Redesigned SourceStream to be more safe

Cargo.toml

@@ -1,5 +1,5 @@
 [package]
-name = "source_stream_0"
+name = "source-stream-0"
 edition = "2024"
 
 [lib]

src/lib.rs

@@ -24,10 +24,23 @@ pub trait CollectedSubstring<C> {
     fn compareKeyword(&self, kw: impl _Keyword<C>);
 }
 
-pub trait SourceStream<C, P: Pos, CS: CollectedSubstring<C>> {
-    fn skip(&mut self, predicate: impl Predicate<C>);
-    fn collect(&mut self, predicate: impl Predicate<C>) -> CS;
-
-    fn pos(&mut self) -> P;
-    fn currentChar(&mut self) -> C;
+pub enum CollectResult<T> {
+    EOF,
+    NotMatches,
+    Matches(T)
+}
+
+pub trait SourceStream<C, P: Pos, CS: CollectedSubstring<C>> {
+    /**
+     * Returns `true` if the end of stream reached.
+     */
+    fn skip(&mut self, predicate: impl Predicate<C>) -> bool;
+    fn collect(&mut self, predicate: impl Predicate<C>) -> CollectResult<CS>;
+
+    fn pos(&self) -> P;
+
+    fn currentChar(&self) -> Option<C>;
+    fn nextChar(&mut self) -> Option<C>;
+
+    fn isEnded(&self) -> bool;
 }