cgen: fix optional void return error

vlib/v/checker/checker.v

@@ -1259,7 +1259,8 @@ pub fn (mut c Checker) return_stmt(mut return_stmt ast.Return) {
 		c.error('too many arguments to return, current function does not return anything',
 			return_stmt.pos)
 		return
-	} else if return_stmt.exprs.len == 0 && c.expected_type != table.void_type {
+	} else if return_stmt.exprs.len == 0 && !(c.expected_type == table.void_type ||
+			c.table.get_type_symbol(c.expected_type).kind == .void) {
 		c.error('too few arguments to return', return_stmt.pos)
 		return
 	}

vlib/v/gen/cgen.v

@@ -375,12 +375,12 @@ fn (g &Gen) optional_type_text(styp, base string) string {
 	// replace void with something else
 	size := if base == 'void' { 'int' } else { base }
 	ret := 'struct $x {
- bool ok;
- bool is_none;
- string v_error;
- int ecode;
- byte data[sizeof($size)];
-} '
+	bool ok;
+	bool is_none;
+	string v_error;
+	int ecode;
+	byte data[sizeof($size)];
+}'
 	return ret
 }
 
@@ -2309,6 +2309,19 @@ fn (mut g Gen) return_statement(node ast.Return) {
 	sym := g.table.get_type_symbol(g.fn_decl.return_type)
 	fn_return_is_multi := sym.kind == .multi_return
 	fn_return_is_optional := g.fn_decl.return_type.has_flag(.optional)
+
+	if node.exprs.len == 0 {
+		if fn_return_is_optional {
+			tmp := g.new_tmp_var()
+			styp := g.typ(g.fn_decl.return_type)
+			g.writeln('$styp $tmp;')
+			g.writeln('${tmp}.ok = true;')
+			g.writeln('return $tmp;')
+		} else {
+			g.writeln('return;')
+		}
+		return
+	}
 	// handle promoting none/error/function returning 'Option'
 	if fn_return_is_optional {
 		optional_none := node.exprs[0] is ast.None
@@ -2317,7 +2330,7 @@ fn (mut g Gen) return_statement(node ast.Return) {
 			tmp := g.new_tmp_var()
 			g.write('/*opt promotion*/ Option $tmp = ')
 			g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
-			g.write(';')
+			g.writeln(';')
 			styp := g.typ(g.fn_decl.return_type)
 			g.writeln('return *($styp*)&$tmp;')
 			return

vlib/v/gen/fn.v

@@ -330,7 +330,7 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 	}
 	if gen_or {
 		g.or_block(tmp_opt, node.or_block, node.return_type)
-		g.write('\n${cur_line}${tmp_opt}')
+		g.write('\n\t${cur_line}${tmp_opt}')
 	}
 }
 

vlib/v/tests/option_test.v

@@ -274,34 +274,6 @@ fn test_multi_return_opt() {
 	}
 }
 */
-fn foo() ? {
-	return error('something')
-}
-
-fn test_optional_void() {
-	foo() or {
-		println(err)
-		assert err == 'something'
-		return
-	}
-}
-
-fn bar() ? {
-	return error('bar error')
-}
-
-fn test_optional_void_only_question() {
-	bar() or {
-		println(err)
-		assert err == 'bar error'
-		return
-	}
-}
-
-fn test_optional_void_with_empty_or() {
-	foo() or {}
-	assert true
-}
 
 fn test_optional_val_with_empty_or() {
 	ret_none() or {}

vlib/v/tests/option_void_test.v

@@ -0,0 +1,50 @@
+fn foo() ? {
+	return error('something')
+}
+
+fn test_optional_void() {
+	foo() or {
+		println(err)
+		assert err == 'something'
+		return
+	}
+}
+
+fn bar() ? {
+	return error('bar error')
+}
+
+fn test_optional_void_only_question() {
+	bar() or {
+		println(err)
+		assert err == 'bar error'
+		return
+	}
+}
+
+fn test_optional_void_with_empty_or() {
+	foo() or {}
+	assert true
+}
+
+fn option_void(a int) ? {
+	if a != 0 {
+		return
+	} else {
+		return error('zero error')
+	}
+}
+
+fn test_optional_void_with_return() {
+	option_void(0) or {
+		println(err)
+		assert err == 'zero error'
+		return
+	}
+	option_void(-1) or {
+		println(err)
+		assert err == 'zero error'
+		return
+	}
+	assert true
+}