Stub trim implementation

yash-semantics/src/expansion/initial/param.rs

@@ -47,6 +47,7 @@ impl<'a> From<&'a Param> for ParamRef<'a> {
 mod name;
 mod resolve;
 mod switch;
+mod trim;
 
 use resolve::Resolve;
 pub use switch::EmptyError;
@@ -70,24 +71,31 @@ impl ParamRef<'_> {
         let mut value = resolve.into_owned();
 
         // Switch //
-        if let Modifier::Switch(switch) = &self.modifier {
+        if let Modifier::Switch(switch) = self.modifier {
             if let Some(result) = switch::apply(env, switch, name, &mut value, self.location).await
             {
                 return result;
             }
         }
 
         // TODO Check for nounset error
-        // TODO Trim & Subst
-
-        // Length modifier //
-        if *self.modifier == Modifier::Length {
-            // TODO Reject ${#*} and ${#@} in POSIX mode
-            match &mut value {
-                None => (),
-                Some(Value::Scalar(v)) => to_length(v),
-                Some(Value::Array(vs)) => vs.iter_mut().for_each(to_length),
+        // TODO Reject POSIXly unspecified combinations of name and modifier
+
+        // Other modifiers //
+        match self.modifier {
+            Modifier::None | Modifier::Switch(_) => (),
+
+            Modifier::Length => {
+                // TODO Reject ${#*} and ${#@} in POSIX mode
+                match &mut value {
+                    None => (),
+                    Some(Value::Scalar(v)) => to_length(v),
+                    Some(Value::Array(vs)) => vs.iter_mut().for_each(to_length),
+                }
             }
+
+            Modifier::Trim(trim) => trim::apply(env, trim, &mut value).await?,
+            // TODO Modifier::Subst
         }
 
         let mut phrase = into_phrase(value);

yash-semantics/src/expansion/initial/param/trim.rs

@@ -0,0 +1,31 @@
+// This file is part of yash, an extended POSIX shell.
+// Copyright (C) 2022 WATANABE Yuki
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+//! Parameter expansion trim semantics
+
+use super::Env;
+use super::Error;
+use yash_env::variable::Value;
+use yash_syntax::syntax::Trim;
+
+/// Applies the trim modifier to the value.
+pub async fn apply(
+    _env: &mut Env<'_>,
+    _trim: &Trim,
+    _value: &mut Option<Value>,
+) -> Result<(), Error> {
+    Ok(()) // TODO
+}