fidl/lib/flat_ast.cpp

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "fidl/flat_ast.h"

#include <assert.h>
#include <stdio.h>

#include <algorithm>
#include <regex>
#include <sstream>

#include "fidl/attributes.h"
#include "fidl/lexer.h"
#include "fidl/names.h"
#include "fidl/parser.h"
#include "fidl/raw_ast.h"

namespace fidl {
namespace flat {

namespace {

class ScopeInsertResult {
public:
    explicit ScopeInsertResult(std::unique_ptr<SourceLocation> previous_occurance)
        : previous_occurance_(std::move(previous_occurance)) {}

    static ScopeInsertResult Ok() { return ScopeInsertResult(nullptr); }
    static ScopeInsertResult FailureAt(SourceLocation previous) {
        return ScopeInsertResult(std::make_unique<SourceLocation>(previous));
    }

    bool ok() const {
        return previous_occurance_ == nullptr;
    }

    const SourceLocation& previous_occurance() const {
        assert(!ok());
        return *previous_occurance_;
    }

private:
    std::unique_ptr<SourceLocation> previous_occurance_;
};

template <typename T>
class Scope {
public:
    ScopeInsertResult Insert(const T& t, SourceLocation location) {
        auto iter = scope_.find(t);
        if (iter != scope_.end()) {
            return ScopeInsertResult::FailureAt(iter->second);
        } else {
            scope_.emplace(t, location);
            return ScopeInsertResult::Ok();
        }
    }

    typename std::map<T, SourceLocation>::const_iterator begin() const {
        return scope_.begin();
    }

    typename std::map<T, SourceLocation>::const_iterator end() const {
        return scope_.end();
    }

private:
    std::map<T, SourceLocation> scope_;
};

struct MethodScope {
    Scope<uint32_t> ordinals;
    Scope<StringView> names;
    Scope<const Interface*> interfaces;
};

// A helper class to track when a Decl is compiling and compiled.
class Compiling {
public:
    explicit Compiling(Decl* decl)
        : decl_(decl) {
        decl_->compiling = true;
    }
    ~Compiling() {
        decl_->compiling = false;
        decl_->compiled = true;
    }

private:
    Decl* decl_;
};

constexpr TypeShape kHandleTypeShape = TypeShape(4u, 4u, 0u, 1u);
constexpr TypeShape kInt8TypeShape = TypeShape(1u, 1u);
constexpr TypeShape kInt16TypeShape = TypeShape(2u, 2u);
constexpr TypeShape kInt32TypeShape = TypeShape(4u, 4u);
constexpr TypeShape kInt64TypeShape = TypeShape(8u, 8u);
constexpr TypeShape kUint8TypeShape = TypeShape(1u, 1u);
constexpr TypeShape kUint16TypeShape = TypeShape(2u, 2u);
constexpr TypeShape kUint32TypeShape = TypeShape(4u, 4u);
constexpr TypeShape kUint64TypeShape = TypeShape(8u, 8u);
constexpr TypeShape kBoolTypeShape = TypeShape(1u, 1u);
constexpr TypeShape kFloat32TypeShape = TypeShape(4u, 4u);
constexpr TypeShape kFloat64TypeShape = TypeShape(8u, 8u);

uint32_t AlignTo(uint64_t size, uint64_t alignment) {
    auto mask = alignment - 1;
    size += mask;
    size &= ~mask;
    if (size > std::numeric_limits<uint32_t>::max()) {
        size = std::numeric_limits<uint32_t>::max();
    }
    return size;
}

uint32_t ClampedMultiply(uint32_t a, uint32_t b) {
    uint64_t product = (uint64_t)a * b;
    return std::min(product, (uint64_t)std::numeric_limits<uint32_t>::max());
}

uint32_t ClampedAdd(uint32_t a, uint32_t b) {
    uint64_t sum = (uint64_t)a + b;
    return std::min(sum, (uint64_t)std::numeric_limits<uint32_t>::max());
}

TypeShape CStructTypeShape(std::vector<FieldShape*>* fields, uint32_t extra_handles = 0u) {
    uint32_t size = 0u;
    uint32_t alignment = 1u;
    uint32_t depth = 0u;
    uint32_t max_handles = 0u;
    uint32_t max_out_of_line = 0u;

    for (FieldShape* field : *fields) {
        TypeShape typeshape = field->Typeshape();
        alignment = std::max(alignment, typeshape.Alignment());
        size = AlignTo(size, typeshape.Alignment());
        field->SetOffset(size);
        size += typeshape.Size();
        depth = std::max(depth, typeshape.Depth());
        max_handles = ClampedAdd(max_handles, typeshape.MaxHandles());
        max_out_of_line = ClampedAdd(max_out_of_line, typeshape.MaxOutOfLine());
    }

    max_handles = ClampedAdd(max_handles, extra_handles);

    size = AlignTo(size, alignment);
    return TypeShape(size, alignment, depth, max_handles, max_out_of_line);
}

TypeShape CUnionTypeShape(const std::vector<flat::Union::Member>& members) {
    uint32_t size = 0u;
    uint32_t alignment = 1u;
    uint32_t depth = 0u;
    uint32_t max_handles = 0u;
    uint32_t max_out_of_line = 0u;

    for (const auto& member : members) {
        const auto& fieldshape = member.fieldshape;
        size = std::max(size, fieldshape.Size());
        alignment = std::max(alignment, fieldshape.Alignment());
        depth = std::max(depth, fieldshape.Depth());
        max_handles = std::max(max_handles, fieldshape.Typeshape().MaxHandles());
        max_out_of_line = std::max(max_out_of_line, fieldshape.Typeshape().MaxOutOfLine());
    }

    size = AlignTo(size, alignment);
    return TypeShape(size, alignment, depth, max_handles, max_out_of_line);
}

TypeShape FidlStructTypeShape(std::vector<FieldShape*>* fields) {
    return CStructTypeShape(fields);
}

TypeShape PointerTypeShape(TypeShape element, uint32_t max_element_count = 1u) {
    // Because FIDL supports recursive data structures, we might not have
    // computed the TypeShape for the element we're pointing to. In that case,
    // the size will be zero and we'll use |numeric_limits<uint32_t>::max()| as
    // the depth. We'll never see a zero size for a real TypeShape because empty
    // structs are banned.
    //
    // We're careful to check for saturation before incrementing the depth
    // because recursive data structures have a depth pegged at the numeric
    // limit.
    uint32_t depth = std::numeric_limits<uint32_t>::max();
    if (element.Size() > 0 && element.Depth() < std::numeric_limits<uint32_t>::max())
        depth = ClampedAdd(element.Depth(), 1);

    // The element(s) will be stored out-of-line.
    uint32_t elements_size = ClampedMultiply(element.Size(), max_element_count);
    // Out-of-line data is aligned to 8 bytes.
    elements_size = AlignTo(elements_size, 8);
    // The elements may each carry their own out-of-line data.
    uint32_t elements_out_of_line = ClampedMultiply(element.MaxOutOfLine(), max_element_count);

    uint32_t max_handles = ClampedMultiply(element.MaxHandles(), max_element_count);
    uint32_t max_out_of_line = ClampedAdd(elements_size, elements_out_of_line);

    return TypeShape(8u, 8u, depth, max_handles, max_out_of_line);
}

TypeShape CEnvelopeTypeShape(TypeShape contained_type) {
    auto packed_sizes_field = FieldShape(kUint64TypeShape);
    auto pointer_type = FieldShape(PointerTypeShape(contained_type));
    std::vector<FieldShape*> header{&packed_sizes_field, &pointer_type};
    return CStructTypeShape(&header);
}

