diff --git a/src/atlas.c3 b/src/atlas.c3
index 7f3a40b..c9c5f59 100644
--- a/src/atlas.c3
+++ b/src/atlas.c3
@@ -108,7 +108,7 @@ fn Point? Atlas.place(&atlas, char[] pixels, ushort w, ushort h, ushort stride)
 		if (atlas.row.x + w <= atlas.width && atlas.row.y + h <= atlas.height) {
 			p = atlas.row;
 		} else {
-			return CANNOT_PLACE?;
+			return CANNOT_PLACE~;
 		}
 	}
 
diff --git a/src/cache.c3 b/src/cache.c3
index 5d85494..f6c523b 100644
--- a/src/cache.c3
+++ b/src/cache.c3
@@ -1,4 +1,4 @@
-module cache{Key, Value, SIZE};
+module cache<Key, Value, SIZE>;
 
 /* LRU Cache
  * The cache uses a pool (array) to store all the elements, each element has
@@ -29,7 +29,7 @@ struct Cache {
 }
 
 // Every CACHE_CYCLES operations mark as not-present the unused elements
-macro Cache.cycle(&cache) @private {
+macro Cache.cycle(&cache) {
     cache.cycle_count++;
 	if (cache.cycle_count > CACHE_NCYCLES) {
 		for (usz i = 0; i < cache.present.data.len; i++) {
@@ -64,14 +64,14 @@ fn Value*? Cache.search(&cache, Key id)
 	/* MISS, wrong key */
 	if (entry.key != id) {
 		cache.table.remove(id)!;
-		return NOT_FOUND?;
+		return NOT_FOUND~;
 	}
 
 	/* MISS, the data is not valid (not present) */
 	if (!cache.present[entry.value]) {
 		// if the data is not present but it is still in the table, remove it
 		cache.table.remove(id)!;
-		return NOT_FOUND?;
+		return NOT_FOUND~;
 	}
 
 	/* HIT, set as recently used */
@@ -94,7 +94,7 @@ fn void Cache.remove(&cache, Key id)
 
 /* Look for a free spot in the present bitmap and return its index */
 /* If there is no free space left then just return the first position */
-fn usz Cache.get_free_spot(&cache) @private
+fn usz Cache.get_free_spot(&cache)
 {
 	// TODO: in the upgrade to c3 1.7.5 use @bitsof()
 	const BITS = $typeof(cache.present.data[0]).sizeof*8;
@@ -108,7 +108,7 @@ fn usz Cache.get_free_spot(&cache) @private
 	return 0;
 }
 
-fn Value*? Cache.insert_at(&cache, Value* g, Key id, usz index) @private
+fn Value*? Cache.insert_at(&cache, Value* g, Key id, usz index)
 {
 	// TODO: verify index, g and id
 	Value* spot;
@@ -136,7 +136,7 @@ fn Value*? Cache.get_or_insert(&cache, Value* g, Key id, bool *is_new = null)
 	Value*? c = cache.search(id);
 	if (catch e = c) {
 		if (e != NOT_FOUND) {
-			return e?;
+			return e~;
 		} else {
 			// if the element is new (inserted) set the is_new flag
 			if (is_new) *is_new = true;
diff --git a/src/core.c3 b/src/core.c3
index 8fc1e59..078ea45 100644
--- a/src/core.c3
+++ b/src/core.c3
@@ -183,7 +183,7 @@ fn PElemTuple? Ctx.get_elem(&ctx, Id id, ElemType type)
 	elem.id = id;
 	elem.layout = {};
 	if (is_new == false && elem.type != type) {
-		return WRONG_ELEMENT_TYPE?;
+		return WRONG_ELEMENT_TYPE~;
 	} else {
 		elem.type = type;
 	}
@@ -272,7 +272,7 @@ fn void? Ctx.frame_end(&ctx)
 {
 	Elem* root = ctx.get_active_div()!;
 	if (root.id != ROOT_ID) {
-		return WRONG_ID?;
+		return WRONG_ID~;
 	}
 
 	// 2. clear input fields
diff --git a/src/font.c3 b/src/font.c3
index c7c1d56..afdf1f7 100644
--- a/src/font.c3
+++ b/src/font.c3
@@ -90,7 +90,7 @@ fn void? Font.load(&font, Allocator allocator, String name, ZString path, uint h
 	font.sft.font = schrift::loadfile(path);
 	if (font.sft.font == null) {
 		font.table.free();
-		return TTF_LOAD_FAILED?;
+		return TTF_LOAD_FAILED~;
 	}
 
 	schrift::SftLMetrics lmetrics;
@@ -122,7 +122,7 @@ fn Glyph*? Font.get_glyph(&font, Codepoint code)
 
 	if (catch excuse = gp) {
 		if (excuse != NOT_FOUND) {
-			return excuse?;
+			return excuse~;
 		}
 	} else {
 		return gp;
@@ -136,11 +136,11 @@ fn Glyph*? Font.get_glyph(&font, Codepoint code)
 	schrift::SftGMetrics gmtx;
 
 	if (schrift::lookup(&font.sft, (SftUChar)code, &gid) < 0) {
-		return MISSING_GLYPH?;
+		return MISSING_GLYPH~;
 	}
 
 	if (schrift::gmetrics(&font.sft, gid, &gmtx) < 0) {
-		return BAD_GLYPH_METRICS?;
+		return BAD_GLYPH_METRICS~;
 	}
 
