Migrate remaining `Expression` alternatives to `IndirectValue` (#607)

executable_semantics/ast/expression.cpp

@@ -84,11 +84,12 @@ auto Expression::MakeContinuationType(int line_num) -> const Expression* {
   return type;
 }
 
-auto Expression::MakeFunType(int line_num, const Expression* param,
-                             const Expression* ret) -> const Expression* {
+auto Expression::MakeFunType(int line_num, Expression param, Expression ret)
+    -> const Expression* {
   auto* t = new Expression();
   t->line_num = line_num;
-  t->value = FunctionType({.parameter = param, .return_type = ret});
+  t->value = FunctionType(
+      {.parameter = std::move(param), .return_type = std::move(ret)});
   return t;
 }
 
@@ -99,11 +100,11 @@ auto Expression::MakeVar(int line_num, std::string var) -> const Expression* {
   return v;
 }
 
-auto Expression::MakeVarPat(int line_num, std::string var,
-                            const Expression* type) -> const Expression* {
+auto Expression::MakeVarPat(int line_num, std::string var, Expression type)
+    -> const Expression* {
   auto* v = new Expression();
   v->line_num = line_num;
-  v->value = PatternVariable({.name = std::move(var), .type = type});
+  v->value = PatternVariable({.name = std::move(var), .type = std::move(type)});
   return v;
 }
 
@@ -146,11 +147,11 @@ auto Expression::MakeBinOp(int line_num, enum Operator op, Expression arg1,
   return e;
 }
 
-auto Expression::MakeCall(int line_num, const Expression* fun,
-                          const Expression* arg) -> const Expression* {
+auto Expression::MakeCall(int line_num, Expression fun, Expression arg)
+    -> const Expression* {
   auto* e = new Expression();
   e->line_num = line_num;
-  e->value = Call({.function = fun, .argument = arg});
+  e->value = Call({.function = std::move(fun), .argument = std::move(arg)});
   return e;
 }
 
@@ -186,11 +187,11 @@ auto Expression::MakeTuple(int line_num, std::vector<FieldInitializer> args)
   return e;
 }
 
-auto Expression::MakeIndex(int line_num, const Expression* exp,
-                           const Expression* i) -> const Expression* {
+auto Expression::MakeIndex(int line_num, Expression exp, Expression i)
+    -> const Expression* {
   auto* e = new Expression();
   e->line_num = line_num;
-  e->value = Index({.aggregate = exp, .offset = i});
+  e->value = Index({.aggregate = std::move(exp), .offset = std::move(i)});
   return e;
 }
 
@@ -237,9 +238,9 @@ static void PrintFields(const std::vector<FieldInitializer>& fields) {
 void PrintExp(const Expression* e) {
   switch (e->tag()) {
     case ExpressionKind::Index:
-      PrintExp(e->GetIndex().aggregate);
+      PrintExp(e->GetIndex().aggregate.GetPointer());
       std::cout << "[";
-      PrintExp(e->GetIndex().offset);
+      PrintExp(e->GetIndex().offset.GetPointer());
       std::cout << "]";
       break;
     case ExpressionKind::GetField:
@@ -285,17 +286,17 @@ void PrintExp(const Expression* e) {
       std::cout << e->GetVariable().name;
       break;
     case ExpressionKind::PatternVariable:
-      PrintExp(e->GetPatternVariable().type);
+      PrintExp(e->GetPatternVariable().type.GetPointer());
       std::cout << ": ";
       std::cout << e->GetPatternVariable().name;
       break;
     case ExpressionKind::Call:
-      PrintExp(e->GetCall().function);
+      PrintExp(e->GetCall().function.GetPointer());
       if (e->GetCall().argument->tag() == ExpressionKind::Tuple) {
-        PrintExp(e->GetCall().argument);
+        PrintExp(e->GetCall().argument.GetPointer());
       } else {
         std::cout << "(";
-        PrintExp(e->GetCall().argument);
+        PrintExp(e->GetCall().argument.GetPointer());
         std::cout << ")";
       }
       break;
@@ -316,9 +317,9 @@ void PrintExp(const Expression* e) {
       break;
     case ExpressionKind::FunctionT:
       std::cout << "fn ";
-      PrintExp(e->GetFunctionType().parameter);
+      PrintExp(e->GetFunctionType().parameter.GetPointer());
       std::cout << " -> ";
-      PrintExp(e->GetFunctionType().return_type);
+      PrintExp(e->GetFunctionType().return_type.GetPointer());
       break;
   }
 }

