Allow self in use statements

compiler/noirc_frontend/src/ast/statement.rs

@@ -373,7 +373,9 @@ impl UseTree {
 
         match self.kind {
             UseTreeKind::Path(name, alias) => {
-                vec![ImportStatement { visibility, path: prefix.join(name), alias }]
+                // Desugar `use foo::{self}` to `use foo`
+                let path = if name.0.contents == "self" { prefix } else { prefix.join(name) };
+                vec![ImportStatement { visibility, path, alias }]
             }
             UseTreeKind::List(trees) => {
                 let trees = trees.into_iter();

compiler/noirc_frontend/src/parser/parser/use_tree.rs

@@ -66,6 +66,14 @@ impl<'a> Parser<'a> {
     fn parse_use_tree_in_list(&mut self) -> Option<UseTree> {
         let start_span = self.current_token_span;
 
+        // Special case: "self" cannot be followed by anything else
+        if self.eat_self() {
+            return Some(UseTree {
+                prefix: Path { segments: Vec::new(), kind: PathKind::Plain, span: start_span },
+                kind: UseTreeKind::Path(Ident::new("self".to_string(), start_span), None),
+            });
+        }
+
         let use_tree = self.parse_use_tree_without_kind(
             start_span,
             PathKind::Plain,
@@ -250,4 +258,11 @@ mod tests {
         let (_, errors) = parse_program(src);
         assert!(!errors.is_empty());
     }
+
+    #[test]
+    fn errors_on_double_colon_after_self() {
+        let src = "use foo::{self::bar};";
+        let (_, errors) = parse_program(src);
+        assert!(!errors.is_empty());
+    }
 }

compiler/noirc_frontend/src/tests.rs

@@ -3389,3 +3389,25 @@ fn arithmetic_generics_rounding_fail() {
     let errors = get_program_errors(src);
     assert_eq!(errors.len(), 1);
 }
+
+#[test]
+fn uses_self_in_import() {
+    let src = r#"
+    mod moo {
+        pub mod bar {
+            pub fn foo() -> i32 {
+                1
+            }
+        }
+    }
+
+    use moo::bar::{self};
+
+    pub fn baz() -> i32 {
+        bar::foo()
+    }
+
+    fn main() {}
+    "#;
+    assert_no_errors(src);
+}