Enable control flow checks for functions without body

Except checks for tail recursive calls

 #KT-7796 Fixed

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2016 JetBrains s.r.o.
+ * Copyright 2010-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -879,6 +879,7 @@ class ControlFlowInformationProvider private constructor(
 
     private fun markAndCheckRecursiveTailCalls(subroutineDescriptor: FunctionDescriptor) {
         if (!subroutineDescriptor.isTailrec) return
+        if (subroutine is KtNamedFunction && !subroutine.hasBody()) return
 
         // finally blocks are copied which leads to multiple diagnostics reported on one instruction
         class KindAndCall(var kind: TailRecursionKind, internal val call: ResolvedCall<*>)

compiler/frontend/src/org/jetbrains/kotlin/resolve/ControlFlowAnalyzer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2017 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -103,7 +103,6 @@ public class ControlFlowAnalyzer {
     }
 
     private void checkFunction(@NotNull BodiesResolveContext c, @NotNull KtDeclarationWithBody function, @Nullable KotlinType expectedReturnType) {
-        if (!function.hasBody()) return;
         ControlFlowInformationProvider controlFlowInformationProvider =
                 new ControlFlowInformationProvider(function, trace, languageVersionSettings);
         if (c.getTopDownAnalysisMode().isLocalDeclarations()) {

compiler/testData/diagnostics/tests/DefaultValuesCheckWithoutBody.kt

@@ -0,0 +1,9 @@
+interface Inter {
+    fun foo(x: Int = <!UNINITIALIZED_PARAMETER!>y<!>, y: Int = x)
+}
+
+abstract class Abst {
+    abstract fun foo(x: Int = <!UNINITIALIZED_PARAMETER!>y<!>, y: Int = x)
+}
+
+<!NON_MEMBER_FUNCTION_NO_BODY!>fun extraDiagnostics(<!UNUSED_PARAMETER!>x<!>: Int = <!UNINITIALIZED_PARAMETER!>y<!>, <!UNUSED_PARAMETER!>y<!>: Int)<!>

compiler/testData/diagnostics/tests/DefaultValuesCheckWithoutBody.txt

@@ -0,0 +1,18 @@
+package
+
+public fun extraDiagnostics(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.Int): kotlin.Unit
+
+public abstract class Abst {
+    public constructor Abst()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface Inter {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(/*0*/ x: kotlin.Int = ..., /*1*/ y: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -188,6 +188,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("DefaultValuesCheckWithoutBody.kt")
+        public void testDefaultValuesCheckWithoutBody() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/DefaultValuesCheckWithoutBody.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("DefaultValuesTypechecking.kt")
         public void testDefaultValuesTypechecking() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/DefaultValuesTypechecking.kt");