1 files changed, 102 insertions, 31 deletions

diff --git a/src/lower.c b/src/lower.c
index 141453c..5578319 100644
--- a/src/lower.c
+++ b/src/lower.c
@@ -11,6 +11,9 @@
 #include <fwd/scope.h>
 #include <fwd/vec.h>
 
+/** @todo semantics in this file are a bit unclear, should probably do some kind
+ * of "each function starts and ends on an indented empty line" or something */
+
 struct state {
 	long indent;
 };
@@ -34,9 +37,10 @@ static void indent(struct state *state)
 static int lower_var(struct ast *expr);
 
 static int lower_expr(struct state *state, struct ast *expr);
-static int lower_block(struct state *state, struct ast *block, bool ret);
 static int lower_closure(struct state *state, struct ast *closure);
-static int lower_statement(struct state *state, struct ast *stmt);
+
+static int lower_block(struct state *state, struct ast *block, bool ret);
+static int lower_statement(struct state *state, struct ast *stmt, bool ret);
 
 static int lower_type(struct type *type);
 static int lower_types(struct type *types);
@@ -128,7 +132,7 @@ static int lower_type_callable(struct type *type)
 	 * fib.fwd example, so use std::function for now. Eventually I might
 	 * instead write a C backend or something to have more control over the
 	 * exact semantics, but for now this is good enough. */
-	printf("std::function<void(");
+	printf("std::function<fwd_err_t(");
 
 	if (lower_types(type->t0))
 		return -1;
@@ -289,16 +293,44 @@ static int lower_moves(struct state *state, struct ast *moves)
 
 static int lower_err_branch(struct state *state, struct ast *err)
 {
-	return lower_block(state, err_branch_body(err), false);
+	if (lower_block(state, err_branch_body(err), false))
+		return -1;
+
+	printf("\n");
+	return 0;
 }
 
-static int lower_call(struct state *state, struct ast *call)
+static int lower_mark_moved(struct state *state, struct ast *moves)
+{
+	if (!moves)
+		return 0;
+
+	foreach_node(move, moves) {
+		if (move->k != AST_ID)
+			continue;
+
+		printf("%s_owned = false;\n", id_str(move));
+		indent(state);
+	}
+
+	return 0;
+}
+
+static int lower_call(struct state *state, struct ast *call, bool ret)
 {
 	struct ast *err = call_err(call);
 	/** @todo better default error name? */
 	const char *err_str = err ? err_branch_id(err) : "_fwd_err";
 
-	printf("if (auto %s = ", err_str);
+	if (lower_mark_moved(state, call_args(call)))
+		return -1;
+
+	bool direct_ret = ret && !err;
+	if (direct_ret)
+		printf("return ");
+	else
+		printf("if (auto %s = ", err_str);
+
 	if (lower_expr(state, call_expr(call)))
 		return -1;
 
@@ -307,23 +339,22 @@ static int lower_call(struct state *state, struct ast *call)
 	if (lower_moves(state, call_args(call)))
 		return -1;
 
-	printf("))");
-
-	if (!err) {
-		printf("\n");
-		indent(state);
-		printf(" return %s;\n", err_str);
+	if (direct_ret) {
+		printf(");\n");
 		return 0;
 	}
 
-	if (lower_err_branch(state, call_err(call)))
-		return -1;
+	printf("))");
+	if (err)
+		return lower_err_branch(state, err);
 
 	printf("\n");
+	indent(state);
+	printf(" return %s;\n", err_str);
 	return 0;
 }
 
-static int lower_let(struct state *state, struct ast *let)
+static int lower_let(struct state *state, struct ast *let, bool ret)
 {
 	if (lower_var(let_var(let)))
 		return -1;
@@ -334,10 +365,15 @@ static int lower_let(struct state *state, struct ast *let)
 		return -1;
 
 	printf(";\n");
+	if (ret) {
+		indent(state);
+		printf("return nullptr;\n");
+	}
+
 	return 0;
 }
 
-static int lower_if(struct state *state, struct ast *stmt)
+static int lower_if(struct state *state, struct ast *stmt, bool ret)
 {
 	printf("if (");
 	if (lower_expr(state, if_cond(stmt)))
@@ -345,7 +381,7 @@ static int lower_if(struct state *state, struct ast *stmt)
 
 	printf(") ");
 
-	if (lower_block(state, if_body(stmt), false))
+	if (lower_block(state, if_body(stmt), ret))
 		return -1;
 
 	if (!if_else(stmt)) {
@@ -354,7 +390,7 @@ static int lower_if(struct state *state, struct ast *stmt)
 	}
 
 	printf(" else ");
-	if (lower_block(state, if_else(stmt), false))
+	if (lower_block(state, if_else(stmt), ret))
 		return -1;
 
 	printf("\n");
@@ -374,19 +410,24 @@ static int lower_error(struct ast *err)
 	return 0;
 }
 
-static int lower_own(struct state *state, struct ast *stmt)
+static int lower_own(struct state *state, struct ast *stmt, bool ret)
 {
-	printf("/* TODO own */\n");
+	/** @todo name mangling */
+	printf("if (!%s_owned) ", own_id(stmt));
+	if (lower_block(state, own_body(stmt), ret))
+		return -1;
+
+	printf("\n");
 	return 0;
 }
 
-static int lower_statement(struct state *state, struct ast *stmt)
+static int lower_statement(struct state *state, struct ast *stmt, bool ret)
 {
 	switch (stmt->k) {
-	case AST_OWN:   return lower_own(state, stmt);
-	case AST_LET:   return lower_let(state, stmt);
-	case AST_CALL:  return lower_call(state, stmt);
-	case AST_IF:    return lower_if(state, stmt);
+	case AST_OWN:   return lower_own(state, stmt, ret);
+	case AST_LET:   return lower_let(state, stmt, ret);
+	case AST_CALL:  return lower_call(state, stmt, ret);
+	case AST_IF:    return lower_if(state, stmt, ret);
 	case AST_EMPTY: return 0;
 	default:
 		internal_error("missing statement lowering");
@@ -396,15 +437,50 @@ static int lower_statement(struct state *state, struct ast *stmt)
 	return 0;
 }
 
+static int lower_block_vars(struct state *state, struct ast *block)
+{
+	struct scope *scope = block->scope;
+
+	bool populated = false;
+	foreach_visible(n, scope->symbols) {
+		struct ast *def = n->node;
+		if (def->k != AST_VAR_DEF)
+			continue;
+
+		if (is_trivially_copyable(def->t))
+			continue;
+
+		if (!populated) {
+			indent(state);
+			printf("[[maybe_unused]] bool %s_owned = true",
+					var_id(def));
+
+			populated = true;
+			continue;
+		}
+
+		printf(", %s_owned = true", var_id(def));
+	}
+
+	if (populated)
+		printf(";\n\n");
+
+	return 0;
+}
+
 static int lower_block(struct state *state, struct ast *block, bool ret)
 {
 	printf("{\n");
 	increase_indent(state);
 
+	if (lower_block_vars(state, block))
+		return -1;
+
 	foreach_node(stmt, block_body(block)) {
 		indent(state);
 
-		if (lower_statement(state, stmt))
+		bool returning = block_error(block) ? false : ret && !stmt->n;
+		if (lower_statement(state, stmt, returning))
 			return -1;
 	}
 
@@ -414,11 +490,6 @@ static int lower_block(struct state *state, struct ast *block, bool ret)
 			return -1;
 	}
 
-	if (ret) {
-		indent(state);
-		printf("return nullptr;\n");
-	}
-
 	decrease_indent(state);
 	indent(state);
 	printf("}");