Report warning on modifier list of primary ctor unless 'constructor' keyword specified

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

@@ -159,6 +159,8 @@ public interface Errors {
     DiagnosticFactory0<JetNullableType> NULLABLE_SUPERTYPE = DiagnosticFactory0.create(ERROR, NULLABLE_TYPE);
     DiagnosticFactory0<JetTypeReference> DYNAMIC_SUPERTYPE = DiagnosticFactory0.create(ERROR);
 
+    DiagnosticFactory0<JetElement> MISSING_CONSTRUCTOR_KEYWORD = DiagnosticFactory0.create(WARNING);
+
     // Secondary constructors
 
     DiagnosticFactory0<JetConstructorDelegationReferenceExpression> CYCLIC_CONSTRUCTOR_DELEGATION_CALL = DiagnosticFactory0.create(ERROR);

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

@@ -442,6 +442,8 @@ public class DefaultErrorMessages {
         MAP.put(SMARTCAST_IMPOSSIBLE,
                 "Smart cast to ''{0}'' is impossible, because ''{1}'' could have changed since the is-check", RENDER_TYPE, STRING);
 
+        MAP.put(MISSING_CONSTRUCTOR_KEYWORD, "Use 'constructor' keyword after modifiers of primary constructor");
+
         MAP.put(VARIANCE_ON_TYPE_PARAMETER_OF_FUNCTION_OR_PROPERTY, "Variance annotations are only allowed for type parameters of classes and interfaces");
         MAP.put(TYPE_VARIANCE_CONFLICT, "Type parameter {0} is declared as ''{1}'' but occurs in ''{2}'' position in type {3}",
                 new MultiRenderer<VarianceConflictDiagnosticData>() {

compiler/frontend/src/org/jetbrains/kotlin/psi/JetPrimaryConstructor.java

@@ -82,4 +82,9 @@ public class JetPrimaryConstructor extends JetDeclarationStub<KotlinPlaceHolderS
         assert classOrNull != null : "This method should be called when parent is JetClass";
         return classOrNull;
     }
+
+    public boolean hasConstructorKeyword() {
+        if (getStub() != null) return true;
+        return findChildByType(JetTokens.CONSTRUCTOR_KEYWORD) != null;
+    }
 }

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

@@ -282,6 +282,10 @@ public class DeclarationsChecker {
             }
         }
 
+        if (declaration.getModifierList() != null && !declaration.hasConstructorKeyword()) {
+            trace.report(MISSING_CONSTRUCTOR_KEYWORD.on(declaration.getModifierList()));
+        }
+
         checkConstructorDeclaration(primaryConstructor, declaration);
     }
 

compiler/testData/diagnostics/tests/modifiers/primaryConstructorMissingKeyword.kt

@@ -0,0 +1,9 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+annotation class Ann(val x: Int = 1)
+class A <!MISSING_CONSTRUCTOR_KEYWORD!>private<!> (val x: Int) {
+inner class B <!MISSING_CONSTRUCTOR_KEYWORD!>Ann(2)<!> (val y: Int)
+
+fun foo() {
+    class C <!MISSING_CONSTRUCTOR_KEYWORD!>private @Ann(3)<!> (args: Int)
+    }
+}

compiler/testData/diagnostics/tests/modifiers/primaryConstructorMissingKeyword.txt

@@ -0,0 +1,26 @@
+package
+
+internal final class A {
+    private constructor A(/*0*/ x: kotlin.Int)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal final fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    internal final inner class B {
+        Ann(x = IntegerValueType(2): IntegerValueType(2)) public constructor B(/*0*/ y: kotlin.Int)
+        internal final val y: kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
+
+internal final annotation class Ann : kotlin.Annotation {
+    public constructor Ann(/*0*/ x: kotlin.Int = ...)
+    internal final val x: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    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/JetDiagnosticsTestGenerated.java

@@ -7659,6 +7659,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("primaryConstructorMissingKeyword.kt")
+            public void testPrimaryConstructorMissingKeyword() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/modifiers/primaryConstructorMissingKeyword.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("repeatedModifiers.kt")
             public void testRepeatedModifiers() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/modifiers/repeatedModifiers.kt");