Merge pull request #4269 from dotty-staging/fix-4217

Fix #4217: display warnings in repl

Author: liufengyun

compiler/src/dotty/tools/repl/ReplDriver.scala

@@ -235,6 +235,9 @@ class ReplDriver(settings: Array[String],
             val newImports = newState.imports ++ extractImports(parsed.trees)
             val newStateWithImports = newState.copy(imports = newImports)
 
+            // display warnings
+            displayErrors(newState.run.runContext.flushBufferedMessages())(newState)
+
             displayDefinitions(unit.tpdTree, newestWrapper)(newStateWithImports)
           }
         }

compiler/test-resources/repl/i4217

@@ -0,0 +1,7 @@
+scala> def foo(x: Option[Int]) = x match { case None => }
+1 | def foo(x: Option[Int]) = x match { case None => }
+  |                           ^
+  |                           match may not be exhaustive.
+  |
+  |                           It would fail on pattern case: Some(_)
+def foo(x: Option[Int]): Unit