Implicit Nothing return type is now deprecated

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

@@ -694,6 +694,8 @@ public interface Errors {
 
     DiagnosticFactory2<JetElement, JetType, JetType> INCOMPATIBLE_TYPES = DiagnosticFactory2.create(ERROR);
 
+    DiagnosticFactory0<PsiElement> IMPLICIT_NOTHING_RETURN_TYPE = DiagnosticFactory0.create(WARNING);
+
     // Context tracking
 
     DiagnosticFactory1<JetExpression, JetExpression> EXPRESSION_EXPECTED = DiagnosticFactory1.create(ERROR);

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

@@ -525,6 +525,7 @@ public class DefaultErrorMessages {
                 RENDER_TYPE);
         MAP.put(TYPE_MISMATCH_IN_CONDITION, "Condition must be of type kotlin.Boolean, but is of type {0}", RENDER_TYPE);
         MAP.put(INCOMPATIBLE_TYPES, "Incompatible types: {0} and {1}", RENDER_TYPE, RENDER_TYPE);
+        MAP.put(IMPLICIT_NOTHING_RETURN_TYPE, "''Nothing'' return type needs to be specified explicitly");
         MAP.put(EXPECTED_CONDITION, "Expected condition of type kotlin.Boolean");
 
         MAP.put(CANNOT_CHECK_FOR_ERASED, "Cannot check for instance of erased type: {0}", RENDER_TYPE);

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

@@ -30,6 +30,7 @@ import org.jetbrains.kotlin.lexer.JetTokens;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.types.*;
 import org.jetbrains.kotlin.types.checker.JetTypeChecker;
+import org.jetbrains.kotlin.types.typeUtil.TypeUtilsKt;
 
 import java.util.*;
 
@@ -641,6 +642,9 @@ public class DeclarationsChecker {
         if (!function.hasBody() && !hasAbstractModifier) {
             trace.report(NON_MEMBER_FUNCTION_NO_BODY.on(function, functionDescriptor));
         }
+        if (TypeUtilsKt.isNothing(functionDescriptor.getReturnType()) && !function.hasDeclaredReturnType()) {
+            trace.report(IMPLICIT_NOTHING_RETURN_TYPE.on(function.getNameIdentifier() != null ? function.getNameIdentifier() : function));
+        }
         checkFunctionExposedType(function, functionDescriptor);
     }
 

compiler/testData/codegen/box/functions/coerceVoidToArray.kt

@@ -1,6 +1,6 @@
 fun a(): IntArray? = null
 
-fun b() = throw Exception()
+fun b(): Nothing = throw Exception()
 
 fun foo(): IntArray = a() ?: b()
 

compiler/testData/codegen/box/functions/coerceVoidToObject.kt

@@ -1,6 +1,6 @@
 fun a(): String? = null
 
-fun b() = throw Exception()
+fun b(): Nothing = throw Exception()
 
 fun foo(): String = a() ?: b()
 

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/commasAndWhitespaces.kt

@@ -6,7 +6,7 @@ fun testCommasAndWhitespaces() {
     <!UNREACHABLE_CODE!>bar(<!> 1 , todo() , <!UNREACHABLE_CODE!>"" )<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 
 
 

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/commentsInDeadCode.kt

@@ -15,7 +15,7 @@ fun test3() {
     <!UNREACHABLE_CODE!>bar(<!>11, l@(todo()/*comment*/), <!UNREACHABLE_CODE!>"")<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 
 fun bar(<!UNUSED_PARAMETER!>i<!>: Int, <!UNUSED_PARAMETER!>s<!>: String, <!UNUSED_PARAMETER!>a<!>: Any) {}
 

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCallInInvokeCall.kt

@@ -8,4 +8,4 @@ fun testInvokeWithLambda() {
     todo()<!UNREACHABLE_CODE!>(1){ 42 }<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCallInReceiver.kt

@@ -8,4 +8,4 @@ fun test12() {
     todo()<!UNNECESSARY_SAFE_CALL!>?.<!><!UNREACHABLE_CODE!>bar(1)<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeFromDifferentSources.kt

@@ -14,7 +14,7 @@ fun test3() {
     <!UNREACHABLE_CODE!>bar()<!>
 }
 
-fun throwNPE() = null!!
+fun throwNPE(): Nothing = null!!
 
