Reorder fullfillment errors to keep more interesting ones first

In `report_fullfillment_errors` push back `T: Sized`, `T: WellFormed`
and coercion errors to the end of the list. The pre-existing
deduplication logic eliminates redundant errors better that way, keeping
the resulting output with fewer errors than before, while also having
more detail.

Author: estebank

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -368,7 +368,7 @@ fn check_opaque_type_well_formed<'tcx>(
     if errors.is_empty() {
         Ok(definition_ty)
     } else {
-        Err(infcx.err_ctxt().report_fulfillment_errors(&errors))
+        Err(infcx.err_ctxt().report_fulfillment_errors(errors))
     }
 }
 

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -742,7 +742,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                 let errors = ocx.select_all_or_error();
                 if !errors.is_empty() {
-                    infcx.err_ctxt().report_fulfillment_errors(&errors);
+                    infcx.err_ctxt().report_fulfillment_errors(errors);
                 }
 
                 // Attempting to call a trait method?

compiler/rustc_hir_analysis/src/check/check.rs

@@ -456,7 +456,7 @@ fn check_opaque_meets_bounds<'tcx>(
     // version.
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        let guar = infcx.err_ctxt().report_fulfillment_errors(&errors);
+        let guar = infcx.err_ctxt().report_fulfillment_errors(errors);
         return Err(guar);
     }
     match origin {
@@ -1641,6 +1641,6 @@ pub(super) fn check_generator_obligations(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let errors = fulfillment_cx.select_all_or_error(&infcx);
     debug!(?errors);
     if !errors.is_empty() {
-        infcx.err_ctxt().report_fulfillment_errors(&errors);
+        infcx.err_ctxt().report_fulfillment_errors(errors);
     }
 }

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -322,7 +322,7 @@ fn compare_method_predicate_entailment<'tcx>(
         // FIXME(-Ztrait-solver=next): Not needed when the hack below is removed.
         let errors = ocx.select_where_possible();
         if !errors.is_empty() {
-            let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
+            let reported = infcx.err_ctxt().report_fulfillment_errors(errors);
             return Err(reported);
         }
 
@@ -393,7 +393,7 @@ fn compare_method_predicate_entailment<'tcx>(
                 });
             }
             CheckImpliedWfMode::Skip => {
-                let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
+                let reported = infcx.err_ctxt().report_fulfillment_errors(errors);
                 return Err(reported);
             }
         }
@@ -873,7 +873,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     // RPITs.
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
+        let reported = infcx.err_ctxt().report_fulfillment_errors(errors);
         return Err(reported);
     }
 
@@ -2049,7 +2049,7 @@ fn compare_const_predicate_entailment<'tcx>(
     // version.
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        return Err(infcx.err_ctxt().report_fulfillment_errors(&errors));
+        return Err(infcx.err_ctxt().report_fulfillment_errors(errors));
     }
 
     let outlives_env = OutlivesEnvironment::new(param_env);
@@ -2142,7 +2142,7 @@ fn compare_type_predicate_entailment<'tcx>(
     // version.
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
+        let reported = infcx.err_ctxt().report_fulfillment_errors(errors);
         return Err(reported);
     }
 
@@ -2357,7 +2357,7 @@ pub(super) fn check_type_bounds<'tcx>(
     // version.
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        let reported = infcx.err_ctxt().report_fulfillment_errors(&errors);
+        let reported = infcx.err_ctxt().report_fulfillment_errors(errors);
         return Err(reported);
     }
 

compiler/rustc_hir_analysis/src/check/entry.rs

@@ -158,7 +158,7 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
         ocx.register_bound(cause, param_env, norm_return_ty, term_did);
         let errors = ocx.select_all_or_error();
         if !errors.is_empty() {
-            infcx.err_ctxt().report_fulfillment_errors(&errors);
+            infcx.err_ctxt().report_fulfillment_errors(errors);
             error = true;
         }
         // now we can take the return type of the given main function

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -577,7 +577,7 @@ pub fn check_function_signature<'tcx>(
         Ok(()) => {
             let errors = ocx.select_all_or_error();
             if !errors.is_empty() {
-                infcx.err_ctxt().report_fulfillment_errors(&errors);
+                infcx.err_ctxt().report_fulfillment_errors(errors);
                 return;
             }
         }

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -113,7 +113,7 @@ pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
 
     let errors = wfcx.select_all_or_error();
     if !errors.is_empty() {
-        infcx.err_ctxt().report_fulfillment_errors(&errors);
+        infcx.err_ctxt().report_fulfillment_errors(errors);
         return;
     }
 

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -279,7 +279,7 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
                 }
                 let errors = ocx.select_all_or_error();
                 if !errors.is_empty() {
-                    infcx.err_ctxt().report_fulfillment_errors(&errors);
+                    infcx.err_ctxt().report_fulfillment_errors(errors);
                 }
 
                 // Finally, resolve all regions.
@@ -519,7 +519,7 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) -> Coe
     ocx.register_obligation(obligation);
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        infcx.err_ctxt().report_fulfillment_errors(&errors);
+        infcx.err_ctxt().report_fulfillment_errors(errors);
     }
 
     // Finally, resolve all regions.

compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs

@@ -196,7 +196,7 @@ fn get_impl_args(
 
     let errors = ocx.select_all_or_error();
     if !errors.is_empty() {
-        let guar = ocx.infcx.err_ctxt().report_fulfillment_errors(&errors);
+        let guar = ocx.infcx.err_ctxt().report_fulfillment_errors(errors);
         return Err(guar);
     }
 

compiler/rustc_hir_typeck/src/expr.rs

@@ -3010,7 +3010,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // There should be at least one error reported. If not, we
             // will still delay a span bug in `report_fulfillment_errors`.
             Ok::<_, NoSolution>((
-                self.err_ctxt().report_fulfillment_errors(&errors),
+                self.err_ctxt().report_fulfillment_errors(errors),
                 impl_trait_ref.args.type_at(1),
                 element_ty,
             ))