Move OutFileName writing into rustc_session

compiler/rustc_session/messages.ftl

@@ -26,6 +26,8 @@ session_feature_gate_error = {$explain}
 
 session_file_is_not_writeable = output file {$file} is not writeable -- check its permissions
 
+session_file_write_fail = failed to write `{$path}` due to error `{$err}`
+
 session_hexadecimal_float_literal_not_supported = hexadecimal float literal is not supported
 
 session_incompatible_linker_flavor = linker flavor `{$flavor}` is incompatible with the current target

compiler/rustc_session/src/config.rs

@@ -3,6 +3,7 @@
 
 pub use crate::options::*;
 
+use crate::errors::FileWriteFail;
 use crate::search_paths::SearchPath;
 use crate::utils::{CanonicalizedPath, NativeLib, NativeLibKind};
 use crate::{lint, HashStableContext};
@@ -31,6 +32,7 @@ use std::collections::btree_map::{
 use std::collections::{BTreeMap, BTreeSet};
 use std::ffi::OsStr;
 use std::fmt;
+use std::fs;
 use std::hash::Hash;
 use std::iter;
 use std::path::{Path, PathBuf};
@@ -861,6 +863,17 @@ impl OutFileName {
             OutFileName::Stdout => outputs.temp_path(flavor, codegen_unit_name),
         }
     }
+
+    pub fn overwrite(&self, content: &str, sess: &Session) {
+        match self {
+            OutFileName::Stdout => print!("{content}"),
+            OutFileName::Real(path) => {
+                if let Err(e) = fs::write(path, content) {
+                    sess.emit_fatal(FileWriteFail { path, err: e.to_string() });
+                }
+            }
+        }
+    }
 }
 
 #[derive(Clone, Hash, Debug, HashStable_Generic)]

compiler/rustc_session/src/errors.rs

@@ -163,6 +163,13 @@ pub struct FileIsNotWriteable<'a> {
     pub file: &'a std::path::Path,
 }
 
+#[derive(Diagnostic)]
+#[diag(session_file_write_fail)]
+pub(crate) struct FileWriteFail<'a> {
+    pub path: &'a std::path::Path,
+    pub err: String,
+}
+
 #[derive(Diagnostic)]
 #[diag(session_crate_name_does_not_match)]
 pub struct CrateNameDoesNotMatch {