executable_semantics/ast/expression.h

@@ -70,14 +70,14 @@ struct FieldAccess {
 
 struct Index {
   static constexpr ExpressionKind Kind = ExpressionKind::Index;
-  const Expression* aggregate;
-  const Expression* offset;
+  IndirectValue<Expression> aggregate;
+  IndirectValue<Expression> offset;
 };
 
 struct PatternVariable {
   static constexpr ExpressionKind Kind = ExpressionKind::PatternVariable;
   std::string name;
-  const Expression* type;
+  IndirectValue<Expression> type;
 };
 
 struct IntLiteral {
@@ -103,14 +103,14 @@ struct PrimitiveOperator {
 
 struct Call {
   static constexpr ExpressionKind Kind = ExpressionKind::Call;
-  const Expression* function;
-  const Expression* argument;
+  IndirectValue<Expression> function;
+  IndirectValue<Expression> argument;
 };
 
 struct FunctionType {
   static constexpr ExpressionKind Kind = ExpressionKind::FunctionT;
-  const Expression* parameter;
-  const Expression* return_type;
+  IndirectValue<Expression> parameter;
+  IndirectValue<Expression> return_type;
 };
 
 struct AutoT {
@@ -138,7 +138,7 @@ struct Expression {
   inline auto tag() const -> ExpressionKind;
 
   static auto MakeVar(int line_num, std::string var) -> const Expression*;
-  static auto MakeVarPat(int line_num, std::string var, const Expression* type)
+  static auto MakeVarPat(int line_num, std::string var, Expression type)
       -> const Expression*;
   static auto MakeInt(int line_num, int i) -> const Expression*;
   static auto MakeBool(int line_num, bool b) -> const Expression*;
@@ -148,19 +148,19 @@ struct Expression {
       -> const Expression*;
   static auto MakeBinOp(int line_num, enum Operator op, Expression arg1,
                         Expression arg2) -> const Expression*;
-  static auto MakeCall(int line_num, const Expression* fun,
-                       const Expression* arg) -> const Expression*;
+  static auto MakeCall(int line_num, Expression fun, Expression arg)
+      -> const Expression*;
   static auto MakeGetField(int line_num, const Expression* exp,
                            std::string field) -> const Expression*;
   static auto MakeTuple(int line_num, std::vector<FieldInitializer> args)
       -> const Expression*;
-  static auto MakeIndex(int line_num, const Expression* exp,
-                        const Expression* i) -> const Expression*;
+  static auto MakeIndex(int line_num, Expression exp, Expression i)
+      -> const Expression*;
   static auto MakeTypeType(int line_num) -> const Expression*;
   static auto MakeIntType(int line_num) -> const Expression*;
   static auto MakeBoolType(int line_num) -> const Expression*;
-  static auto MakeFunType(int line_num, const Expression* param,
-                          const Expression* ret) -> const Expression*;
+  static auto MakeFunType(int line_num, Expression param, Expression ret)
+      -> const Expression*;
   static auto MakeAutoType(int line_num) -> const Expression*;
   static auto MakeContinuationType(int line_num) -> const Expression*;
 

