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Convert Statement to use Ptr (#788)

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Note this makes a few cases where the Statement was optional explicit (Block, If, Sequence). I do add a few CHECKs around where statements were optional and assumed but unverified.

I switch TypeCheckStmt to not take an optional Statement because I think it makes the call sites clearer in behavior. It's also a smaller change than the converse, because taking an optional Statement means the returned statement would also need to be optional. Arguably a wrapper for optional statements could be added, but this still seems cleaner to me, and there aren't that many cases of an optional statement.

Co-authored-by: Geoff Romer <gromer@google.com>
This commit is contained in:
Jon Meow
2021-08-30 14:41:14 -07:00
committed by GitHub
co-authored by Geoff Romer
parent ed2d171703
commit 36ed79dc25
12 changed files with 166 additions and 138 deletions
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executable_semantics/interpreter/interpreter.cpp
+13 -14
View File
@@ -812,8 +812,7 @@ auto IsBlockAct(Ptr<Action> act) -> bool {
Transition StepStmt() {
Ptr<Frame> frame = state->stack.Top();
Ptr<Action> act = frame->todo.Top();
const Statement* stmt = cast<StatementAction>(*act).Stmt();
CHECK(stmt != nullptr) << "null statement!";
Ptr<const Statement> stmt = cast<StatementAction>(*act).Stmt();
if (tracing_output) {
llvm::outs() << "--- step stmt ";
stmt->PrintDepth(1, llvm::outs());
@@ -861,9 +860,8 @@ Transition StepStmt() {
vars.push_back(name);
}
frame->scopes.Push(global_arena->New<Scope>(values, vars));
const Statement* body_block =
global_arena->RawNew<Block>(stmt->SourceLoc(), c->second);
auto body_act = global_arena->New<StatementAction>(body_block);
auto body_act = global_arena->New<StatementAction>(
global_arena->New<Block>(stmt->SourceLoc(), c->second));
body_act->IncrementPos();
frame->todo.Pop(1);
frame->todo.Push(body_act);
@@ -925,9 +923,9 @@ Transition StepStmt() {
case Statement::Kind::Block: {
if (act->Pos() == 0) {
const Block& block = cast<Block>(*stmt);
if (block.Stmt() != nullptr) {
if (block.Stmt()) {
frame->scopes.Push(global_arena->New<Scope>(CurrentEnv(state)));
return Spawn{global_arena->New<StatementAction>(block.Stmt())};
return Spawn{global_arena->New<StatementAction>(*block.Stmt())};
} else {
return Done{};
}
@@ -1007,7 +1005,7 @@ Transition StepStmt() {
// S, H}
// -> { { else_stmt :: C, E, F } :: S, H}
return Delegate{
global_arena->New<StatementAction>(cast<If>(*stmt).ElseStmt())};
global_arena->New<StatementAction>(*cast<If>(*stmt).ElseStmt())};
} else {
return Done{};
}
@@ -1030,9 +1028,9 @@ Transition StepStmt() {
if (act->Pos() == 0) {
return Spawn{global_arena->New<StatementAction>(seq.Stmt())};
} else {
if (seq.Next() != nullptr) {
return Delegate{
global_arena->New<StatementAction>(cast<Sequence>(*stmt).Next())};
if (seq.Next()) {
return Delegate{global_arena->New<StatementAction>(
*cast<Sequence>(*stmt).Next())};
} else {
return Done{};
}
@@ -1046,7 +1044,7 @@ Transition StepStmt() {
Stack<Ptr<Scope>>(global_arena->New<Scope>(CurrentEnv(state)));
Stack<Ptr<Action>> todo;
todo.Push(global_arena->New<StatementAction>(
global_arena->RawNew<Return>(stmt->SourceLoc())));
global_arena->New<Return>(stmt->SourceLoc())));
todo.Push(
global_arena->New<StatementAction>(cast<Continuation>(*stmt).Body()));
auto continuation_frame =
@@ -1074,7 +1072,7 @@ Transition StepStmt() {
// Push an expression statement action to ignore the result
// value from the continuation.
auto ignore_result = global_arena->New<StatementAction>(
global_arena->RawNew<ExpressionStatement>(
global_arena->New<ExpressionStatement>(
stmt->SourceLoc(),
global_arena->New<TupleLiteral>(stmt->SourceLoc())));
frame->todo.Push(ignore_result);
@@ -1172,8 +1170,9 @@ struct DoTransition {
params.push_back(name);
}
auto scopes = Stack<Ptr<Scope>>(global_arena->New<Scope>(values, params));
CHECK(call.function->Body()) << "Calling a function that's missing a body";
auto todo = Stack<Ptr<Action>>(
global_arena->New<StatementAction>(call.function->Body()));
global_arena->New<StatementAction>(*call.function->Body()));
auto frame = global_arena->New<Frame>(call.function->Name(), scopes, todo);
state->stack.Push(frame);
}