 	schrift::SftImage img = {
@@ -150,7 +150,7 @@ fn Glyph*? Font.get_glyph(&font, Codepoint code)
 	char[] pixels = mem::new_array(char, (usz)img.width * img.height);
 	img.pixels = pixels;
 	if (schrift::render(&font.sft, gid, img) < 0) {
-		return RENDER_ERROR?;
+		return RENDER_ERROR~;
 	}
 
 	glyph.code = code;
@@ -217,7 +217,7 @@ fn Atlas*? Ctx.get_font_atlas(&ctx, String name)
 {
 	// TODO: use the font name, for now there is only one font
 	if (name.hash() != ctx.font.id) {
-		return WRONG_ID?;
+		return WRONG_ID~;
 	}
 
 	return &ctx.font.atlas;
diff --git a/src/input.c3 b/src/input.c3
index 5bc7c31..f01322e 100644
--- a/src/input.c3
+++ b/src/input.c3
@@ -88,7 +88,7 @@ fn bool Ctx.check_key_combo(&ctx, ModKeys mod, String ...keys)
 fn void? Ctx.input_window_size(&ctx, short width, short height)
 {
 	if (width <= 0 || height <= 0) {
-		return INVALID_SIZE?;
+		return INVALID_SIZE~;
 	}
 	ctx.current_input.events.resize = ctx.width != width || ctx.height != height;
 	ctx.width = width;
diff --git a/src/mtree.c3 b/src/mtree.c3
index 0481048..39536c0 100644
--- a/src/mtree.c3
+++ b/src/mtree.c3
@@ -1,4 +1,4 @@
-module mtree{Type};
+module mtree<Type>;
 
 /* ================================================================================================
  * MTree, Bitmap-based tree
@@ -127,7 +127,7 @@ fn int? MTree.get_free_spot(&tree)
 			return spot;
 		}
 	}
-	return CAPACITY_EXCEEDED?;
+	return CAPACITY_EXCEEDED~;
 }
 
 <* @require idx >= 0 *>
@@ -207,7 +207,7 @@ fn int? MTree.add(&tree, int parent, Type t)
 		// if the new node does not land in the same subtree as the child we cannot do
 		// anything since the references are immutable
 		if (new_next/BITS != subtree) {
-			return CAPACITY_EXCEEDED?;
+			return CAPACITY_EXCEEDED~;
 		}
 		tree.set_used(new_next);
 		tree.elements++;
@@ -330,13 +330,13 @@ fn void MTree.prune(&tree, int parent)
 fn Type? MTree.get(&tree, int ref) @operator([])
 {
 	if (tree.is_used(ref)) return tree.elem_vec[ref];
-	return NOT_FOUND?;
+	return NOT_FOUND~;
 }
 
 <* @param [&in] tree *>
 fn Type? MTree.parentof(&tree, int ref)
 {
-	if (!tree.is_used(ref)) return NOT_FOUND?;
+	if (!tree.is_used(ref)) return NOT_FOUND~;
 	return tree.refs_vec[ref].parent;
 }
 
diff --git a/src/sprite.c3 b/src/sprite.c3
index ab4127b..4057ae7 100644
--- a/src/sprite.c3
+++ b/src/sprite.c3
@@ -35,7 +35,7 @@ fn void? SpriteAtlas.init(&this, String name, AtlasType type, ushort width, usho
 {
 	// FIXME: for now only R8G8B8A8 format is supported
 	if (type != ATLAS_R8G8B8A8) {
-		return INVALID_TYPE?;
+		return INVALID_TYPE~;
 	}
 
 	this.id = name.hash();
diff --git a/src/string.c3 b/src/string.c3
index e6561f2..b5029cd 100644
--- a/src/string.c3
+++ b/src/string.c3
@@ -13,7 +13,7 @@ macro usz LineInfo.len(li) => li.end-li.start;
 
 alias LineStack @local = list::List{LineInfo};
 
-fn short Rect.y_off(Rect bounds, short height, Anchor anchor) @local
+fn short Rect.y_off(Rect bounds, short height, Anchor anchor)
 {
 	short off;
 
@@ -34,7 +34,7 @@ fn short Rect.y_off(Rect bounds, short height, Anchor anchor) @local
 	return off;
 }
 
-fn short Rect.x_off(Rect bounds, short width, Anchor anchor) @local
+fn short Rect.x_off(Rect bounds, short width, Anchor anchor)
 {
 	short off;
 
@@ -205,7 +205,7 @@ fn Rect? GlyphIterator.next(&self)
 	// check if there is a next glyph and maybe update the line and offset indices
 	if (self.anchor != TOP_LEFT) {
 		if (self.line_idx >= self.lines.len()) {
-			return NO_MORE_ELEMENT?;
+			return NO_MORE_ELEMENT~;
 		}
 	
 		LineInfo li = self.lines[self.line_idx];
@@ -213,7 +213,7 @@ fn Rect? GlyphIterator.next(&self)
 			self.line_idx++;
 			
 			if (self.line_idx >= self.lines.len()) {
-				return NO_MORE_ELEMENT?;
+				return NO_MORE_ELEMENT~;
 			}
 			
 			self.line_off = 0;
@@ -223,7 +223,7 @@ fn Rect? GlyphIterator.next(&self)
 			self.o.x = self.bounds.x + self.bounds.x_off(li.width, self.anchor) - li.first_off;
 		}
 	} else if (self.line_off >= self.text.len) {
-		return NO_MORE_ELEMENT?;
+		return NO_MORE_ELEMENT~;
 	}
 
 	String t;