scala/scala — comment on commit 2b731911e97a281e324060099631e2374b2144ec
File: src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala line 721
By hubertp:

Setting error does not always work when we want to backtrack. On the other hand duplicating the tree and setting error on it also fails in other situations when we are working on a tree reference (see some of the Typers functions).

Documenting this stuff would deserve another refactoring step (but considerably smaller one) which atm I don't really have time for. I will add it to my todo.