[FIR] Missing NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE

^KT-59433 Fixed

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

@@ -524,6 +524,13 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE) { firDiagnostic ->
+        NestedClassAccessedViaInstanceReferenceImpl(
+            firSymbolBuilder.classifierBuilder.buildClassLikeSymbol(firDiagnostic.a),
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.SUPER_IS_NOT_AN_EXPRESSION) { firDiagnostic ->
         SuperIsNotAnExpressionImpl(
             firDiagnostic as KtPsiDiagnostic,

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

@@ -414,6 +414,11 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         val suggestedFunction: String
     }
 
+    interface NestedClassAccessedViaInstanceReference : KtFirDiagnostic<PsiElement> {
+        override val diagnosticClass get() = NestedClassAccessedViaInstanceReference::class
+        val symbol: KtClassLikeSymbol
+    }
+
     interface SuperIsNotAnExpression : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = SuperIsNotAnExpression::class
     }

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

@@ -480,6 +480,12 @@ internal class DeprecatedBinaryModImpl(
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.DeprecatedBinaryMod
 
+internal class NestedClassAccessedViaInstanceReferenceImpl(
+    override val symbol: KtClassLikeSymbol,
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.NestedClassAccessedViaInstanceReference
+
 internal class SuperIsNotAnExpressionImpl(
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -225,6 +225,9 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirBasedSymbol<*>>("forbiddenFunction")
             parameter<String>("suggestedFunction")
         }
+        val NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE by error<PsiElement> {
+            parameter<FirClassLikeSymbol<*>>("symbol")
+        }
     }
 
     val SUPER by object : DiagnosticGroup("Super") {

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -194,6 +194,7 @@ object FirErrors {
     val AMBIGUOUS_ALTERED_ASSIGN by error1<PsiElement, List<String?>>()
     val FORBIDDEN_BINARY_MOD by error2<PsiElement, FirBasedSymbol<*>, String>(SourceElementPositioningStrategies.OPERATOR_MODIFIER)
     val DEPRECATED_BINARY_MOD by error2<PsiElement, FirBasedSymbol<*>, String>(SourceElementPositioningStrategies.OPERATOR_MODIFIER)
+    val NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE by error1<PsiElement, FirClassLikeSymbol<*>>()
 
     // Super
     val SUPER_IS_NOT_AN_EXPRESSION by error0<PsiElement>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt

@@ -68,6 +68,7 @@ val FIR_NON_SUPPRESSIBLE_ERROR_NAMES: Set<String> = setOf(
     "AMBIGUOUS_ALTERED_ASSIGN",
     "FORBIDDEN_BINARY_MOD",
     "DEPRECATED_BINARY_MOD",
+    "NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE",
     "SUPER_IS_NOT_AN_EXPRESSION",
     "SUPER_NOT_AVAILABLE",
     "ABSTRACT_SUPER_CALL",

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt

@@ -127,6 +127,8 @@ private fun ConeDiagnostic.toKtDiagnostic(
         FirErrors.TYPE_ARGUMENTS_NOT_ALLOWED.createOn(this.source)
     is ConeTypeArgumentsForOuterClassWhenNestedReferencedError ->
         FirErrors.TYPE_ARGUMENTS_FOR_OUTER_CLASS_WHEN_NESTED_REFERENCED.createOn(this.source)
+    is ConeNestedClassAccessedViaInstanceReference ->
+        FirErrors.NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE.createOn(this.source, this.symbol)
 
     is ConeOuterClassArgumentsRequired ->
         FirErrors.OUTER_CLASS_ARGUMENTS_REQUIRED.createOn(callOrAssignmentSource ?: source, this.symbol)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/FirCallResolver.kt

@@ -352,7 +352,7 @@ class FirCallResolver(
                     referencedSymbol,
                     qualifiedAccess.source,
                     qualifiedAccess.typeArguments,
-                    diagnostic,
+                    diagnostic ?: extractNestedClassAccessDiagnostic(nameReference.source, qualifiedAccess.explicitReceiver, referencedSymbol),
                     nonFatalDiagnostics = extractNonFatalDiagnostics(
                         nameReference.source,
                         qualifiedAccess.explicitReceiver,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/QualifiedNameResolution.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.fir.resolve.BodyResolveComponents
 import org.jetbrains.kotlin.fir.resolve.calls.getSingleVisibleClassifier
 import org.jetbrains.kotlin.fir.resolve.createCurrentScopeList
 import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeDeprecated
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeNestedClassAccessedViaInstanceReference
 import org.jetbrains.kotlin.fir.resolve.setTypeOfQualifier
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.name.ClassId
@@ -184,6 +185,16 @@ private fun FqName.continueQualifierInPackage(
     }
 }
 
+internal fun extractNestedClassAccessDiagnostic(
+    source: KtSourceElement?,
+    explicitReceiver: FirExpression?,
+    symbol: FirClassLikeSymbol<*>
+): ConeDiagnostic? {
+    if ((explicitReceiver as? FirResolvedQualifier)?.typeArguments?.isNotEmpty() == true)
+        return ConeNestedClassAccessedViaInstanceReference(source!!, symbol)
+    return null
+}
+
 internal fun extractNonFatalDiagnostics(
     source: KtSourceElement?,
     explicitReceiver: FirExpression?,

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/diagnostics/ConeDiagnostics.kt

@@ -272,6 +272,13 @@ class ConeTypeArgumentsForOuterClassWhenNestedReferencedError(source: KtSourceEl
     override val reason: String get() = "Type arguments for outer class are redundant when nested class is referenced"
 }
 
+class ConeNestedClassAccessedViaInstanceReference(
+    source: KtSourceElement,
+    val symbol: FirClassLikeSymbol<*>,
+) : ConeDiagnosticWithSource(source) {
+    override val reason: String get() = "Nested ${symbol.classId} accessed via instance reference"
+}
+
 class ConeNoTypeArgumentsOnRhsError(
     override val desiredCount: Int,
     override val symbol: FirClassLikeSymbol<*>

compiler/testData/diagnostics/tests/inference/regressions/kt34029.fir.kt

@@ -3,4 +3,4 @@ open class MyClass<T> {
 }
 
 val foo1 = MyClass.MyObject // it's ok
-val foo2 = MyClass<Boolean>.MyObject // here's stofl
+val foo2 = MyClass<Boolean>.<!NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE!>MyObject<!> // here's stofl