KT-2484 Type inferred for function literal is (...) -> Int instead of (...) -> Unit, when function literal parameter is explicit

#KT-2484 fixed

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

@@ -135,8 +135,7 @@ public class ClosureExpressionsTypingVisitor extends ExpressionTypingVisitor {
         JetType safeReturnType = returnType == null ? ErrorUtils.createErrorType("<return type>") : returnType;
         functionDescriptor.setReturnType(safeReturnType);
 
-        boolean hasDeclaredValueParameters = functionLiteral.getValueParameterList() != null;
-        if (!hasDeclaredValueParameters && functionTypeExpected) {
+        if (!functionLiteral.hasDeclaredReturnType() && functionTypeExpected) {
             JetType expectedReturnType = JetStandardClasses.getReturnTypeFromFunctionType(expectedType);
             if (JetStandardClasses.isUnit(expectedReturnType)) {
                 functionDescriptor.setReturnType(JetStandardClasses.getUnitType());

compiler/testData/diagnostics/tests/inference/regressions/kt2484.kt

@@ -0,0 +1,23 @@
+//KT-2484 Type inferred for function literal is (...) -> Int instead of (...) -> Unit, when function literal parameter is explicit 
+
+package a
+//+JDK
+import java.util.List
+
+fun <T> Array<T>.forEach(operation: (T) -> Unit) : Unit = for (element in this) operation(element)
+
+fun bar(operation: (String) -> Unit) = operation("")
+
+fun main(args: Array<String>) {
+    args.forEach { (a : String) : Unit -> a.length } // Type mismatch: (String) -> Unit required, (String) -> Int found
+    args.forEach { (a) : Unit -> a.length } // Type mismatch: (String) -> Unit required, (String) -> Int found
+    args.forEach { (a : String) -> a.length } // Type mismatch: (String) -> Unit required, (String) -> Int found
+    args.forEach { a -> a.length } // Type mismatch: (String) -> Unit required, (String) -> Int found
+    args.forEach { it.length }     // This works!
+
+    bar { (a: String) : Unit -> a.length }
+    bar { (a) : Unit -> a.length }
+    bar { (a: String) -> a.length }
+    bar { a -> a.length }
+    bar { it.length }
+}

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

@@ -1380,6 +1380,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                     doTest("compiler/testData/diagnostics/tests/inference/regressions/kt2324.kt");
                 }
                 
+                @TestMetadata("kt2484.kt")
+                public void testKt2484() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/inference/regressions/kt2484.kt");
+                }
+                
                 @TestMetadata("kt2514.kt")
                 public void testKt2514() throws Exception {
                     doTest("compiler/testData/diagnostics/tests/inference/regressions/kt2514.kt");