refactor: apply for-comprehension to more array-building loops

argparse/parser.mbt

@@ -161,16 +161,13 @@ fn group_usage_expr(
     if group.name != name {
       continue
     }
-    let members = []
-    for member_name in group.args {
-      if args.search_by(arg => arg.name == member_name) is Some(idx) {
-        let item = args[idx]
-        if item.hidden {
-          continue
-        }
-        members.push(arg_usage_token_for_group(item))
-      }
-    }
+    let members = [
+      for member_name in group.args if args.search_by(arg => {
+        arg.name == member_name
+      })
+      is Some(idx) &&
+      !args[idx].hidden => arg_usage_token_for_group(args[idx])
+    ]
     if members.length() == 0 {
       return None
     }

argparse/parser_lookup.mbt

@@ -98,10 +98,7 @@ fn resolve_help_target(
 
 ///|
 fn split_long(arg : String) -> (String, String?) {
-  let parts = []
-  for part in arg.split("=") {
-    parts.push(part.to_string())
-  }
+  let parts = [ for part in arg.split("=") => part.to_string() ]
   if parts.length() <= 1 {
     let name = match parts[0].strip_prefix("--") {
       Some(view) => view.to_string()

env/env_native.mbt

@@ -17,12 +17,9 @@ fn get_cli_args_ffi() -> FixedArray[Bytes] = "$moonbit.get_cli_args"
 
 ///|
 fn get_cli_args_internal() -> Array[String] {
-  let tmp = get_cli_args_ffi()
-  let res = Array::new(capacity=tmp.length())
-  for t in tmp {
-    res.push(utf8_bytes_to_mbt_string(t))
-  }
-  res
+  [
+    for t in get_cli_args_ffi() => utf8_bytes_to_mbt_string(t)
+  ]
 }
 
 ///|

hashset/hashset.mbt

@@ -672,13 +672,11 @@ pub fn[K] HashSet::copy(self : HashSet[K]) -> HashSet[K] {
 ///|
 /// ToJson implementation for hashset
 pub impl[X : ToJson] ToJson for HashSet[X] with to_json(self) {
-  let res = Array::new(capacity=self.size)
-  for entry in self.entries {
-    if entry is Some({ key, .. }) {
-      res.push(key.to_json())
-    }
-  }
-  Json::array(res)
+  Json::array(
+    [
+      for entry in self.entries if entry is Some({ key, .. }) => key.to_json()
+    ],
+  )
 }
 
 ///|

set/linked_hash_set.mbt

@@ -594,11 +594,7 @@ pub fn[K : Hash + Eq] Set::intersection(
 
 ///|
 pub impl[X : ToJson] ToJson for Set[X] with to_json(self) {
-  let res = Array::new(capacity=self.size)
-  for v in self {
-    res.push(v.to_json())
-  }
-  Json::array(res)
+  Json::array([ for v in self => v.to_json() ])
 }
 
 ///|