crates/lang/src/lst_parser/error.rs

@@ -10,4 +10,6 @@ pub enum SyntaxError {
     CommaInMatOrVec,
     UnterminatedTopLevelItem,
     UnclosedModuleBody,
+    UnfinishedPath,
+    PathSepContainsSemicolon,
 }

crates/lang/src/lst_parser/grammar/module.rs

@@ -20,6 +20,7 @@ pub fn mod_body(p: &mut Parser) {
 fn mod_decl(p: &mut Parser) -> Option<CompletedMarker> {
     let mod_start = p.start("module");
     if !p.eat(MOD_KW) {
+        mod_start.abandon(p);
         return None;
     }
 
@@ -54,7 +55,7 @@ pub fn top_level_item(p: &mut Parser) -> Option<CompletedMarker> {
     if !TOP_LEVEL_ITEM_START.contains(p.current()) {
         return None;
     }
-    def(p).or_else(|| mod_decl(p))
+    def(p).or_else(|| mod_decl(p)).or_else(|| r#use(p))
 }
 
 fn def(p: &mut Parser) -> Option<CompletedMarker> {
@@ -98,9 +99,81 @@ fn def(p: &mut Parser) -> Option<CompletedMarker> {
 }
 
 fn r#use(p: &mut Parser) -> Option<CompletedMarker> {
+    let use_start = p.start("use_start");
     if !p.eat(USE_KW) {
+        use_start.abandon(p);
         return None;
     }
 
-    todo!()
+    if use_pat(p).is_none() {
+        p.start("expected_use_pat")
+            .error(p, SyntaxError::Expected(vec![USE_PAT]));
+    }
+
+    let use_item = use_start.complete(p, DEF);
+    Some(if p.eat(SEMICOLON) {
+        use_item
+    } else if TOP_LEVEL_ITEM_START.contains(p.current()) || p.at(EOF) {
+        use_item
+            .precede(p, "unterminated_tl_item")
+            .error(p, SyntaxError::UnterminatedTopLevelItem)
+    } else {
+        use_item
+            .precede(p, "err_unexpected")
+            .error(p, SyntaxError::Expected(vec![SEMICOLON]))
+    })
+}
+
+fn use_pat(p: &mut Parser) -> Option<CompletedMarker> {
+    let use_pat_marker = p.start("use_pat");
+    if !p.eat(IDENT) {
+        return None;
+    }
+
+    loop {
+        if p.eat(PATH_SEP) {
+            if pat_item(p).is_none() {
+                break Some(use_pat_marker.error(p, SyntaxError::UnfinishedPath));
+            }
+        } else if p.at(SEMICOLON) && p.nth_at(1, COLON) {
+            let broken_sep = p.start("broken_path_sep");
+            let wrong_semi = p.start("semi_typo");
+            p.eat(SEMICOLON);
+            wrong_semi.error(p, SyntaxError::PathSepContainsSemicolon);
+            p.eat(COLON);
+            broken_sep.complete(p, PATH_SEP);
+        } else if p.at(COLON) && p.nth_at(1, SEMICOLON) {
+            let broken_sep = p.start("broken_path_sep");
+            p.eat(COLON);
+            let wrong_semi = p.start("semi_typo");
+            p.eat(SEMICOLON);
+            wrong_semi.error(p, SyntaxError::PathSepContainsSemicolon);
+            broken_sep.complete(p, PATH_SEP);
+        } else if p.at(SEMICOLON) && p.nth_at(1, SEMICOLON) {
+            let broken_sep = p.start("broken_path_sep");
+            p.eat(SEMICOLON);
+            p.eat(SEMICOLON);
+            broken_sep
+                .complete(p, PATH_SEP)
+                .precede(p, "semi_typo_err")
+                .error(p, SyntaxError::PathSepContainsSemicolon);
+        } else if p.at(SEMICOLON) {
+            break Some(use_pat_marker.complete(p, USE_PAT));
+        } else {
+            break Some(use_pat_marker.error(p, SyntaxError::Expected(vec![PATH_SEP, SEMICOLON])));
+        }
+    }
+}
+
+fn pat_item(p: &mut Parser) -> Option<CompletedMarker> {
+    let item_start = p.start("pat_item_start");
+    if p.eat(IDENT) {
+        Some(item_start.complete(p, PAT_ITEM))
+    } else if p.eat(STAR) {
+        Some(item_start.complete(p, PAT_GLOB))
+    } else if p.eat(L_BRACE) {
+        todo!("write PAT_GROUPs")
+    } else {
+        None
+    }
 }

crates/lang/src/lst_parser/syntax_kind.rs

@@ -27,14 +27,20 @@ pub enum SyntaxKind {
     #[token("in")]
     IN_KW,
     LET_IN,
+    #[token("::")]
+    PATH_SEP,
     #[token("mod")]
     MOD_KW,
     MODULE,
     MODULE_NAME,
     MODULE_BODY,
+    USE,
     #[token("use")]
     USE_KW,
     USE_PAT,
+    PAT_ITEM,
+    PAT_GLOB,
+    PAT_GROUP,
     #[regex("[\\d]+")]
     INT_NUM,
     #[regex("[+-]?([\\d]+\\.[\\d]*|[\\d]*\\.[\\d]+)")]

testfiles/test.owo

@@ -1,4 +1,6 @@
-def hello_world = meow [ 1 2 ]
+use hello::meow;
+
+def hello_world = meow [ 1 2 ];
 
 def test