prevent alias name from being filesize or number (#6595)

* prevent alias name from being filesize or number

* add test

* fmt

crates/nu-command/tests/commands/alias.rs

@@ -40,3 +40,25 @@ fn alias_hiding_2() {
 
     assert_eq!(actual.out, "0");
 }
+
+#[test]
+fn alias_fails_with_invalid_name() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            alias 1234 = echo "test"   
+        "#
+    ));
+    assert!(actual
+        .err
+        .contains("alias name can't be a number or a filesize"));
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            alias 5gib = echo "test"   
+        "#
+    ));
+    assert!(actual
+        .err
+        .contains("alias name can't be a number or a filesize"));
+}