Make arg_expand_all not short-circuit on first error

compiler/rustc_driver_impl/src/args.rs

@@ -4,6 +4,7 @@ use std::fs;
 use std::io;
 
 use rustc_session::EarlyDiagCtxt;
+use rustc_span::ErrorGuaranteed;
 
 /// Expands argfiles in command line arguments.
 #[derive(Default)]
@@ -86,7 +87,7 @@ impl Expander {
     fn read_file(path: &str) -> Result<String, Error> {
         fs::read_to_string(path).map_err(|e| {
             if e.kind() == io::ErrorKind::InvalidData {
-                Error::Utf8Error(Some(path.to_string()))
+                Error::Utf8Error(path.to_string())
             } else {
                 Error::IOError(path.to_string(), e)
             }
@@ -94,23 +95,30 @@ impl Expander {
     }
 }
 
+/// Replaces any `@file` arguments with the contents of `file`, with each line of `file` as a
+/// separate argument.
+///
 /// **Note:** This function doesn't interpret argument 0 in any special way.
 /// If this function is intended to be used with command line arguments,
 /// `argv[0]` must be removed prior to calling it manually.
 #[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-pub fn arg_expand_all(early_dcx: &EarlyDiagCtxt, at_args: &[String]) -> Vec<String> {
+pub fn arg_expand_all(
+    early_dcx: &EarlyDiagCtxt,
+    at_args: &[String],
+) -> Result<Vec<String>, ErrorGuaranteed> {
     let mut expander = Expander::default();
+    let mut result = Ok(());
     for arg in at_args {
         if let Err(err) = expander.arg(arg) {
-            early_dcx.early_fatal(format!("Failed to load argument file: {err}"));
+            result = Err(early_dcx.early_err(format!("failed to load argument file: {err}")));
         }
     }
-    expander.finish()
+    result.map(|()| expander.finish())
 }
 
 #[derive(Debug)]
-pub enum Error {
-    Utf8Error(Option<String>),
+enum Error {
+    Utf8Error(String),
     IOError(String, io::Error),
     ShellParseError(String),
 }
@@ -118,10 +126,9 @@ pub enum Error {
 impl fmt::Display for Error {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Error::Utf8Error(None) => write!(fmt, "Utf8 error"),
-            Error::Utf8Error(Some(path)) => write!(fmt, "Utf8 error in {path}"),
-            Error::IOError(path, err) => write!(fmt, "IO Error: {path}: {err}"),
-            Error::ShellParseError(path) => write!(fmt, "Invalid shell-style arguments in {path}"),
+            Error::Utf8Error(path) => write!(fmt, "UTF-8 error in {path}"),
+            Error::IOError(path, err) => write!(fmt, "IO error: {path}: {err}"),
+            Error::ShellParseError(path) => write!(fmt, "invalid shell-style arguments in {path}"),
         }
     }
 }