K2: add ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE for clashing functions

This diagnostic is reported on an explicitly-declared function which
overrides a regular Java function with the same signature as a hidden
one from the same scope.

#KT-64846 Fixed

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

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.psi.KtAnnotationEntry
 import org.jetbrains.kotlin.psi.KtDeclaration
 import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.kotlin.psi.KtNamedFunction
 
 /**
  * Generated from: [org.jetbrains.kotlin.fir.checkers.generator.diagnostics.JVM_DIAGNOSTICS_LIST]
@@ -50,6 +51,7 @@ object FirJvmErrors {
     val VALUE_CLASS_WITHOUT_JVM_INLINE_ANNOTATION: KtDiagnosticFactory0 by error0<PsiElement>()
     val JVM_INLINE_WITHOUT_VALUE_CLASS: KtDiagnosticFactory0 by error0<PsiElement>()
     val WRONG_NULLABILITY_FOR_JAVA_OVERRIDE: KtDiagnosticFactory2<FirCallableSymbol<*>, FirCallableSymbol<*>> by warning2<PsiElement, FirCallableSymbol<*>, FirCallableSymbol<*>>(SourceElementPositioningStrategies.OVERRIDE_MODIFIER)
+    val ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE: KtDiagnosticFactory3<FirNamedFunctionSymbol, String, FirNamedFunctionSymbol> by error3<KtNamedFunction, FirNamedFunctionSymbol, String, FirNamedFunctionSymbol>(SourceElementPositioningStrategies.DECLARATION_NAME)
 
     // Types
     val JAVA_TYPE_MISMATCH: KtDiagnosticFactory2<ConeKotlinType, ConeKotlinType> by error2<KtExpression, ConeKotlinType, ConeKotlinType>()

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

@@ -12,9 +12,11 @@ import org.jetbrains.kotlin.diagnostics.rendering.BaseDiagnosticRendererFactory
 import org.jetbrains.kotlin.diagnostics.rendering.CommonRenderers.NAME
 import org.jetbrains.kotlin.diagnostics.rendering.CommonRenderers.STRING
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.DECLARATION_NAME
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.FQ_NAMES_IN_TYPES
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.OPTIONAL_SENTENCE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.RENDER_TYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.SYMBOL
+import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.CONCURRENT_HASH_MAP_CONTAINS_OPERATOR
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.DELEGATION_BY_IN_JVM_RECORD
 import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.DEPRECATED_JAVA_ANNOTATION
@@ -115,6 +117,15 @@ object FirJvmErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             SYMBOL,
         )
 
+        map.put(
+            ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE,
+            "This function accidentally overrides both ''{0}'' and {1} ''{2}'' from JVM point of view because of mixed Java/Kotlin hierarchy.\n" +
+                    "This situation provokes a JVM clash and thus is forbidden. To fix it, you have to delete either this function or one of overridden functions.",
+            FQ_NAMES_IN_TYPES,
+            STRING,
+            FQ_NAMES_IN_TYPES,
+        )
+
         map.put(
             UPPER_BOUND_VIOLATED_BASED_ON_JAVA_ANNOTATIONS,
             "Type argument is not within its bounds: should be subtype of ''{0}''.",

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/checkers/JvmDeclarationCheckers.kt

@@ -58,6 +58,7 @@ object JvmDeclarationCheckers : DeclarationCheckers() {
     override val simpleFunctionCheckers: Set<FirSimpleFunctionChecker>
         get() = setOf(
             FirInlineBodySimpleFunctionChecker,
+            FirAccidentalOverrideClashChecker,
         )
 
     override val valueParameterCheckers: Set<FirValueParameterChecker>

compiler/fir/checkers/checkers.jvm/src/org/jetbrains/kotlin/fir/analysis/jvm/checkers/declaration/FirAccidentalOverrideClashChecker.kt

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.jvm.checkers.declaration
+
+import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.MppCheckerKind
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirSimpleFunctionChecker
+import org.jetbrains.kotlin.fir.analysis.checkers.unsubstitutedScope
+import org.jetbrains.kotlin.fir.analysis.diagnostics.jvm.FirJvmErrors.ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE
+import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
+import org.jetbrains.kotlin.fir.declarations.isHiddenToOvercomeSignatureClash
+import org.jetbrains.kotlin.fir.declarations.utils.isOverride
+import org.jetbrains.kotlin.fir.initialSignatureAttr
+import org.jetbrains.kotlin.fir.resolve.getContainingClass
+import org.jetbrains.kotlin.fir.scopes.jvm.computeJvmDescriptor
+import org.jetbrains.kotlin.fir.symbols.SymbolInternals
+import org.jetbrains.kotlin.load.java.SpecialGenericSignatures.Companion.JVM_SHORT_NAME_TO_BUILTIN_SHORT_NAMES_MAP
+import org.jetbrains.kotlin.load.java.SpecialGenericSignatures.Companion.sameAsBuiltinMethodWithErasedValueParameters
+
+object FirAccidentalOverrideClashChecker : FirSimpleFunctionChecker(MppCheckerKind.Platform) {
+    override fun check(
+        declaration: FirSimpleFunction,
+        context: CheckerContext,
+        reporter: DiagnosticReporter,
+    ) {
+        if (!declaration.isOverride) return
+        val name = declaration.name
+        val mayBeRenamedBuiltIn = name in namesPossibleForRenamedBuiltin
+        val mayBeSameAsBuiltInWithErasedParameters = name.sameAsBuiltinMethodWithErasedValueParameters
+        if (!mayBeRenamedBuiltIn && !mayBeSameAsBuiltInWithErasedParameters) return
+        val containingClass = declaration.getContainingClass(context.session) ?: return
+
+        var reported = false
+        containingClass.unsubstitutedScope(context).processFunctionsByName(name) {
+            @OptIn(SymbolInternals::class)
+            val hiddenFir = it.fir
+            if (!reported && hiddenFir.isHiddenToOvercomeSignatureClash == true) {
+                if (declaration.computeJvmDescriptor() == hiddenFir.computeJvmDescriptor()) {
+                    val regularBase = hiddenFir.initialSignatureAttr as? FirSimpleFunction ?: return@processFunctionsByName
+                    val description = when {
+                        mayBeRenamedBuiltIn -> "a renamed function"
+                        else -> "a function with erased parameters"
+                    }
+                    reporter.reportOn(
+                        declaration.source, ACCIDENTAL_OVERRIDE_CLASH_BY_JVM_SIGNATURE, it, description, regularBase.symbol, context
+                    )
+                    reported = true
+                }
+            }
+        }
+    }
+
+    private val namesPossibleForRenamedBuiltin = JVM_SHORT_NAME_TO_BUILTIN_SHORT_NAMES_MAP.values.toSet()
+}