FirForLoopChecker: report also OPERATOR_MODIFIER if appropriate + minor

This commits checks iterator/hasNext/next functions whether they are
declared as operator or not. Also, it changes logic of hasNext/next
error reporting, now we're able to report errors about both these
functions.

idea/idea-frontend-fir/idea-frontend-fir-generator/src/org/jetbrains/kotlin/idea/frontend/api/fir/generator/HLDiagnosticConverter.kt

@@ -186,6 +186,11 @@ private object FirToKtConversionCreator {
             KtSymbol::class.createType(),
             importsToAdd = listOf("org.jetbrains.kotlin.fir.declarations.FirDeclaration")
         ),
+        FirNamedFunctionSymbol::class to HLFunctionCallConversion(
+            "firSymbolBuilder.functionLikeBuilder.buildFunctionSymbol({0}.fir)",
+            KtFunctionLikeSymbol::class.createType(),
+            importsToAdd = listOf("org.jetbrains.kotlin.fir.declarations.FirSimpleFunction")
+        ),
     )
 
     private val allowedTypesWithoutTypeParams = setOf(

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
 import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.psi
@@ -630,6 +631,14 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.OPERATOR_MODIFIER_REQUIRED) { firDiagnostic ->
+        OperatorModifierRequiredImpl(
+            firSymbolBuilder.functionLikeBuilder.buildFunctionSymbol(firDiagnostic.a.fir),
+            firDiagnostic.b,
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.INLINE_CLASS_NOT_TOP_LEVEL) { firDiagnostic ->
         InlineClassNotTopLevelImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.diagnostics.WhenMissingCase
 import org.jetbrains.kotlin.idea.frontend.api.diagnostics.KtDiagnosticWithPsi
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -459,6 +460,12 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val target: String
     }
 
+    abstract class OperatorModifierRequired : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = OperatorModifierRequired::class
+        abstract val functionSymbol: KtFunctionLikeSymbol
+        abstract val name: String
+    }
+
     abstract class InlineClassNotTopLevel : KtFirDiagnostic<KtDeclaration>() {
         override val diagnosticClass get() = InlineClassNotTopLevel::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirPsiDiagnostic
 import org.jetbrains.kotlin.idea.frontend.api.fir.utils.weakRef
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtCallableSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtClassLikeSymbol
+import org.jetbrains.kotlin.idea.frontend.api.symbols.KtFunctionLikeSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtTypeParameterSymbol
 import org.jetbrains.kotlin.idea.frontend.api.symbols.KtVariableLikeSymbol
@@ -727,6 +728,15 @@ internal class WrongModifierTargetImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class OperatorModifierRequiredImpl(
+    override val functionSymbol: KtFunctionLikeSymbol,
+    override val name: String,
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.OperatorModifierRequired(), KtAbstractFirDiagnostic<PsiElement> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class InlineClassNotTopLevelImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,