rust: allow any constexpr to be used as param default

Signed-off-by: Gary Guo <[email protected]>

Author: nbdd0121

rust/macros/module.rs

@@ -238,13 +238,23 @@ fn param_ops_path(param_type: &str) -> &'static str {
     }
 }
 
+fn parse_expr(it: &mut Cursor<'_>) -> TokenStream {
+    let mut tt = Vec::new();
+    while !it.eof() {
+        if let Some((punct, _)) = it.punct() {
+            if let ',' | ';' = punct.as_char() {
+                break;
+            }
+        }
+        let (token, next) = it.token_tree().unwrap();
+        tt.push(token);
+        *it = next;
+    }
+    tt.into_iter().collect()
+}
+
 fn expect_simple_param_val(param_type: &str) -> Box<dyn Fn(&mut Cursor<'_>) -> String> {
     match param_type {
-        "bool" => Box::new(|param_it| {
-            let (ident, next) = param_it.ident().expect("Expected ident");
-            *param_it = next;
-            ident.to_string()
-        }),
         "str" => Box::new(|param_it| {
             let s = expect_string(param_it);
             format!(
@@ -253,9 +263,11 @@ fn expect_simple_param_val(param_type: &str) -> Box<dyn Fn(&mut Cursor<'_>) -> S
             )
         }),
         _ => Box::new(|param_it| {
-            let (lit, next) = param_it.literal().expect("Expected literal");
-            *param_it = next;
-            lit.to_string()
+            let expr = parse_expr(param_it);
+            if expr.is_empty() {
+                panic!("Expected expression");
+            }
+            expr.to_string()
         }),
     }
 }