From e325ad24f2ef170b2913d97a69da38ca664cb621 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 23 Dec 2019 17:44:02 +0100
Subject: [PATCH] support main functions with Result return type

---
 src/eval.rs                   | 5 ++---
 tests/run-pass/main_result.rs | 3 +++
 2 files changed, 5 insertions(+), 3 deletions(-)
 create mode 100644 tests/run-pass/main_result.rs

diff --git a/src/eval.rs b/src/eval.rs
index 4ed1b272b228..0cc302b967b2 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -62,9 +62,8 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
     // Setup first stack-frame
     let main_instance = ty::Instance::mono(tcx, main_id);
     let main_mir = ecx.load_mir(main_instance.def, None)?;
-
-    if !main_mir.return_ty().is_unit() || main_mir.arg_count != 0 {
-        throw_unsup_format!("miri does not support main functions without `fn()` type signatures");
+    if main_mir.arg_count != 0 {
+        bug!("main function must not take any arguments");
     }
 
     let start_id = tcx.lang_items().start_fn().unwrap();
diff --git a/tests/run-pass/main_result.rs b/tests/run-pass/main_result.rs
new file mode 100644
index 000000000000..078760ee6667
--- /dev/null
+++ b/tests/run-pass/main_result.rs
@@ -0,0 +1,3 @@
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    Ok(())
+}