Make infix modifier diagnostic message more informative (KT-12589)

(cherry picked from commit 2744309)

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/java/descriptors/JavaMethodDescriptor.java

@@ -87,7 +87,7 @@ public class JavaMethodDescriptor extends SimpleFunctionDescriptorImpl implement
         SimpleFunctionDescriptorImpl descriptor = super.initialize(
                 receiverParameterType, dispatchReceiverParameter, typeParameters, unsubstitutedValueParameters,
                 unsubstitutedReturnType, modality, visibility);
-        setOperator(OperatorChecks.INSTANCE.checkOperator(descriptor).isSuccess());
+        setOperator(OperatorChecks.INSTANCE.check(descriptor).isSuccess());
         return descriptor;
     }
 

core/descriptors/src/org/jetbrains/kotlin/util/modifierChecks.kt

@@ -68,11 +68,11 @@ interface Check {
 }
 
 sealed class MemberKindCheck(override val description: String) : Check {
-    object MemberOrExtension : MemberKindCheck("must be a member or an extension") {
+    object MemberOrExtension : MemberKindCheck("must be a member or an extension function") {
         override fun check(functionDescriptor: FunctionDescriptor) =
                 functionDescriptor.isExtension || functionDescriptor.containingDeclaration is ClassDescriptor
     }
-    object Member : MemberKindCheck("must be a member") {
+    object Member : MemberKindCheck("must be a member function") {
         override fun check(functionDescriptor: FunctionDescriptor) = functionDescriptor.containingDeclaration is ClassDescriptor
     }
 }
@@ -92,6 +92,13 @@ sealed class ValueParameterCountCheck(override val description: String) : Check
     }
 }
 
+private object HasDispatchOrExtensionReceiverParameter : Check {
+    override val description = "must be a member of an extension function"
+    override fun check(functionDescriptor: FunctionDescriptor): Boolean {
+        return functionDescriptor.dispatchReceiverParameter != null || functionDescriptor.extensionReceiverParameter != null
+    }
+}
+
 private object NoDefaultAndVarargsCheck : Check {
     override val description = "should not have varargs or parameters with default values"
     override fun check(functionDescriptor: FunctionDescriptor) =
@@ -120,7 +127,7 @@ sealed class ReturnsCheck(val name: String, val type: KotlinBuiltIns.() -> Kotli
     object ReturnsUnit : ReturnsCheck("Unit", { unitType })
 }
 
-private class Checks private constructor(
+internal class Checks private constructor(
         val name: Name?,
         val regex: Regex?,
         val nameList: Collection<Name>?,
@@ -150,6 +157,8 @@ private class Checks private constructor(
         return CheckResult.SuccessCheck
     }
 
+    constructor(vararg checks: Check, additionalChecks: FunctionDescriptor.() -> String? = { null })
+            : this(null, null, null, additionalChecks, *checks)
     constructor(name: Name, vararg checks: Check, additionalChecks: FunctionDescriptor.() -> String? = { null })
             : this(name, null, null, additionalChecks, *checks)
     constructor(regex: Regex, vararg checks: Check, additionalChecks: FunctionDescriptor.() -> String? = { null })
@@ -158,10 +167,23 @@ private class Checks private constructor(
             : this(null, null, nameList, additionalChecks, *checks)
 }
 
-object OperatorChecks {
-    private inline fun ensure(cond: Boolean, msg: () -> String) = if (!cond) msg() else null
+abstract class AbstractModifierChecks {
+    abstract internal val checks: List<Checks>
+    
+    inline fun ensure(cond: Boolean, msg: () -> String) = if (!cond) msg() else null
 
-    private val CHECKS = listOf(
+    fun check(functionDescriptor: FunctionDescriptor): CheckResult {
+        for (check in checks) {
+            if (!check.isApplicable(functionDescriptor)) continue
+            return check.checkAll(functionDescriptor)
+        }
+
+        return CheckResult.IllegalFunctionName
+    }
+}
+
+object OperatorChecks : AbstractModifierChecks() {
+    override val checks = listOf(
             Checks(GET, MemberOrExtension, ValueParameterCountCheck.AtLeast(1)),
             Checks(SET, MemberOrExtension, ValueParameterCountCheck.AtLeast(2)) {
                 val lastIsOk = valueParameters.lastOrNull()?.let { !it.hasDefaultValue() && it.varargElementType == null } ?: false
@@ -212,15 +234,11 @@ object OperatorChecks {
             "Second parameter should be Continuation<Nothing>"
         }
     }
-
-    fun checkOperator(functionDescriptor: FunctionDescriptor): CheckResult {
-        for (check in CHECKS) {
-            if (!check.isApplicable(functionDescriptor)) continue
-            return check.checkAll(functionDescriptor)
-        }
-
-        return CheckResult.IllegalFunctionName
-    }
 }
 
-fun FunctionDescriptor.isValidOperator() = isOperator && OperatorChecks.checkOperator(this).isSuccess
+object InfixChecks : AbstractModifierChecks() {
+    override val checks = listOf(
+            Checks(HasDispatchOrExtensionReceiverParameter, SingleValueParameter, NoDefaultAndVarargsCheck))
+}
+
+fun FunctionDescriptor.isValidOperator() = isOperator && OperatorChecks.check(this).isSuccess