More precise diagnostic messages about "operator modifier is not applicable"

idea/src/org/jetbrains/kotlin/idea/intentions/AddOperatorModifierIntention.kt

@@ -28,7 +28,7 @@ class AddOperatorModifierIntention : SelfTargetingRangeIntention<KtNamedFunction
     override fun applicabilityRange(element: KtNamedFunction): TextRange? {
         val nameIdentifier = element.nameIdentifier ?: return null
         val functionDescriptor = element.resolveToDescriptor() as? FunctionDescriptor ?: return null
-        if (functionDescriptor.isOperator || !OperatorChecks.canBeOperator(functionDescriptor)) return null
+        if (functionDescriptor.isOperator || !OperatorChecks.checkOperator(functionDescriptor).isSuccess) return null
         return nameIdentifier.textRange
     }
 

idea/src/org/jetbrains/kotlin/idea/quickfix/ExclExclCallFixes.kt

@@ -37,8 +37,8 @@ import org.jetbrains.kotlin.psi.KtPostfixExpression
 import org.jetbrains.kotlin.psi.KtPsiFactory
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.types.TypeUtils
-import org.jetbrains.kotlin.util.OperatorChecks
 import org.jetbrains.kotlin.util.OperatorNameConventions
+import org.jetbrains.kotlin.util.isValidOperator
 
 abstract class ExclExclCallFix : IntentionAction {
     override fun getFamilyName(): String = text
@@ -126,7 +126,7 @@ object MissingIteratorExclExclFixFactory : KotlinSingleIntentionActionFactory()
             val memberScope = descriptor.unsubstitutedMemberScope
             val functions = memberScope.getContributedFunctions(OperatorNameConventions.ITERATOR, NoLookupLocation.FROM_IDE)
 
-            return functions.any { it.isOperator && OperatorChecks.canBeOperator(it) }
+            return functions.any { it.isValidOperator() }
         }
 
         when (descriptor) {

idea/testData/intentions/conventionNameCalls/replaceGetOrSet/setWithVararg.kt

@@ -1,5 +1,5 @@
 // IS_APPLICABLE: false
-// ERROR: operator modifier is inapplicable on this function: last parameter must not have a default value or be a vararg
+// ERROR: operator modifier is inapplicable on this function: last parameter should not have a default value or be a vararg
 
 class C {
     operator fun set(s: String, vararg value: Int): Boolean = true

idea/testData/intentions/toInfixCall/noExplicitReceiver.kt

@@ -1,3 +1,4 @@
 // IS_APPLICABLE: false
+// ERROR: 'infix' modifier is inapplicable on this function
 infix fun id(s: String) = s
 val x = <caret>id("0").get(0)