From 9adae9c262f15fc1ea8b4266ce8bb238a4fc0070 Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Sun, 21 Nov 2021 02:30:45 -0800
Subject: [PATCH] Disallow empty import groups

---
 schala-lang/src/parsing/combinator.rs |  2 +-
 schala-lang/src/parsing/peg_parser.rs |  8 +++++++-
 schala-lang/src/parsing/test.rs       | 10 +---------
 3 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/schala-lang/src/parsing/combinator.rs b/schala-lang/src/parsing/combinator.rs
index bac392d..67f596c 100644
--- a/schala-lang/src/parsing/combinator.rs
+++ b/schala-lang/src/parsing/combinator.rs
@@ -197,7 +197,7 @@ fn import(input: Span) -> ParseResult<ImportSpecifier> {
             map(
                 preceded(
                     tag("::"),
-                    delimited(char('{'), separated_list0(tok(char(',')), identifier), char('}')),
+                    delimited(char('{'), cut(separated_list1(tok(char(',')), identifier)), char('}')),
                 ),
                 |names| ImportedNames::List(names.into_iter().map(|n| rc_string(n.fragment())).collect()),
             ),
diff --git a/schala-lang/src/parsing/peg_parser.rs b/schala-lang/src/parsing/peg_parser.rs
index 3e07b18..a010677 100644
--- a/schala-lang/src/parsing/peg_parser.rs
+++ b/schala-lang/src/parsing/peg_parser.rs
@@ -78,7 +78,13 @@ peg::parser! {
 
         rule import_suffix() -> ImportedNames =
             "::*" { ImportedNames::All } /
-            "::{" __ names:(identifier() ** (_ "," _)) __ "}" { ImportedNames::List(names.into_iter().map(rc_string).collect()) }
+            "::{" __ names:(identifier() ** (_ "," _)) __ "}" {?
+                if names.is_empty() {
+                    Err("import groups must have at least one item")
+                } else {
+                    Ok(ImportedNames::List(names.into_iter().map(rc_string).collect()))
+                }
+            }
 
         rule declaration(parser: &mut Parser) -> Declaration =
             binding(parser) / type_decl(parser) / annotation(parser) / func(parser) / interface(parser) /
diff --git a/schala-lang/src/parsing/test.rs b/schala-lang/src/parsing/test.rs
index 6e10f81..751934c 100644
--- a/schala-lang/src/parsing/test.rs
+++ b/schala-lang/src/parsing/test.rs
@@ -1106,15 +1106,7 @@ fn imports() {
         }))]
     };
 
-    //TODO this shouldn't be legal
-    assert_ast! {
-        "import bespouri::{}",
-        vec![stmt(StatementKind::Import(ImportSpecifier {
-            id: Default::default(),
-            path_components: vec![rc("bespouri")],
-            imported_names: ImportedNames::List(vec![]),
-        }))]
-    };
+    assert_fail!("import bespouri::{}");
 
     assert_ast! {
         "import bespouri::*",