Ensure input errors can be catched by user of rustc_driver

Author: bjorn3

compiler/rustc_driver/src/lib.rs

@@ -35,7 +35,7 @@ use rustc_session::config::{ErrorOutputType, Input, OutputType, PrintRequest};
 use rustc_session::getopts;
 use rustc_session::lint::{Lint, LintId};
 use rustc_session::{config, DiagnosticOutput, Session};
-use rustc_session::{early_error, early_warn};
+use rustc_session::{early_error, early_error_no_abort, early_warn};
 use rustc_span::source_map::{FileLoader, FileName};
 use rustc_span::symbol::sym;
 
@@ -233,7 +233,8 @@ fn run_compiler(
             if let Some(err) = input_err {
                 // Immediately stop compilation if there was an issue reading
                 // the input (for example if the input stream is not UTF-8).
-                early_error(config.opts.error_format, &err.to_string());
+                early_error_no_abort(config.opts.error_format, &err.to_string());
+                return Err(ErrorReported);
             }
 
             config.input = input;

compiler/rustc_session/src/session.rs

@@ -1637,7 +1637,7 @@ pub enum IncrCompSession {
     InvalidBecauseOfErrors { session_directory: PathBuf },
 }
 
-pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
+pub fn early_error_no_abort(output: config::ErrorOutputType, msg: &str) {
     let emitter: Box<dyn Emitter + sync::Send> = match output {
         config::ErrorOutputType::HumanReadable(kind) => {
             let (short, color_config) = kind.unzip();
@@ -1649,6 +1649,10 @@ pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
     };
     let handler = rustc_errors::Handler::with_emitter(true, None, emitter);
     handler.struct_fatal(msg).emit();
+}
+
+pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
+    early_error_no_abort(output, msg);
     rustc_errors::FatalError.raise();
 }