 class A {
     operator fun plus(<!UNUSED_PARAMETER!>a<!>: A): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInArrayAccess.kt

@@ -37,4 +37,4 @@ fun testArrayPlusAssign(array: Array<Any>) {
     array[1] <!UNREACHABLE_CODE!>+=<!> todo()
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInAssignment.kt

@@ -15,4 +15,4 @@ fun testPlusAssign() {
 }
 
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInBinaryExpressions.kt

@@ -35,5 +35,5 @@ fun returnInBinary2(): Boolean {
     (return true) <!UNREACHABLE_CODE!>|| (return false)<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 fun bar() {}

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInCalls.kt

@@ -10,4 +10,4 @@ fun testArgumentInVariableAsFunctionCall(f: (Any) -> Unit) {
     f<!UNREACHABLE_CODE!>(<!>todo()<!UNREACHABLE_CODE!>)<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInDeadCode.kt

@@ -21,4 +21,4 @@ fun unreachable4(array: Array<Any>) {
 }
 
 fun bar(a: Any) {}
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInIf.kt

@@ -8,5 +8,5 @@ fun testIf1(b: Boolean) {
     bar()
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 fun bar() {}

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInInnerExpressions.kt

@@ -10,4 +10,4 @@ fun testCompound1() {
     <!UNREACHABLE_CODE!>(<!>todo() <!UNREACHABLE_CODE!>* "")[1]<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInLocalDeclarations.kt

@@ -32,5 +32,5 @@ fun testFunctionDefaultArgument() {
 
 open class Foo(i: Int) {}
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 fun bar() {}

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInLoops.kt

@@ -17,5 +17,5 @@ fun testDoWhile() {
     <!UNREACHABLE_CODE!>bar()<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()
 fun bar() {}

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInReturn.kt

@@ -2,4 +2,4 @@ fun testReturn() {
     <!UNREACHABLE_CODE!>return<!> todo()
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/controlFlowAnalysis/deadCode/deadCodeInUnaryExpr.kt

@@ -12,4 +12,4 @@ fun testPostfixSpecial() {
     todo()<!UNNECESSARY_NOT_NULL_ASSERTION, UNREACHABLE_CODE!>!!<!>
 }
 
-fun todo() = throw Exception()
+fun todo(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/implicitNothing.kt

@@ -0,0 +1,7 @@
+fun <!IMPLICIT_NOTHING_RETURN_TYPE!>foo<!>() = throw Exception()
+
+fun <!IMPLICIT_NOTHING_RETURN_TYPE!>bar<!>() = null!!
+
+fun <!IMPLICIT_NOTHING_RETURN_TYPE!>baz<!>() = bar()
+
+fun gav(): Any = null!!

compiler/testData/diagnostics/tests/implicitNothing.txt

@@ -0,0 +1,6 @@
+package
+
+public fun bar(): kotlin.Nothing
+public fun baz(): kotlin.Nothing
+public fun foo(): kotlin.Nothing
+public fun gav(): kotlin.Any

compiler/testData/diagnostics/tests/inference/kt6175.kt

@@ -45,4 +45,4 @@ fun test4() {
     }
 }
 
-fun fail() = throw Exception()
+fun fail(): Nothing = throw Exception()

compiler/testData/diagnostics/tests/smartCasts/inference/kt4009.kt

@@ -19,4 +19,4 @@ fun foo1(e: PsiElement) {
 }
 
 //from library
-fun println(any: Any?) = throw Exception("$any")
+fun println(any: Any?): Nothing = throw Exception("$any")

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

@@ -265,6 +265,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("implicitNothing.kt")
+        public void testImplicitNothing() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/implicitNothing.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("IncDec.kt")
         public void testIncDec() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/IncDec.kt");

js/js.translator/testData/_commonFiles/asserts.kt

@@ -2,7 +2,7 @@ package kotlin
 // This file should be excluded from tests using StdLib, as these methods conflict with corresponding methods from kotlin.test
 // see StdLibTestBase.removeAdHocAssertions
 
-fun fail(message: String? = null) = throw Exception(message)
+fun fail(message: String? = null): Nothing = throw Exception(message)
 
 fun assertEquals<T>(expected: T, actual: T, message: String? = null) {
     if (expected != actual) {