TypeShape CTableTypeShape(std::vector<TypeShape*>* fields, uint32_t extra_handles = 0u) {
    uint32_t element_depth = 0u;
    uint32_t max_handles = 0u;
    uint32_t max_out_of_line = 0u;
    uint32_t array_size = 0u;
    for (auto field : *fields) {
        if (field == nullptr) {
            continue;
        }
        auto envelope = CEnvelopeTypeShape(*field);
        element_depth = std::max(element_depth, envelope.Depth());
        array_size = ClampedAdd(array_size, envelope.Size());
        max_handles = ClampedAdd(max_handles, envelope.MaxHandles());
        max_out_of_line = ClampedAdd(max_out_of_line, envelope.MaxOutOfLine());
        assert(envelope.Alignment() == 8u);
    }
    auto pointer_element = TypeShape(array_size, 8u, 1 + element_depth,
                                     max_handles, max_out_of_line);
    auto num_fields = FieldShape(kUint32TypeShape);
    auto data_field = FieldShape(PointerTypeShape(pointer_element));
    std::vector<FieldShape*> header{&num_fields, &data_field};
    return CStructTypeShape(&header, extra_handles);
}

TypeShape ArrayTypeShape(TypeShape element, uint32_t count) {
    return TypeShape(element.Size() * count,
                     element.Alignment(),
                     element.Depth(),
                     ClampedMultiply(element.MaxHandles(), count));
}

TypeShape VectorTypeShape(TypeShape element, uint32_t max_element_count) {
    auto size = FieldShape(kUint64TypeShape);
    auto data = FieldShape(PointerTypeShape(element, max_element_count));
    std::vector<FieldShape*> header{&size, &data};
    return CStructTypeShape(&header);
}

TypeShape StringTypeShape(uint32_t max_length) {
    auto size = FieldShape(kUint64TypeShape);
    auto data = FieldShape(PointerTypeShape(kUint8TypeShape, max_length));
    std::vector<FieldShape*> header{&size, &data};
    return CStructTypeShape(&header, 0);
}

TypeShape PrimitiveTypeShape(types::PrimitiveSubtype type) {
    switch (type) {
    case types::PrimitiveSubtype::kInt8:
        return kInt8TypeShape;
    case types::PrimitiveSubtype::kInt16:
        return kInt16TypeShape;
    case types::PrimitiveSubtype::kInt32:
        return kInt32TypeShape;
    case types::PrimitiveSubtype::kInt64:
        return kInt64TypeShape;
    case types::PrimitiveSubtype::kUint8:
        return kUint8TypeShape;
    case types::PrimitiveSubtype::kUint16:
        return kUint16TypeShape;
    case types::PrimitiveSubtype::kUint32:
        return kUint32TypeShape;
    case types::PrimitiveSubtype::kUint64:
        return kUint64TypeShape;
    case types::PrimitiveSubtype::kBool:
        return kBoolTypeShape;
    case types::PrimitiveSubtype::kFloat32:
        return kFloat32TypeShape;
    case types::PrimitiveSubtype::kFloat64:
        return kFloat64TypeShape;
    }
}

std::unique_ptr<PrimitiveType> MakePrimitiveType(const raw::PrimitiveType* primitive_type) {
    return std::make_unique<PrimitiveType>(primitive_type->subtype);
}

} // namespace

bool Decl::HasAttribute(fidl::StringView name) const {
    if (!attributes)
        return false;
    return attributes->HasAttribute(name);
}

fidl::StringView Decl::GetAttribute(fidl::StringView name) const {
    if (!attributes)
        return fidl::StringView();
    for (const auto& attribute : attributes->attributes_->attributes_) {
        if (StringView(attribute->name) == name) {
            if (attribute->value != "") {
                const auto& value = attribute->value;
                return fidl::StringView(value.data(), value.size());
            }
            // Don't search for another attribute with the same name.
            break;
        }
    }
    return fidl::StringView();
}

std::string Decl::GetName() const {
    return name.name().data();
}

bool Interface::Method::Parameter::IsSimple() const {
    switch (type->kind) {
    case Type::Kind::kVector: {
        auto vector_type = static_cast<VectorType*>(type.get());
        if (vector_type->element_count.Value() == Size::Max().Value())
            return false;
        switch (vector_type->element_type->kind) {
        case Type::Kind::kHandle:
        case Type::Kind::kRequestHandle:
        case Type::Kind::kPrimitive:
            return true;
        case Type::Kind::kArray:
        case Type::Kind::kVector:
        case Type::Kind::kString:
        case Type::Kind::kIdentifier:
            return false;
        }
    }
    case Type::Kind::kString: {
        auto string_type = static_cast<StringType*>(type.get());
        return string_type->max_size.Value() < Size::Max().Value();
    }
    case Type::Kind::kArray:
    case Type::Kind::kHandle:
    case Type::Kind::kRequestHandle:
    case Type::Kind::kPrimitive:
        return fieldshape.Depth() == 0u;
    case Type::Kind::kIdentifier: {
        auto identifier_type = static_cast<IdentifierType*>(type.get());
        switch (identifier_type->nullability) {
        case types::Nullability::kNullable:
            // If the identifier is nullable, then we can handle a depth of 1
            // because the secondary object is directly accessible.
            return fieldshape.Depth() <= 1u;
        case types::Nullability::kNonnullable:
            return fieldshape.Depth() == 0u;
        }
    }
    }
}

bool Libraries::Insert(std::unique_ptr<Library> library) {
    std::vector<fidl::StringView> library_name = library->name();
    auto iter = all_libraries_.emplace(library_name, std::move(library));
    return iter.second;
}

bool Libraries::Lookup(const std::vector<StringView>& library_name,
                       Library** out_library) const {
    auto iter = all_libraries_.find(library_name);
    if (iter == all_libraries_.end()) {
        return false;
    }

    *out_library = iter->second.get();
    return true;
}

bool Dependencies::Register(StringView filename, Library* dep_library,
                            const std::unique_ptr<raw::Identifier>& maybe_alias) {
    auto library_name = dep_library->name();
    if (!InsertByName(filename, library_name, dep_library)) {
        return false;
    }

    if (maybe_alias) {
        std::vector<StringView> alias_name = {maybe_alias->location().data()};
        if (!InsertByName(filename, alias_name, dep_library)) {
            return false;
        }
    }

    dependencies_aggregate_.insert(dep_library);

    return true;
}

bool Dependencies::InsertByName(StringView filename, const std::vector<StringView>& name,
                                Library* library) {
    auto iter = dependencies_.find(filename);
    if (iter == dependencies_.end()) {
        dependencies_.emplace(filename, std::make_unique<ByName>());
    }

    iter = dependencies_.find(filename);
    assert(iter != dependencies_.end());

    auto insert = iter->second->emplace(name, library);
    return insert.second;
}

bool Dependencies::Lookup(StringView filename, const std::vector<StringView>& name,
                          Library** out_library) {
    auto iter1 = dependencies_.find(filename);
    if (iter1 == dependencies_.end()) {
        return false;
    }

    auto iter2 = iter1->second->find(name);
    if (iter2 == iter1->second->end()) {
        return false;
    }

    *out_library = iter2->second;
    return true;
}

// Consuming the AST is primarily concerned with walking the tree and
// flattening the representation. The AST's declaration nodes are
// converted into the Library's foo_declaration structures. This means pulling
// a struct declaration inside an interface out to the top level and
// so on.

std::string LibraryName(const Library* library, StringView separator) {
    if (library != nullptr) {
        return StringJoin(library->name(), separator);
    }
    return std::string();
}

bool Library::Fail(StringView message) {
    error_reporter_->ReportError(message);
    return false;
}

bool Library::Fail(const SourceLocation& location, StringView message) {
    error_reporter_->ReportError(location, message);
    return false;
}

bool Library::CompileCompoundIdentifier(const raw::CompoundIdentifier* compound_identifier,
                                        SourceLocation location, Name* name_out) {
    const auto& components = compound_identifier->components;
    assert(components.size() >= 1);

    SourceLocation decl_name = components.back()->location();

    if (components.size() == 1) {
        *name_out = Name(this, decl_name);
        return true;
    }

    std::vector<StringView> library_name;
    for (auto iter = components.begin();
         iter != components.end() - 1;
         ++iter) {
        library_name.push_back((*iter)->location().data());
    }

    auto filename = location.source_file().filename();
    Library* dep_library = nullptr;
    if (!dependencies_.Lookup(filename, library_name, &dep_library)) {
        std::string message("Unknown dependent library ");
        message += NameLibrary(library_name);
        message += ". Did you require it with `using`?";
        const auto& location = components[0]->location();
        return Fail(location, message);
    }

