Merge pull request #21926 from A4-Tacks/inlayhint-empty-arg

fix: Fix param inlayHints on empty expr and comma

Author: ChayimFriedman2

crates/ide/src/inlay_hints/param_name.rs

@@ -37,8 +37,9 @@ pub(super) fn hints(
     let hints = callable
         .params()
         .into_iter()
-        .zip(arg_list.args())
+        .zip(arg_list.args_maybe_empty())
         .filter_map(|(p, arg)| {
+            let arg = arg?;
             // Only annotate hints for expressions that exist in the original file
             let range = sema.original_range_opt(arg.syntax())?;
             if range.file_id != file_id {
@@ -561,6 +562,19 @@ fn main() {
         )
     }
 
+    #[test]
+    fn param_name_hints_show_after_empty_arg() {
+        check_params(
+            r#"pub fn test(a: i32, b: i32, c: i32) {}
+fn main() {
+    test(, 2,);
+         //^ b
+    test(, , 3);
+           //^ c
+}"#,
+        )
+    }
+
     #[test]
     fn function_call_parameter_hint() {
         check_params(

crates/syntax/src/ast/node_ext.rs

@@ -77,6 +77,15 @@ fn text_of_first_token(node: &SyntaxNode) -> TokenText<'_> {
     }
 }
 
+fn into_comma(it: NodeOrToken<SyntaxNode, SyntaxToken>) -> Option<SyntaxToken> {
+    let token = match it {
+        NodeOrToken::Token(it) => it,
+        NodeOrToken::Node(node) if node.kind() == SyntaxKind::ERROR => node.first_token()?,
+        NodeOrToken::Node(_) => return None,
+    };
+    (token.kind() == T![,]).then_some(token)
+}
+
 impl ast::Abi {
     pub fn abi_string(&self) -> Option<ast::String> {
         support::token(&self.syntax, SyntaxKind::STRING).and_then(ast::String::cast)
@@ -1037,6 +1046,21 @@ impl ast::GenericParamList {
     }
 }
 
+impl ast::ArgList {
+    /// Comma separated args, argument may be empty
+    pub fn args_maybe_empty(&self) -> impl Iterator<Item = Option<ast::Expr>> {
+        // (Expr? ','?)*
+        let mut after_arg = false;
+        self.syntax().children_with_tokens().filter_map(move |it| {
+            if into_comma(it.clone()).is_some() {
+                if std::mem::take(&mut after_arg) { None } else { Some(None) }
+            } else {
+                Some(ast::Expr::cast(it.into_node()?).inspect(|_| after_arg = true))
+            }
+        })
+    }
+}
+
 impl ast::ForExpr {
     pub fn iterable(&self) -> Option<ast::Expr> {
         // If the iterable is a BlockExpr, check if the body is missing.