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[executable semantics] class-ify Declaration (#307)

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* [executable semantics] class-ify Declaration

NFC (no functional change).

Proof of concept that we can simplify code by replacing unions with safer, more
regular types.  Hand-rolled existentials (type-erasing CoW wrappers) are a follow-on
step that will further simplify usage.

Began adding `const` where possible, and replacing `std::string*` with
`std::string`.  Most `const`s can disappear as we replace reference semantics
with value semantics, but in the meantime it's an important step in the right
direction.
This commit is contained in:
Dave Abrahams
2021-02-27 13:32:03 -08:00
committed by GitHub
parent cd57024042
commit 2205fd52ce
14 changed files with 191 additions and 210 deletions
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executable_semantics/ast/declaration.h
+53 -25
View File
@@ -14,36 +14,64 @@
namespace Carbon {
enum class DeclarationKind {
FunctionDeclaration,
StructDeclaration,
ChoiceDeclaration
};
struct Value;
template <class K, class V>
struct AssocList;
using Address = unsigned int;
using TypeEnv = AssocList<std::string, Value*>;
using Env = AssocList<std::string, Address>;
/// TODO:explain this. Also name it if necessary. Consult with jsiek.
using ExecutionEnvironment = std::pair<TypeEnv*, Env*>;
struct Declaration {
DeclarationKind tag;
union {
struct FunctionDefinition* fun_def;
struct StructDefinition* struct_def;
struct {
int line_num;
std::string* name;
std::list<std::pair<std::string, Expression*>>* alternatives;
} choice_def;
} u;
virtual void Print() const = 0;
virtual auto Name() const -> std::string = 0;
virtual auto TypeChecked(TypeEnv* env, Env* ct_env) const
-> const Declaration* = 0;
virtual void InitGlobals(Env*& globals) const = 0;
virtual auto TopLevel(ExecutionEnvironment&) const -> void = 0;
};
auto MakeFunDecl(struct FunctionDefinition* f) -> Declaration*;
auto MakeStructDecl(int line_num, std::string name, std::list<Member*>* members)
-> Declaration*;
auto MakeChoiceDecl(int line_num, std::string name,
std::list<std::pair<std::string, Expression*>>* alts)
-> Declaration*;
struct FunctionDeclaration : Declaration {
const FunctionDefinition* definition;
explicit FunctionDeclaration(const FunctionDefinition* definition)
: definition(definition) {}
void PrintDecl(Declaration* d);
void Print() const;
auto Name() const -> std::string;
auto TypeChecked(TypeEnv* env, Env* ct_env) const -> const Declaration*;
void InitGlobals(Env*& globals) const;
auto TopLevel(ExecutionEnvironment&) const -> void;
};
struct StructDeclaration : Declaration {
StructDefinition definition;
StructDeclaration(int line_num, std::string name, std::list<Member*>* members)
: definition{line_num, new std::string(name), members} {}
void Print() const;
auto Name() const -> std::string;
auto TypeChecked(TypeEnv* env, Env* ct_env) const -> const Declaration*;
void InitGlobals(Env*& globals) const;
auto TopLevel(ExecutionEnvironment&) const -> void;
};
struct ChoiceDeclaration : Declaration {
int line_num;
std::string name;
std::list<std::pair<std::string, Expression*>> alternatives;
ChoiceDeclaration(int line_num, std::string name,
std::list<std::pair<std::string, Expression*>> alternatives)
: line_num(line_num), name(name), alternatives(alternatives) {}
void Print() const;
auto Name() const -> std::string;
auto TypeChecked(TypeEnv* env, Env* ct_env) const -> const Declaration*;
void InitGlobals(Env*& globals) const;
auto TopLevel(ExecutionEnvironment&) const -> void;
};
} // namespace Carbon