    // Resolve the name.
    *name_out = Name(dep_library, decl_name);
    return true;
}

bool Library::ParseSize(std::unique_ptr<Constant> constant, Size* out_size) {
    uint32_t value;
    if (!ParseIntegerConstant(constant.get(), &value)) {
        *out_size = Size();
        return false;
    }
    *out_size = Size(std::move(constant), value);
    return true;
}

void Library::RegisterConst(Const* decl) {
    const Name* name = &decl->name;
    constants_.emplace(name, decl);
    switch (decl->type->kind) {
    case Type::Kind::kString:
        string_constants_.emplace(name, decl);
        break;
    case Type::Kind::kPrimitive:
        primitive_constants_.emplace(name, decl);
        break;
    default:
        break;
    }
}

bool Library::RegisterDecl(Decl* decl) {
    const Name* name = &decl->name;
    auto iter = declarations_.emplace(name, decl);
    if (!iter.second) {
        std::string message = "Name collision: ";
        message.append(name->name().data());
        return Fail(*name, message);
    }
    return true;
}

bool Library::ConsumeConstant(std::unique_ptr<raw::Constant> raw_constant, SourceLocation location,
                              std::unique_ptr<Constant>* out_constant) {
    switch (raw_constant->kind) {
    case raw::Constant::Kind::kIdentifier: {
        auto identifier = static_cast<raw::IdentifierConstant*>(raw_constant.get());
        Name name;
        if (!CompileCompoundIdentifier(identifier->identifier.get(), location, &name)) {
            return false;
        }
        *out_constant = std::make_unique<IdentifierConstant>(std::move(name));
        break;
    }
    case raw::Constant::Kind::kLiteral: {
        auto literal = static_cast<raw::LiteralConstant*>(raw_constant.get());
        *out_constant = std::make_unique<LiteralConstant>(std::move(literal->literal));
        break;
    }
    }
    return true;
}

bool Library::ConsumeType(std::unique_ptr<raw::Type> raw_type, SourceLocation location,
                          std::unique_ptr<Type>* out_type) {
    switch (raw_type->kind) {
    case raw::Type::Kind::kArray: {
        auto array_type = static_cast<raw::ArrayType*>(raw_type.get());
        std::unique_ptr<Type> element_type;
        if (!ConsumeType(std::move(array_type->element_type), location, &element_type))
            return false;
        std::unique_ptr<Constant> constant;
        if (!ConsumeConstant(std::move(array_type->element_count), location, &constant))
            return false;
        Size element_count;
        if (!ParseSize(std::move(constant), &element_count))
            return Fail(location, "Unable to parse array element count");
        uint32_t size;
        if (__builtin_mul_overflow(element_count.Value(), element_type->size, &size)) {
            return Fail(location, "The array's size overflows a uint32_t");
        }
        *out_type =
            std::make_unique<ArrayType>(size, std::move(element_type), std::move(element_count));
        break;
    }
    case raw::Type::Kind::kVector: {
        auto vector_type = static_cast<raw::VectorType*>(raw_type.get());
        std::unique_ptr<Type> element_type;
        if (!ConsumeType(std::move(vector_type->element_type), location, &element_type))
            return false;
        Size element_count = Size::Max();
        if (vector_type->maybe_element_count) {
            std::unique_ptr<Constant> constant;
            if (!ConsumeConstant(std::move(vector_type->maybe_element_count), location, &constant))
                return false;
            if (!ParseSize(std::move(constant), &element_count))
                return Fail(location, "Unable to parse vector size bound");
        }
        *out_type = std::make_unique<VectorType>(std::move(element_type), std::move(element_count),
                                                 vector_type->nullability);
        break;
    }
    case raw::Type::Kind::kString: {
        auto string_type = static_cast<raw::StringType*>(raw_type.get());
        Size element_count = Size::Max();
        if (string_type->maybe_element_count) {
            std::unique_ptr<Constant> constant;
            if (!ConsumeConstant(std::move(string_type->maybe_element_count), location, &constant))
                return false;
            if (!ParseSize(std::move(constant), &element_count))
                return Fail(location, "Unable to parse string size bound");
        }
        *out_type =
            std::make_unique<StringType>(std::move(element_count), string_type->nullability);
        break;
    }
    case raw::Type::Kind::kHandle: {
        auto handle_type = static_cast<raw::HandleType*>(raw_type.get());
        *out_type = std::make_unique<HandleType>(handle_type->subtype, handle_type->nullability);
        break;
    }
    case raw::Type::Kind::kRequestHandle: {
        auto request_type = static_cast<raw::RequestHandleType*>(raw_type.get());
        Name name;
        if (!CompileCompoundIdentifier(request_type->identifier.get(), location, &name)) {
            return false;
        }
        *out_type = std::make_unique<RequestHandleType>(std::move(name), request_type->nullability);
        break;
    }
    case raw::Type::Kind::kPrimitive: {
        auto primitive_type = static_cast<raw::PrimitiveType*>(raw_type.get());
        *out_type = MakePrimitiveType(primitive_type);
        break;
    }
    case raw::Type::Kind::kIdentifier: {
        auto identifier_type = static_cast<raw::IdentifierType*>(raw_type.get());
        Name name;
        if (!CompileCompoundIdentifier(identifier_type->identifier.get(), location, &name)) {
            return false;
        }
        auto primitive_type = LookupTypeAlias(name);
        if (primitive_type != nullptr) {
            *out_type = std::make_unique<PrimitiveType>(*primitive_type);
        } else {
            *out_type = std::make_unique<IdentifierType>(std::move(name), identifier_type->nullability);
        }
        break;
    }
    }
    return true;
}

bool Library::ConsumeUsing(std::unique_ptr<raw::Using> using_directive) {
    if (using_directive->maybe_primitive)
        return ConsumeTypeAlias(std::move(using_directive));

    std::vector<StringView> library_name;
    for (const auto& component : using_directive->using_path->components) {
        library_name.push_back(component->location().data());
    }

    Library* dep_library = nullptr;
    if (!all_libraries_->Lookup(library_name, &dep_library)) {
        std::string message("Could not find library named ");
        message += NameLibrary(library_name);
        message += ". Did you include its sources with --files?";
        const auto& location = using_directive->using_path->components[0]->location();
        return Fail(location, message);
    }

    auto filename = using_directive->location().source_file().filename();
    if (!dependencies_.Register(filename, dep_library, using_directive->maybe_alias)) {
        std::string message("Library ");
        message += NameLibrary(library_name);
        message += " already imported. Did you require it twice?";
        return Fail(message);
    }

    // Import declarations, and type aliases of dependent library.
    const auto& declarations = dep_library->declarations_;
    declarations_.insert(declarations.begin(), declarations.end());
    const auto& type_aliases = dep_library->type_aliases_;
    type_aliases_.insert(type_aliases.begin(), type_aliases.end());
    return true;
}

bool Library::ConsumeTypeAlias(std::unique_ptr<raw::Using> using_directive) {
    assert(using_directive->maybe_primitive);
    auto location = using_directive->using_path->components[0]->location();
    auto name = Name(this, location);
    auto using_dir = std::make_unique<Using>(std::move(name), MakePrimitiveType(using_directive->maybe_primitive.get()));
    type_aliases_.emplace(&using_dir->name, using_dir.get());
    using_.push_back(std::move(using_dir));
    return true;
}

bool Library::ConsumeConstDeclaration(std::unique_ptr<raw::ConstDeclaration> const_declaration) {
    auto attributes = std::move(const_declaration->attributes);
    auto location = const_declaration->identifier->location();
    auto name = Name(this, location);
    std::unique_ptr<Type> type;
    if (!ConsumeType(std::move(const_declaration->type), location, &type))
        return false;

    std::unique_ptr<Constant> constant;
    if (!ConsumeConstant(std::move(const_declaration->constant), location, &constant))
        return false;

