go/analysis/passes/deepequalerrors: audit for types.Alias safety

Updates golang/go#65294

Change-Id: I00543b00c830ff5a4fe442f1bcf6f21ab0b12d97
Reviewed-on: https://go-review.googlesource.com/c/tools/+/559916
Reviewed-by: Tim King <taking@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

go/analysis/passes/deepequalerrors/deepequalerrors.go

@@ -15,6 +15,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/go/ast/inspector"
 	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/aliases"
 )
 
 const Doc = `check for calls of reflect.DeepEqual on error values
@@ -101,7 +102,8 @@ func containsError(typ types.Type) bool {
 					return true
 				}
 			}
-		case *types.Named:
+		case *types.Named,
+			*aliases.Alias:
 			return check(t.Underlying())
 
 		// We list the remaining valid type kinds for completeness.