Underscore names are now forbidden

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -558,7 +558,7 @@ public interface Errors {
 
     DiagnosticFactory1<JetSimpleNameExpression, JetType> COMPARE_TO_TYPE_MISMATCH = DiagnosticFactory1.create(ERROR);
 
-    DiagnosticFactory0<PsiElement> UNDERSCORE_IS_DEPRECATED = DiagnosticFactory0.create(WARNING);
+    DiagnosticFactory0<PsiElement> UNDERSCORE_IS_RESERVED = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory1<PsiElement, String> INVALID_CHARACTERS = DiagnosticFactory1.create(ERROR);
 
     DiagnosticFactory0<PsiElement> INAPPLICABLE_OPERATOR_MODIFIER = DiagnosticFactory0.create(WARNING);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -365,7 +365,7 @@ public class DefaultErrorMessages {
 
         MAP.put(COMPARE_TO_TYPE_MISMATCH, "''compareTo()'' must return kotlin.Int, but returns {0}", RENDER_TYPE);
 
-        MAP.put(UNDERSCORE_IS_DEPRECATED, "Names _, __, ___, ..., are deprecated");
+        MAP.put(UNDERSCORE_IS_RESERVED, "Names _, __, ___, ..., are reserved in Kotlin");
         MAP.put(INVALID_CHARACTERS, "Name {0}", STRING);
 
         MAP.put(INAPPLICABLE_OPERATOR_MODIFIER, "'operator' modifier is inapplicable on this function");

compiler/frontend/src/org/jetbrains/kotlin/resolve/UnderscoreChecker.kt

@@ -30,7 +30,7 @@ object UnderscoreChecker : DeclarationChecker {
     fun checkIdentifier(identifier: PsiElement?, diagnosticHolder: DiagnosticSink) {
         if (identifier == null || identifier.text.isEmpty()) return
         if (identifier.text.all { it == '_' }) {
-            diagnosticHolder.report(Errors.UNDERSCORE_IS_DEPRECATED.on(identifier))
+            diagnosticHolder.report(Errors.UNDERSCORE_IS_RESERVED.on(identifier))
         }
     }
 

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/LazyImportScope.kt

@@ -102,7 +102,7 @@ class LazyImportResolver(
         }
         for ((alias, import) in explicitClassImports.entries()) {
             if (alias.all { it == '_' }) {
-                traceForImportResolve.report(Errors.UNDERSCORE_IS_DEPRECATED.on(import))
+                traceForImportResolve.report(Errors.UNDERSCORE_IS_RESERVED.on(import))
             }
         }
         for (alias in explicitClassImports.keySet()) {