Remove impl TryFrom<ProcessState> for ExitStatus

The conversion from ProcessState to ExitStatus is now done by the
System trait as it depends on the system implementation. This commit
removes the TryFrom implementation and replaces it with a call to
System::exit_status_for_process_state.

yash-builtin/src/fg.rs

@@ -92,7 +92,6 @@ use yash_env::job::id::parse;
 use yash_env::job::JobList;
 use yash_env::job::Pid;
 use yash_env::job::ProcessState;
-use yash_env::semantics::ExitStatus;
 use yash_env::semantics::Field;
 use yash_env::system::Errno;
 use yash_env::system::System as _;
@@ -189,7 +188,11 @@ pub async fn main(env: &mut Env, args: Vec<Field>) -> crate::Result {
     };
 
     match result {
-        Ok(state) => ExitStatus::try_from(state).unwrap().into(),
+        Ok(state) => env
+            .system
+            .exit_status_for_process_state(state)
+            .unwrap()
+            .into(),
         Err(error) => report_simple_failure(env, &error.to_string()).await,
     }
 }
@@ -208,6 +211,7 @@ mod tests {
     use yash_env::job::ProcessState;
     use yash_env::option::Option::Monitor;
     use yash_env::option::State::On;
+    use yash_env::semantics::ExitStatus;
     use yash_env::subshell::JobControl;
     use yash_env::subshell::Subshell;
     use yash_env::system::r#virtual::Process;

yash-env/src/job.rs

@@ -141,28 +141,6 @@ impl ProcessState {
     }
 }
 
-/// Error value indicating that the process is running.
-///
-/// This error value may be returned by [`TryFrom<ProcessState>::try_from`].
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
-pub struct RunningProcess;
-
-/// Converts `ProcessState` to `ExitStatus`.
-///
-/// For the `Running` state, the conversion fails with [`RunningProcess`].
-impl TryFrom<ProcessState> for ExitStatus {
-    type Error = RunningProcess;
-    fn try_from(state: ProcessState) -> Result<Self, RunningProcess> {
-        match state {
-            ProcessState::Exited(exit_status) => Ok(exit_status),
-            ProcessState::Signaled { signal, .. } | ProcessState::Stopped(signal) => {
-                Ok(ExitStatus::from(signal))
-            }
-            ProcessState::Running => Err(RunningProcess),
-        }
-    }
-}
-
 /// Set of one or more processes executing a pipeline
 ///
 /// In the current implementation, a job contains the process ID of one child

yash-env/src/lib.rs

@@ -361,7 +361,8 @@ impl Env {
         loop {
             let (pid, state) = self.wait_for_subshell(target).await?;
             if !state.is_alive() {
-                return Ok((pid, state.try_into().unwrap()));
+                let exit_status = self.system.exit_status_for_process_state(state).unwrap();
+                return Ok((pid, exit_status));
             }
         }
     }

yash-semantics/src/command/compound_command/subshell.rs

@@ -28,6 +28,7 @@ use yash_env::semantics::ExitStatus;
 use yash_env::semantics::Result;
 use yash_env::subshell::JobControl;
 use yash_env::subshell::Subshell;
+use yash_env::system::SystemEx as _;
 use yash_env::Env;
 use yash_syntax::source::Location;
 use yash_syntax::syntax::List;
@@ -47,7 +48,7 @@ pub async fn execute(env: &mut Env, body: Rc<List>, location: &Location) -> Resu
                 env.jobs.add(job);
             }
 
-            env.exit_status = state.try_into().unwrap();
+            env.exit_status = env.system.exit_status_for_process_state(state).unwrap();
             env.apply_errexit()
         }
         Err(errno) => {

yash-semantics/src/command/pipeline.rs

@@ -36,7 +36,7 @@ use yash_env::subshell::JobControl;
 use yash_env::subshell::Subshell;
 use yash_env::system::Errno;
 use yash_env::system::FdFlag;
-use yash_env::system::SystemEx;
+use yash_env::system::SystemEx as _;
 use yash_env::Env;
 use yash_env::System;
 use yash_syntax::syntax;
@@ -152,7 +152,7 @@ async fn execute_job_controlled_pipeline(
                 env.jobs.add(job);
             }
 
-            env.exit_status = state.try_into().unwrap();
+            env.exit_status = env.system.exit_status_for_process_state(state).unwrap();
             Continue(())
         }
         Err(errno) => {

yash-semantics/src/command/simple_command/absent.rs

@@ -32,6 +32,7 @@ use yash_env::semantics::ExitStatus;
 use yash_env::semantics::Result;
 use yash_env::subshell::JobControl;
 use yash_env::subshell::Subshell;
+use yash_env::system::SystemEx as _;
 use yash_env::Env;
 use yash_syntax::syntax::Assign;
 use yash_syntax::syntax::Redir;
@@ -81,7 +82,7 @@ pub async fn execute_absent_target(
                     env.jobs.add(job);
                 }
 
-                state.try_into().unwrap()
+                env.system.exit_status_for_process_state(state).unwrap()
             }
             Err(errno) => {
                 print_error(

yash-semantics/src/command/simple_command/external.rs

@@ -34,6 +34,7 @@ use yash_env::semantics::Result;
 use yash_env::subshell::JobControl;
 use yash_env::subshell::Subshell;
 use yash_env::system::Errno;
+use yash_env::system::SystemEx as _;
 use yash_env::variable::Context;
 use yash_env::Env;
 use yash_env::System;
@@ -120,7 +121,7 @@ pub async fn start_external_utility_in_subshell_and_wait(
                 env.jobs.add(job);
             }
 
-            state.try_into().unwrap()
+            env.system.exit_status_for_process_state(state).unwrap()
         }
         Err(errno) => {
             print_error(