From 94fe79578e29ee1f33180d8b6e4d4d003fac898b Mon Sep 17 00:00:00 2001
From: Mikhail Glukhikh <mikhail.glukhikh@jetbrains.com>
Date: Thu, 19 Mar 2020 14:19:43 +0300
Subject: [PATCH] [FIR2IR] Generate unconditional branch in exhaustive whens

---
 .../kotlin/fir/backend/Fir2IrVisitor.kt          | 16 +++++++++++++++-
 compiler/testData/codegen/box/sealed/objects.kt  |  1 -
 compiler/testData/codegen/box/sealed/simple.kt   |  1 -
 .../box/when/enumOptimization/nullableEnum.kt    |  1 -
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
index 09e209a94b1..1f90227e5d8 100644
--- a/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
+++ b/compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt
@@ -504,11 +504,25 @@ class Fir2IrVisitor(
                     whenExpression.typeRef.toIrType(),
                     origin
                 ).apply {
+                    var unconditionalBranchFound = false
                     for (branch in whenExpression.branches) {
-                        if (branch.condition !is FirElseIfTrueCondition || branch.result.statements.isNotEmpty()) {
+                        if (branch.condition !is FirElseIfTrueCondition) {
                             branches += branch.accept(this@Fir2IrVisitor, data) as IrBranch
+                        } else {
+                            unconditionalBranchFound = true
+                            if (branch.result.statements.isNotEmpty()) {
+                                branches += branch.accept(this@Fir2IrVisitor, data) as IrBranch
+                            }
                         }
                     }
+                    if (whenExpression.isExhaustive && !unconditionalBranchFound) {
+                        val irResult = IrCallImpl(
+                            startOffset, endOffset, irBuiltIns.nothingType, irBuiltIns.noWhenBranchMatchedExceptionSymbol
+                        )
+                        branches += IrElseBranchImpl(
+                            IrConstImpl.boolean(startOffset, endOffset, irBuiltIns.booleanType, true), irResult
+                        )
+                    }
                 }
                 if (subjectVariable == null) {
                     irWhen
diff --git a/compiler/testData/codegen/box/sealed/objects.kt b/compiler/testData/codegen/box/sealed/objects.kt
index 0873aef3d9f..c33a71d498f 100644
--- a/compiler/testData/codegen/box/sealed/objects.kt
+++ b/compiler/testData/codegen/box/sealed/objects.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 sealed class Season {
     object Warm: Season()
     object Cold: Season()
diff --git a/compiler/testData/codegen/box/sealed/simple.kt b/compiler/testData/codegen/box/sealed/simple.kt
index e342bbbd968..01ae3af2c95 100644
--- a/compiler/testData/codegen/box/sealed/simple.kt
+++ b/compiler/testData/codegen/box/sealed/simple.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 sealed class Season {
     class Warm: Season()
     class Cold: Season()
diff --git a/compiler/testData/codegen/box/when/enumOptimization/nullableEnum.kt b/compiler/testData/codegen/box/when/enumOptimization/nullableEnum.kt
index 1554e319646..20d5f740782 100644
--- a/compiler/testData/codegen/box/when/enumOptimization/nullableEnum.kt
+++ b/compiler/testData/codegen/box/when/enumOptimization/nullableEnum.kt
@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // CHECK_CASES_COUNT: function=test count=0
 // CHECK_IF_COUNT: function=test count=3