    const_declarations_.push_back(std::make_unique<Const>(std::move(attributes), std::move(name),
                                                          std::move(type), std::move(constant)));
    auto decl = const_declarations_.back().get();
    RegisterConst(decl);
    return RegisterDecl(decl);
}

bool Library::ConsumeEnumDeclaration(std::unique_ptr<raw::EnumDeclaration> enum_declaration) {
    std::vector<Enum::Member> members;
    for (auto& member : enum_declaration->members) {
        auto location = member->identifier->location();
        std::unique_ptr<Constant> value;
        if (!ConsumeConstant(std::move(member->value), location, &value))
            return false;
        auto attributes = std::move(member->attributes);
        members.emplace_back(location, std::move(value), std::move(attributes));
    }
    auto type = types::PrimitiveSubtype::kUint32;
    if (enum_declaration->maybe_subtype)
        type = enum_declaration->maybe_subtype->subtype;

    auto attributes = std::move(enum_declaration->attributes);
    auto name = Name(this, enum_declaration->identifier->location());

    enum_declarations_.push_back(
        std::make_unique<Enum>(std::move(attributes), std::move(name), type, std::move(members)));
    return RegisterDecl(enum_declarations_.back().get());
}

bool Library::ConsumeInterfaceDeclaration(
    std::unique_ptr<raw::InterfaceDeclaration> interface_declaration) {
    auto attributes = std::move(interface_declaration->attributes);
    auto name = Name(this, interface_declaration->identifier->location());

    std::vector<Name> superinterfaces;
    for (auto& superinterface : interface_declaration->superinterfaces) {
        Name superinterface_name;
        auto location = superinterface->components[0]->location();
        if (!CompileCompoundIdentifier(superinterface.get(), location, &superinterface_name)) {
            return false;
        }
        superinterfaces.push_back(std::move(superinterface_name));
    }

    std::vector<Interface::Method> methods;
    for (auto& method : interface_declaration->methods) {
        auto attributes = std::move(method->attributes);
        auto ordinal_literal = std::move(method->ordinal);
        uint32_t value;
        if (!ParseOrdinal<decltype(value)>(ordinal_literal.get(), &value))
            return Fail(ordinal_literal->location(), "Unable to parse ordinal");
        if (value == 0u)
            return Fail(ordinal_literal->location(), "Fidl ordinals cannot be 0");
        Ordinal ordinal(std::move(ordinal_literal), value);

        SourceLocation method_name = method->identifier->location();

        std::unique_ptr<Interface::Method::Message> maybe_request;
        if (method->maybe_request != nullptr) {
            maybe_request.reset(new Interface::Method::Message());
            for (auto& parameter : method->maybe_request->parameter_list) {
                SourceLocation parameter_name = parameter->identifier->location();
                std::unique_ptr<Type> type;
                if (!ConsumeType(std::move(parameter->type), parameter_name, &type))
                    return false;
                maybe_request->parameters.emplace_back(std::move(type), std::move(parameter_name));
            }
        }

        std::unique_ptr<Interface::Method::Message> maybe_response;
        if (method->maybe_response != nullptr) {
            maybe_response.reset(new Interface::Method::Message());
            for (auto& parameter : method->maybe_response->parameter_list) {
                SourceLocation parameter_name = parameter->identifier->location();
                std::unique_ptr<Type> type;
                if (!ConsumeType(std::move(parameter->type), parameter_name, &type))
                    return false;
                maybe_response->parameters.emplace_back(std::move(type), parameter_name);
            }
        }

        assert(maybe_request != nullptr || maybe_response != nullptr);

        methods.emplace_back(std::move(attributes),
                             std::move(ordinal),
                             std::move(method_name), std::move(maybe_request),
                             std::move(maybe_response));
    }

    interface_declarations_.push_back(
        std::make_unique<Interface>(std::move(attributes), std::move(name),
                                    std::move(superinterfaces), std::move(methods)));
    return RegisterDecl(interface_declarations_.back().get());
}

bool Library::ConsumeStructDeclaration(std::unique_ptr<raw::StructDeclaration> struct_declaration) {
    auto attributes = std::move(struct_declaration->attributes);
    auto name = Name(this, struct_declaration->identifier->location());

    std::vector<Struct::Member> members;
    for (auto& member : struct_declaration->members) {
        std::unique_ptr<Type> type;
        auto location = member->identifier->location();
        if (!ConsumeType(std::move(member->type), location, &type))
            return false;
        std::unique_ptr<Constant> maybe_default_value;
        if (member->maybe_default_value != nullptr) {
            if (!ConsumeConstant(std::move(member->maybe_default_value), location,
                                 &maybe_default_value))
                return false;
        }
        auto attributes = std::move(member->attributes);
        members.emplace_back(std::move(type), member->identifier->location(),
                             std::move(maybe_default_value), std::move(attributes));
    }

    struct_declarations_.push_back(
        std::make_unique<Struct>(std::move(attributes), std::move(name), std::move(members)));
    return RegisterDecl(struct_declarations_.back().get());
}

bool Library::ConsumeTableDeclaration(std::unique_ptr<raw::TableDeclaration> table_declaration) {
    auto attributes = std::move(table_declaration->attributes);
    auto name = Name(this, table_declaration->identifier->location());

    std::vector<Table::Member> members;
    for (auto& member : table_declaration->members) {
        auto ordinal_literal = std::move(member->ordinal);
        uint32_t value;
        if (!ParseOrdinal<decltype(value)>(ordinal_literal.get(), &value))
            return Fail(ordinal_literal->location(), "Unable to parse ordinal");
        if (value == 0u)
            return Fail(ordinal_literal->location(), "Fidl ordinals cannot be 0");
        auto ordinal = std::make_unique<Ordinal>(std::move(ordinal_literal), value);

        if (member->maybe_used) {
            std::unique_ptr<Type> type;
            if (!ConsumeType(std::move(member->maybe_used->type), member->location(), &type))
                return false;
            std::unique_ptr<Constant> maybe_default_value;
            if (member->maybe_used->maybe_default_value != nullptr) {
                if (!ConsumeConstant(std::move(member->maybe_used->maybe_default_value),
                                     member->location(), &maybe_default_value))
                    return false;
            }
            if (type->nullability != types::Nullability::kNonnullable) {
                return Fail(member->location(), "Table members cannot be nullable");
            }
            auto attributes = std::move(member->maybe_used->attributes);
            members.emplace_back(std::move(ordinal), std::move(type),
                                 member->maybe_used->identifier->location(),
                                 std::move(maybe_default_value), std::move(attributes));
        } else {
            members.emplace_back(std::move(ordinal));
        }
    }

    table_declarations_.push_back(
        std::make_unique<Table>(std::move(attributes), std::move(name), std::move(members)));
    return RegisterDecl(table_declarations_.back().get());
}

bool Library::ConsumeUnionDeclaration(std::unique_ptr<raw::UnionDeclaration> union_declaration) {
    std::vector<Union::Member> members;
    for (auto& member : union_declaration->members) {
        auto location = member->identifier->location();
        std::unique_ptr<Type> type;
        if (!ConsumeType(std::move(member->type), location, &type))
            return false;
        auto attributes = std::move(member->attributes);
        members.emplace_back(std::move(type), location, std::move(attributes));
    }

    auto attributes = std::move(union_declaration->attributes);
    auto name = Name(this, union_declaration->identifier->location());

    union_declarations_.push_back(
        std::make_unique<Union>(std::move(attributes), std::move(name), std::move(members)));
    return RegisterDecl(union_declarations_.back().get());
}

bool Library::ConsumeFile(std::unique_ptr<raw::File> file) {
    if (file->attributes) {
        if (!attributes_) {
            attributes_ = std::move(file->attributes);
        } else {
            for (auto& attribute : std::move(file->attributes)->attributes_->attributes_) {
                auto attribute_name = attribute->name;
                auto loc = attribute->location();
                if (!attributes_->Insert(std::move(attribute))) {
                    std::string message("Duplicate attribute with name '");
                    message += attribute_name;
                    message += "'";
                    return Fail(loc, message);
                }
            }
        }
    }

