1 files changed, 8 insertions, 4 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
index e11a42201..5eef54c63 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
@@ -1,17 +1,17 @@
 use super::{
     ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote, PredicateObligation,
 };
-use crate::infer::InferCtxt;
+use crate::infer::error_reporting::TypeErrCtxt;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::subst::{Subst, SubstsRef};
+use rustc_middle::ty::SubstsRef;
 use rustc_middle::ty::{self, GenericParamDefKind};
 use rustc_span::symbol::sym;
 use std::iter;
 
 use super::InferCtxtPrivExt;
 
-pub trait InferCtxtExt<'tcx> {
+pub trait TypeErrCtxtExt<'tcx> {
     /*private*/
     fn impl_similar_to(
         &self,
@@ -29,7 +29,7 @@ pub trait InferCtxtExt<'tcx> {
     ) -> OnUnimplementedNote;
 }
 
-impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
+impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     fn impl_similar_to(
         &self,
         trait_ref: ty::PolyTraitRef<'tcx>,
@@ -164,6 +164,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             flags.push((sym::from_desugaring, Some(format!("{:?}", k))));
         }
 
+        if let ObligationCauseCode::MainFunctionType = obligation.cause.code() {
+            flags.push((sym::cause, Some("MainFunctionType".to_string())));
+        }
+
         // Add all types without trimmed paths.
         ty::print::with_no_trimmed_paths!({
             let generics = self.tcx.generics_of(def_id);