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https://github.com/carbon-language/carbon-lang.git
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Migrate Declaration to variant (#644)
Note this makes some structural choices that I'm not sure how popular they'll be... Most notably, I could remove `DeclarationKind` because I'm using `std::visit` and `Declaration::Visitor` in reality. I could go to `switch(tag())` instead, but I'm wondering if this approach will be well received for the separation of ownership. Alternatively, I could move `Declaration` around so that it actually implements the things like `TopLevel` -- I did feel weird with the old structure of typecheck.cpp implementing members of declaration.h, though.
This commit is contained in:
Jon Meow
GitHub
@@ -8,33 +8,101 @@
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namespace Carbon {
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void FunctionDeclaration::Print() const { definition.Print(); }
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void StructDeclaration::Print() const {
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std::cout << "struct " << *definition.name << " {" << std::endl;
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for (auto& member : *definition.members) {
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member->Print();
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}
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std::cout << "}" << std::endl;
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auto Declaration::MakeFunctionDeclaration(FunctionDefinition definition)
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-> const Declaration {
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Declaration d;
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d.value = FunctionDeclaration({.definition = definition});
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return d;
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}
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void ChoiceDeclaration::Print() const {
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std::cout << "choice " << name << " {" << std::endl;
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for (const auto& [name, signature] : alternatives) {
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std::cout << "alt " << name << " ";
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PrintExp(signature);
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std::cout << ";" << std::endl;
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}
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std::cout << "}" << std::endl;
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auto Declaration::MakeStructDeclaration(int line_num, std::string name,
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std::list<Member*> members)
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-> const Declaration {
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Declaration d;
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d.value = StructDeclaration(
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{.definition = StructDefinition({.line_num = line_num,
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.name = std::move(name),
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.members = std::move(members)})});
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return d;
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}
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// Print a global variable declaration to standard out.
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void VariableDeclaration::Print() const {
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std::cout << "var ";
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PrintExp(type);
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std::cout << " : " << name << " = ";
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PrintExp(initializer);
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std::cout << std::endl;
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auto Declaration::MakeChoiceDeclaration(
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int line_num, std::string name,
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std::list<std::pair<std::string, const Expression*>> alternatives)
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-> const Declaration {
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Declaration d;
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d.value = ChoiceDeclaration({.line_num = line_num,
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.name = std::move(name),
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.alternatives = std::move(alternatives)});
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return d;
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}
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auto Declaration::MakeVariableDeclaration(int source_location, std::string name,
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const Expression* type,
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const Expression* initializer)
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-> const Declaration {
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Declaration d;
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d.value = VariableDeclaration({.source_location = source_location,
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.name = std::move(name),
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.type = type,
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.initializer = initializer});
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return d;
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}
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auto Declaration::GetFunctionDeclaration() const -> const FunctionDeclaration& {
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return std::get<FunctionDeclaration>(value);
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}
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auto Declaration::GetStructDeclaration() const -> const StructDeclaration& {
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return std::get<StructDeclaration>(value);
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}
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auto Declaration::GetChoiceDeclaration() const -> const ChoiceDeclaration& {
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return std::get<ChoiceDeclaration>(value);
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}
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auto Declaration::GetVariableDeclaration() const -> const VariableDeclaration& {
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return std::get<VariableDeclaration>(value);
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}
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void Declaration::Print() const {
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switch (tag()) {
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case DeclarationKind::FunctionDeclaration:
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GetFunctionDeclaration().definition.Print();
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break;
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case DeclarationKind::StructDeclaration: {
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const StructDefinition& struct_def = GetStructDeclaration().definition;
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std::cout << "struct " << struct_def.name << " {" << std::endl;
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for (Member* m : struct_def.members) {
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m->Print();
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}
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std::cout << "}" << std::endl;
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break;
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}
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case DeclarationKind::ChoiceDeclaration: {
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const auto& choice = GetChoiceDeclaration();
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std::cout << "choice " << choice.name << " {" << std::endl;
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for (const auto& [name, signature] : choice.alternatives) {
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std::cout << "alt " << name << " ";
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PrintExp(signature);
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std::cout << ";" << std::endl;
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}
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std::cout << "}" << std::endl;
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break;
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}
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case DeclarationKind::VariableDeclaration: {
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const auto& var = GetVariableDeclaration();
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std::cout << "var ";
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PrintExp(var.type);
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std::cout << " : " << var.name << " = ";
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PrintExp(var.initializer);
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std::cout << std::endl;
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break;
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}
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}
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}
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} // namespace Carbon
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@@ -14,10 +14,6 @@
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#include "executable_semantics/interpreter/address.h"
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#include "executable_semantics/interpreter/dictionary.h"
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namespace yy {
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class parser;
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}
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namespace Carbon {
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struct Value;
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@@ -32,148 +28,72 @@ struct TypeCheckContext {
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Env values;
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};
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// An existential AST declaration satisfying the Declaration concept.
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class Declaration {
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public: // ValueSemantic concept API.
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Declaration(const Declaration& other) = default;
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Declaration& operator=(const Declaration& other) = default;
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// Constructs an instance equivalent to `d`, where `Model` satisfies the
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// Declaration concept.
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template <class Model>
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Declaration(Model d) : box(std::make_shared<Boxed<Model>>(d)) {}
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public: // Declaration concept API, in addition to ValueSemantic.
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void Print() const { box->Print(); }
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auto Name() const -> std::string { return box->Name(); }
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// Signals a type error if the declaration is not well typed,
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// otherwise returns this declaration with annotated types.
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//
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// - Parameter env: types of run-time names.
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// - Paraemter ct_env: values of compile-time names.
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration {
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return box->TypeChecked(env, ct_env);
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}
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// Add an entry in the runtime global symbol table for this declaration.