    // All fidl files in a library should agree on the library name.
    std::vector<StringView> new_name;
    for (const auto& part : file->library_name->components) {
        new_name.push_back(part->location().data());
    }
    if (!library_name_.empty()) {
        if (new_name != library_name_) {
            return Fail(file->library_name->components[0]->location(),
                        "Two files in the library disagree about the name of the library");
        }
    } else {
        library_name_ = new_name;
    }

    auto using_list = std::move(file->using_list);
    for (auto& using_directive : using_list) {
        if (!ConsumeUsing(std::move(using_directive))) {
            return false;
        }
    }

    auto const_declaration_list = std::move(file->const_declaration_list);
    for (auto& const_declaration : const_declaration_list) {
        if (!ConsumeConstDeclaration(std::move(const_declaration))) {
            return false;
        }
    }

    auto enum_declaration_list = std::move(file->enum_declaration_list);
    for (auto& enum_declaration : enum_declaration_list) {
        if (!ConsumeEnumDeclaration(std::move(enum_declaration))) {
            return false;
        }
    }

    auto interface_declaration_list = std::move(file->interface_declaration_list);
    for (auto& interface_declaration : interface_declaration_list) {
        if (!ConsumeInterfaceDeclaration(std::move(interface_declaration))) {
            return false;
        }
    }

    auto struct_declaration_list = std::move(file->struct_declaration_list);
    for (auto& struct_declaration : struct_declaration_list) {
        if (!ConsumeStructDeclaration(std::move(struct_declaration))) {
            return false;
        }
    }

    auto table_declaration_list = std::move(file->table_declaration_list);
    for (auto& table_declaration : table_declaration_list) {
        if (!ConsumeTableDeclaration(std::move(table_declaration))) {
            return false;
        }
    }

    auto union_declaration_list = std::move(file->union_declaration_list);
    for (auto& union_declaration : union_declaration_list) {
        if (!ConsumeUnionDeclaration(std::move(union_declaration))) {
            return false;
        }
    }

    return true;
}

// Library resolution is concerned with resolving identifiers to their
// declarations, and with computing type sizes and alignments.

bool Library::TypecheckString(const IdentifierConstant* identifier) {
    auto iter = string_constants_.find(&identifier->name);
    if (iter == string_constants_.end())
        return Fail(identifier->name.name(), "Unable to find string constant");
    // TODO(kulakowski) Check string bounds.
    return true;
}

bool Library::TypecheckPrimitive(const IdentifierConstant* identifier) {
    auto iter = primitive_constants_.find(&identifier->name);
    if (iter == primitive_constants_.end())
        return Fail(identifier->name.name(), "Unable to find primitive constant");
    // TODO(kulakowski) Check numeric values.
    return true;
}

bool Library::TypecheckConst(const Const* const_declaration) {
    auto type = const_declaration->type.get();
    auto constant = const_declaration->value.get();
    switch (type->kind) {
    case Type::Kind::kArray:
        return Fail("Tried to generate an array constant");
    case Type::Kind::kVector:
        return Fail("Tried to generate an vector constant");
    case Type::Kind::kHandle:
        return Fail("Tried to generate a handle constant");
    case Type::Kind::kRequestHandle:
        return Fail("Tried to generate a request handle constant");
    case Type::Kind::kString: {
        switch (constant->kind) {
        case Constant::Kind::kIdentifier: {
            auto identifier_constant = static_cast<const IdentifierConstant*>(constant);
            return TypecheckString(identifier_constant);
        }
        case Constant::Kind::kLiteral: {
            auto literal_constant = static_cast<const LiteralConstant*>(constant);
            switch (literal_constant->literal->kind) {
            case raw::Literal::Kind::kString:
                return true;
            case raw::Literal::Kind::kNumeric:
                return Fail("Tried to assign a numeric literal into a string");
            case raw::Literal::Kind::kTrue:
            case raw::Literal::Kind::kFalse:
                return Fail("Tried to assign a bool literal into a string");
            }
        }
        }
    }
    case Type::Kind::kPrimitive: {
        auto primitive_type = static_cast<const PrimitiveType*>(type);
        switch (constant->kind) {
        case Constant::Kind::kIdentifier: {
            auto identifier_constant = static_cast<const IdentifierConstant*>(constant);
            return TypecheckPrimitive(identifier_constant);
        }
        case Constant::Kind::kLiteral: {
            auto literal_constant = static_cast<const LiteralConstant*>(constant);
            switch (literal_constant->literal->kind) {
            case raw::Literal::Kind::kString:
                return Fail("Tried to assign a string literal to a numeric constant");
            case raw::Literal::Kind::kNumeric:
                // TODO(kulakowski) Check the constants of numbers.
                switch (primitive_type->subtype) {
                case types::PrimitiveSubtype::kUint8:
                case types::PrimitiveSubtype::kUint16:
                case types::PrimitiveSubtype::kUint32:
                case types::PrimitiveSubtype::kUint64:
                case types::PrimitiveSubtype::kInt8:
                case types::PrimitiveSubtype::kInt16:
                case types::PrimitiveSubtype::kInt32:
                case types::PrimitiveSubtype::kInt64:
                case types::PrimitiveSubtype::kFloat32:
                case types::PrimitiveSubtype::kFloat64:
                    return true;
                case types::PrimitiveSubtype::kBool:
                    return Fail("Tried to assign a numeric literal into a bool");
                }
            case raw::Literal::Kind::kTrue:
            case raw::Literal::Kind::kFalse:
                switch (primitive_type->subtype) {
                case types::PrimitiveSubtype::kBool:
                    return true;
                case types::PrimitiveSubtype::kUint8:
                case types::PrimitiveSubtype::kUint16:
                case types::PrimitiveSubtype::kUint32:
                case types::PrimitiveSubtype::kUint64:
                case types::PrimitiveSubtype::kInt8:
                case types::PrimitiveSubtype::kInt16:
                case types::PrimitiveSubtype::kInt32:
                case types::PrimitiveSubtype::kInt64:
                case types::PrimitiveSubtype::kFloat32:
                case types::PrimitiveSubtype::kFloat64:
                    return Fail("Tried to assign a bool into a numeric type");
                }
            }
        }
        }
    }
    case Type::Kind::kIdentifier: {
        auto identifier_type = static_cast<const IdentifierType*>(type);
        auto decl = LookupDeclByType(identifier_type, LookupOption::kIgnoreNullable);
        switch (decl->kind) {
        case Decl::Kind::kConst:
            assert(false && "const declarations don't make types!");
            return false;
        case Decl::Kind::kEnum:
            return true;
        case Decl::Kind::kInterface:
            return Fail("Tried to create a const declaration of interface type");
        case Decl::Kind::kStruct:
            return Fail("Tried to create a const declaration of struct type");
        case Decl::Kind::kTable:
            return Fail("Tried to create a const declaration of table type");
        case Decl::Kind::kUnion:
            return Fail("Tried to create a const declaration of union type");
        }
    }
    }
}

Decl* Library::LookupConstant(const Type* type, const Name& name) {
    auto decl = LookupDeclByType(type, LookupOption::kIgnoreNullable);
    if (decl == nullptr) {
        // This wasn't a named type. Thus we are looking up a
        // top-level constant, of string or primitive type.
        assert(type->kind == Type::Kind::kString || type->kind == Type::Kind::kPrimitive);
        auto iter = constants_.find(&name);
        if (iter == constants_.end()) {
            return nullptr;
        }
        return iter->second;
    }
    // We must otherwise be looking for an enum member.
    if (decl->kind != Decl::Kind::kEnum) {
        return nullptr;
    }
    auto enum_decl = static_cast<Enum*>(decl);
    for (auto& member : enum_decl->members) {
        if (member.name.data() == name.name().data()) {
            return enum_decl;
        }
    }
    // The enum didn't have a member of that name!
    return nullptr;
}

PrimitiveType* Library::LookupTypeAlias(const Name& name) const {
    auto it = type_aliases_.find(&name);
    if (it == type_aliases_.end())
        return nullptr;
    return it->second->type.get();
}

