Add an implicit cast to Unit in returns from a constructor.

compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/transformations/InsertImplicitCasts.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.ir.declarations.IrVariable
 import org.jetbrains.kotlin.ir.descriptors.IrBuiltIns
 import org.jetbrains.kotlin.ir.expressions.*
 import org.jetbrains.kotlin.ir.expressions.impl.IrTypeOperatorCallImpl
+import org.jetbrains.kotlin.ir.symbols.IrConstructorSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classifierOrFail
 import org.jetbrains.kotlin.ir.types.impl.originalKotlinType
@@ -107,7 +108,11 @@ open class InsertImplicitCasts(
 
     override fun visitReturn(expression: IrReturn): IrExpression =
         expression.transformPostfix {
-            value = value.cast(expression.returnTarget.returnType)
+            value = if (expression.returnTargetSymbol is IrConstructorSymbol) {
+                value.coerceToUnit()
+            } else {
+                value.cast(expression.returnTarget.returnType)
+            }
         }
 
     override fun visitSetVariable(expression: IrSetVariable): IrExpression =

compiler/testData/codegen/box/secondaryConstructors/withReturn.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 class A {
     val prop: Int
     constructor(arg: Boolean) {

compiler/testData/codegen/box/secondaryConstructors/withReturnUnit.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JVM_IR
 class A {
     val prop: Int
     constructor(arg: Boolean) {

compiler/testData/ir/irText/expressions/implicitCastInReturnFromConstructor.kt

@@ -0,0 +1,5 @@
+class C() {
+    constructor(x: Any?) : this() {
+        if (x is Unit) return x
+    }
+}

compiler/testData/ir/irText/expressions/implicitCastInReturnFromConstructor.txt

@@ -0,0 +1,31 @@
+FILE fqName:<root> fileName:/implicitCastInReturnFromConstructor.kt
+  CLASS CLASS name:C modality:FINAL visibility:public superTypes:[kotlin.Any]
+    $this: VALUE_PARAMETER INSTANCE_RECEIVER name:<this> type:<root>.C
+    CONSTRUCTOR visibility:public <> () returnType:<root>.C [primary]
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in kotlin.Any'
+        INSTANCE_INITIALIZER_CALL classDescriptor='CLASS CLASS name:C modality:FINAL visibility:public superTypes:[kotlin.Any]'
+    CONSTRUCTOR visibility:public <> (x:kotlin.Any?) returnType:<root>.C
+      VALUE_PARAMETER name:x index:0 type:kotlin.Any?
+      BLOCK_BODY
+        DELEGATING_CONSTRUCTOR_CALL 'public constructor <init> () [primary] declared in <root>.C'
+        WHEN type=kotlin.Unit origin=IF
+          BRANCH
+            if: TYPE_OP type=kotlin.Boolean origin=INSTANCEOF typeOperand=kotlin.Unit
+              GET_VAR 'x: kotlin.Any? declared in <root>.C.<init>' type=kotlin.Any? origin=null
+            then: RETURN type=kotlin.Nothing from='public constructor <init> (x: kotlin.Any?) declared in <root>.C'
+              TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
+                GET_VAR 'x: kotlin.Any? declared in <root>.C.<init>' type=kotlin.Any? origin=null
+    FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean
+      overridden:
+        public open fun equals (other: kotlin.Any?): kotlin.Boolean declared in kotlin.Any
+      $this: VALUE_PARAMETER name:<this> type:kotlin.Any
+      VALUE_PARAMETER name:other index:0 type:kotlin.Any?
+    FUN FAKE_OVERRIDE name:hashCode visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:kotlin.Int
+      overridden:
+        public open fun hashCode (): kotlin.Int declared in kotlin.Any
+      $this: VALUE_PARAMETER name:<this> type:kotlin.Any
+    FUN FAKE_OVERRIDE name:toString visibility:public modality:OPEN <> ($this:kotlin.Any) returnType:kotlin.String
+      overridden:
+        public open fun toString (): kotlin.String declared in kotlin.Any
+      $this: VALUE_PARAMETER name:<this> type:kotlin.Any

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -907,6 +907,11 @@ public class IrTextTestCaseGenerated extends AbstractIrTextTestCase {
             runTest("compiler/testData/ir/irText/expressions/ifElseIf.kt");
         }
 
+        @TestMetadata("implicitCastInReturnFromConstructor.kt")
+        public void testImplicitCastInReturnFromConstructor() throws Exception {
+            runTest("compiler/testData/ir/irText/expressions/implicitCastInReturnFromConstructor.kt");
+        }
+
         @TestMetadata("implicitCastOnPlatformType.kt")
         public void testImplicitCastOnPlatformType() throws Exception {
             runTest("compiler/testData/ir/irText/expressions/implicitCastOnPlatformType.kt");