executable_semantics/interpreter/interpreter.cpp

@@ -646,7 +646,7 @@ void StepLvalue() {
     case ExpressionKind::Index: {
       //    { {e[i] :: C, E, F} :: S, H}
       // -> { e :: [][i] :: C, E, F} :: S, H}
-      frame->todo.Push(MakeExpAct(exp->GetIndex().aggregate));
+      frame->todo.Push(MakeExpAct(exp->GetIndex().aggregate.GetPointer()));
       act->pos++;
       break;
     }
@@ -689,14 +689,14 @@ void StepExp() {
   }
   switch (exp->tag()) {
     case ExpressionKind::PatternVariable: {
-      frame->todo.Push(MakeExpAct(exp->GetPatternVariable().type));
+      frame->todo.Push(MakeExpAct(exp->GetPatternVariable().type.GetPointer()));
       act->pos++;
       break;
     }
     case ExpressionKind::Index: {
       //    { { e[i] :: C, E, F} :: S, H}
       // -> { { e :: [][i] :: C, E, F} :: S, H}
-      frame->todo.Push(MakeExpAct(exp->GetIndex().aggregate));
+      frame->todo.Push(MakeExpAct(exp->GetIndex().aggregate.GetPointer()));
       act->pos++;
       break;
     }
@@ -764,7 +764,7 @@ void StepExp() {
     case ExpressionKind::Call:
       //    { {e1(e2) :: C, E, F} :: S, H}
       // -> { {e1 :: [](e2) :: C, E, F} :: S, H}
-      frame->todo.Push(MakeExpAct(exp->GetCall().function));
+      frame->todo.Push(MakeExpAct(exp->GetCall().function.GetPointer()));
       act->pos++;
       break;
     case ExpressionKind::IntT: {
@@ -792,7 +792,8 @@ void StepExp() {
       break;
     }
     case ExpressionKind::FunctionT: {
-      frame->todo.Push(MakeExpAct(exp->GetFunctionType().parameter));
+      frame->todo.Push(
+          MakeExpAct(exp->GetFunctionType().parameter.GetPointer()));
       act->pos++;
       break;
     }
@@ -1093,7 +1094,7 @@ void HandleValue() {
         case ExpressionKind::Index: {
           if (act->pos == 1) {
             frame->todo.Pop(1);
-            frame->todo.Push(MakeExpAct(exp->GetIndex().offset));
+            frame->todo.Push(MakeExpAct(exp->GetIndex().offset.GetPointer()));
           } else if (act->pos == 2) {
             //    { v :: [][i] :: C, E, F} :: S, H}
             // -> { { &v[i] :: C, E, F} :: S, H }
@@ -1163,7 +1164,7 @@ void HandleValue() {
         case ExpressionKind::Index: {
           if (act->pos == 1) {
             frame->todo.Pop(1);
-            frame->todo.Push(MakeExpAct(exp->GetIndex().offset));
+            frame->todo.Push(MakeExpAct(exp->GetIndex().offset.GetPointer()));
           } else if (act->pos == 2) {
             auto tuple = act->results[0];
             switch (tuple->tag) {
@@ -1227,7 +1228,7 @@ void HandleValue() {
             //    { { v :: [](e) :: C, E, F} :: S, H}
             // -> { { e :: v([]) :: C, E, F} :: S, H}
             frame->todo.Pop(1);
-            frame->todo.Push(MakeExpAct(exp->GetCall().argument));
+            frame->todo.Push(MakeExpAct(exp->GetCall().argument.GetPointer()));
           } else if (act->pos == 2) {
             //    { { v2 :: v1([]) :: C, E, F} :: S, H}
             // -> { {C',E',F'} :: {C, E, F} :: S, H}
@@ -1252,7 +1253,8 @@ void HandleValue() {
             //    { { pt :: fn [] -> e :: C, E, F} :: S, H}
             // -> { { e :: fn pt -> []) :: C, E, F} :: S, H}
             frame->todo.Pop(1);
-            frame->todo.Push(MakeExpAct(exp->GetFunctionType().return_type));
+            frame->todo.Push(
+                MakeExpAct(exp->GetFunctionType().return_type.GetPointer()));
           }
           break;
         }
@@ -1500,7 +1502,7 @@ auto InterpProgram(std::list<Declaration>* fs) -> int {
 
   const Expression* arg = Expression::MakeTuple(0, {});
   const Expression* call_main =
-      Expression::MakeCall(0, Expression::MakeVar(0, "main"), arg);
+      Expression::MakeCall(0, *Expression::MakeVar(0, "main"), *arg);
   auto todo = Stack(MakeExpAct(call_main));
   auto* scope = new Scope(globals, std::list<std::string>());
   auto* frame = new Frame("top", Stack(scope), todo);