Decl* Library::LookupDeclByType(const Type* type, LookupOption option) const {
    for (;;) {
        switch (type->kind) {
        case flat::Type::Kind::kString:
        case flat::Type::Kind::kHandle:
        case flat::Type::Kind::kRequestHandle:
        case flat::Type::Kind::kPrimitive:
            return nullptr;
        case flat::Type::Kind::kVector: {
            type = static_cast<const flat::VectorType*>(type)->element_type.get();
            continue;
        }
        case flat::Type::Kind::kArray: {
            type = static_cast<const flat::ArrayType*>(type)->element_type.get();
            continue;
        }
        case flat::Type::Kind::kIdentifier: {
            auto identifier_type = static_cast<const flat::IdentifierType*>(type);
            if (identifier_type->nullability == types::Nullability::kNullable && option == LookupOption::kIgnoreNullable) {
                return nullptr;
            }
            return LookupDeclByName(identifier_type->name);
        }
        }
    }
}

Decl* Library::LookupDeclByName(const Name& name) const {
    auto iter = declarations_.find(&name);
    if (iter == declarations_.end()) {
        return nullptr;
    }
    return iter->second;
}

// An edge from D1 to D2 means that a C needs to see the declaration
// of D1 before the declaration of D2. For instance, given the fidl
//     struct D2 { D1 d; };
//     struct D1 { int32 x; };
// D1 has an edge pointing to D2. Note that struct and union pointers,
// unlike inline structs or unions, do not have dependency edges.
bool Library::DeclDependencies(Decl* decl, std::set<Decl*>* out_edges) {
    std::set<Decl*> edges;
    auto maybe_add_decl = [this, &edges](const Type* type, LookupOption option) {
        auto type_decl = LookupDeclByType(type, option);
        if (type_decl != nullptr) {
            edges.insert(type_decl);
        }
    };
    auto maybe_add_name = [this, &edges](const Name& name) {
        auto type_decl = LookupDeclByName(name);
        if (type_decl != nullptr) {
            edges.insert(type_decl);
        }
    };
    auto maybe_add_constant = [this, &edges](const Type* type, const Constant* constant) -> bool {
        switch (constant->kind) {
        case Constant::Kind::kIdentifier: {
            auto identifier = static_cast<const flat::IdentifierConstant*>(constant);
            auto decl = LookupConstant(type, identifier->name);
            if (decl == nullptr) {
                std::string message("Unable to find the constant named: ");
                message += identifier->name.name().data();
                return Fail(identifier->name, message.data());
            }
            edges.insert(decl);
            break;
        }
        case Constant::Kind::kLiteral: {
            // Literals have no dependencies on other declarations.
            break;
        }
        }
        return true;
    };
    switch (decl->kind) {
    case Decl::Kind::kConst: {
        auto const_decl = static_cast<const Const*>(decl);
        if (!maybe_add_constant(const_decl->type.get(), const_decl->value.get()))
            return false;
        break;
    }
    case Decl::Kind::kEnum: {
        break;
    }
    case Decl::Kind::kInterface: {
        auto interface_decl = static_cast<const Interface*>(decl);
        for (const auto& superinterface : interface_decl->superinterfaces) {
            maybe_add_name(superinterface);
        }
        for (const auto& method : interface_decl->methods) {
            if (method.maybe_request != nullptr) {
                for (const auto& parameter : method.maybe_request->parameters) {
                    maybe_add_decl(parameter.type.get(), LookupOption::kIncludeNullable);
                }
            }
            if (method.maybe_response != nullptr) {
                for (const auto& parameter : method.maybe_response->parameters) {
                    maybe_add_decl(parameter.type.get(), LookupOption::kIncludeNullable);
                }
            }
        }
        break;
    }
    case Decl::Kind::kStruct: {
        auto struct_decl = static_cast<const Struct*>(decl);
        for (const auto& member : struct_decl->members) {
            maybe_add_decl(member.type.get(), LookupOption::kIgnoreNullable);
            if (member.maybe_default_value) {
                if (!maybe_add_constant(member.type.get(), member.maybe_default_value.get()))
                    return false;
            }
        }
        break;
    }
    case Decl::Kind::kTable: {
        auto table_decl = static_cast<const Table*>(decl);
        for (const auto& member : table_decl->members) {
            if (!member.maybe_used)
                continue;
            maybe_add_decl(member.maybe_used->type.get(), LookupOption::kIgnoreNullable);
            if (member.maybe_used->maybe_default_value) {
                if (!maybe_add_constant(member.maybe_used->type.get(),
                                        member.maybe_used->maybe_default_value.get()))
                    return false;
            }
        }
        break;
    }
    case Decl::Kind::kUnion: {
        auto union_decl = static_cast<const Union*>(decl);
        for (const auto& member : union_decl->members) {
            maybe_add_decl(member.type.get(), LookupOption::kIgnoreNullable);
        }
        break;
    }
    }
    *out_edges = std::move(edges);
    return true;
}

namespace {
// To compare two Decl's in the same library, it suffices to compare the unqualified names of the Decl's.
struct CmpDeclInLibrary {
    bool operator()(const Decl* a, const Decl* b) const {
        assert(a->name != b->name || a == b);
        return a->name < b->name;
    }
};
} // namespace

bool Library::SortDeclarations() {
    // |degree| is the number of undeclared dependencies for each decl.
    std::map<Decl*, uint32_t, CmpDeclInLibrary> degrees;
    // |inverse_dependencies| records the decls that depend on each decl.
    std::map<Decl*, std::vector<Decl*>, CmpDeclInLibrary> inverse_dependencies;
    for (auto& name_and_decl : declarations_) {
        Decl* decl = name_and_decl.second;
        degrees[decl] = 0u;
    }
    for (auto& name_and_decl : declarations_) {
        Decl* decl = name_and_decl.second;
        std::set<Decl*> deps;
        if (!DeclDependencies(decl, &deps))
            return false;
        degrees[decl] += deps.size();
        for (Decl* dep : deps) {
            inverse_dependencies[dep].push_back(decl);
        }
    }

    // Start with all decls that have no incoming edges.
    std::vector<Decl*> decls_without_deps;
    for (const auto& decl_and_degree : degrees) {
        if (decl_and_degree.second == 0u) {
            decls_without_deps.push_back(decl_and_degree.first);
        }
    }

    while (!decls_without_deps.empty()) {
        // Pull one out of the queue.
        auto decl = decls_without_deps.back();
        decls_without_deps.pop_back();
        assert(degrees[decl] == 0u);
        declaration_order_.push_back(decl);

        // Decrement the incoming degree of all the other decls it
        // points to.
        auto& inverse_deps = inverse_dependencies[decl];
        for (Decl* inverse_dep : inverse_deps) {
            uint32_t& degree = degrees[inverse_dep];
            assert(degree != 0u);
            degree -= 1;
            if (degree == 0u)
                decls_without_deps.push_back(inverse_dep);
        }
    }

    if (declaration_order_.size() != degrees.size()) {
        // We didn't visit all the edges! There was a cycle.
        return Fail("There is an includes-cycle in declarations");
    }

    return true;
}

bool Library::CompileConst(Const* const_declaration) {
    Compiling guard(const_declaration);
    TypeShape typeshape;
    if (!CompileType(const_declaration->type.get(), &typeshape)) {
        return false;
    }
    if (!TypecheckConst(const_declaration)) {
        return false;
    }
    return true;
}

bool Library::CompileEnum(Enum* enum_declaration) {
    Compiling guard(enum_declaration);
    switch (enum_declaration->type) {
    case types::PrimitiveSubtype::kInt8:
    case types::PrimitiveSubtype::kInt16:
    case types::PrimitiveSubtype::kInt32:
    case types::PrimitiveSubtype::kInt64:
    case types::PrimitiveSubtype::kUint8:
    case types::PrimitiveSubtype::kUint16:
    case types::PrimitiveSubtype::kUint32:
    case types::PrimitiveSubtype::kUint64:
        // These are allowed as enum subtypes. Compile the size and alignment.
        enum_declaration->typeshape = PrimitiveTypeShape(enum_declaration->type);
        break;

    case types::PrimitiveSubtype::kBool:
    case types::PrimitiveSubtype::kFloat32:
    case types::PrimitiveSubtype::kFloat64:
        // These are not allowed as enum subtypes.
        return Fail(*enum_declaration, "Enums cannot be bools, statuses, or floats");
    }

