Fix some parser bugs

crates/libsyntax2/src/grammar/paths.rs

@@ -62,7 +62,7 @@ fn path_segment(p: &mut Parser, mode: Mode, first: bool) {
         }
         SELF_KW | SUPER_KW => p.bump(),
         _ => {
-            p.error("expected identifier");
+            p.err_and_bump("expected identifier");
         }
     };
     segment.complete(p, PATH_SEGMENT);

crates/libsyntax2/src/grammar/patterns.rs

@@ -60,6 +60,7 @@ fn atom_pat(p: &mut Parser) -> Option<CompletedMarker> {
 //     let Bar(..) = ();
 // }
 fn path_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(paths::is_path_start(p));
     let m = p.start();
     paths::expr_path(p);
     let kind = match p.current() {
@@ -116,8 +117,11 @@ fn struct_pat_fields(p: &mut Parser) {
                 p.bump();
                 pattern(p);
             }
-            _ => {
+            REF_KW | MUT_KW | IDENT => {
                 bind_pat(p, false);
+            },
+            _ => {
+                p.err_and_bump("expected ident");
             }
         }
         if !p.at(R_CURLY) {

crates/libsyntax2/src/grammar/type_params.rs

@@ -121,7 +121,12 @@ fn where_predicate(p: &mut Parser) {
         lifetime_bounds(p)
     } else {
         types::path_type(p);
-        bounds(p);
+        if p.at(COLON) {
+            bounds(p);
+        } else {
+            p.error("expected colon")
+        }
+
     }
     m.complete(p, WHERE_PRED);
 }

crates/libsyntax2/src/grammar/types.rs

@@ -166,8 +166,11 @@ fn fn_pointer_type(p: &mut Parser) {
         p.error("expected `fn`");
         return;
     }
-
-    params::param_list_opt_patterns(p);
+    if p.at(L_PAREN) {
+        params::param_list_opt_patterns(p);
+    } else {
+        p.error("expected parameters")
+    }
     // test fn_pointer_type_with_ret
     // type F = fn() -> ();
     fn_ret_type(p);