executable_semantics/interpreter/typecheck.cpp

@@ -67,8 +67,8 @@ auto ReifyType(const Value* t, int line_num) -> const Expression* {
       return Expression::MakeContinuationType(0);
     case ValKind::FunctionTV:
       return Expression::MakeFunType(
-          0, ReifyType(t->GetFunctionType().param, line_num),
-          ReifyType(t->GetFunctionType().ret, line_num));
+          0, *ReifyType(t->GetFunctionType().param, line_num),
+          *ReifyType(t->GetFunctionType().ret, line_num));
     case ValKind::TupleV: {
       std::vector<FieldInitializer> args;
       for (const TupleElement& field : *t->GetTuple().elements) {
@@ -144,7 +144,7 @@ auto TypeCheckExp(const Expression* e, TypeEnv types, Env values,
             << std::endl;
         exit(-1);
       }
-      auto t = InterpExp(values, e->GetPatternVariable().type);
+      auto t = InterpExp(values, e->GetPatternVariable().type.GetPointer());
       if (t->tag == ValKind::AutoTV) {
         if (expected == nullptr) {
           std::cerr << e->line_num
@@ -157,18 +157,20 @@ auto TypeCheckExp(const Expression* e, TypeEnv types, Env values,
       } else if (expected) {
         ExpectType(e->line_num, "pattern variable", t, expected);
       }
-      auto new_e = Expression::MakeVarPat(
-          e->line_num, e->GetPatternVariable().name, ReifyType(t, e->line_num));
+      auto new_e =
+          Expression::MakeVarPat(e->line_num, e->GetPatternVariable().name,
+                                 *ReifyType(t, e->line_num));
       types.Set(e->GetPatternVariable().name, t);
       return TCResult(new_e, t, types);
     }
     case ExpressionKind::Index: {
-      auto res = TypeCheckExp(e->GetIndex().aggregate, types, values, nullptr,
-                              TCContext::ValueContext);
+      auto res = TypeCheckExp(e->GetIndex().aggregate.GetPointer(), types,
+                              values, nullptr, TCContext::ValueContext);
       auto t = res.type;
       switch (t->tag) {
         case ValKind::TupleV: {
-          auto i = ToInteger(InterpExp(values, e->GetIndex().offset));
+          auto i =
+              ToInteger(InterpExp(values, e->GetIndex().offset.GetPointer()));
           std::string f = std::to_string(i);
           std::optional<Address> field_address = FindTupleField(f, t);
           if (field_address == std::nullopt) {
@@ -180,7 +182,7 @@ auto TypeCheckExp(const Expression* e, TypeEnv types, Env values,
           }
           auto field_t = state->heap.Read(*field_address, e->line_num);
           auto new_e = Expression::MakeIndex(
-              e->line_num, res.exp, Expression::MakeInt(e->line_num, i));
+              e->line_num, *res.exp, *Expression::MakeInt(e->line_num, i));
           return TCResult(new_e, field_t, res.types);
         }
         default:
@@ -372,18 +374,18 @@ auto TypeCheckExp(const Expression* e, TypeEnv types, Env values,
       break;
     }
     case ExpressionKind::Call: {
-      auto fun_res = TypeCheckExp(e->GetCall().function, types, values, nullptr,
-                                  TCContext::ValueContext);
+      auto fun_res = TypeCheckExp(e->GetCall().function.GetPointer(), types,
+                                  values, nullptr, TCContext::ValueContext);
       switch (fun_res.type->tag) {
         case ValKind::FunctionTV: {
           auto fun_t = fun_res.type;
           auto arg_res =
-              TypeCheckExp(e->GetCall().argument, fun_res.types, values,
-                           fun_t->GetFunctionType().param, context);
+              TypeCheckExp(e->GetCall().argument.GetPointer(), fun_res.types,
+                           values, fun_t->GetFunctionType().param, context);
           ExpectType(e->line_num, "call", fun_t->GetFunctionType().param,
                      arg_res.type);
           auto new_e =
-              Expression::MakeCall(e->line_num, fun_res.exp, arg_res.exp);
+              Expression::MakeCall(e->line_num, *fun_res.exp, *arg_res.exp);
           return TCResult(new_e, fun_t->GetFunctionType().ret, arg_res.types);
         }
         default: {
@@ -401,22 +403,25 @@ auto TypeCheckExp(const Expression* e, TypeEnv types, Env values,
       switch (context) {
         case TCContext::ValueContext:
         case TCContext::TypeContext: {
-          auto pt = InterpExp(values, e->GetFunctionType().parameter);
-          auto rt = InterpExp(values, e->GetFunctionType().return_type);
+          auto pt =
+              InterpExp(values, e->GetFunctionType().parameter.GetPointer());
+          auto rt =
+              InterpExp(values, e->GetFunctionType().return_type.GetPointer());
           auto new_e =
-              Expression::MakeFunType(e->line_num, ReifyType(pt, e->line_num),
-                                      ReifyType(rt, e->line_num));
+              Expression::MakeFunType(e->line_num, *ReifyType(pt, e->line_num),
+                                      *ReifyType(rt, e->line_num));
           return TCResult(new_e, Value::MakeTypeTypeVal(), types);
         }
         case TCContext::PatternContext: {
-          auto param_res = TypeCheckExp(e->GetFunctionType().parameter, types,
-                                        values, nullptr, context);
-          auto ret_res =
-              TypeCheckExp(e->GetFunctionType().return_type, param_res.types,
+          auto param_res =
+              TypeCheckExp(e->GetFunctionType().parameter.GetPointer(), types,
                            values, nullptr, context);
+          auto ret_res =
+              TypeCheckExp(e->GetFunctionType().return_type.GetPointer(),
+                           param_res.types, values, nullptr, context);
           auto new_e = Expression::MakeFunType(
-              e->line_num, ReifyType(param_res.type, e->line_num),
-              ReifyType(ret_res.type, e->line_num));
+              e->line_num, *ReifyType(param_res.type, e->line_num),
+              *ReifyType(ret_res.type, e->line_num));
           return TCResult(new_e, Value::MakeTypeTypeVal(), ret_res.types);
         }
       }

