diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala | 16 |
1 files changed, 11 insertions, 5 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala index c6f80c9b20..4b53802d95 100644 --- a/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala +++ b/src/compiler/scala/tools/nsc/typechecker/PatternMatching.scala @@ -3792,11 +3792,17 @@ trait PatternMatching extends Transform with TypingTransformers with ast.TreeDSL // nextBinder: T // next == MatchMonad[U] // returns MatchMonad[U] - def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = - ifThenElseZero(cond, BLOCK( - VAL(nextBinder) === res, - next - )) + def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = { + val rest = + // only emit a local val for `nextBinder` if it's actually referenced in `next` + if (next.exists(_.symbol eq nextBinder)) + BLOCK( + VAL(nextBinder) === res, + next + ) + else next + ifThenElseZero(cond, rest) + } // guardTree: Boolean // next: MatchMonad[T] |