Add some more assertions for type relations not used during coherence

compiler/rustc_infer/src/infer/combine.rs

@@ -548,7 +548,7 @@ impl<'tcx> TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
     }
 
     fn mark_ambiguous(&mut self) {
-        self.infcx.tcx.sess.delay_span_bug(self.cause.span, "opaque types are handled in `tys`");
+        self.infcx.tcx.sess.delay_span_bug(self.cause.span, "we only generalize opaque types in situations where we already error for them elsewhere in coherence");
     }
 
     fn binders<T>(
@@ -818,7 +818,8 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
     }
 
     fn intercrate(&self) -> bool {
-        self.infcx.intercrate
+        assert!(!self.infcx.intercrate);
+        false
     }
 
     fn param_env(&self) -> ty::ParamEnv<'tcx> {

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -2938,7 +2938,8 @@ impl<'tcx> TypeRelation<'tcx> for SameTypeModuloInfer<'_, 'tcx> {
     }
 
     fn intercrate(&self) -> bool {
-        self.0.intercrate
+        assert!(!self.0.intercrate);
+        false
     }
 
     fn param_env(&self) -> ty::ParamEnv<'tcx> {

compiler/rustc_infer/src/infer/glb.rs

@@ -31,7 +31,8 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
     }
 
     fn intercrate(&self) -> bool {
-        self.fields.infcx.intercrate
+        assert!(!self.fields.infcx.intercrate);
+        false
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
@@ -47,7 +48,7 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
     }
 
     fn mark_ambiguous(&mut self) {
-        self.fields.mark_ambiguous();
+        bug!("mark_ambiguous used outside of coherence");
     }
 
     fn relate_with_variance<T: Relate<'tcx>>(

compiler/rustc_infer/src/infer/lub.rs

@@ -31,7 +31,8 @@ impl<'tcx> TypeRelation<'tcx> for Lub<'_, '_, 'tcx> {
     }
 
     fn intercrate(&self) -> bool {
-        self.fields.infcx.intercrate
+        assert!(!self.fields.infcx.intercrate);
+        false
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
@@ -47,7 +48,7 @@ impl<'tcx> TypeRelation<'tcx> for Lub<'_, '_, 'tcx> {
     }
 
     fn mark_ambiguous(&mut self) {
-        self.fields.mark_ambiguous();
+        bug!("mark_ambiguous used outside of coherence");
     }
 
     fn relate_with_variance<T: Relate<'tcx>>(

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -914,7 +914,8 @@ where
     }
 
     fn intercrate(&self) -> bool {
-        self.infcx.intercrate
+        assert!(!self.infcx.intercrate);
+        false
     }
 
     fn param_env(&self) -> ty::ParamEnv<'tcx> {