SI-8849 Makes `ExecutionContext.Implicits.global` ambiguous

There was an unfortunate side-effect from having `Implicits.global` be
of type `ExecutionContextExecutor`; it is more specific than `ExecutionContext`,
as such it would be picked over other `ExecutionContexts` in the implicit scope.

1 files changed, 10 insertions, 0 deletions

diff --git a/test/files/neg/t8849.scala b/test/files/neg/t8849.scala
new file mode 100644
index 0000000000..336f16b40f
--- /dev/null
+++ b/test/files/neg/t8849.scala
@@ -0,0 +1,10 @@
+import scala.concurrent.ExecutionContext
+import ExecutionContext.Implicits.global
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    implicit val dummy: ExecutionContext = null
+    require(scala.concurrent.ExecutionContext.Implicits.global ne null)
+    require(implicitly[ExecutionContext] eq dummy)
+  }
+}
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