executable_semantics/syntax/parser.ypp

@@ -205,9 +205,9 @@ expression:
 | expression designator
     { $$ = Carbon::Expression::MakeGetField(yylineno, $1, $2); }
 | expression "[" expression "]"
-    { $$ = Carbon::Expression::MakeIndex(yylineno, $1, $3); }
+    { $$ = Carbon::Expression::MakeIndex(yylineno, *$1, *$3); }
 | identifier ":" expression
-    { $$ = Carbon::Expression::MakeVarPat(yylineno, $1, $3); }
+    { $$ = Carbon::Expression::MakeVarPat(yylineno, $1, *$3); }
 | integer_literal
     { $$ = Carbon::Expression::MakeInt(yylineno, $1); }
 | TRUE
@@ -246,13 +246,13 @@ expression:
 | UNARY_STAR expression %prec PREFIX_STAR
     { $$ = Carbon::Expression::MakeUnOp(yylineno, Carbon::Operator::Deref, *$2); }
 | expression tuple
-    { $$ = Carbon::Expression::MakeCall(yylineno, $1, $2); }
+    { $$ = Carbon::Expression::MakeCall(yylineno, *$1, *$2); }
 | expression POSTFIX_STAR
     { $$ = Carbon::Expression::MakeUnOp(yylineno, Carbon::Operator::Ptr, *$1); }
 | expression UNARY_STAR
     { $$ = Carbon::Expression::MakeUnOp(yylineno, Carbon::Operator::Ptr, *$1); }
 | FNTY tuple return_type
-    { $$ = Carbon::Expression::MakeFunType(yylineno, $2, $3); }
+    { $$ = Carbon::Expression::MakeFunType(yylineno, *$2, *$3); }
 ;
 designator: "." identifier { $$ = $2; }
 ;
@@ -297,7 +297,7 @@ clause:
 | DEFAULT DBLARROW statement
     {
       auto vp = Carbon::Expression::MakeVarPat(yylineno, "_",
-                                   Carbon::Expression::MakeAutoType(yylineno));
+                                   *Carbon::Expression::MakeAutoType(yylineno));
       $$ = new std::pair<const Carbon::Expression*, const Carbon::Statement*>(vp, $3);
     }
 ;