fix handling short-only args. limitation: long args and short args now share the same namespace, effectively

crates/nu-engine/src/compile/call.rs

@@ -124,8 +124,12 @@ pub(crate) fn compile_call(
                     ast_ref,
                 ))
             }
-            Argument::Named((name, _, _)) => compiled_args.push(CompiledArg::Named(
+            Argument::Named((name, short, _)) => compiled_args.push(CompiledArg::Named(
-                name.item.as_str(),
+                if name.item.is_empty() {
+                    &short.as_ref().expect("no long name and no short name").item
+                } else {
+                    &name.item
+                },
                 arg_reg,
                 arg.span(),
                 ast_ref,

crates/nu-engine/src/eval_ir.rs

@@ -968,7 +968,15 @@ fn eval_call<D: DebugContext>(
 fn find_named_var_id(sig: &Signature, name: &[u8], span: Span) -> Result<VarId, ShellError> {
     sig.named
         .iter()
-        .find(|n| n.long.as_bytes() == name)
+        .find(|n| {
+            if !n.long.is_empty() {
+                n.long.as_bytes() == name
+            } else {
+                // If the arg has no long name, then compare against its short name
+                n.short
+                    .is_some_and(|s| s.encode_utf8(&mut [0; 4]).as_bytes() == name)
+            }
+        })
         .ok_or_else(|| ShellError::IrEvalError {
             msg: format!(
                 "block does not have an argument named `{}`",