override val isSuspend: Boolean
        get() = withValidityAssertion { psi.hasModifier(KtTokens.SUSPEND_KEYWORD) }

    override val isOperator: Boolean
        get() = withValidityAssertion { psi.hasModifier(KtTokens.OPERATOR_KEYWORD) }

    override val isExternal: Boolean
        get() = withValidityAssertion { psi.hasModifier(KtTokens.EXTERNAL_KEYWORD) }

    override val isInline: Boolean

internal class EqualityNotApplicableImpl(
    override val operator: String,
    override val leftType: KtType,
    override val rightType: KtType,
    firDiagnostic: KtPsiDiagnostic,
    token: KtLifetimeToken,
) : KtAbstractFirDiagnostic<KtBinaryExpression>(firDiagnostic, token), KtFirDiagnostic.EqualityNotApplicable

internal class EqualityNotApplicableWarningImpl(
    override val operator: String,
    override val leftType: KtType,

        }

    val ConeKotlinType.candidateClassId: ClassId?
        get() {
            return when (this) {
                is ConeErrorType -> when (val diagnostic = this.diagnostic) {
                    // Tolerate code that misses type parameters while shortening it.
                    is ConeUnmatchedTypeArgumentsError -> diagnostic.symbol.classId
                    else -> null
                }

        val fullQualifiedAccess = when (val psi = fir.source.psi) {
            // for cases like `Foo.Bar()`, where `Foo.Bar` is an object, and `Foo.Bar()` is a call to `invoke` operator
            is KtSimpleNameExpression -> psi.getQualifiedElement()
            else -> psi
        }
        if (fullQualifiedAccess !is KtDotQualifiedExpression) return referencedSymbolsByFir

            token,
        )
    }
    add(FirErrors.OPERATOR_MODIFIER_REQUIRED) { firDiagnostic ->
        OperatorModifierRequiredImpl(
            firSymbolBuilder.functionLikeBuilder.buildFunctionSymbol(firDiagnostic.a),
            firDiagnostic.b,
            firDiagnostic as KtPsiDiagnostic,
            token,
        )
    }
    add(FirErrors.OPERATOR_CALL_ON_CONSTRUCTOR) { firDiagnostic ->

            // cannot do so:
            // ```
            // fun x(c: Char) {}
            // fun call(x: kotlin.Int) {
            //   operator fun Int.invoke(a: Int) {}
            //   operator fun Int.invoke(b: Boolean) {}
            //   <expr>x()</expr>
            // }
            // ```

- [`KT-56659`](https://youtrack.jetbrains.com/issue/KT-56659) FIR: Increment operator on object leads to exception from resolve
- [`KT-56771`](https://youtrack.jetbrains.com/issue/KT-56771) FIR: Increment operator on qualified expressions leads to exception from resolve

        val receiverExpression: KtExpression
        val operator: String
        val argumentExpression: KtExpression?
    }

    interface UnsafeOperatorCall : KtFirDiagnostic<KtExpression> {
        override val diagnosticClass get() = UnsafeOperatorCall::class
        val receiverType: KtType
        val receiverExpression: KtExpression
        val operator: String
        val argumentExpression: KtExpression?
    }

        private val mapping = HashMap<FirElement, Optional<FirElement>>()
        private var unmappedCount = statements.size

        private val stack = ArrayDeque<FirElement>()

        operator fun get(fir: FirElement): FirElement? {
            return mapping[fir]?.getOrNull()
        }

        override fun visitElement(element: FirElement) {
            withElement(element) {

    private fun getExpectedTypeOfElvisOperand(expression: PsiElement): KtType? {
        val binaryExpression = expression.unwrapQualified<KtBinaryExpression> { binaryExpression, operand ->
            binaryExpression.operationToken == KtTokens.ELVIS && (operand == binaryExpression.left || operand == binaryExpression.right)
        } ?: return null
        if (expression !is KtExpression) return null