From 66577fa6ec07de9769150019deeafb25a1e5422a Mon Sep 17 00:00:00 2001 From: Eugene Burmako Date: Fri, 22 Nov 2013 22:13:44 +0100 Subject: SI-8001 spurious "pure expression does nothing" warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit `isPureExprForWarningPurposes` doesn’t warn on `()`, but `(): Unit` leaves it confused. This patch fixes the problem. The fix is important in the context of the recent split between blackbox and whitebox macros. Macro engines wrap expansions of blackbox macros in type ascriptions, so a macro that expands into `()` would actually produce `(): Unit`, which would trigger a spurious warning. Thanks @milessabin for spotting this problem! --- src/reflect/scala/reflect/internal/TreeInfo.scala | 3 ++- test/files/pos/t8001.check | 0 test/files/pos/t8001.flags | 1 + test/files/pos/t8001/Macros_1.scala | 10 ++++++++++ test/files/pos/t8001/Test_2.scala | 4 ++++ test/files/run/macro-system-properties.check | 6 ------ 6 files changed, 17 insertions(+), 7 deletions(-) create mode 100644 test/files/pos/t8001.check create mode 100644 test/files/pos/t8001.flags create mode 100644 test/files/pos/t8001/Macros_1.scala create mode 100644 test/files/pos/t8001/Test_2.scala diff --git a/src/reflect/scala/reflect/internal/TreeInfo.scala b/src/reflect/scala/reflect/internal/TreeInfo.scala index 8982fd4246..48db8f7bf7 100644 --- a/src/reflect/scala/reflect/internal/TreeInfo.scala +++ b/src/reflect/scala/reflect/internal/TreeInfo.scala @@ -199,7 +199,8 @@ abstract class TreeInfo { * don't reuse it for important matters like inlining * decisions. */ - def isPureExprForWarningPurposes(tree: Tree) = tree match { + def isPureExprForWarningPurposes(tree: Tree): Boolean = tree match { + case Typed(expr, _) => isPureExprForWarningPurposes(expr) case EmptyTree | Literal(Constant(())) => false case _ => def isWarnableRefTree = tree match { diff --git a/test/files/pos/t8001.check b/test/files/pos/t8001.check new file mode 100644 index 0000000000..e69de29bb2 diff --git a/test/files/pos/t8001.flags b/test/files/pos/t8001.flags new file mode 100644 index 0000000000..e8fb65d50c --- /dev/null +++ b/test/files/pos/t8001.flags @@ -0,0 +1 @@ +-Xfatal-warnings \ No newline at end of file diff --git a/test/files/pos/t8001/Macros_1.scala b/test/files/pos/t8001/Macros_1.scala new file mode 100644 index 0000000000..1f8dab51c1 --- /dev/null +++ b/test/files/pos/t8001/Macros_1.scala @@ -0,0 +1,10 @@ +import scala.language.experimental.macros +import scala.reflect.macros.BlackboxContext + +object Macros { + def foo = macro impl + def impl(c: BlackboxContext) = { + import c.universe._ + q"()" + } +} \ No newline at end of file diff --git a/test/files/pos/t8001/Test_2.scala b/test/files/pos/t8001/Test_2.scala new file mode 100644 index 0000000000..6d72d96070 --- /dev/null +++ b/test/files/pos/t8001/Test_2.scala @@ -0,0 +1,4 @@ +object Test extends App { + Macros.foo + (): Unit +} \ No newline at end of file diff --git a/test/files/run/macro-system-properties.check b/test/files/run/macro-system-properties.check index b102d319ec..ea4c5a664a 100644 --- a/test/files/run/macro-system-properties.check +++ b/test/files/run/macro-system-properties.check @@ -14,15 +14,9 @@ scala> object GrabContext { defined object GrabContext scala> object Test { class C(implicit a: Any) { GrabContext.grab } } -:12: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses - object Test { class C(implicit a: Any) { GrabContext.grab } } - ^ defined object Test scala> object Test { class C(implicit a: Any) { GrabContext.grab } } -:12: warning: a pure expression does nothing in statement position; you may be omitting necessary parentheses - object Test { class C(implicit a: Any) { GrabContext.grab } } - ^ defined object Test scala> -- cgit v1.2.3