Fix CANNOT_CHECK_FOR_ERASED for when()

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/PatternMatchingTypingVisitor.java

@@ -214,6 +214,9 @@ public class PatternMatchingTypingVisitor extends ExpressionTypingVisitor {
                 if (typeReference == null) return;
                 JetType type = context.expressionTypingServices.getTypeResolver().resolveType(context.scope, typeReference, context.trace, true);
                 checkTypeCompatibility(type, subjectType, typePattern);
+                if (BasicExpressionTypingVisitor.isCastErased(subjectType, type, JetTypeChecker.INSTANCE)) {
+                    context.trace.report(Errors.CANNOT_CHECK_FOR_ERASED.on(typeReference, type));
+                }
                 result.set(Pair.create(context.dataFlowInfo.establishSubtyping(subjectVariables, type), context.dataFlowInfo));
             }
 
@@ -334,10 +337,6 @@ public class PatternMatchingTypingVisitor extends ExpressionTypingVisitor {
                 if (type == JetStandardClasses.getNullableNothingType() && !subjectType.isNullable()) {
                     context.trace.report(SENSELESS_NULL_IN_WHEN.on(reportErrorOn));
                 }
-
-                if (BasicExpressionTypingVisitor.isCastErased(subjectType, type, JetTypeChecker.INSTANCE)) {
-                    context.trace.report(Errors.CANNOT_CHECK_FOR_ERASED.on(reportErrorOn, type));
-                }
             }
 
             @Override

compiler/testData/diagnostics/tests/cast/WhenWithExpression.kt

@@ -0,0 +1,9 @@
+enum class List<out T>(val size : Int) {
+    Nil : List<Nothing>(0)
+}
+
+fun List<String>.join() =
+        when (this) {
+            List.Nil -> "[]" // CANNOT_CHECK_FOR_ERASED was reported
+            else -> ""
+        }

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -183,16 +183,16 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
             doTest("compiler/testData/diagnostics/tests/DelegationNotTotrait.kt");
         }
         
-        @TestMetadata("Delegation_ScopeInitializationOrder.kt")
-        public void testDelegation_ScopeInitializationOrder() throws Exception {
-            doTest("compiler/testData/diagnostics/tests/Delegation_ScopeInitializationOrder.kt");
-        }
-
         @TestMetadata("DelegationToJavaIface.kt")
         public void testDelegationToJavaIface() throws Exception {
             doTest("compiler/testData/diagnostics/tests/DelegationToJavaIface.kt");
         }
         
+        @TestMetadata("Delegation_ScopeInitializationOrder.kt")
+        public void testDelegation_ScopeInitializationOrder() throws Exception {
+            doTest("compiler/testData/diagnostics/tests/Delegation_ScopeInitializationOrder.kt");
+        }
+        
         @TestMetadata("DiamondFunction.kt")
         public void testDiamondFunction() throws Exception {
             doTest("compiler/testData/diagnostics/tests/DiamondFunction.kt");
@@ -740,6 +740,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                 doTest("compiler/testData/diagnostics/tests/cast/WhenErasedDisallowFromAny.kt");
             }
             
+            @TestMetadata("WhenWithExpression.kt")
+            public void testWhenWithExpression() throws Exception {
+                doTest("compiler/testData/diagnostics/tests/cast/WhenWithExpression.kt");
+            }
+            
         }
         
         @TestMetadata("compiler/testData/diagnostics/tests/checkArguments")