    // TODO(TO-702) Validate values.
    return true;
}

bool Library::CompileInterface(Interface* interface_declaration) {
    Compiling guard(interface_declaration);
    MethodScope method_scope;
    auto CheckScopes = [this, &interface_declaration, &method_scope](const Interface* interface, auto Visitor) -> bool {
        for (const auto& name : interface->superinterfaces) {
            auto decl = LookupDeclByName(name);
            if (decl == nullptr)
                return Fail(name, "There is no declaration with this name");
            if (decl->kind != Decl::Kind::kInterface)
                return Fail(name, "This superinterface declaration is not an interface");
            auto superinterface = static_cast<const Interface*>(decl);
            if (method_scope.interfaces.Insert(superinterface, superinterface->name.name()).ok()) {
                if (!Visitor(superinterface, Visitor))
                    return false;
            } else {
                // Otherwise we have already seen this interface in
                // the inheritance graph.
            }
        }
        for (const auto& method : interface->methods) {
            auto name_result = method_scope.names.Insert(method.name.data(), method.name);
            if (!name_result.ok())
                return Fail(method.name,
                            "Multiple methods with the same name in an interface; last occurance was at " +
                                name_result.previous_occurance().position());
            auto ordinal_result = method_scope.ordinals.Insert(method.ordinal.Value(), method.name);
            if (!ordinal_result.ok())
                return Fail(method.name,
                            "Mulitple methods with the same ordinal in an interface; last occurance was at " +
                                ordinal_result.previous_occurance().position());

            // Add a pointer to this method to the interface_declarations list.
            interface_declaration->all_methods.push_back(&method);
        }
        return true;
    };
    if (!CheckScopes(interface_declaration, CheckScopes))
        return false;

    for (auto& method : interface_declaration->methods) {
        auto CreateMessage = [&](Interface::Method::Message* message) -> bool {
            Scope<StringView> scope;
            auto header_field_shape = FieldShape(TypeShape(16u, 4u));
            std::vector<FieldShape*> message_struct;
            message_struct.push_back(&header_field_shape);
            for (auto& param : message->parameters) {
                if (!scope.Insert(param.name.data(), param.name).ok())
                    return Fail(param.name, "Multiple parameters with the same name in a method");
                if (!CompileType(param.type.get(), &param.fieldshape.Typeshape()))
                    return false;
                message_struct.push_back(&param.fieldshape);
            }
            message->typeshape = FidlStructTypeShape(&message_struct);
            return true;
        };
        if (method.maybe_request) {
            if (!CreateMessage(method.maybe_request.get()))
                return false;
        }
        if (method.maybe_response) {
            if (!CreateMessage(method.maybe_response.get()))
                return false;
        }
    }

    if (HasSimpleLayout(interface_declaration)) {
        for (const auto& method_pointer : interface_declaration->all_methods) {
            auto CheckSimpleMessage = [&](const Interface::Method::Message* message) -> bool {
                for (const auto& parameter : message->parameters) {
                    if (!parameter.IsSimple())
                        return Fail(parameter.name, "Non-simple parameter in interface with [Layout=\"Simple\"]");
                }
                return true;
            };
            if (method_pointer->maybe_request) {
                if (!CheckSimpleMessage(method_pointer->maybe_request.get()))
                    return false;
            }
            if (method_pointer->maybe_response) {
                if (!CheckSimpleMessage(method_pointer->maybe_response.get()))
                    return false;
            }
        }
    }

    return true;
}

bool Library::CompileStruct(Struct* struct_declaration) {
    Compiling guard(struct_declaration);
    Scope<StringView> scope;
    std::vector<FieldShape*> fidl_struct;

    uint32_t max_member_handles = 0;
    for (auto& member : struct_declaration->members) {
        auto name_result = scope.Insert(member.name.data(), member.name);
        if (!name_result.ok())
            return Fail(member.name,
                        "Multiple struct fields with the same name; previous was at " +
                            name_result.previous_occurance().position());
        if (!CompileType(member.type.get(), &member.fieldshape.Typeshape()))
            return false;
        fidl_struct.push_back(&member.fieldshape);
    }

    if (struct_declaration->recursive) {
        max_member_handles = std::numeric_limits<uint32_t>::max();
    } else {
        // Member handles will be counted by CStructTypeShape.
        max_member_handles = 0;
    }

    struct_declaration->typeshape = CStructTypeShape(&fidl_struct, max_member_handles);

    return true;
}

bool Library::CompileTable(Table* table_declaration) {
    Compiling guard(table_declaration);
    Scope<StringView> name_scope;
    Scope<uint32_t> ordinal_scope;

    uint32_t max_member_handles = 0;
    for (auto& member : table_declaration->members) {
        auto ordinal_result = ordinal_scope.Insert(member.ordinal->Value(), member.ordinal->source_element()->location());
        if (!ordinal_result.ok())
            return Fail(member.ordinal->source_element()->location(),
                        "Multiple table fields with the same ordinal; previous was at " +
                            ordinal_result.previous_occurance().position());
        if (member.maybe_used) {
            auto name_result = name_scope.Insert(member.maybe_used->name.data(), member.maybe_used->name);
            if (!name_result.ok())
                return Fail(member.maybe_used->name,
                            "Multiple table fields with the same name; previous was at " +
                                name_result.previous_occurance().position());
            if (!CompileType(member.maybe_used->type.get(), &member.maybe_used->typeshape))
                return false;
        }
    }

    uint32_t last_ordinal_seen = 0;
    for (const auto& ordinal_and_loc : ordinal_scope) {
        if (ordinal_and_loc.first != last_ordinal_seen + 1) {
            return Fail(ordinal_and_loc.second,
                        "Missing ordinal (table ordinals do not form a dense space)");
        }
        last_ordinal_seen = ordinal_and_loc.first;
    }

    if (table_declaration->recursive) {
        max_member_handles = std::numeric_limits<uint32_t>::max();
    } else {
        // Member handles will be counted by CTableTypeShape.
        max_member_handles = 0;
    }

    std::vector<TypeShape*> fields(table_declaration->members.size());
    for (auto& member : table_declaration->members) {
        if (member.maybe_used) {
            fields[member.ordinal->Value() - 1] = &member.maybe_used->typeshape;
        }
    }

    table_declaration->typeshape = CTableTypeShape(&fields, max_member_handles);

    return true;
}

bool Library::CompileUnion(Union* union_declaration) {
    Compiling guard(union_declaration);
    Scope<StringView> scope;
    for (auto& member : union_declaration->members) {
        auto name_result = scope.Insert(member.name.data(), member.name);
        if (!name_result.ok())
            return Fail(member.name,
                        "Multiple union members with the same name; previous was at " +
                            name_result.previous_occurance().position());
        if (!CompileType(member.type.get(), &member.fieldshape.Typeshape()))
            return false;
    }

    auto tag = FieldShape(kUint32TypeShape);
    union_declaration->membershape = FieldShape(CUnionTypeShape(union_declaration->members));
    uint32_t extra_handles = 0;
    if (union_declaration->recursive && union_declaration->membershape.MaxHandles()) {
        extra_handles = std::numeric_limits<uint32_t>::max();
    }
    std::vector<FieldShape*> fidl_union = {&tag, &union_declaration->membershape};
    union_declaration->typeshape = CStructTypeShape(&fidl_union, extra_handles);

    // This is either 4 or 8, depending on whether any union members
    // have alignment 8.
    auto offset = union_declaration->membershape.Offset();
    for (auto& member : union_declaration->members) {
        member.fieldshape.SetOffset(offset);
    }

    return true;
}

bool Library::CompileLibraryName() {
    const std::regex pattern("^[a-z][a-z0-9]*$");
    for (const auto& part_view : library_name_) {
        std::string part = part_view;
        if (!std::regex_match(part, pattern)) {
            return Fail("Invalid library name part " + part);
        }
    }
    return true;
}

bool Library::Compile() {
    for (const auto& dep_library : dependencies_.dependencies()) {
        constants_.insert(dep_library->constants_.begin(), dep_library->constants_.end());
    }

