scala/bug#10719 is an example where a settings.future check was left in place longer than it should have been

for 2.13, we should at least audit all such checks that remain in the codebase

and perhaps once that audit is complete we'll find we can eliminate -Xfuture entirely; I bet we will

this is really just a piece of #430, but it's a nice manageable piece for a volunteer to tackle

• Octal scape literal (https://github.com/scala/scala/blob/v2.13.0-M3/src/compiler/scala/tools/nsc/ast/parser/Scanners.scala#L874-L876)
• View bounds (https://github.com/scala/scala/blob/v2.13.0-M3/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala#L2424-L2426)
• Procedure syntax (https://github.com/scala/scala/blob/v2.13.0-M3/src/compiler/scala/tools/nsc/ast/parser/Parsers.scala#L2723-L2735)
• Adaptation of nullary method (https://github.com/scala/scala/blob/v2.13.0-M4/src/compiler/scala/tools/nsc/typechecker/Adaptations.scala#L71-L86)
• Unsound type for ident/literal patterns (https://github.com/scala/scala/blob/v2.13.0-M3/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala#L37-L65)