expr: fix escape

src/uu/expr/src/tokens.rs

@@ -16,8 +16,6 @@
 
 // spell-checker:ignore (ToDO) paren
 
-use num_bigint::BigInt;
-
 #[derive(Debug, Clone)]
 pub enum Token {
     Value {
@@ -59,11 +57,8 @@ impl Token {
         }
     }
 
-    fn is_a_number(&self) -> bool {
-        match self {
-            Self::Value { value, .. } => value.parse::<BigInt>().is_ok(),
-            _ => false,
-        }
+    fn is_a_value(&self) -> bool {
+        matches!(*self, Self::Value { .. })
     }
 
     fn is_a_close_paren(&self) -> bool {
@@ -131,14 +126,14 @@ fn maybe_dump_tokens_acc(tokens_acc: &[(usize, Token)]) {
 }
 
 fn push_token_if_not_escaped(acc: &mut Vec<(usize, Token)>, tok_idx: usize, token: Token, s: &str) {
-    // Smells heuristics... :(
+    // `+` may escaped such as `expr + 1` and `expr 1 + + 1`
     let prev_is_plus = match acc.last() {
         None => false,
         Some(t) => t.1.is_infix_plus(),
     };
     let should_use_as_escaped = if prev_is_plus && acc.len() >= 2 {
         let pre_prev = &acc[acc.len() - 2];
-        !(pre_prev.1.is_a_number() || pre_prev.1.is_a_close_paren())
+        !(pre_prev.1.is_a_value() || pre_prev.1.is_a_close_paren())
     } else {
         prev_is_plus
     };