    // Verify that the library's name is valid.
    if (!CompileLibraryName()) {
        return false;
    }

    if (!SortDeclarations()) {
        return false;
    }

    // We process declarations in topologically sorted order. For
    // example, we process a struct member's type before the entire
    // struct.
    for (Decl* decl : declaration_order_) {
        switch (decl->kind) {
        case Decl::Kind::kConst: {
            auto const_decl = static_cast<Const*>(decl);
            if (!CompileConst(const_decl)) {
                return false;
            }
            break;
        }
        case Decl::Kind::kEnum: {
            auto enum_decl = static_cast<Enum*>(decl);
            if (!CompileEnum(enum_decl)) {
                return false;
            }
            break;
        }
        case Decl::Kind::kInterface: {
            auto interface_decl = static_cast<Interface*>(decl);
            if (!CompileInterface(interface_decl)) {
                return false;
            }
            break;
        }
        case Decl::Kind::kStruct: {
            auto struct_decl = static_cast<Struct*>(decl);
            if (!CompileStruct(struct_decl)) {
                return false;
            }
            break;
        }
        case Decl::Kind::kTable: {
            auto table_decl = static_cast<Table*>(decl);
            if (!CompileTable(table_decl)) {
                return false;
            }
            break;
        }
        case Decl::Kind::kUnion: {
            auto union_decl = static_cast<Union*>(decl);
            if (!CompileUnion(union_decl)) {
                return false;
            }
            break;
        }
        default:
            abort();
        }
        assert(!decl->compiling);
        assert(decl->compiled);
    }

    return true;
}

bool Library::CompileArrayType(flat::ArrayType* array_type, TypeShape* out_typeshape) {
    TypeShape element_typeshape;
    if (!CompileType(array_type->element_type.get(), &element_typeshape))
        return false;
    *out_typeshape = ArrayTypeShape(element_typeshape, array_type->element_count.Value());
    return true;
}

bool Library::CompileVectorType(flat::VectorType* vector_type, TypeShape* out_typeshape) {
    // All we need from the element typeshape is the maximum number of handles.
    TypeShape element_typeshape;
    if (!CompileType(vector_type->element_type.get(), &element_typeshape))
        return false;
    uint32_t max_element_count = vector_type->element_count.Value();
    if (max_element_count == Size::Max().Value()) {
        // No upper bound specified on vector.
        max_element_count = std::numeric_limits<uint32_t>::max();
    }
    *out_typeshape = VectorTypeShape(element_typeshape, max_element_count);
    return true;
}

bool Library::CompileStringType(flat::StringType* string_type, TypeShape* out_typeshape) {
    *out_typeshape = StringTypeShape(string_type->max_size.Value());
    return true;
}

bool Library::CompileHandleType(flat::HandleType* handle_type, TypeShape* out_typeshape) {
    // Nothing to check.
    *out_typeshape = kHandleTypeShape;
    return true;
}

bool Library::CompileRequestHandleType(flat::RequestHandleType* request_type,
                                       TypeShape* out_typeshape) {
    auto named_decl = LookupDeclByName(request_type->name);
    if (!named_decl || named_decl->kind != Decl::Kind::kInterface) {
        std::string message = "Undefined reference \"";
        message.append(request_type->name.name().data());
        message.append("\" in request handle name");
        return Fail(request_type->name, message);
    }

    *out_typeshape = kHandleTypeShape;
    return true;
}

bool Library::CompilePrimitiveType(flat::PrimitiveType* primitive_type, TypeShape* out_typeshape) {
    *out_typeshape = PrimitiveTypeShape(primitive_type->subtype);
    return true;
}

bool Library::CompileIdentifierType(flat::IdentifierType* identifier_type,
                                    TypeShape* out_typeshape) {
    TypeShape typeshape;

    auto named_decl = LookupDeclByName(identifier_type->name);
    if (!named_decl) {
        std::string message("Undefined reference \"");
        message.append(identifier_type->name.name().data());
        message.append("\" in identifier type name");
        return Fail(identifier_type->name, message);
    }

    switch (named_decl->kind) {
    case Decl::Kind::kConst: {
        // A constant isn't a type!
        return Fail(identifier_type->name,
                    "The name of a constant was used where a type was expected");
    }
    case Decl::Kind::kEnum: {
        if (identifier_type->nullability == types::Nullability::kNullable) {
            // Enums aren't nullable!
            return Fail(identifier_type->name, "An enum was referred to as 'nullable'");
        } else {
            typeshape = static_cast<const Enum*>(named_decl)->typeshape;
        }
        break;
    }
    case Decl::Kind::kInterface: {
        typeshape = kHandleTypeShape;
        break;
    }
    case Decl::Kind::kStruct: {
        Struct* struct_decl = static_cast<Struct*>(named_decl);
        if (!struct_decl->compiled) {
            if (struct_decl->compiling) {
                struct_decl->recursive = true;
            } else {
                if (!CompileStruct(struct_decl)) {
                    return false;
                }
            }
        }
        typeshape = struct_decl->typeshape;
        if (identifier_type->nullability == types::Nullability::kNullable)
            typeshape = PointerTypeShape(typeshape);
        break;
    }
    case Decl::Kind::kTable: {
        Table* table_decl = static_cast<Table*>(named_decl);
        if (!table_decl->compiled) {
            if (table_decl->compiling) {
                table_decl->recursive = true;
            } else {
                if (!CompileTable(table_decl)) {
                    return false;
                }
            }
        }
        typeshape = table_decl->typeshape;
        if (identifier_type->nullability == types::Nullability::kNullable)
            typeshape = PointerTypeShape(typeshape);
        break;
    }
    case Decl::Kind::kUnion: {
        Union* union_decl = static_cast<Union*>(named_decl);
        if (!union_decl->compiled) {
            if (union_decl->compiling) {
                union_decl->recursive = true;
            } else {
                if (!CompileUnion(union_decl)) {
                    return false;
                }
            }
        }
        typeshape = union_decl->typeshape;
        if (identifier_type->nullability == types::Nullability::kNullable)
            typeshape = PointerTypeShape(typeshape);
        break;
    }
    default: { abort(); }
    }

    identifier_type->size = typeshape.Size();
    *out_typeshape = typeshape;
    return true;
}

bool Library::CompileType(Type* type, TypeShape* out_typeshape) {
    switch (type->kind) {
    case Type::Kind::kArray: {
        auto array_type = static_cast<ArrayType*>(type);
        return CompileArrayType(array_type, out_typeshape);
    }

    case Type::Kind::kVector: {
        auto vector_type = static_cast<VectorType*>(type);
        return CompileVectorType(vector_type, out_typeshape);
    }

    case Type::Kind::kString: {
        auto string_type = static_cast<StringType*>(type);
        return CompileStringType(string_type, out_typeshape);
    }

    case Type::Kind::kHandle: {
        auto handle_type = static_cast<HandleType*>(type);
        return CompileHandleType(handle_type, out_typeshape);
    }

    case Type::Kind::kRequestHandle: {
        auto request_type = static_cast<RequestHandleType*>(type);
        return CompileRequestHandleType(request_type, out_typeshape);
    }

    case Type::Kind::kPrimitive: {
        auto primitive_type = static_cast<PrimitiveType*>(type);
        return CompilePrimitiveType(primitive_type, out_typeshape);
    }

    case Type::Kind::kIdentifier: {
        auto identifier_type = static_cast<IdentifierType*>(type);
        return CompileIdentifierType(identifier_type, out_typeshape);
    }
    }
}

bool Library::HasAttribute(fidl::StringView name) const {
    if (!attributes_)
        return false;
    return attributes_->HasAttribute(name);
}

const std::set<Library*>& Library::dependencies() const {
    return dependencies_.dependencies();
}

} // namespace flat
} // namespace fidl