;
case Action::Kind::PatternAction:
StepPattern();
break;
case Action::Kind::StatementAction:
StepStmt();
break;
case Action::Kind::ScopeAction:
FATAL() << "ScopeAction escaped ActionStack";
} // switch
}
auto Interpreter::ExecuteAction(std::unique_ptr<Action> action, Env values,
bool trace_steps) -> Nonnull<const Value*> {
todo_.Start(std::move(action), Scope(values, &heap_));
while (!todo_.IsEmpty()) {
Step();
if (trace_steps) {
PrintState(llvm::outs());
}
}
// Clean up any remaining suspended continuations.
for (Nonnull<ContinuationValue::StackFragment*> fragment : stack_fragments_) {
fragment->Clear();
}
return todo_.result();
}
auto Interpreter::InterpProgram(llvm::ArrayRef<Nonnull<Declaration*>> fs,
Nonnull<const Expression*> call_main) -> int {
// Check that the interpreter is in a clean state.
CHECK(globals_.IsEmpty());
CHECK(todo_.IsEmpty());
if (trace_) {
llvm::outs() << "********** initializing globals **********\n";
}
InitGlobals(fs);
if (trace_) {
llvm::outs() << "********** calling main function **********\n";
PrintState(llvm::outs());
}
return cast<IntValue>(
*ExecuteAction(std::make_unique<ExpressionAction>(call_main),
globals_, trace_))
.value();
}
auto Interpreter::InterpExp(Env values, Nonnull<const Expression*> e)
-> Nonnull<const Value*> {
return ExecuteAction(std::make_unique<ExpressionAction>(e), values,
/*trace_steps=*/false);
}
auto Interpreter::InterpPattern(Env values, Nonnull<const Pattern*> p)
-> Nonnull<const Value*> {
return ExecuteAction(std::make_unique<PatternAction>(p), values,
/*trace_steps=*/false);
}
} // namespace Carbon
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