disable SetDefTreeOff

Author: liufengyun

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -69,8 +69,8 @@ class Compiler {
          new ByNameClosures,         // Expand arguments to by-name parameters to closures
          new HoistSuperArgs,         // Hoist complex arguments of supercalls to enclosing scope
          new ClassOf,                // Expand `Predef.classOf` calls.
-         new RefChecks,              // Various checks mostly related to abstract members and overriding
-         new SetDefTreeOff) ::       // unset `symbol.defTree`
+         new RefChecks) ::           // Various checks mostly related to abstract members and overriding
+         // new SetDefTreeOff) ::       // unset `symbol.defTree`
     List(new ElimOpaque,             // Turn opaque into normal aliases
          new TryCatchPatterns,       // Compile cases in try/catch
          new PatternMatcher,         // Compile pattern matches