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void InitGlobals(Env& globals) const { return box->InitGlobals(globals); }
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// Add an entry in the compile time global symbol tables for this declaration.
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auto TopLevel(TypeCheckContext& e) const -> void { return box->TopLevel(e); }
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private:
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// A base class that erases the type of a `Boxed<Content>`, where `Content`
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// satisfies the Declaration concept.
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struct Box {
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protected:
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Box() {}
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public:
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Box(const Box& other) = delete;
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Box& operator=(const Box& other) = delete;
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virtual ~Box() {}
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virtual auto Print() const -> void = 0;
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virtual auto Name() const -> std::string = 0;
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virtual auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration = 0;
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virtual auto InitGlobals(Env& globals) const -> void = 0;
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virtual auto TopLevel(TypeCheckContext&) const -> void = 0;
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};
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// The derived class that holds an instance of `Content` satisfying the
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// Declaration concept.
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template <class Content>
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struct Boxed final : Box {
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const Content content;
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explicit Boxed(Content content) : Box(), content(content) {}
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auto Print() const -> void override { return content.Print(); }
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auto Name() const -> std::string override { return content.Name(); }
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration override {
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return content.TypeChecked(env, ct_env);
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}
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auto InitGlobals(Env& globals) const -> void override {
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content.InitGlobals(globals);
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}
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auto TopLevel(TypeCheckContext& e) const -> void override {
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content.TopLevel(e);
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}
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};
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// Constructs an instance in a "partially formed" state, which can only be
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// assigned to or destroyed.
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Declaration() = default;
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// Give Bison access to the default constructor.
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friend class yy::parser;
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// Note: the pointee is const as long as we have no mutating methods. When
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std::shared_ptr<const Box> box;
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enum class DeclarationKind {
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FunctionDeclaration,
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StructDeclaration,
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ChoiceDeclaration,
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VariableDeclaration,
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};
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struct FunctionDeclaration {
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static constexpr DeclarationKind Kind = DeclarationKind::FunctionDeclaration;
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FunctionDefinition definition;
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explicit FunctionDeclaration(FunctionDefinition definition)
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: definition(std::move(definition)) {}
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auto Print() const -> void;
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auto Name() const -> std::string;
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration;
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auto InitGlobals(Env& globals) const -> void;
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auto TopLevel(TypeCheckContext&) const -> void;
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};
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struct StructDeclaration {
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static constexpr DeclarationKind Kind = DeclarationKind::StructDeclaration;
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StructDefinition definition;
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StructDeclaration(int line_num, std::string name, std::list<Member*>* members)
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: definition{line_num, new std::string(name), members} {}
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void Print() const;
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auto Name() const -> std::string;
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration;
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void InitGlobals(Env& globals) const;
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auto TopLevel(TypeCheckContext&) const -> void;
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};
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struct ChoiceDeclaration {
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static constexpr DeclarationKind Kind = DeclarationKind::ChoiceDeclaration;
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int line_num;
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std::string name;
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std::list<std::pair<std::string, const Expression*>> alternatives;
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ChoiceDeclaration(
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int line_num, std::string name,
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std::list<std::pair<std::string, const Expression*>> alternatives)
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: line_num(line_num), name(name), alternatives(std::move(alternatives)) {}
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void Print() const;
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auto Name() const -> std::string;
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration;
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void InitGlobals(Env& globals) const;
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auto TopLevel(TypeCheckContext&) const -> void;
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};
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// Global variable definition implements the Declaration concept.
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class VariableDeclaration {
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public:
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VariableDeclaration(int source_location, std::string name,
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const Expression* type, const Expression* initializer)
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: source_location(source_location),
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name(name),
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type(type),
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initializer(initializer) {}
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void Print() const;
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auto Name() const -> std::string;
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auto TypeChecked(TypeEnv env, Env ct_env) const -> Declaration;
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void InitGlobals(Env& globals) const;
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auto TopLevel(TypeCheckContext&) const -> void;
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private:
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struct VariableDeclaration {
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static constexpr DeclarationKind Kind = DeclarationKind::VariableDeclaration;
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int source_location;
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std::string name;
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const Expression* type;
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const Expression* initializer;
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};
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class Declaration {
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public:
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static auto MakeFunctionDeclaration(FunctionDefinition definition)
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-> const Declaration;
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static auto MakeStructDeclaration(int line_num, std::string name,
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std::list<Member*> members)
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-> const Declaration;
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static auto MakeChoiceDeclaration(
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int line_num, std::string name,
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std::list<std::pair<std::string, const Expression*>> alternatives)
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-> const Declaration;
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static auto MakeVariableDeclaration(int source_location, std::string name,
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const Expression* type,
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const Expression* initializer)
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-> const Declaration;
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auto GetFunctionDeclaration() const -> const FunctionDeclaration&;
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auto GetStructDeclaration() const -> const StructDeclaration&;
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auto GetChoiceDeclaration() const -> const ChoiceDeclaration&;
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auto GetVariableDeclaration() const -> const VariableDeclaration&;
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void Print() const;
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inline auto tag() const -> DeclarationKind {
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return std::visit([](const auto& t) { return t.Kind; }, value);
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}
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private:
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std::variant<FunctionDeclaration, StructDeclaration, ChoiceDeclaration,
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VariableDeclaration>
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value;
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};
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} // namespace Carbon
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#endif // EXECUTABLE_SEMANTICS_AST_DECLARATION_H_
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@@ -14,8 +14,8 @@ namespace Carbon {
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struct StructDefinition {
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int line_num;
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std::string* name;
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std::list<Member*>* members;
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std::string name;
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std::list<Member*> members;
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};
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} // namespace Carbon
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