JVM IR: Avoid IMPLICIT_NOTNULL checks on special bridge methods

...with dynamic type checks, except for the `@PlatformDependent`
methods, for which the JVM backend adds null checks.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/SpecialBridgeMethods.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.backend.common.ir.allOverridden
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
 import org.jetbrains.kotlin.ir.expressions.IrConstKind
 import org.jetbrains.kotlin.ir.expressions.IrExpression
@@ -107,8 +108,14 @@ class SpecialBridgeMethods(val context: CommonBackendContext) {
     val specialMethodNames = (specialMethodsWithDefaults + specialMethods).map { (description) -> description.name }.toHashSet()
     val specialPropertyNames = specialProperties.map { (description) -> description.name }.toHashSet()
 
-    fun findSpecialWithOverride(irFunction: IrSimpleFunction): Pair<IrSimpleFunction, SpecialMethodWithDefaultInfo>? {
-        for (overridden in irFunction.allOverridden()) {
+    fun findSpecialWithOverride(
+        irFunction: IrSimpleFunction,
+        includeSelf: Boolean = false
+    ): Pair<IrSimpleFunction, SpecialMethodWithDefaultInfo>? {
+        if (irFunction.parent !is IrClass)
+            return null
+
+        for (overridden in irFunction.allOverridden(includeSelf)) {
             val description = overridden.toDescription()
             specialMethodsWithDefaults[description]?.let {
                 return Pair(overridden, it)

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/JvmArgumentNullabilityAssertionsLowering.kt

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.backend.common.FileLoweringPass
 import org.jetbrains.kotlin.backend.common.lower.SpecialBridgeMethods
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
+import org.jetbrains.kotlin.backend.jvm.ir.hasPlatformDependent
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.declarations.IrFile
@@ -30,7 +31,8 @@ private enum class AssertionScope {
     Enabled, Disabled
 }
 
-private class JvmArgumentNullabilityAssertionsLowering(context: JvmBackendContext) : FileLoweringPass, IrElementTransformer<AssertionScope> {
+private class JvmArgumentNullabilityAssertionsLowering(context: JvmBackendContext) : FileLoweringPass,
+    IrElementTransformer<AssertionScope> {
 
     private val isWithUnifiedNullChecks = context.state.unifiedNullChecks
     private val isCallAssertionsDisabled = context.state.isCallAssertionsDisabled
@@ -90,7 +92,13 @@ private class JvmArgumentNullabilityAssertionsLowering(context: JvmBackendContex
     }
 
     private fun isCallToMethodWithTypeCheckBarrier(expression: IrMemberAccessExpression<*>): Boolean =
-        expression.symbol.owner.safeAs<IrSimpleFunction>()?.let { specialBridgeMethods.findSpecialWithOverride(it) != null } == true
+        expression.symbol.owner.safeAs<IrSimpleFunction>()
+            ?.let {
+                val bridgeInfo = specialBridgeMethods.findSpecialWithOverride(it, includeSelf = true)
+                // The JVM BE adds null checks around platform dependent special bridge methods (Map.getOrDefault and the version of
+                // MutableMap.remove with two arguments).
+                bridgeInfo != null && !bridgeInfo.first.hasPlatformDependent()
+            } == true
 
     private val IrStatementOrigin?.isOperatorWithNoNullabilityAssertionsOnExtensionReceiver
         get() = this is IrStatementOrigin.COMPONENT_N || this in operatorsWithNoNullabilityAssertionsOnExtensionReceiver