Generate IMPLICIT_NOTNULL for (nullability flexible type) -> (non-null type) implicit conversion.

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/IrUtils.kt

@@ -17,25 +17,26 @@
 package org.jetbrains.kotlin.psi2ir
 
 import org.jetbrains.kotlin.ir.declarations.IrVariable
-import org.jetbrains.kotlin.ir.expressions.IrExpression
-import org.jetbrains.kotlin.ir.expressions.IrGetVariableExpressionImpl
-import org.jetbrains.kotlin.ir.expressions.IrTypeOperator
-import org.jetbrains.kotlin.ir.expressions.IrTypeOperatorExpressionImpl
+import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker
+import org.jetbrains.kotlin.types.isNullabilityFlexible
 
 fun IrExpression.toExpectedType(expectedType: KotlinType?): IrExpression {
     if (expectedType == null) return this
     val valueType = type ?: throw AssertionError("expectedType != null, valueType == null: $this")
-    if (KotlinTypeChecker.DEFAULT.isSubtypeOf(valueType, expectedType)) {
-        return this
+
+    if (valueType.isNullabilityFlexible() && !expectedType.isMarkedNullable) {
+        return IrUnaryOperatorExpressionImpl(startOffset, endOffset, expectedType,
+                                             IrOperator.IMPLICIT_NOTNULL, null, this)
     }
 
-    return IrTypeOperatorExpressionImpl(
-            startOffset, endOffset, expectedType,
-            IrTypeOperator.IMPLICIT_CAST, expectedType,
-            this
-    )
+    if (!KotlinTypeChecker.DEFAULT.isSubtypeOf(valueType, expectedType)) {
+        return IrTypeOperatorExpressionImpl(startOffset, endOffset, expectedType,
+                                            IrTypeOperator.IMPLICIT_CAST, expectedType, this)
+    }
+
+    return this
 }
 
 fun IrVariable.load(): IrExpression =

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/expressions/IrOperator.kt

@@ -21,6 +21,8 @@ interface IrOperator {
     object EXCL : IrOperatorImpl("EXCL"), IrUnaryOperator
     object EXCLEXCL : IrOperatorImpl("EXCLEXCL"), IrUnaryOperator
 
+    object IMPLICIT_NOTNULL : IrOperatorImpl("IMPLICIT_NOTNULL"), IrUnaryOperator
+
     object ELVIS : IrOperatorImpl("ELVIS"), IrBinaryOperator
 
     object LT : IrOperatorImpl("LT"), IrBinaryOperator
@@ -38,8 +40,6 @@ interface IrOperator {
     object ANDAND : IrOperatorImpl("ANDAND"), IrBinaryOperator
     object OROR : IrOperatorImpl("OROR"), IrBinaryOperator
 
-
-
     object PLUS : IrOperatorImpl("PLUS"), IrBinaryOperator
     object MINUS : IrOperatorImpl("MINUS"), IrBinaryOperator
     object MUL : IrOperatorImpl("MUL"), IrBinaryOperator